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Find video protocols related to scientific articles indexed in Pubmed.
ESBL-producing Enterobacteriaceae in environmental water in Dhaka, Bangladesh.
J. Infect. Chemother.
PUBLISHED: 08-05-2014
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Pathogens encoding extended-spectrum ?-lactamase (ESBL) genes represent a threat for failure of empirical antibiotic therapy and are associated with high mortality, morbidity and expenses. We examined surface water in Dhaka, capital of Bangladesh and isolated ESBL-producing Escherichia coli, Klebsiella pneumoniae and Enterobacter cloacae, suggesting the potential role of water for the dissemination and transmission of resistant genes among microorganisms. E. coli found most prevalent among isolated Enterobacteriaceae from environmental water. Molecular and genetic analysis revealed CTX-M-type and SHV-type ESBL genes in isolates that may influence the spread of multidrug resistant pathogenic bacteria causing human and animal infections in Bangladesh.
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[Nationwide surveillance of parenteral antibiotics containing meropenem activities against clinically isolated strains in 2012].
Jpn J Antibiot
PUBLISHED: 06-25-2014
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The nationwide surveillance of antibacterial susceptibility to meropenem (MEPM) and other parenteral antibiotics against clinical isolates during 2012 in Japan was conducted. A total of 2985 strains including 955 strains of Gram-positive bacteria, 1782 strains of Gram-negative bacteria, and 248 strains of anaerobic bacteria obtained from 31 medical institutions were examined. The results were as follows; 1. MEPM was more active than the other carbapenem antibiotics tested against Gram-negative bacteria, especially against enterobacteriaceae and Haemophilus influenzae. MEPM was also active against most of the species tested in Gram-positive and anaerobic bacteria, except for multi-drug resistant strains including methicillin-resistant Staphylococcus aureus (MRSA). 2. Of all species tested, there were no species, which MIC90 of MEPM was more than 4-fold higher than those in our previous studies in 2009 or 2006. Therefore, the tendency to increase in antimicrobial resistance rates was not observed. 3. MEPM resistance against Pseudomonas aeruginosa was 17.8% (56/315 strains). Compared to our previous results, it was the lowest than that in 2006 and 2009. 4. Carbapenem-resistant Klebsiella pneumoniae, and multi-drug-resistant Acinetobacter species, which emerged in worldwide, were not observed. 5. The proportion of extended-spectrum beta-lactamase (ESBL) strains was 6.2% (59/951 strains) in enterobacteriaceae, which increased compared with that of our previous studies in 2009 or before. Whereas, the proportion of metallo-beta-lactamase strains was 1.6% (5/315 strains) in P. aeruginosa, which was stable. In conclusion, the results from this surveillance suggest that MEPM retains its potent and broad antibacterial activity and therefore is a clinically useful carbapenem for serious infections treatment at present, 17 years passed after available for commercial use in Japan.
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Crystal structure of Mox-1, a unique plasmid-mediated class C ?-lactamase with hydrolytic activity towards moxalactam.
Antimicrob. Agents Chemother.
PUBLISHED: 04-28-2014
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Mox-1 is a unique plasmid-mediated class C ?-lactamase that hydrolyzes penicillins, cephalothin, and the expanded-spectrum cephalosporins cefepime and moxalactam. In order to understand the unique substrate profile of this enzyme, we determined the X-ray crystallographic structure of Mox-1 ?-lactamase at a 1.5-Å resolution. The overall structure of Mox-1 ?-lactamase resembles that of other AmpC enzymes, with some notable exceptions. First, comparison with other enzymes whose structures have been solved reveals significant differences in the composition of amino acids that make up the hydrogen-bonding network and the position of structural elements in the substrate-binding cavity. Second, the main-chain electron density is not observed in two regions, one containing amino acid residues 214 to 216 positioned in the ? loop and the other in the N terminus of the B3 ?-strand corresponding to amino acid residues 303 to 306. The last two observations suggest that there is significant structural flexibility of these regions, a property which may impact the recognition and binding of substrates in Mox-1. These important differences allow us to propose that the binding of moxalactam in Mox-1 is facilitated by the avoidance of steric clashes, indicating that a substrate-induced conformational change underlies the basis of the hydrolytic profile of Mox-1 ?-lactamase.
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Daptomycin susceptibility of 833 strains of Gram-positive cocci from a university hospital in Japan (2009-2011).
Diagn. Microbiol. Infect. Dis.
PUBLISHED: 02-24-2014
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The aim of this study was to confirm the daptomycin (DAP) susceptibility of bacteria isolated before the launch of DAP in Japan. DAP showed good activity against all 833 isolates (MIC90 = 0.25-0.5 mg/L for staphylococci, 0.5-4 mg/L for enterococci, and 0.25-0.5 mg/L for streptococci). This is the first report of the in vitro activity of DAP against Gram-positive cocci, including methicillin-resistant Staphylococcus aureus and enterococci, isolated in Japan.
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Spread of CTX-M-15 extended-spectrum ?-lactamase-producing Escherichia coli isolates through household contact and plasmid transfer.
J. Clin. Microbiol.
PUBLISHED: 02-19-2014
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We document the household spread of extended-spectrum ?-lactamase-producing Escherichia coli. One isolate belonged to sequence type 1193 and caused urinary tract infection in a 4-month-old female, and the other isolate belonged to sequence type 131 and colonized three family members, including the index patient. These isolates carried similar Inc-I1-I? plasmids, harboring blaCTX-M-15.
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Contradiction between in vitro and clinical outcome: intravenous followed by oral azithromycin therapy demonstrated clinical efficacy in macrolide-resistant pneumococcal pneumonia.
J. Infect. Chemother.
PUBLISHED: 01-31-2014
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We conducted a multicenter, unblinded, non-comparative, phase 3 trial of azithromycin-intravenous therapy followed by oral administration in Japanese adults to evaluate clinical efficacy and safety against community-acquired pneumonia in order to obtain regulatory approval for the intravenous formulation in Japan. Azithromycin (500 mg, once daily) was intravenously administered for 2-5 days followed by oral 500 mg once daily administration to complete a total of 7-10 days treatment in 102 adults with moderate-to-severe community-acquired pneumonia. The efficacy rate in the Clinical Per Protocol Set overall was 84.5% (60/71 subjects) on Day 15 (primary analysis). The most common causative pathogen was Haemophilus influenzae (17 strains), followed by Streptococcus pneumoniae (14 strains), Moraxella catarrhalis (5 strains) and Mycoplasma pneumoniae (5 strains). Eleven of 14 S. pneumoniae isolates were resistant to azithromycin (MIC ?2.0 ?g/ml), of which 5 strains with a relatively low MIC of <32 ?g/ml had only mef A gene and 6 strains with a high MIC of >64 ?g/ml had only the erm B gene except for 2 isolates having both the mef A and erm B genes. Despite dominance of macrolide-resistant strains in Japan, clinical efficacy and bacterial eradication were achieved in 10 of 11 patients (90.9%). Intravenous-to-oral azithromycin therapy demonstrated excellent clinical and bacteriological effects on moderate-to-severe pneumococcal pneumonia despite a high MIC and resistance gene development. This discrepancy is referred to as the "in vivo-in vitro paradox". The current study results provide an insight into this paradox.
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Antibiotic susceptibility survey of blood-borne MRSA isolates in Japan from 2008 through 2011.
J. Infect. Chemother.
PUBLISHED: 01-27-2014
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We conducted an antibiotic susceptibility survey of 830 blood-borne methicillin resistant Staphylococcus aureus collected from nationwide hospitals in Japan over a three-year period from January 2008 through May 2011. Antibiotic susceptibility was judged according to the criteria recommended by the Clinical Laboratory Standard Institute. Over 99% of the MRSA showed to be susceptible to teicoplanin, linezolid, sulfamethoxazole/trimethoprim and vancomycin, and over 97% of them were susceptible to daptomycin, arbekacin and rifampin. The majority of the MRSA strains showed resistant to minocycline, meropenem, imipenem, clindamycin, ciprofloxacin, cefoxitin, and oxacillin in the rates of 56.6, 72.9, 73.7, 78.7, 89.0, 99.5, and 99.9%, respectively. Among the MRSA strains, 72 showed reduced susceptibility to vancomycin, including 8 strains (0.96%) of vancomycin-intermediate S. aureus (VISA), 54 (6.51%) of heterogeneous vancomycin-intermediate S. aureus (hVISA), and 55 (5.63%) of ?-lactam antibiotics-induced vancomycin resistant S. aureus (BIVR). Unexpectedly, among the 54 hVISA and 55 BIVR, 45 isolates (83.3% and 81.8%, respectively) showed both hVISA and BIVR phenotypes. A new trend of vancomycin resistance found in this study was that VISA strains were still prevalent among the bacteremic specimens. The high rates of the hVISA/BIVR two-phenotypic vancomycin resistance, and the prevalence of VISA in the bloodborne MRSA call attention in the MRSA epidemiology in Japan.
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Changes in Streptococcus pneumoniae serotypes in the nasopharynx of Japanese children after inoculation with a heptavalent pneumococcal conjugate vaccine.
Jpn. J. Infect. Dis.
PUBLISHED: 01-24-2014
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In this study, we prospectively investigated changes in Streptococcus pneumoniae serotypes among Japanese children after heptavalent pneumococcal conjugate vaccine (PCV7) inoculation. We acquired nasopharyngeal swabs from the children at each routine PCV7 inoculation and again at least 2 months after the last PCV7 inoculation. We defined 2 periods with regard to each culture: the inoculation period as "the period of pre- or incomplete vaccination" and post-inoculation as "the period of post- or completed vaccination." The prevalence of vaccine-type (VT) pneumococci was significantly reduced from 9.5% in the inoculation-period cultures to 2.9% in the post-inoculation cultures (P < 0.01). There was no statistical difference in the prevalence of non-vaccine-type pneumococci between the inoculation-period and post-inoculation cultures (24.1% versus 23.4%). The protection of PCV7 against nasopharyngeal colonization was inferred from the decrease in VT carriage post-inoculation. The decrease in VT carriage may be conducive to reducing VT transmission within the study area.
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Purification, crystallization and preliminary X-ray analysis of IMP-18, a class B carbapenemase from Pseudomonas aeruginosa.
Acta Crystallogr. Sect. F Struct. Biol. Cryst. Commun.
PUBLISHED: 10-08-2013
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Class B ?-lactamases are known as metallo-?-lactamases (MBLs) and they hydrolyze most ?-lactams, including carbapenems. IMP-18, an MBL cloned from Pseudomonas aeruginosa, was overexpressed, purified and crystallized by vapour diffusion for X-ray crystallographic analysis. Preliminary X-ray analysis showed that the crystal diffracted to 2.4?Å resolution and belonged to the tetragonal space group P41212, with unit-cell parameters a = b = 120.77, c = 96.54?Å, ? = ? = ? = 90°, suggesting the presence of two molecules in the asymmetric unit.
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The impact of anaerobiosis on strain-dependent phenotypic variations in Pseudomonas aeruginosa.
Biosci. Biotechnol. Biochem.
PUBLISHED: 08-07-2013
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Bacteria participate in social behaviors by communicating with each other and forming surface-associated biofilms. In Pseudomonas aeruginosa, such social behaviors are affected greatly by the environment. Although P. aeruginosa survive under anaerobic conditions, previous studies indicate that quorum sensing is attenuated under such conditions, and that this leads to decreased activity of extracellular virulence factors as compared to aerobic conditions. Hence it has come into question whether P. aeruginosa are virulent under anaerobic conditions. Here, we compared various phenotypes between PAO1 and clinical isolates under anaerobic conditions. Our data revealed that when grown anaerobically, growth and cell morphology greatly differed among the strains. One of the clinical isolates produced comparable amounts of quorum-sensing signaling molecules and extracellular virulence factors under aerobic and anaerobic conditions, while the other strains showed low production under anaerobic conditions. Biofilm formation also exhibited strain-dependent variations, suggesting that there are several mechanisms that lead to biofilm formation under anaerobic conditions. Taken together, these results indicate that the impact of anaerobiosis on the social interactions of P. aeruginosa is strain dependent, and suggest that multiple regulatory mechanisms are involved in the regulation of quorum sensing and biofilm formation under anaerobic conditions.
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Protective effect of procysteine on Acinetobacter pneumonia in hyperoxic conditions.
J. Antimicrob. Chemother.
PUBLISHED: 05-16-2013
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Ventilator-associated pneumonia (VAP) is an important cause of morbidity and mortality in critical care settings. Acinetobacter has become a leading cause of VAP. In particular, the appearance and spread of multidrug-resistant Acinetobacter is of great concern. In this study, we examined the effect of the antioxidant procysteine on Acinetobacter murine pneumonia in hyperoxic conditions in order to simulate VAP.
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Characterization of qnrB-like genes in Citrobacter species of the American Type Culture Collection.
Antimicrob. Agents Chemother.
PUBLISHED: 03-25-2013
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Among five American Type Culture Collection (ATCC) Citrobacter strains, qnrB60 in Citrobacter freundii ATCC 6879, an isolate from the preantibiotic era, and qnrB61 in Citrobacter braakii ATCC 51113(T), a type strain belonging to the C. freundii complex, were identified. Meanwhile, a truncated qnrB-like pseudogene was identified in C. freundii ATCC 8090(T) and ATCC 43864. No qnrB-like sequence was found in Citrobacter koseri ATCC 27028(T). These findings underscore the close relationship between this species and qnrB.
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Molecular characterization of extraintestinal Escherichia coli isolates in Japan: relationship between sequence types and mutation patterns of quinolone resistance-determining regions analyzed by pyrosequencing.
J. Clin. Microbiol.
PUBLISHED: 03-20-2013
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Infection from fluoroquinolone-resistant Enterobacteriaceae is an increasing health problem worldwide. In the present study, we developed a pyrosequencing-based high-throughput method for analyzing the nucleotide sequence of the quinolone resistance-determining regions (QRDRs) of gyrA and parC. By using this method, we successfully determined the QRDR sequences of 139 out of 140 clinical Escherichia coli isolates, 28% of which were nonsusceptible to ciprofloxacin. Sequence results obtained by the pyrosequencing method were in complete agreement with those obtained by the Sanger method. All fluoroquinolone-resistant isolates (n = 35; 25%) contained mutations leading to three or four amino acid substitutions in the QRDRs. In contrast, all isolates lacking a mutation in the QRDR (n = 81; 57%) were susceptible to ciprofloxacin, levofloxacin, and nalidixic acid. The qnr determinants, namely, the qnrA, qnrB, and qnrS genes, were not detected in the isolates, and the aac(6)-Ib-cr gene was detected in 2 (1.4%) of the isolates. Multilocus sequence typing of 34 randomly selected isolates revealed that sequence type 131 (ST131) (n = 7; 20%) is the most prevalent lineage and is significantly resistant to quinolones (P < 0.01). The genetic background of quinolone-susceptible isolates seemed more diverse, and interestingly, neighboring STs of ST131 in the phylogenetic tree were all susceptible to ciprofloxacin. In conclusion, our investigation reveals the relationship between fluoroquinolone resistance caused by mutations of QRDRs and the population structure of clinical extraintestinal E. coli isolates. This high-throughput method for analyzing QRDR mutations by pyrosequencing is a powerful tool for epidemiological studies of fluoroquinolone resistance in bacteria.
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Prevalence and risk factors of nasopharyngeal carriage of Streptococcus pneumoniae in healthy children in Japan.
Jpn. J. Infect. Dis.
PUBLISHED: 02-23-2013
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The findings of this study revealed a 22% prevalence of Streptococcus pneumoniae among healthy children in Japan; the prevalence tended to increase with age. We identified attendance at day-care facilities and the presence of older siblings as the major risk factors associated with pneumococcal carriage. A significant decrease in pneumococcal colonization was observed among children during the summer; however, a seasonal variation was independent of various factors. Our findings suggest that prior immunization with heptavalent pneumococcal conjugate vaccine within the current recommended schedule is required for children exposed to these risk factors.
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Effects of slow-releasing colistin microspheres on endotoxin-induced sepsis.
J. Infect. Chemother.
PUBLISHED: 01-25-2013
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Lipopolysaccharide (LPS) is a major contributing factor to endotoxic shock. Colistin specifically binds to LPS. However, it has the disadvantages that adverse reactions are common and it has a short half-life. To overcome these disadvantages, we prepared slow-releasing colistin microspheres and examined the efficacy of these colistin microspheres in a mouse model of endotoxin-induced sepsis. We prepared the colistin microspheres using poly-lactic-co-glycolic acid. For acute toxicity investigations, mice were overdosed with colistin sulfate or colistin microspheres. The group administered with colistin microspheres was associated with less acute toxicity and fewer nephrotoxic changes on histopathological examination compared to the group administered with colistin sulfate alone. For pharmacokinetic analysis, mice were subcutaneously administered with colistin microspheres or colistin sulfate alone. The plasma concentration of colistin was higher in the colistin microspheres group than in the colistin sulfate group at 12 and 24 h after administration. Moreover, mice were intraperitoneally injected with LPS and then immediately subcutaneously administered with blank microspheres, colistin microspheres or colistin sulfate alone. The levels of endotoxin in the sera and cytokine in the spleens were then measured. A significant reduction in the serum endotoxin level in the colistin microspheres group was observed at 24 h. The reduced endotoxin levels in the sera were correlated with the lower cytokine levels in the spleens of mice treated with colistin microspheres. Our results suggest that the use of colistin microspheres may help to maintain a higher colistin concentration in blood, reduce the levels of endotoxin and cytokines in endotoxin-induced sepsis, and lead to decreased toxicity.
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Use of culture-independent analysis to reveal alteration of intestinal microflora by heat-killed Lactobacillus pentosus in a mouse model of endogenous sepsis.
J. Infect. Chemother.
PUBLISHED: 01-01-2013
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In this study we evaluated alteration of intestinal microflora by terminal-restriction fragment length polymorphism (T-RFLP) analysis and quantitative PCR (qPCR) for specific microbes. The effects of orally administered heat-killed Lactobacillus pentosus strain b240 (HK-b240) in immunosuppressed mice with endogenous Pseudomonas aeruginosa sepsis was estimated. By T-RFLP analysis, 5 dominant operational taxonomic units (OTUs) including Bacteroides spp. (OTU460) and Lactobacillus spp. (OTU657) were consistently observed, irrespective of treatment, at all time points. A significantly higher population of segmented filamentous bacteria (SFB) was observed by qPCR after 3 weeks of HK-b240 administration; thereafter, the difference was not sustained during immunosuppression and progression of sepsis. Although not significant, Lactobacillus spp. accounted for a larger population in the HK-b240-treated group. In conclusion, this study demonstrated successful application of culture-independent assays for evaluating biological agents by detecting changes in microflora even if the protection was not sufficient to result in significant survival change.
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Roles of interleukin-17 in an experimental Legionella pneumophila pneumonia model.
Infect. Immun.
PUBLISHED: 12-05-2011
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Interleukin-17 (IL-17) is a key factor in T helper type 17 (Th17) lineage host responses and plays critical roles in immunological control of a variety of infectious diseases. Although Legionella pneumophila, an intracellular bacterium found widely in the environment, often causes a serious and life-threatening pneumonia in humans, the contribution of IL-17 to immune function during Legionella pneumonia is unknown. In the present study, we used an experimental Legionella pneumonia infection to clarify the role of IL-17 in the resulting immune response. We observed robust production of pulmonary IL-17A and IL-17F (IL-17A/F), peaking on day 1 and declining thereafter. Upregulated production of tumor necrosis factor alpha (TNF-?), IL-6, and IL-1?, but not monocyte chemotactic protein 1 (MCP-1), was observed in Legionella-infected bone marrow-derived macrophages from BALB/c mice that had been stimulated with IL-17A or IL-17F. A significant decrease in the production of proinflammatory cytokines IL-6 and TNF-? was observed in IL-17A/F-deficient mice (BALB/c background) infected with L. pneumophila. Moreover, we found impaired neutrophil migration and lower numbers of chemokines (KC, LIX, and MIP-2) in IL-17A/F-deficient mice. IL-17A/F-deficient mice also eliminated L. pneumophila more slowly and were less likely to survive a lethal challenge. These results demonstrate that IL-17A/F plays a critical role in L. pneumophila pneumonia, probably through induction of proinflammatory cytokines and accumulation of neutrophils at the infection site.
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Chromosomal integration and location on IncT plasmids of the blaCTX-M-2 gene in Proteus mirabilis clinical isolates.
Antimicrob. Agents Chemother.
PUBLISHED: 11-21-2011
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Analysis of five CTX-M-2-producing Proteus mirabilis isolates in Japan demonstrated that bla(CTX-M-2) was located on the chromosome in four isolates and on IncT plasmids in three isolates, including two isolates that also carried the gene on the chromosome. In all four isolates with chromosomal bla(CTX-M-2), ISEcp1 was responsible for the integration of the gene into the chromosome. Three different sites in the P. mirabilis genomic sequence were utilized as integration sites.
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Compliance with oral antibiotic regimens and associated factors in Japan: compliance survey of multiple oral antibiotics (COSMOS).
Scand. J. Infect. Dis.
PUBLISHED: 10-22-2011
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To provide an overall picture of oral antibiotic use in Japan, we conducted a survey of patients who had been prescribed oral antibiotics. In addition, factors potentially associated with compliance were evaluated.
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Pravastatin inhibits farnesol production in Candida albicans and improves survival in a mouse model of systemic candidiasis.
Med. Mycol.
PUBLISHED: 09-28-2011
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Candidemia remains a major cause of morbidity and mortality, especially in immunocompromised patients. A strategy of reducing virulence and virulence factors of Candida spp. is an attractive approach for the treatment of serious infections caused by these yeasts. Recently, farnesol has been reported to be a quorum-sensing autoinducer, as well as a virulence factor of C. albicans. In the present study, we examined the effects of pravastatin, a 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase inhibitor on the in vitro production of farnesol. In addition, the synergistic effects of pravastatin with fluconazole (FLC) were examined in a mouse model of systemic infections. In vitro experiments demonstrated that pravastatin had synergistic activity with FLC as judged by fractional inhibitory concentration index (FICI) and suppression of farnesol production at sub-minimum inhibitory concentrations. Furthermore, significant improvement of survival in systemic infection models was shown with pravastatin supplementation. The survival benefits of pravastatin were correlated with reductions of fungal burden. These data suggest the potential of pravastatin as a supportive therapy against C. albicans infections. Synergistic antifungal activity and suppression of HMG-CoA reductase-associated Candida virulence factors, including farnesol, may explain, at least in part, the in vivo efficacy of pravastatin.
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Efficacy of human-simulated exposures of tomopenem (formerly CS-023) in a murine model of Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus infection.
Antimicrob. Agents Chemother.
PUBLISHED: 08-15-2011
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Tomopenem (formerly CS-023) is a novel carbapenem with improved activity against diverse hospital pathogens, including Pseudomonas aeruginosa and methicillin-resistant Staphylococcus aureus (MRSA), and has a half-life about twice longer than the half-lives of other carbapenems such as imipenem and meropenem. Our objective in this study was to estimate the efficacy of tomopenem in humans by human-simulated exposures in a neutropenic murine thigh infection model against 9 clinical isolates of P. aeruginosa with MICs of 4 to 32 ?g/ml and 9 clinical isolates of MRSA with MICs of 4 to 16 ?g/ml. Human-simulated dosing regimens in neutropenic mice were designed to approximate the cumulative percentage of a 24-h period that the free drug concentration exceeds the MIC under steady-state pharmacokinetic conditions (f%T(MIC)) observed with tomopenem at 750 and 1,500 mg given as a 0.5-h infusion three times a day (TID) in humans. As reported previously, there was no difference between the target values of P. aeruginosa and MRSA required for efficacy (K. Sugihara et al., Antimicrob. Agents Chemother. 54:5298-5302, 2010). Tomopenem at 750 mg showed bactericidal or bacteriostatic effects against 10 of 11 strains of P. aeruginosa and MRSA with MICs of ? 8 ?g/ml (f%T(MIC) ? 41), and tomopenem at 1,500 mg showed bactericidal effects against 16 of 17 strains of P. aeruginosa and MRSA with MICs of ? 16 ?g/ml (f%T(MIC) ? 43). Meropenem at 1,000 mg TID was tested for comparison purposes and showed bactericidal or bacteriostatic effects against 3 of 4 strains of P. aeruginosa with MICs of ? 4 ?g/ml (f%T(MIC) ? 33). From these results, tomopenem is expected to be effective with an f%T(MIC) of over 40 against P. aeruginosa and MRSA strains with MICs of ? 8 ?g/ml at doses of 750 mg TID and strains with MICs of ? 16 ?g/ml at doses of 1,500 mg TID.
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In vitro and in vivo antibacterial activity of modithromycin against streptococci and Haemophilus influenzae.
J. Antimicrob. Chemother.
PUBLISHED: 04-21-2011
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In vitro and in vivo antibacterial activities of modithromycin against Streptococcus pneumoniae, Streptococcus pyogenes and Haemophilus influenzae were examined.
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Familial spread of a virulent clone of Klebsiella pneumoniae causing primary liver abscess.
J. Clin. Microbiol.
PUBLISHED: 04-13-2011
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Capsule-forming Klebsiella pneumoniae K1 caused primary liver abscess in two household members of a family. The causative isolates had identical pulsed-field gel electrophoresis patterns and were determined to be sequence type 23. An additional member of the family was found to carry the same strain without clinical manifestation.
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Roles of Pseudomonas aeruginosa autoinducers and their degradation products, tetramic acids, in bacterial survival and behavior in ecological niches.
Microbes Environ.
PUBLISHED: 03-29-2011
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Pseudomonas aeruginosa, an opportunistic pathogen, is known to mainly use N-acylhomoserine lactones (AHLs) as autoinducers. Recent progress in this field demonstrated that not only AHLs, but also their degradation products, tetramic acids, may have some biological activities. The present study examined the roles of Pseudomonas autoinducers and tetramic acids in bacterial survival and behavior in ecological niches. P. aeruginosa autoinducers and the tetramic acid derivatives were chemically synthesized, and the structure-activity correlation was investigated. Some tetramic acids derived from AHLs caused a significant reduction in the viability of P. aeruginosa in a concentration dependent manner (30-300 µM). The smaller the inoculum of bacteria, the stronger the bactericidal activity that was observed. The data from tetramic acid derivatives indicated the keto-enol structure of tetramic acid to be critical for the antibacterial activity. Exogenous tetramic acid did not induce significant changes in the formation of biofilm or production of exoproducts such as pyocyanin and elastase. Tetramic acid and disinfectants acted synergistically to kill P. aeruginosa. These results suggest the AHL-degradation product tetramic acid to be useful for bacterial control.
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Evaluation of antimicrobial susceptibility for ?-lactams against clinical isolates from 51 medical centers in Japan (2008).
Diagn. Microbiol. Infect. Dis.
PUBLISHED: 03-15-2011
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This antimicrobial resistance surveillance study was performed in 51 medical centers in Japan over an 11-year period. The susceptibilities of 4228 strains including Escherichia coli (491 strains), Klebsiella spp. (462 strains), Enterobacter spp. (459 strains), Citrobacter freundii (358 strains), indole-positive Proteus spp. (386 strains), Serratia spp. (443 strains), Acinetobacter spp. (327 strains), Pseudomonas aeruginosa (473 strains), oxacillin-susceptible Staphylococcus aureus (481 strains), and coagulase-negative staphylococci (CoNS; 348 strains) were tested with 7 ?-lactams (cefepime, cefpirome, ceftazidime, cefoperazone/sulbactam, imipenem, and piperacillin for gram-negative bacteria, or oxacillin for gram-positive bacteria). No resistance to these ?-lactams (with the exception of ceftazidime) was found in oxacillin-susceptible S. aureus and CoNS. Of the E. coli clinical isolates, 24.6% were resistant to piperacillin, whereas 3.5% or less (cefpirome = 4.5%) were resistant to other ?-lactam agents. Klebsiella spp. isolates were more susceptible to imipenem (99.6%), cefepime (98.7%), ceftazidime (98.5%), cefpirome (97.6%), and cefoperazone/sulbactam (97.6%). Isolates of Enterobacter spp., C. freundii, and Serratia spp. were susceptible to imipenem, cefepime, and cefpirome as well. The sensitivities of these organisms against cefepime and cefoperazone/sulbactam were 100%. Acinetobacter spp. isolates were less resistant to cefoperazone/sulbactam (0.6% resistance), imipenem (0.9%), and ceftazidime (2.8%) compared with other ?-lactam antibiotics tested. Isolates of P. aeruginosa were more susceptible to piperacillin (9.1% resistance), cefoperazone/sulbactam (9.5%), and cefepime (6.6%) compared with ceftazidime (10.8%), cefpirome (16.3%), and imipenem (23.5%). The proportion of strains resistant to ?-lactam antimicrobials has decreased compared with data from 2006 (Diagn. Microbiol. Infect. Dis. 60:177-183), reflecting the reduced consumption of ?-lactams in Japan.
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Evidence of intravenous immunoglobulin as a critical supportive therapy against Clostridium difficile toxin-mediated lethality in mice.
J. Antimicrob. Chemother.
PUBLISHED: 02-22-2011
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Clostridium difficile produces toxins and is an aetiological organism of pseudomembranous colitis. Immunoglobulin is one of the treatment strategies against fulminant C. difficile infections, but the clinical evidence is still limited. We examined the efficacy of intravenous immunoglobulin (IVIg) in C. difficile toxin (CDT)-mediated lethality and cellular injury in mice.
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Clinical and radiological features of acute-onset diffuse interstitial lung diseases in patients with rheumatoid arthritis receiving treatment with biological agents: importance of Pneumocystis pneumonia in Japan revealed by a multicenter study.
Intern. Med.
PUBLISHED: 02-15-2011
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Acute-onset diffuse interstitial lung disease (AoDILD) in patients with rheumatoid arthritis (RA) has been a serious concern, especially for those under treatment with biological agents which may affect the presentation and outcome of AoDILD, including Pneumocystis pneumonia (PCP). Therefore, we conducted a retrospective, multi-center study of AoDILD in RA patients receiving biological agents.
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In vitro antibacterial activity of modithromycin, a novel 6,11-bridged bicyclolide, against respiratory pathogens, including macrolide-resistant Gram-positive cocci.
Antimicrob. Agents Chemother.
PUBLISHED: 01-10-2011
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The in vitro activities of modithromycin against Gram-positive and -negative respiratory pathogens, including macrolide-resistant cocci with different resistance mechanisms, were compared with those of other macrolide and ketolide agents. MICs were determined by the broth microdilution method. All 595 test strains used in this study were isolated from Japanese medical facilities. The erm (ribosome methylase) and/or mef (efflux pump) gene, which correlated with resistance to erythromycin as well as clarithromycin and azithromycin, was found in 81.8%, 21.3%, and 23.2% of Streptococcus pneumoniae, Streptococcus pyogenes, and methicillin-susceptible Staphylococcus aureus (MSSA) strains, respectively. Modithromycin showed MIC(90)s of 0.125 ?g/ml against these three cocci, including macrolide-resistant strains. In particular, the MIC of modithromycin against ermB-carrying S. pyogenes was ? 32-fold lower than that of telithromycin. The activities of modithromycin as well as telithromycin were little affected by the presence of mefA or mefE in both streptococci. Against Gram-negative pathogens, modithromycin showed MIC(90)s of 0.5, 8, and 0.031 ?g/ml against Moraxella catarrhalis, Haemophilus influenzae, and Legionella spp., respectively. The MICs of modithromycin against M. catarrhalis and H. influenzae were higher than those of telithromycin and azithromycin. However, modithromycin showed the most potent anti-Legionella activity among the macrolide and ketolide agents tested. These results suggested that the bicyclolide agent modithromycin is a novel class of macrolides with improved antibacterial activity against Gram-positive cocci, including telithromycin-resistant streptococci and intracellular Gram-negative bacteria of the Legionella species.
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In vitro intracellular activity and in vivo efficacy of modithromycin, a novel bicyclolide, against Legionella pneumophila.
Antimicrob. Agents Chemother.
PUBLISHED: 01-10-2011
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The in vitro and in vivo activities of modithromycin, a novel bicyclolide, against Legionella pneumophila were compared with those of telithromycin, clarithromycin, azithromycin, and levofloxacin. All the test agents decreased the intracellular growth of viable L. pneumophila bacteria over 96 h of incubation in both types of cells used, A/J mouse-derived macrophages and A549 human alveolar epithelial cells, at extracellular concentrations of 4× and 16× MIC, respectively. However, when the agents were removed from the medium after exposure for 2 h, regrowth of intracellular bacteria occurred in both cell systems when they were exposed to telithromycin, clarithromycin, and levofloxacin but not when they were exposed to modithromycin and azithromycin. Once-daily administration of modithromycin at a dose of 10 mg/kg of body weight for 5 days led to a significant decrease of intrapulmonary viable L. pneumophila bacteria in immunosuppressed A/J mice. The efficacy of modithromycin was superior to the efficacies of telithromycin and clarithromycin and comparable to the efficacies of azithromycin and levofloxacin. In addition, modithromycin and azithromycin inhibited the intrapulmonary regrowth of bacteria even at 72 h after the last treatment, but telithromycin and levofloxacin did not. These results suggested that modithromycin has longer-lasting cellular pharmacokinetic features like azithromycin. In conclusion, modithromycin, as well as azithromycin, has excellent in vitro and in vivo bactericidal activities and persistent efficacy against intracellular L. pneumophila. Modithromycin should be a useful agent for treatment of pulmonary infections caused by this pathogen.
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Efficacy of calcium-EDTA as an inhibitor for metallo-?-lactamase in a mouse model of Pseudomonas aeruginosa pneumonia.
Antimicrob. Agents Chemother.
PUBLISHED: 08-16-2010
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In this study, we have evaluated the efficacy of calcium-EDTA (Ca-EDTA) as an inhibitor of bacterial metalloenzymes, such as metallo-?-lactamase (MBL) and other proteases, in a mouse model of Pseudomonas aeruginosa pneumonia. The simultaneous presence of Ca-EDTA (32 ?g/ml) reduced the MICs of imipenem (IPM) in all MBL-producing P. aeruginosa isolates (IMP-1, -2, -7, and -10 and VIM-2) but not non-MBL-producing strains. In the pneumonia model, mice were intranasally infected with MBL-producing P. aeruginosa and then kept under conditions of hyperoxia to mimic ventilator-associated pneumonia. With both intranasal and subcutaneous administrations, Ca-EDTA significantly potentiated survival benefits of IPM compared to those of IPM alone. Ca-EDTA combination therapy induced a significant reduction of the bacterial burden in the lungs (P < 0.05). Furthermore, the inhibition activity of Ca-EDTA against MBL activity was confirmed by using the purified IMP-1 enzyme, which was characterized by a 50% inhibitory concentration (IC(50)) of 55 ± 8.2 ?M. Finally, the protective effects of Ca-EDTA were demonstrated by culture supernatant-induced epithelial cell damage and acute lung injury in mice. These data suggest the therapeutic potential of Ca-EDTA not only by the blocking of MBLs but also by neutralizing tissue-damaging metalloproteases in P. aeruginosa infections.
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In vitro potentiation of carbapenems with ME1071, a novel metallo-beta-lactamase inhibitor, against metallo-beta-lactamase- producing Pseudomonas aeruginosa clinical isolates.
Antimicrob. Agents Chemother.
PUBLISHED: 07-06-2010
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ME1071, a maleic acid derivative, is a novel specific inhibitor for metallo-beta-lactamases (MBL). In this study, the potentiation of ME1071 in combination with several beta-lactams was evaluated using MBL-producing Pseudomonas aeruginosa isolates. The rates of susceptibility of MBL producers to carbapenems (imipenem, biapenem, and doripenem) and ceftazidime were increased by 8 to 27% in the presence of 32 microg/ml of ME1071. The corresponding resistance rates were decreased by 13 to 46%, respectively. On the other hand, ME1071 showed weaker or no potentiation with non-MBL producers. The K(i) value of ME1071 for IMP-1 was 0.4 microM, significantly lower than the K(m) values of carbapenems for the IMP-1 enzyme. On the other hand, the K(i) value of ME1071 for VIM-2 was 120 microM, higher than the K(m) values of carbapenems for the VIM-2 enzyme. Results of this study indicate that ME1071 can potentiate the activity of ceftazidime and carbapenems against MBL-producing strains of P. aeruginosa.
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Chromosomally encoded blaCMY-2 located on a novel SXT/R391-related integrating conjugative element in a Proteus mirabilis clinical isolate.
Antimicrob. Agents Chemother.
PUBLISHED: 06-21-2010
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Integrating conjugative elements (ICEs) are mobile genetic elements that can transfer from the chromosome of a host to the chromosome of a new host through the process of excision, conjugation, and integration. Although SXT/R391-related ICEs, originally demonstrated in Vibrio cholerae O139 isolates, have become prevalent among V. cholerae isolates in Asia, the prevalence of the ICEs among gram-negative bacteria other than Vibrio spp. remains unknown. In addition, SXT/R391-related ICEs carrying genes conferring resistance to extended-spectrum cephalosporins have never been described. Here we carried out a genetic analysis of a cefoxitin-resistant Proteus mirabilis clinical isolate, TUM4660, which revealed the presence of a novel SXT/R391-related ICE, ICEPmiJpn1. ICEPmiJpn1 had a core genetic structure showing high similarity to that of R391 and carried xis and int genes completely identical to those of R391, while an IS10-mediated composite transposon carrying bla(CMY-2) was integrated into the ICE. A nucleotide sequence identical to the 3 part of ISEcp1 was located upstream of the bla(CMY-2) gene, and other genes observed around bla(CMY-2) in earlier studies were also present. Furthermore, the nucleotide sequences of hot spot 2 and hot spot 4 in ICEPmiJpn1 showed high similarity to that of hot spot 2 in SXT(MO10) and with a part of the nucleotide sequence found in P. mirabilis ATCC 29906, respectively. ICEPmiJpn1 was successfully transferred to Escherichia coli, Klebsiella pneumoniae, Salmonella enterica serovar Typhimurium, and Citrobacter koseri in conjugation experiments. These observations suggest that ICEs may contribute to the dissemination of antimicrobial resistance genes among clinically relevant Enterobacteriaceae, which warrants careful observation of the prevalence of ICEs, including SXT/R391-related ICEs.
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Involvement of endotoxin in the mortality of mice with gut-derived sepsis due to methicillin-resistant Staphylococcus aureus.
Microbiol. Immunol.
PUBLISHED: 06-12-2010
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MRSA causes a wide diversity of diseases, ranging from benign skin infections to life-threatening diseases, such as sepsis. However, there have been few reports of the pathophysiology and mechanisms of sepsis resulting from the gut-derived origin of MRSA. Therefore, we established a murine model of gut-derived sepsis with MRSA and factors of MRSA sepsis that cause deterioration. We separated mice into four groups according to antibiotic treatment as follows: (i) ABPC 40 mg/kg; (ii) CAZ 80 mg/kg; (iii) CAZ 80 mg/kg + endotoxin 10 microg/mouse; and (iv) saline-treated control groups. Gut-derived sepsis was induced by i.p. injection of cyclophosphamide after colonization of MRSA strain 334 in the intestine. After the induction of sepsis, significantly more CAZ-treated mice survived compared with ABPC-treated and control groups. MRSA were detected in the blood and liver among all groups. Endotoxin levels were significantly lower in the CAZ-treated group compared to other groups. Inflammatory cytokine levels in the serum were lower in the CAZ-treated group compared to other groups. Fecal culture showed a lower level of colonization of E. coli in the CAZ-treated group compared to other groups. In conclusion, we found that CAZ-treatment ameliorates infection and suppresses endotoxin level by the elimination of E. coli from the intestinal tract of mice. However, giving endotoxin in the CAZ-treated group increased mortality to almost the same level as in the ABPC-treated group. These results suggest endotoxin released from resident E. coli in the intestine is involved in clinical deterioration resulting from gut-derived MRSA sepsis.
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[Isolation rate and susceptibilities of Candida species from blood, vascular catheter, urine and stool].
Kansenshogaku Zasshi
PUBLISHED: 04-28-2010
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We evaluated species distribution and antifungal susceptibility of Candida isolates during 2002-2008. Of 177 Candida isolates from blood, species distribution was 90 (51%) Candida albicans, 30 (17%) C. parapsilosis, 22 (12%) C. glabrata, 6 (3%) C. tropicalis and 29 (16%) other Candida spp.. Of 162 Candida isolates from vascular catheter, species distribution was 87 (54%) C. albicans, 14 (9%) C. parapsilosis, 36 (22%) C. glabrata, 5 (3%), C. tropicalis, 2 (1%) C. krusei and 18 (11%) other Candida spp.. Of 1889 Candida isolates from urine, species distribution was 1165 (62%) C. albicans, 22 (1%) C. parapsilosis, 484 (26%) C. glabrata, 83 (4%) C. tropicalis, 26 (1%) C. krusei and 109 (6%) other Candida spp.. Of 782 Candida isolates from stool, species distribution was 425 (54%) C. albicans, 3 (1%) C. parapsilosis, 103 (13%) C. glabrata, 28 (4%) C. tropicalis, 5 (1%), C. krusei and 218 (28%) other Candida spp.. Both C. albicans and non-Candida spp. isolated from urine increased slightly over the past 7 years. Flucytosine, fluconazole, itraconazole and micafungin still have strong activity against Candida isolates.
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Development of interpretive criteria for tebipenem disk diffusion susceptibility testing with Staphylococcus spp. and Haemophilus influenzae.
J. Infect. Chemother.
PUBLISHED: 03-17-2010
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Disk diffusion susceptibility interpretive criteria for tebipenem against Staphylococcus spp. and Haemophilus influenzae were developed using the Clinical and Laboratory Standards Institute (CLSI) guidelines. Tebipenem was tested by disk diffusion and broth microdilution methods against 119 clinical isolates of Staphylococcus spp. and 102 clinical isolates of H. influenzae. The zone diameters of 5-, 10-, and 30-?g disks were compared with broth microdilution minimum inhibitory concentration (MIC) results by scattergram and regression analysis. When the MIC breakpoint of 1 ?g/ml was applied to the scattergrams, the 10-?g disk showed good correlation between the zone diameters and the MIC values. The corresponding disk diffusion zone diameter breakpoints with the 10-?g disk for Staphylococcus spp. were ?22 mm (MIC ?1 ?g/ml) for susceptible, 20-21 mm (MIC = 2 ?g/ml) for intermediate, and ?19 mm (MIC ?4 ?g/ml) for resistant. We also proposed the breakpoint zone diameter of H. influenzae: ?22 mm (MIC ?1 ?g/ml) for susceptible. These criteria demonstrated that the categorical agreements between disk diffusion and broth microdilution methods for Staphylococcus spp. and H. influenzae were 95.0% and 99.0%, respectively. The discrepancy rates of these criteria were acceptable to the CLSI guidelines.
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[Antimicrobial susceptibility patterns of Legionella isolates in the environment and in patients].
Korean J Lab Med
PUBLISHED: 03-04-2010
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Antimicrobial susceptibility of Legionella spp. has rarely been studied in Korea. Therefore, we aimed to determine the susceptibility of Legionella spp. to various antibiotics.
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Sequential changes of Legionella antigens and bacterial load in the lungs and urines of a mouse model of pneumonia.
Diagn. Microbiol. Infect. Dis.
PUBLISHED: 02-18-2010
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Legionella pneumophila is an important cause of community- and hospital-acquired pneumonia. In spite of the introduction of the urinary antigen detection method, Legionella pneumonia may be still underdiagnosed. We performed kinetic and quantitative analysis of diagnostic markers, such as bacterial loads, DNA assays, and antigen titers, in a 28-day time course murine model of L. pneumophila pneumonia. L. pneumophila replicated approximately 100-fold in the lungs of A/J mice in the first 48 h, and then became undetectable on day 14. Unexpectedly, pathogens other than L. pneumophila were consistently recovered from the lungs and livers at the acute phases, although those numbers were far below Legionella loads in the lungs. The peaks of specific antigen titer were observed on 48 h in the lungs, bronchoalveolar lavage (BAL) fluids, and urines and sustained positive even at 28 days after the infection. Especially, the lung homogenates and BAL fluids demonstrated 16 to 64 times higher levels of antigen titer than the urines by the end of observation. Legionella-specific DNA in the lungs was detected by polymerase chain reaction and loop-mediated isothermal amplification methods until 7 and 14 days after the infection, respectively. The inflammatory cytokines, such as tumor necrosis factor (TNF)-alpha, interleukin 6, and MIP-2, exhibited a peak on the acute phase, whereas the maximal production of high mobility group box 1 in the serum was observed on day 7. These results characterized the kinetic nature of diagnostic markers in L. pneumophila pneumonia. The present data suggested prolonged and compartmentalized deposition of antigen in the lungs, which may have an impact on the diagnosis of L. pneumophila pneumonia, especially in missed cases even after recovery from disease.
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Comparison of clinical and radiological features of pneumocystis pneumonia between malignancy cases and acquired immunodeficiency syndrome cases: a multicenter study.
Intern. Med.
PUBLISHED: 02-15-2010
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The clinical features of pneumocystis pneumonia (PCP) differ according to the predisposing factors responsible for immunosuppression. Although PCP in patients with acquired immunodeficiency syndrome (AIDS) has been extensively described, its characteristics in non-AIDS patients, such as those with malignancies, are not thoroughly documented.
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Anti-Clostridium difficile potential of tetramic acid derivatives from Pseudomonas aeruginosa quorum-sensing autoinducers.
Antimicrob. Agents Chemother.
PUBLISHED: 11-16-2009
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We have examined the potential bactericidal activities of several tetramic acids derived from Pseudomonas autoinducers against Clostridium difficile, a cause of antibiotic-associated pseudomembranous colitis. Clinical isolates of C. difficile (n=4) were incubated in broth with a chemically synthesized Pseudomonas autoinducer and its tetramic acid derivatives. The structure-activity relationship and the mechanisms of action were examined by a time-killing assay and by determination of the morphological/staining characteristics. The use of some tetramic acids derived from N-3-oxododecanoyl L-homoserine lactone resulted in more than 3-log reductions in the viability of C. difficile within 30 min at 30 microM. The outer membrane was suggested to be one of the targets for the bactericidal activity of tetramic acid, because disturbance of the bacterial outer surface was demonstrated by alteration of the Gram-staining characteristic and electron microscopy. The data for the tetramic acid derivatives demonstrate that the keto-enol structure and the length of the acyl side chain of tetramic acid may be essential for the antibacterial activity of this molecule. These results suggest the potential for tetramic acid derivatives to be novel agents with activity against C. difficile.
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[In vitro susceptibilities to levofloxacin and various antibacterial agents of 12,919 clinical isolates obtained from 72 centers in 2007].
Keizo Yamaguchi, Akira Ohno, Yoshikazu Ishii, Kazuhiro Tateda, Morihiro Iwata, Makoto Kanda, Kouji Akizawa, Chikara Shimizu, Shinichirou Kon, Kastushi Nakamura, Keiko Matsuda, Makoto Tominaga, Takuo Nakagawa, Akihiro Sugita, Tatsumi Ito, Jun Kato, Akira Suwabe, Kumiko Yamahata, Chizuko Kawamura, Hiromi Tashiro, Hiroko Horiuchi, Yosei Katayama, Shigemi Kondou, Shigeki Misawa, Misturu Murata, Yoshio Kobayashi, Hideyuki Okamoto, Kenichiro Yamazaki, Motoi Okada, Kosuke Haruki, Harushige Kanno, Masanori Aihara, Shigefumi Maesaki, Giichi Hashikita, Eiji Miyajima, Midori Sumitomo, Takefumi Saito, Nobuo Yamane, Chieko Kawashima, Takahisa Akiyama, Tamio Ieiri, Yoshitaka Yamamoto, Yuki Okamoto, Hidetoshi Okabe, Kunihiko Moro, Masayo Shigeta, Haruyoshi Yoshida, Masanobu Yamashita, Yukio Hida, Takayuki Takubo, Tadashi Kusakabe, Hiroya Masaki, Hitoshi Heijyou, Hideo Nakaya, Kunimitsu Kawahara, Reiko Sano, Syuji Matsuo, Hisashi Kono, Yosuke Yuzuki, Norio Ikeda, Masayo Idomuki, Masayuki Soma, Go Yamamoto, Syohiro Kinoshita, Seiji Kawano, Mikio Oka, Nobuchika Kusano, Dongchon Kang, Junko Ono, Minoru Yasujima, Makoto Miki, Masato Hayashi, Syunji Okubo, Syunkou Toyoshima, Mitsuo Kaku, Imao Sekine, Joji Shiotani, Hajime Horiuchi, Yoko Tazawa, Akiko Yoneyama, Kazunari Kumasaka, Kazuhiko Koike, Nobuyuki Taniguchi, Yukio Ozaki, Takashi Uchida, Masami Murakami, Kazuhisa Inuzuka, Hideo Gonda, Ikuo Yamaguchi, Yoshinori Fujimoto, Junji Iriyama, Yuko Asano, Hitoshi Genma, Masato Maekawa, Hitoshi Yoshimura, Kaname Nakatani, Hisashi Baba, Satoshi Ichiyama, Shinichi Fujita, Masao Kuwabara, Toshiro Okazaki, Hiromitsu Fujiwara, Hiromi Ota, Astushi Nagai, Jun Fujita, Kiyoshi Negayama, Tetsuro Sugiura, Mikio Kamioka, Mitsuharu Murase, Nobuhisa Yamane, Isamu Nakasone, Akihiko Okayama, Yosuke Aoki, Koji Kusaba, Yukari Nakashima, Hiroaki Miyanohara, Kazufumi Hiramatsu, Tetsunori Saikawa, Katsunori Yanagihara, Junichi Matsuda, Shigeru Kohno, Koichi Mashiba.
Jpn J Antibiot
PUBLISHED: 10-29-2009
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We have reported in this journal in vitro susceptibilities of clinical isolates to antibiotics every year since 1992. In this paper, we report the results of an analysis of in vitro susceptibilities of 12,919 clinical isolates from 72 centers in Japan to selected antibiotics in 2007 compared with the results from previous years. The common respiratory pathogens, Streptococcus pyogenes, Streptococcus pneumoniae, Moraxella catarrhalis and Haemophilus influenzae maintained a high susceptibility to fluoroquinolones (FQs). The resistance of S. pyogenes to macrolides has been increasing every year and this was especially clear this year. Most strains of Enterobacteriaceae except for Escherichia coli showed a high susceptibility to FQs. Almost 30% of E. coli strains were resistant to FQs and the resistance increased further this year. FQs resistance of methicillin-resistant Staphylococcus aureus (MRSA) was approximately 95% with the exception of 45% for sitafloxacin (STFX). FQs resistance of methicillin-susceptible S. aureus (MSSA) was low at about 10%. FQs resistance of methicillin-resistant coagulase negative Staphylococci (MRCNS) was higher than that of methicillin-susceptible coagulase negative Staphylococci (MSCNS), but it was lower than that of MRSA. However, FQs resistance of MSCNS was higher than that of MSSA. FQs resistance of Enterococcus faecalis was 22.5% to 29.6%, while that of Enterococcusfaecium was more than 85% except for STFX (58.3%). In clinical isolates of Pseudomonas aeruginosa derived from urinary tract infections, FQs resistance was 21-27%, which was higher than that of P. aeruginosa from respiratory tract infections at 13-21%, which was the same trend as in past years. Multidrug resistant strains accounted for 5.6% in the urinary tract and 1.8% in the respiratory tract. Acinetobacter spp. showed high susceptibility to FQs. The carbapenem resistant strains, which present a problem at present, accounted for 2.7%. Neisseria gonorrhoeae showed high resistance of 86-88% to FQs. The results of the present survey indicated that although methicillin-resistant Staphylococci, Enterococci, E. coli, P. aeruginosa, and N. gonorrhoeae showed resistance tendencies, and other species maintained high susceptibility rates more than 90% against FQs, which have been used clinically for over 15 years.
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Interleukin-1 deficiency in combination with macrophage depletion increases susceptibility to Pseudomonas aeruginosa bacteremia.
Microbiol. Immunol.
PUBLISHED: 08-26-2009
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We evaluated the role of IL-1 during Pseudomonas aeruginosa bacteremia by intravenously injecting P. aeruginosa strain D4 into IL-1-deficient and WT mice. The two strains showed equivalent mortality rates. However, when the mice were pretreated with cyclophosphamide, bacteremia-induced mortality was significantly greater in the IL-1-deficient mice than in the WT mice (P < 0.01). We then investigated the role of neutrophils and macrophages in protecting IL-1-deficient mice from bacteremia by administering anti-Gr-1 antibody or liposomes containing dichloromethylene diphosphonate, respectively. After P. aeruginosa inoculation survival was significantly lower in the macrophage-depleted IL-1-deficient mice than in the WT mice. In contrast, neutrophil depletion did not have this effect. Compared to the macrophage-depleted WT mice, the macrophage-depleted IL-1-deficient bacteremic mice had higher bacterial counts in various organs 48 and 72 hr post-infection. They also had lower TNF-alpha, IL-6, and INF-gamma concentrations in their livers during the early phase of sepsis. Thus, IL-1 deficiency becomes disadvantageous during P. aeruginosa bacteremia when it is accompanied by immunosuppression, particularly when macrophage functions are seriously impaired.
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Pseudomonas aeruginosa Las quorum sensing autoinducer suppresses growth and biofilm production in Legionella species.
Microbiology (Reading, Engl.)
PUBLISHED: 04-21-2009
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Bacteria commonly communicate with each other by a cell-to-cell signalling mechanism known as quorum sensing (QS). Recent studies have shown that the Las QS autoinducer N-(3-oxododecanoyl)-l-homoserine lactone (3-oxo-C(12)-HSL) of Pseudomonas aeruginosa performs a variety of functions not only in intraspecies communication, but also in interspecies and interkingdom interactions. In this study, we report the effects of Pseudomonas 3-oxo-C(12)-HSL on the growth and suppression of virulence factors in other bacterial species that frequently co-exist with Ps. aeruginosa in nature. It was found that 3-oxo-C(12)-HSL, but not its analogues, suppressed the growth of Legionella pneumophila in a dose-dependent manner. However, 3-oxo-C(12)-HSL did not exhibit a growth-suppressive effect on Serratia marcescens, Proteus mirabilis, Escherichia coli, Alcaligenes faecalis and Stenotrophomonas maltophilia. A concentration of 50 microM 3-oxo-C(12)-HSL completely inhibited the growth of L. pneumophila. Additionally, a significant suppression of biofilm formation was demonstrated in L. pneumophila exposed to 3-oxo-C(12)-HSL. Our results suggest that the Pseudomonas QS autoinducer 3-oxo-C(12)-HSL exerts both bacteriostatic and virulence factor-suppressive activities on L. pneumophila alone.
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Efficacy of colistin combination therapy in a mouse model of pneumonia caused by multidrug-resistant Pseudomonas aeruginosa.
J. Antimicrob. Chemother.
PUBLISHED: 01-14-2009
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Multidrug-resistant Pseudomonas aeruginosa (MDRP) is becoming a serious problem in hospitals, especially in patients on ventilators. Recent data demonstrate that colistin may be effective for these patients, although limited in vitro and in vivo data are available. Our aim was to identify further characteristics of colistin for the therapy of pneumonia caused by MDRP.
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Hyperoxia exaggerates bacterial dissemination and lethality in Pseudomonas aeruginosa pneumonia.
Pulm Pharmacol Ther
PUBLISHED: 01-08-2009
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Effects of hyperoxia on lethality in mice with Pseudomonas aeruginosa pneumonia were defined, and protective roles of macrolides were examined both in vitro and in vivo. Sub-lethal hyperoxia accelerated lethality of mice with P. aeruginosa pneumonia. Bacterial number was not different in the lungs, but higher in the liver of mice in hyperoxic conditions. Filter-sterilized culture supernatants of bacteria induced loss of viability of alveolar epithelial cells, which was exaggerated in hyperoxia. Metalloprotease blocking by inhibitor or gene-disruption in bacteria resulted in partial reduction of cytotoxic activity in culture supernatants. Co-culture of bacteria with sub-inhibitory concentrations of macrolides, such as azithromycin, reduced cytotoxic activity in the culture supernatants. Azithromycin provided significant survival benefit in hyperoxia-pneumonia model, which was associated with suppression of bacterial dissemination to extra-pulmonary organs. These results suggest that hyperoxia serves as an important cofactor for bacterial dissemination and lethality of P. aeruginosa pneumonia. Our data identify the potential of macrolides to protect individuals with P. aeruginosa pneumonia in the setting of hyperoxia.
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A low concentration of azithromycin inhibits the mRNA expression of N-acyl homoserine lactone synthesis enzymes, upstream of lasI or rhlI, in Pseudomonas aeruginosa.
Pulm Pharmacol Ther
PUBLISHED: 01-07-2009
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Low-dose macrolides are effective therapy in patients with chronic lung infections, but the mechanisms of action are unclear. In this study, we performed DNA microarray analysis of Pseudomonas aeruginosa after treatment with a low concentration of azithromycin. We found that a sub-MIC of azithromycin didnt change mRNA expression of quorum-sensing related genes (lasI, lasR, rhlI, rhlR, vft, rsaL), but lowered expression of most N-acyl homoserine lactone (AHL) synthesis enzymes upstream of lasI and rhlI. We propose that small down regulation of these enzymes cumulatively resulted in a larger decrease of AHL production and inhibition of quorum-sensing in P. aeruginosa.
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Efficacies of calcium-EDTA in combination with imipenem in a murine model of sepsis caused by Escherichia coli with NDM-1 ?-lactamase.
J. Infect. Chemother.
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We evaluated the efficacy of ethylenediamine-N,N,N,N-tetraacetic acid, disodium calcium salt (Ca-EDTA), as an inhibitor for New Delhi metallo-?-lactamase-1 (NDM-1) in vitro antibiotic susceptibility and in a mouse model of sepsis caused by Escherichia coli. Ca-EDTA drastically reduced the MICs of carbapenems for all NDM-producing bacteria [imipenem (IPM) ?1-2 ?g/ml; meropenem (MEPM) ?1-4 µg/ml]. In the neutropenic murine model of sepsis, the bacterial burden was further reduced by combination therapy using imipenem/cilastatin sodium (IPM/CS) and Ca-EDTA to 2.3 × 10(3) CFU/liver, compared with 2.9 × 10(4) CFU/liver for IPM/CS alone. These data demonstrated the possibility of Ca-EDTA for clinical applications. In our understanding, this is the first report examining the effect of Ca-EDTA on a mouse sepsis model caused by NDM-1-producing bacteria.
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[In vitro susceptibilities to levofloxacin and various antibacterial agents of 12,866 clinical isolates obtained from 72 centers in 2010].
Jpn J Antibiot
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Postmarketing surveillance of levofloxacin (LVFX) has been conducted continuously since 1992. The present survey was performed to investigate in vitro susceptibility of recent clinical isolates in Japan to 30 selected antibacterial agents, focusing on fluoroquinolones (FQs). The common respiratory pathogens Streptococcus pyogenes, Streptococcus pneumoniae, Moraxella catarrhalis, and Haemophilus influenzae continue to show a high susceptibility to FQs. In contrast, widely-prevailing resistance to macrolides was markedly noted among S pneumoniae and S. pyogenes. Regarding H. influenzae, the prevalence of beta-lactamase-negative ampicillin-resistant isolates has been increasing year by year (25.8% in 2002, 40.0% in 2004, 50.1% in 2007, and 57.9% in 2010). Enterobacteriaceae showed high susceptibility to FQs, however, prevalence of LVFX-resistant Escherichia coli, including intermediate resistance, was 29.3%, showing an increase over time. Nevertheless, the increase in the prevalence of LVFX-resistant E. coli isolates has slowed since 2007 (8.2% in 2000, 11.8% in 2002, 18.8% in 2004, 26.2% in 2007, and 29.3% in 2010), suggesting the influence of LVFX 500 mg tablets since its approval in 2009. Another Enterobacteriaceae member, Klebsiella pneumoniae, showed low resistance to FQs, in contrast with E. coli. In methicillin-resistant Staphylococcus aureus (MRSA), the percentage of FQ-susceptible isolates was low, at 51.6% for susceptibility to sitafloxacin, and at only around 10% for susceptibility to other FQs. However, methicillin-susceptible S. aureus (MSSA) isolates were highly susceptible to FQs, with the percentage ranging from 88.5% to 99.1%. The prevalence of FQs-resistant isolates in methicillin-resistant coagulase-negative staphylococci was higher than that in methicillin-susceptible coagulase-negative staphylococci, although it was lower than the prevalence of FQ-resistance in MRSA. The prevalence of FQs-resistant Pseudomonas aeruginosa isolates derived from urinary tract infections (UTIs) was 15.4-21.3%, higher than the prevalence of 6.1-12.3% in P. aeruginosa isolates from respiratory tract infections (RTIs). While this trend was consistent with the results of previous surveillance, gradual decreases were noted in the prevalence of FQ-resistant P. aeruginosa isolates derived from UTIs. The prevalence of multidrug-resistant P. aeruginosa was 2.3% among isolates derived from UTIs and 0.3% among isolates from RTIs, a decrease from the results of 2007. Acinetobacter spp. showed high susceptibility to FQs. Imipenem-resistant Acinetobacter baumannii, which is currently an emerging issue, was detected at a prevalence of 2.4% (13 isolates). Neisseria gonorrhoeae showed a high resistance of 81.3-82.5%, to FQs. Ceftriaxone (CTRX) continued to show 100% susceptibility until 2007, but the present survey revealed the advent of resistance to CTRX in some clinical isolates. The result of the present survey indicated that although methicillin-resistant staphylococci, Enterococcus faecium, P. aeruginosa from UTIs, N. gonorrhoeae, and E. coli showed resistance of about 20% or more (19.5-89.2%) against the FQs which have been used clinically for over 17 years, the trends observed were similar to the results of previous surveillance. While FQ resistance has been prevailing in E. coli, E. coli still shows more than 70% susceptibility to FQs. The other bacterial species maintained high susceptibility rates of greater than 80%, against FQs.
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Genotyping of skin and soft tissue infection (SSTI)-associated methicillin-resistant Staphylococcus aureus (MRSA) strains among outpatients in a teaching hospital in Japan: application of a phage-open reading frame typing (POT) kit.
J. Infect. Chemother.
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We aimed to elucidate the current epidemiological features of outpatient skin and soft tissue infection (SSTI)-associated methicillin-resistant Staphylococcus aureus (MRSA) in Japan. Altogether, we evaluated the performance of a phage-open reading frame typing (POT) kit for genotyping these MRSA strains. We collected 57 MRSA strains from all outpatients with SSTIs attending a teaching hospital in Japan. Drug susceptibility measurement and genotyping including SCCmec typing, spa typing, multilocus sequence typing, pulsed-field gel electrophoresis, and commercial POT-kit were performed. The majority of strains (39 strains, 68 %) had the SCCmec-II element. Seventeen strains (30 %) with SCCmec-IV accounted for the second largest population. Strains with SCCmec-IV and SCCmec-V appeared multiclonal, and a predominance of Panton-Valentine leukocidin (PVL) gene-negative CC8/spa-CC008 strains, as well as the first isolate of an ST93 strain in Japan, was observed among them. Only one USA300 strain was identified. Strains with SCCmec-IV and SCCmec-V were significantly susceptible to antimicrobials. The PVL gene was found in 5 SCCmec-IV strains and 1 SCCmec-V strain. The POT-kit successfully predicted the SCCmec type in 54 strains (95 %), and typing by POT1 scores was highly concordant with SCCmec typing and spa typing. Moreover, three PVL-positive strains fell into a particular POT type (POT scores, 106-77-113). Simpsons index of the POT-kit was 0.977. In conclusion, the present study clarified the multiclonal nature of outpatient SSTI-associated MRSA in a teaching hospital in Japan. These data also underscore the utility of the POT-kit for non-outbreak surveillance through its simple platform consisting of two multiplex PCRs without sequencing.
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Evaluation of Camellia sinensis catechins as a swine antimicrobial feed additive that does not cause antibiotic resistance.
Microbes Environ.
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Antimicrobial growth promoters (AGPs) have been banned and phased out because their use has been linked to the emergence and spread of antibiotic-resistant pathogens; however, the ban has had a marked impact on livestock production, and feed additive alternatives to AGPs are required. We focused on green tea leaves as potential alternatives to AGPs because they contain significant amounts of polyphenol catechins, which have antivirus and antimicrobial effects. We examined cross-resistance between epigallocatechin gallate (EGCG), which is the most abundant catechin of green tea leaves, and commercially available antimicrobials in clinically problematic antimicrobial-resistant bacteria, and whether bacteria have the ability to acquire resistance by consecutive passage in sub-inhibitory concentrations of EGCG. EGCG did not display any cross-resistance with reference antimicrobials and the bacteria did not acquire EGCG resistance. Further, we examined the growth-promoting effects of dried green tea leaves on the breeding of a new Japanese breed, Tokyo-X pigs. While the mortality rates of the green tea leaf (GTL) and AGP groups were both 11.1% (one in nine piglets), the mortality rate was 50% for the control group with an additive-free diet (four in eight piglets). The rate of body weight increase in both the GTL and AGP groups was approximately the same. The growth-promoting effects of green tea leaves and AGPs were similar, and there was no possibility that the antimicrobial properties of catechins caused the same problem as AGPs. Thus, it can be concluded that green tea leaves are a safe feed additive alternative to AGPs.
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[Isolation rate and susceptibilities of candida species from blood, vascular catheter, urine and stool].
Kansenshogaku Zasshi
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We evaluated species distribution and antifungal susceptibility of Candida isolates during 2002-2008. Of 177 Candida isolates from blood, species distribution was 90 (51%) Candida albicans, 30 (17%) C. parapsilosis, 22 (12%) C. glabrata, 6 (3%) C. tropicalis and 29 (16%) other Candida spp.. Of 162 Candida isolates from vascular catheter, species distribution was 87 (54%) C. albicans, 14 (9%) C. parapsilosis, 36 (22%) C. glabrata, 5 (3%), C. tropicalis, 2 (1%) C. krusei and 18 (11%) other Candida spp.. Of 1889 Candida isolates from urine, species distribution was 1165 (62%) C. albicans, 22 (1%) C. parapsilosis, 484 (26%) C. glabrata, 83 (4%) C. tropicalis, 26 (1%) C. krusei and 109 (6%) other Candida spp.. Of 782 Candida isolates from stool, species distribution was 425 (54%) C. albicans, 3 (1%) C. parapsilosis, 103 (13%) C. glabrata, 28 (4%) C. tropicalis, 5 (1%), C. krusei and 218 (28%) other Candida spp. Both C. albicans and non-Candida spp. isolated from urine increased slightly over the past 7 years. Flucytosine, fluconazole, itraconazole and micafungin still have strong activity against Candida isolates.
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Diagnostic usefulness of ribosomal protein l7/l12 for pneumococcal pneumonia in a mouse model.
J. Clin. Microbiol.
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The capsular antigen detection (CAD) kit is widely used in clinics to detect Streptococcus pneumoniae infection from urine, because it is rapid, convenient, and effective. However, there are several disadvantages, including false-positive results in children colonized with S. pneumoniae and prolonged positive readings even after the bacteria have been cleared. RP-L7/L12 is a component of the 50S ribosome that is abundant in all bacteria and is specific for each bacterial species. We investigated whether RP-L7/L12 could be used to accurately diagnose pneumococcal pneumonia infection in mouse models of pneumonia and colonization generated by infecting CBA/JN or CBA/N mice, respectively, with S. pneumoniae strain 741. RP-L7/L12 detection by enzyme-linked immunosorbent assay accurately assessed active lung infection, as RP-L7/L12 levels decreased simultaneously with the bacterial lung burden after imipenem administration in the pneumonia mouse model. Based on the data, antibodies detecting RP-L7/L12 were applied to rapid immunochromatographic strips (ICS) for urine sample testing. When we compared the ICS test with the CAD kit in the pneumonia model, the results correlated well. Interestingly, however, when the lung bacterial burden became undetectable after antibiotic treatment, the ICS test was correspondingly negative, even though the same samples tested by the CAD kit remained positive. Similarly, while the ICS test exhibited negative results in the nasal colonization model, the CAD kit demonstrated positive results. Bacterial RP-L7/L12 may be a promising target for the development of new methods to diagnose infectious disease. Further studies are warranted to determine whether such a test could be useful in children.
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Successful treatment of fulminant community-acquired Pseudomonas aeruginosa necrotizing pneumonia in a previously healthy young man.
Intern. Med.
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This report presents a case of fulminant community-acquired Pseudomonas aeruginosa necrotizing pneumonia in a previously healthy young man, including an analysis of the virulence of the P.aeruginosa isolated from the patient. The patient was successfully treated with intensive care and antibiotic treatment. This study analyzed the pathogenicity of the isolated strain both in vivo (using a mouse pneumonia model) and in vitro (using biofilm production), but could not explain how an otherwise healthy young man developed such severe community-acquired P.aeruginosa pneumonia. Although rare in community-acquired pneumonia, P.aeruginosa infection should be considered in patients with severe rapidly progressive pneumonia.
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A case of NDM-1-producing Acinetobacter baumannii transferred from India to Japan.
J. Infect. Chemother.
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A 52-year-old male Japanese businessman with massive cerebral bleeding was transferred from India to Japan and was admitted to our hospital. Multidrug-resistant Acinetobacter baumannii was isolated from his sputum. The minimum inhibitory concentrations for this strain were as follows: imipenem, 64 ?g/ml; meropenem, 32 ?g/ml; ciprofloxacin, 16 ?g/ml; amikacin, 16 ?g/ml; aztreonam, 16 ?g/ml; colistin, <1 ?g/ml. This A. baumannii strain had both bla NDM-1 and bla OXA-23 by polymerase chain reaction analysis. In Japan, NDM-1-producing bacteria are extremely rare in clinical specimens. To date, three NDM-1-positive cases have been detected in Japan, and this is the first case of A. baumannii-producing NDM-1 in Japan. Our case suggests that NDM-1-producing bacteria could be introduced into our country easily. There is concern that various resistant bacteria may be transferred from epidemic countries as a result of international medical care.
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Immunoprotective effects of oral intake of heat-killed Lactobacillus pentosus strain b240 in elderly adults: a randomised, double-blind, placebo-controlled trial.
Br. J. Nutr.
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Oral intake of Lactobacillus pentosus strain b240 (b240) has been shown to enhance the secretion of salivary secretory IgA in elderly adults. However, its clinical benefits remain to be determined. We tested the hypothesis that b240 exerts a protective effect against the common cold in elderly adults. The design of the present study was a randomised, double-blind, placebo-controlled trial (RCT) with parallel three-group comparison. For this purpose, 300 eligible elderly adults were randomly allocated to one of three groups, namely a placebo, low-dose or high-dose b240 group. Participants in the low-dose and high-dose b240 groups were given tablets containing 2 × 10(9) or 2 × 10(10) cells, respectively, of heat-killed b240, while those in the placebo group were given tablets without b240. Each group consumed their respective tablets once daily for 20 weeks. The common cold was assessed on the basis of a diary. Change in quality of life was evaluated using the SF-36. Of the total participants, 280 completed the 20-week RCT. The accumulated incidence rate of the common cold was 47·3, 34·8 and 29·0 % for the placebo, low-dose b240 and high-dose b240 groups, respectively (P for trend = 0·012). Lower incidence rates were consistently observed throughout the experimental period in the b240 groups (log-rank test, P= 0·034). General health perception, as determined by the SF-36, dose-dependently increased in the b240 groups (P for trend = 0·016). In conclusion, oral intake of b240 significantly reduced the incidence rate of the common cold in elderly adults, indicating that b240 might be useful in improving resistance against infection through mucosal immunity.
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[Antibiotic-resistant bacteria and new directions of antimicrobial chemotherapy].
Rinsho Byori
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The emergence and spread of antibiotic-resistant organisms are becoming more and more serious and are a worldwide problem. Recent trends in new antibiotic-resistant organisms include multiple-drug resistant Pseudomonas aeruginosa (MDRP), MDR-Acinetobacter baumannii (MDR-AB) and New Deli metallo beta-lactamase-1 (NDM-1) -producing bacteria. Antibiotic combination therapy is an option to overcome these MDR organisms. A breakpoint checkerboard plate was created to measure antibiotic combination effects at breakpoint concentrations, making it possible to evaluate the synergy of antibiotic combination within 24 hours. In this article, recent topics regarding antibiotic-resistant organisms are briefly reviewed and the directions of antibiotic chemotherapy against these organisms are discussed.
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Nationwide surveillance of bacterial respiratory pathogens conducted by the Surveillance Committee of Japanese Society of Chemotherapy, Japanese Association for Infectious Diseases, and Japanese Society for Clinical Microbiology in 2009: general view of t
J. Infect. Chemother.
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For the purpose of nationwide surveillance of antimicrobial susceptibility of bacterial respiratory pathogens from patients in Japan, the Japanese Society of Chemotherapy (JSC) started a survey in 2006. From 2009, JSC continued the survey in collaboration with the Japanese Association for Infectious Diseases and the Japanese Society for Clinical Microbiology. The fourth-year survey was conducted during the period from January and April 2009 by the three societies. A total of 684 strains were collected from clinical specimens obtained from well-diagnosed adult patients with respiratory tract infections. Susceptibility testing was evaluable with 635 strains (130 Staphylococcus aureus, 127 Streptococcus pneumoniae, 4 Streptococcus pyogenes, 123 Haemophilus influenzae, 70 Moraxella catarrhalis, 78 Klebsiella pneumoniae, and 103 Pseudomonas aeruginosa). A maximum of 45 antibacterial agents including 26 ?-lactams (four penicillins, three penicillins in combination with ?-lactamase inhibitors, four oral cephems, eight parenteral cephems, one monobactam, five carbapenems, and one penem), four aminoglycosides, four macrolides (including ketolide), one lincosamide, one tetracycline, two glycopeptides, six fluoroquinolones, and one oxazolidinone were used for the study. Analysis was conducted at the central reference laboratory according to the method recommended by the Clinical and Laboratory Standard Institute (CLSI). Incidence of methicillin-resistant S. aureus (MRSA) was as high as 58.5 %, and that of penicillin-intermediate and penicillin-resistant S. pneumoniae (PISP and PRSP) was 6.3 % and 0.0 %, respectively. Among H. influenzae, 21.1 % of them were found to be ?-lactamase-non-producing ampicillin (ABPC)-intermediately resistant (BLNAI), 18.7 % to be ?-lactamase-non-producing ABPC-resistant (BLNAR), and 5.7 % to be ?-lactamase-producing ABPC-resistant (BLPAR) strains. A high frequency (76.5 %) of ?-lactamase-producing strains has been suspected in Moraxella catarrhalis isolates. Four (3.2 %) extended-spectrum ?-lactamase-producing K. pneumoniae were found among 126 strains. Four isolates (2.5 %) of P. aeruginosa were found to be metallo-?-lactamase-producing strains, including three (1.9 %) suspected multi-drug resistant strains showing resistance against imipenem, amikacin, and ciprofloxacin. Continuous national surveillance of the antimicrobial susceptibility of respiratory pathogens is crucial to monitor changing patterns of susceptibility and to be able to update treatment recommendations on a regular basis.
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A peptide based on homologous sequences of the ?-barrel assembly machinery component BamD potentiates antibiotic susceptibility of Pseudomonas aeruginosa.
J. Antimicrob. Chemother.
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The ?-barrel assembly machinery (BAM) complex plays a critical role in outer membrane protein (OMP) biogenesis. The outer membrane (OM) of Pseudomonas aeruginosa is centrally involved in mechanisms of antibiotic resistance. This study aimed to identify effects of a synthetic peptide based on conserved sequences in the putative BamA-binding region of BamD, focusing on antibiotic susceptibility and OMP characteristics in P. aeruginosa.
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Molecular characterization of carbapenem-non-susceptible Acinetobacter spp. in Japan: predominance of multidrug-resistant Acinetobacter baumannii clonal complex 92 and IMP-type metallo-?-lactamase-producing non-baumannii Acinetobacter species.
J. Infect. Chemother.
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We conducted an epidemiological study concerning carbapenem-non-susceptible clinical isolates of Acinetobacter spp. in Japan by molecular procedures including carbapenemase gene identification and amplified ribosomal DNA restriction analysis. Among 598 clinically isolated Acinetobacter spp. in 2007, 27 (4.5%) were non-susceptible to carbapenems. Most carbapenem-non-susceptible Acinetobacter baumannii (13/14) belonged to clonal complex (CC) 92, harbored bla (OXA-51-like) genes, including novel bla (OXA-206), downstream of ISAba1, and were recovered mainly from the Kanto region. Carbapenem-non-susceptible A. baumannii CC92 isolates were further divided by pulsed-field gel electrophoresis into two groups, one of which was characterized by the presence of bla (OXA-23). One A. baumannii CC276 isolate carried bla (IMP-1) and bla (OXA-58). Almost all non-baumannii Acinetobacter isolates (12/13), including Acinetobacter pittii (formerly Acinetobacter genomic species 3) and Acinetobacter nosocomialis (formerly Acinetobacter genomic species 13TU), produced IMP-type metallo-?-lactamases, and were recovered from various regions in Japan. This is the first report describing the nationwide molecular epidemiology of carbapenem-non-susceptible Acinetobacter spp. with genomic species-level identification in Japan.
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Virulence-suppressing effects of linezolid on methicillin-resistant Staphylococcus aureus: possible contribution to early defervescence.
Antimicrob. Agents Chemother.
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In the present study, immunomodulatory effects of linezolid (LZD) on methicillin-resistance Staphylococcus aureus (MRSA) infections were evaluated. We have retrospectively reviewed treatment effects of LZD on 52 patients with severe MRSA infections. Sixty-four percent of the febrile patients demonstrated significant defervescence within 3 days, despite the presence of positive culture results. We speculated that this finding might be due to early anti-inflammatory effects of LZD, and to investigate this further we initiated in vivo experiments using mice MRSA pneumonia models. Mice were treated with either LZD or vancomycin (VCM) immediately after intranasal administration of MRSA. Bacterial numbers and levels of inflammatory cytokines in the lungs were determined. Although the bacterial burden in the lungs was not apparently different between the two groups, LZD but not VCM treatment significantly reduced induction of inflammatory cytokines in the lungs (P < 0.05). To evaluate whether this anti-inflammatory response was due to suppression of virulence factor expression, filter-sterilized supernatants of MRSA incubated in broth overnight with sub-MICs of LZD were subcutaneously administered to mice. To clarify whether LZD possesses direct host-modulating activity, cytokine responses to the supernatants were examined in mice pretreated with LZD. Interestingly, MRSA solutions prepared in the presence of sub-MICs of LZD revealed significant suppression of interleukin 6 (IL-6) in a dose-dependent manner (P < 0.05), but pretreatment of mice with LZD revealed no changes in cytokines. These findings suggest that sub-MICs of LZD might suppress virulence factors of MRSA, which may be associated with a reduction in endogenous pyrogens. These data may explain at least in part early defervescence observed in LZD-treated individuals.
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In vitro combination effects of aztreonam and aminoglycoside against multidrug-resistant Pseudomonas aeruginosa in Japan.
Jpn. J. Infect. Dis.
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The aim of this study was to evaluate the in vitro combination effects of aztreonam (AZT) and aminoglycosides against multidrug-resistant (MDR) Pseudomonas aeruginosa strains in Japan. We investigated 47 MDR P. aeruginosa strains collected from 8 facilities. We selected the aminoglycosides amikacin (AMK), gentamicin (GM), and arbekacin (ABK) to examine their effects when combined with AZT using the checkerboard method. Of the 47 MDR P. aeruginosa strains, 41 tested positive for metallo-?-lactamase (MBL). In all combinations, aminoglycosides decreased the minimum inhibitory concentrations of AZT in a dose-dependent manner, and there was no apparent antagonism. The combination effects were scored on a scale of 0 to 4, and statistical analysis was performed using the Wilcoxon signed-rank test. In all 47 strains, AZT + ABK (mean score, 2.02) had the highest score, followed by AZT + AMK (1.68) and AZT + GM (1.38) (ABK versus GM, P < 0.0001). In 41 MBL-positive strains, AZT + ABK (mean score, 2.05) had the highest score, followed by AZT + AMK (1.56) and AZT + GM (1.37) (ABK versus AMK, P = 0.02, and ABK versus GM, P < 0.0001). AZT + ABK was the most promising combination regimen against MDR P. aeruginosa strains; the other promising combinations were AZT + AMK and AZT + GM.
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