Foodborne infections are of public health importance and deeply impact the global economy. Consumption of bivalve mollusks generates risk for humans because these filtering aquatic invertebrates often concentrate microbial pathogens from their environment. Among them, Giardia, Cryptosporidium, and Toxoplasma are major parasites of humans and animals that may retain their infectivity in raw or undercooked mollusks. This review aims to detail current and future tools and methods for ascertaining the load and potential infectivity of these parasites in marine bivalve mollusks, including sampling strategies, parasite extraction procedures, and their characterization by using microscopy and/or molecular techniques. Method standardization should lead to better risk assessment of mollusks as a source of these major environmental parasitic pathogens and to the development of safety regulations, similar to those existing for bacterial and viral pathogens encountered in the same mollusk species.
The ability of microorganisms to survive under extreme conditions is closely related to the physicochemical properties of their wall. In the ubiquitous protozoan parasite Toxoplasma gondii, the oocyst stage possesses a bilayered wall that protects the dormant but potentially infective parasites from harsh environmental conditions until their ingestion by the host. None of the common disinfectants are effective in killing the parasite because the oocyst wall acts as a primary barrier to physical and chemical attacks. Here, we address the structure and chemistry of the wall of the T. gondii oocyst by combining wall surface treatments, fluorescence imaging, EM, and measurements of its mechanical characteristics by using atomic force microscopy. Elasticity and indentation measurements indicated that the oocyst wall resembles common plastic materials, based on the Young moduli, E, evaluated by atomic force microscopy. Our study demonstrates that the inner layer is as robust as the bilayered wall itself. Besides wall mechanics, our results suggest important differences regarding the nonspecific adhesive properties of each layer. All together, these findings suggest a key biological role for the oocyst wall mechanics in maintaining the integrity of the T. gondii oocysts in the environment or after exposure to disinfectants, and therefore their potential infectivity to humans and animals.
We validated a new method, based on luciferine/luciferase bioluminescence, for drug screening on promastigotes of different Leishmania species. Results obtained with this new, rapid, reproducible, and reliable method are in good accordance with results obtained by the conventional MTT assay. This bioluminescence assay has a lower detection limit.
Plasmodium falciparum has a specific metabolism of particular interest because several of its features, with respect to the host human ones, are potential pharmacological targets. Such features have been more intensely investigated since 2002, thanks to the full sequencing of the genome of P. falciparum. In this review, we are interested in the potential metabolic targets of therapeutic interest identified and investigated over the past decade in terms of lead-to-drug development.
The protozoan parasites Giardia duodenalis, Cryptosporidium spp., and Toxoplasma gondii are pathogens that are resistant to a number of environmental factors and pose significant risks to public health worldwide. Their environmental transmission is closely governed by the physicochemical properties of their cysts (Giardia) and oocysts (Cryptosporidium and Toxoplasma), allowing their transport, retention, and survival for months in water, soil, vegetables, and mollusks, which are the main reservoirs for human infection. Importantly, the cyst/oocyst wall plays a key role in that regard by exhibiting a complex polymeric coverage that determines the charge and hydrophobic characteristics of parasites surfaces. Interaction forces between parasites and other environmental particles may be, in a first approximation, evaluated following the Derjaguin-Landau-Verwey-Overbeek (DLVO) theory of colloidal stability. However, due to the molecular topography and nano- to microstructure of the cyst/oocyst surface, non-DVLO hydrophobic forces together with additional steric attractive and/or repulsive forces may play a pivotal role in controlling the parasite behavior when the organism is subjected to various external conditions. Here, we review several parameters that enhance or hinder the adhesion of parasites to other particles and surfaces and address the role of fast-emerging techniques for mapping the cyst/oocyst surface, e.g., by measuring its topology and the generated interaction forces at the nano- to microscale. We discuss why characterizing these interactions could be a crucial step for managing the environmental matrices at risk of microbial pollution.
A series of original quinazolines bearing a 4-thiophenoxy and a 2-trichloromethyl group was synthesized in a convenient and efficient way and was evaluated toward its in vitro antiplasmodial potential. The series revealed global good activity against the K1-multi-resistant Plasmodium falciparum strain, especially with hit compound 5 (IC(50)=0.9 ?M), in comparison with chloroquine and doxycycline chosen as reference-drugs. Both the in vitro cytotoxicity study which was conducted on the human HepG2 cell line and the in vitro antitoxoplasmic screening against Toxoplasma gondii indicate that this series presents an interesting selective antiplasmodial profile. Structure-activity- and toxicity relationships highlight that the trichloromethyl group plays a key role in the antiplasmodial activity and also show that the modulation of the thiophenol moiety influences the toxicity/activity ratio.
Toxoplasmosis is a world-wide infection caused by Toxoplasma gondii. Oocysts disseminated in the environment by infected cats provide a major source of infection for humans and intermediate hosts. The level of soil contamination and the dynamics of this contamination are mostly unknown due to the lack of sensitivity of detection method. Our aim was to improve the detection of T. gondii oocysts in soil samples by comparing three extraction protocols (A, B and C) on unsporulated and sporulated oocysts of different strains and ages, and by testing the effect of sporulation and soil characteristics on oocyst recovery using the most efficient method. The oocyst recovery obtained using protocol C, in which the flotation solution was placed under the sample solution after the dispersion step, was at least ten-fold higher than protocols A and B, in which the sample was just filtered before flotation. The efficiency of protocol C, tested on five artificial soil matrices and four natural soils inoculated with oocysts, was lowest in soils with high proportions of sand. We recommend the protocol C for field investigations, and we advise that results should be interpreted with caution, considering the effect of soil characteristics, especially sand content, on oocyst recovery.
From the promising results we previously obtained in quinazoline series and to complete the evaluation of the in vitro antiplasmodial activity of original 2-trichloromethylquinazolines, we synthesized new quinazolines possessing a variously substituted phenoxy group at position 4 through a simple and efficient two-step-synthesis approach. The studies of their activity toward the multi-resistant W2 Plasmodium falciparum strain and of their cytotoxicity on the human hepatocyte HepG2 cell line highlighted a hit compound (molecule 7) displaying a W2 IC(50) value of 1.1 ?M and a HepG2 CC(50) value of 50 ?M, comparable to chloroquine and doxycycline. Structure-activity- and toxicity relationships indicate that the trichloromethyl group plays a key role in the antiplasmodial activity of such chemical scaffold and also that the phenoxy group substitution as a direct influence on the molecules selectivity. Moreover, molecule 7 displays significant specific activity against the Plasmodium genus in comparison with Toxoplasma and does not show any mutagenic property at the Ames test.
A new series of monoamidoxime derivatives was synthesized using manganese(III) acetate by microwave irradiation. Several amidoximes (27-31, 33, 38) showed valuable in vitro activities toward Leishmania donovani promastigotes, exhibiting IC(50) values between 5.21 and 7.89 ?M. In parallel, the cytotoxicity of these compounds was evaluated on murine J774A.1 cells, revealing the corresponding selectivity index (SI). Among the 13 tested compounds, 4 monoamidoximes (27-30) exhibited an SI more than 20 times better than pentamidine. Moreover, monoamidoxime 28 (4-[5-Benzyl-3-(4-fluorophenylsulfonyl)-5-methyl-4,5-dihydrofuran-2-yl]-N-hydroxybenzimidamide) is 40 times more selective than pentamidine, and 1.6 times more than amphotericin B, used as reference drug compounds.
An original series of amidoxime derivatives was synthesized using manganese(III) acetate, Buchwald-Hartwig and Heck reactions. Two amidoximes (39 and 52) showed interesting in vitro activities toward Leishmania donovani promastigotes, exhibiting 8.3 and 8.8 ?M IC(50) values. Moreover, the cytotoxicity of these compounds was evaluated on human THP1 cells, giving access to the corresponding selectivity index. Among the 25 tested compounds, amidoximes 38 and 39 and diamidoximes 50 and 52 exhibited a better selectivity index than pentamidine used as a drug compound reference.
In our search for potent anti-HIV and antiplasmodial agents, novel series of flavonoid derivatives and their chalcone intermediates were synthesized and evaluated for inhibition of HIV multiplication and antiproliferative activity on Plasmodium falciparum parasites. Chalcones exhibited a more selective antiplasmodial activity than flavonoids. Methoxyflavone 7e was the only one compound active in both P. falciparum and HIV-1 whereas aminomethoxyflavones showed activity against HIV-2. Para substitution on the B ring seemed to increase HIV-2 potency.
Urban part of Seine River serving as drinking water supply in Paris can be heavily contaminated by Cryptosporidium spp. and Giardia duodenalis. In the absence of agricultural practice in this highly urbanized area, we investigated herein the contribution of treated wastewater to the microbiological quality of this river focusing on these two parasites. Other microorganisms such as faecal bacterial indicators, enteroviruses and oocysts of Toxoplasma gondii were assessed concurrently. Raw wastewaters were heavily contaminated by Cryptosporidium and Giardia (oo)cysts, whereas concentrations of both protozoa in treated wastewater were lower. Treated wastewater, flowed into Seine River, had a parasite concentration closed to the one found along the river, in particular at the entry of a drinking water plant (DWP). Even if faecal bacteria were reliable indicators of a reduction in parasite concentrations during the wastewater treatment, they were not correlated to protozoal contamination of wastewater and river water. Oocysts of T. gondii were not found in both raw and treated wastewater, or in Seine River. Parasitic contamination was shown to be constant in the Seine River up to 40 km upstream Paris. Altogether, these results strongly suggest that treated wastewater does not contribute to the main parasitic contamination of the Seine River usually observed in this urbanized area.
The multistep synthesis of new quinazoline-derived molecules and their in vitro antiplasmodial evaluation on the W2 chloroquino-resistant Plasmodium falciparum strain is described herein. These molecules have also been studied concerning their in vitro cytotoxicity toward two human cell lines (K652 and HepG2) in order to calculate their respective selectivity indexes (S.I.). Among the fourteen tested molecules, two exhibited both significant antiplasmodial activity (IC(50)=0.95 and 1.3 microM) and low toxicity (IC(50)>100 or 125 microM), compared with two reference drugs: chloroquine and doxycycline. The structure activity relationships establish that the molecular scaffold which exerts the best profile is the 6-nitro-2-(tosylmethyl)-N-(3-substituted-phenyl)-quinazolin-4-amine. The hit molecules were finally investigated regarding their potential action toward two other protozoa, Leishmania donovani and Toxoplasma gondii, showing that these molecules display a selective antiplasmodial activity.
We have synthesized quinolinones with potential antiparasitic and anti-HIV activities by an original two-step method involving microwave irradiation and have evaluated their activities against Plasmodium falciparum, Leishmania donovani, Trichomonas vaginalis, and HIV. None of the tested compounds had been previously described using this method of synthesis. One of the compounds had interesting antiparasitic and anti-HIV activity, which could be improved by substitution with different radicals.
A large series of 4-arylcoumarins was synthesized by Suzuki-Miyaura cross-coupling reaction and evaluated for antiprotozoal activity against Plasmodium falciparum and Leishmania donovani. Several compounds were found to strongly inhibit the proliferation of human cell line and/or parasites. The 4-(3,4-dimethoxyphenyl)-6,7-dimethoxycoumarin exhibit a potent activity on L. donovani amastigotes with a selectivity index (SI=265) twice than amphotericin B (SI=140).
To identify a new safe antiplasmodial molecular scaffold, an original series of 2-trichloromethylquinazolines, functionalized in position 4 by an alkyl- or arylamino substituent, was synthesized from 4-chloro-2-trichloromethylquinazoline 1, via a cheap, fast and efficient solvent-free operating procedure. Among the 40 molecules prepared, several exhibit a good profile with both a significant antiplasmodial activity on the W2 Plasmodium falciparum strain (IC(50) values: 0.4-2.2 microM) and a promising toxicological behavior regarding human cells (HepG2/W2 selectivity indexes: 40-83), compared to the antimalarial drug compounds chloroquine and doxycycline. The in vitro antitoxoplasmic and antileishmanial evaluations were conducted in parallel on the most active molecules, showing that these ones specifically display antiplasmodial properties.
We present a case of disseminated congenital toxoplasmosis in a newborn born to a mother who had been immunized against toxoplasmosis before conception. The mother was reinfected, likely by ingestion of imported raw horse meat during pregnancy. This clinical presentation is exceptional in France and raised the possibility of infection by a highly virulent Toxoplasma strain. The strain responsible was isolated from the peripheral blood of the newborn, and when genotyped with microsatellite markers, it exhibited an atypical genotype, one which is very uncommon in Europe but had been described in South America. We tested the hypothesis of a reinfection with a different genotype by using an experimental mouse model, which confirmed that acquired immunity against European Toxoplasma strains may not protect against reinfection by atypical strains acquired during travel outside Europe or by eating imported meat.
This study evaluates the protozoan contamination of river waters, which are used for drinking water in Paris and its surrounding area (about 615,000 m(3) per day in total, including 300,000 m(3) for Paris area). Twenty litre samples of Seine and Marne Rivers were collected over 30 months and analyzed for Cryptosporidium oocysts and Giardia cysts detection according to standard national or international methods. Cryptosporidium oocysts and Giardia cysts were found, respectively, in 45.7% and 93.8% of a total of 162 river samples, with occasional high concentration peaks. A significant seasonal pattern was observed, with positive samples for Cryptosporidium more frequent in autumn than spring, summer and winter, and positive samples for Giardia less frequent in summer. Counts of enterococci and rainfalls were significantly associated with Giardia concentration but not Cryptosporidium. Other faecal bacteria were not correlated with monitored protozoan. Marne seems to contribute mainly to the parasitic contamination observed in Seine. Based on seasonal pattern and rainfall correlation, we hypothesize that the origin of contamination is agricultural practices and possible dysfunction of sewage treatment plants during periods of heavy rainfalls. High concentrations of protozoa found at the entry of drinking water plants justify the use of efficient water treatment methods. Treatment performances must be regularly monitored to ensure efficient disinfection according to the French regulations.
Stephania rotunda Lour. (Menispermaceae) is a creeper growing in many countries of Asia and commonly found in the mountainous areas of Cambodia. As a folk medicine, it has been mainly used for the treatment of fever and malaria. The pharmacological activity is mostly due to alkaloids. Thus the aim of this study is to isolate new bioactive alkaloids from Stephania rotunda and to evaluate their in vitro antiplasmodial activity.
We report herein a simple and efficient two-step synthetic approach to new 2-trichloromethylquinazolines possessing a variously substituted sulfonamide group at position 4 used to prepare new quinazolines with antiparasitic properties. Thus, an original series of 20 derivatives was synthesized, which proved to be less-toxic than previously synthesized hits on the human HepG2 cell line, but did not display significant antiplasmodial activity. A brief Structure-Activity Relationship (SAR) evaluation shows that a more restricted conformational freedom is probably necessary for providing antiplasmodial activity.
A series of nitrated 2-substituted-quinolines was synthesized and evaluated in vitro toward Leishmania donovani promastigotes. In parallel, the in vitro cytotoxicity of these molecules was assessed on the murine J774 and human HepG2 cell lines. Thus, a very promising antileishmanial hit molecule was identified (compound 21), displaying an IC(50) value of 6.6 ?M and CC(50) values ? 100 ?M, conferring quite good selectivity index to this molecule, in comparison with 3 drug-compounds of reference (amphotericin B, miltefosine and pentamidine). Compound 21 also appears as an efficient in vitro antileishmanial molecule against both Leishmania infantum promastigotes and the intracellular L. donovani amastigotes (respective IC(50) = 7.6 and 6.5 ?M). Moreover, hit quinoline 21 does not show neither significant antiplasmodial nor antitoxoplasmic in vitro activity and though, presents a selective antileishmanial activity. Finally, a structure-activity relationships study enabled to define precisely the antileishmanial pharmacophore based on this nitroquinoline scaffold: 2-hydroxy-8-nitroquinoline.
Toxoplasma gondii oocysts spread in the environment are an important source of toxoplasmosis for humans and animal species. Although the life expectancy of oocysts has been studied through the infectivity of inoculated soil samples, the survival dynamics of oocysts in the environment are poorly documented. The aim of this study was to quantify oocyst viability in soil over time under two rain conditions. Oocysts were placed in 54 sentinel chambers containing soil and 18 sealed water tubes, all settled in two containers filled with soil. Containers were watered to simulate rain levels of arid and wet climates and kept at stable temperature for 21.5 months. At nine sampling dates during this period, we sampled six chambers and two water tubes. Three methods were used to measure oocyst viability: microscopic counting, quantitative PCR (qPCR), and mouse inoculation. In parallel, oocysts were kept refrigerated during the same period to analyze their detectability over time. Microscopic counting, qPCR, and mouse inoculation all showed decreasing values over time and highly significant differences between the decreases under dry and damp conditions. The proportion of oocysts surviving after 100 days was estimated to be 7.4% (95% confidence interval [95% CI] = 5.1, 10.8) under dry conditions and 43.7% (5% CI = 35.6, 53.5) under damp conditions. The detectability of oocysts by qPCR over time decreased by 0.5 cycle threshold per 100 days. Finally, a strong correlation between qPCR results and the dose infecting 50% of mice was found; thus, qPCR results may be used as an estimate of the infectivity of soil samples.
Stephania rotunda (Menispermaceae), a creeper commonly found in the mountainous areas of Cambodia, has been mainly used for the treatment of fever and malaria. Thus, the aim of this study is to investigate the chemical composition and antiplasmodial activity of different samples of S. rotunda and compare their antiplasmodial activity with their alkaloid content. Sixteen samples from different parts (roots, stem, and tuber) of S. rotunda were collected from four regions of Cambodia (Battambang, Pailin, Siem Reap, and Kampot). Reversed-phase HPLC was used to determine the content of three bioactive alkaloids (cepharanthine, tetrahydropalmatine, and xylopinine). These three alkaloids have been found in all samples from Battambang and Pailin (samples I-IX), whereas only tetrahydropalmatine was present in samples from Siem Reap and Kampot (samples X-XVI). The analyzed extracts were evaluated for their antiplasmodial activity on W2 strain of Plasmodium falciparum. Among them, 13 extracts were significantly active with inhibitory concentration 50 (IC(50) ) from 1.2 to 3.7?µg/mL and 2 extracts were moderately active (IC(50) ?=?6.1 and 10?µg/mL, respectively), whereas sample XI was not active (IC(50) ?=?19.6?µg/mL). A comparison between antiplasmodial activity and concentration of the three bioactive alkaloids in S. rotunda extracts has been realized.
The synthesis of ?-carbolines and their in vitro antiplasmodial and antileishmanial activities were described herein. These molecules have also been studied concerning their in vitro cytotoxicity toward the human cell line THP1, in order to calculate their respective selectivity indexes (SI). Among the 20 tested molecules, four exhibited significant antiplasmodial activity on the W2 multi-resistant Plasmodium falciparum strain (0.7 < IC?? < 1.7 ?M), in comparison with two references drugs (chloroquine and doxycycline), and a low cytotoxicity. These ?-carbolines were also evaluated concerning their in vitro antileshmanial activity on Leishmania donovani promastigotes, permitting to identify an antileshmanial hit compound, displaying quite promising activity (IC?? = 6.1 ?M) in comparison with amphotericin B and pentamidine chosen as reference drugs. Finally, structure-activity relationships were discussed, pointing out that molecules presenting a para-substituted phenyl moiety at position 1 of the ?-carboline ring displayed the best biological profile.
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