Members of the genus Campylobacter are frequently responsible for human enteric disease, often through consumption of contaminated poultry products. Bacteriophages are viruses that have the potential to control pathogenic bacteria, but understanding their complex life cycles is key to their successful exploitation. Treatment of Campylobacter jejuni biofilms with bacteriophages led to the discovery that phages had established a relationship with their hosts typical of the carrier state life cycle (CSLC), where bacteria and bacteriophages remain associated in equilibrium. Significant phenotypic changes include improved aerotolerance under nutrient-limited conditions that would confer an advantage to survive in extra-intestinal environments, but a lack in motility eliminated their ability to colonize chickens. Under these circumstances, phages can remain associated with a compatible host and continue to produce free virions to prospect for new hosts. Moreover, we demonstrate that CSLC host bacteria can act as expendable vehicles for the delivery of bacteriophages to new host bacteria within pre-colonized chickens. The CSLC represents an important phase in the ecology of Campylobacter bacteriophage.
Bacteria in their natural environments frequently exist as mixed surface-associated communities, protected by extracellular material, termed biofilms. Biofilms formed by the human pathogen Campylobacter jejuni may arise in the gastrointestinal tract of animals but also in water pipes and other industrial situations, leading to their possible transmission into the human food chain either directly or via farm animals. Bacteriophages are natural predators of bacteria that usually kill their prey by cell lysis and have potential application for the biocontrol and dispersal of target bacteria in biofilms. The effects of virulent Campylobacter specific-bacteriophages CP8 and CP30 on C. jejuni biofilms formed on glass by strains NCTC 11168 and PT14 at 37°C under microaerobic conditions were investigated. Independent bacteriophage treatments (n ? 3) led to 1 to 3 log?? CFU/cm² reductions in the viable count 24 h postinfection compared with control levels. In contrast, bacteriophages applied under these conditions effected a reduction of less than 1 log?? CFU/ml in planktonic cells. Resistance to bacteriophage in bacteria surviving bacteriophage treatment of C. jejuni NCTC 11168 biofilms was 84% and 90% for CP8 and CP30, respectively, whereas bacteriophage resistance was not found in similarly recovered C. jejuni PT14 cells. Dispersal of the biofilm matrix by bacteriophage was demonstrated by crystal violet staining and transmission electron microscopy. Bacteriophage may play an important role in the control of attachment and biofilm formation by Campylobacter in situations where biofilms occur in nature, and they have the potential for application in industrial situations leading to improvements in food safety.
It was noted that quantitative and qualitative differences occurred between the growth of Campylobacter in microaerobic atmospheres provided by a gas replacement jar and that in a modular atmosphere controlled system cabinet, despite the fact that oxygen levels were comparable. Hydrogen was, however, only present in the replacement mixture (3%). Investigations were therefore carried out to examine any accompanying physiological or transcriptional differences. Growth curves and motility studies using Campylobacter jejuni HPC5 showed that cultures growing in the cabinet were impaired, but only in the early stages of growth compared to growth in the jar. However, transcriptome studies highlighted profound changes in the transcript profiles of exponential cultures grown in the cabinet compared to the jar, including genes indicative of oxidative stress. Genes involved in detoxification, synthesis and modification of macromolecules, probable prophage genes and genes associated with inhibition of natural transformation showed relative increases in expression in the cabinet. Conversely, genes that function in energy metabolism, chaperones, heat shock and motility were increased in the jar, which was indicative of balanced growth. This work highlights the need to carefully annotate the different methods of atmosphere generation in the description of experiments in microarray databases; the assessment of these experimental details is crucial to overcome difficulties in comparing transcriptomic studies of campylobacter cultures between different laboratories.
Our understanding of the dynamics of genome stability versus gene flux within bacteriophage lineages is limited. Recently, there has been a renewed interest in the use of bacteriophages as therapeutic agents; a prerequisite for their use in such therapies is a thorough understanding of their genetic complement, genome stability and their ecology to avoid the dissemination or mobilisation of phage or bacterial virulence and toxin genes. Campylobacter, a food-borne pathogen, is one of the organisms for which the use of bacteriophage is being considered to reduce human exposure to this organism.
Members of the genus Campylobacter are frequently responsible for human enteric disease worldwide. Persistent Campylobacter contamination of poultry meat is a common problem that represents a significant food safety risk through the consumption of undercooked poultry meat or through cross-contamination of other foods during the preparation of poultry. Bacteriophage therapy is one possible means by which this colonization of poultry could be controlled, thus limiting the entry of Campylobacter into the human food chain. Previously group III phages with genome sizes of approximately 140 kb had been administered to Campylobacter jejuni-colonized poultry. The application of a group II Campylobacter phage, CP220, with a genome size of 197 kb is described here. Phage CP220 was administered to both C. jejuni- and C. coli-colonized birds. A 2-log CFU/g decline in cecal Campylobacter counts was observed after 48 h in birds colonized with C. jejuni HPC5 and administered with a single 7-log PFU dose of CP220. The incidence of phage resistance developing in Campylobacter-colonized chickens upon exposure to virulent phages was determined to be 2%, and the resistant types remained a minor component of the population. To achieve a similar reduction in Campylobacter numbers in C. coli OR12-colonized birds, a 9-log PFU dose of CP220 was required. Using phage to reduce Campylobacter colonization in poultry offers the prospect of a sustainable intervention measure that may limit the entry of these pathogens into the human food chain.
Campylobacter is considered to be the most common cause of bacterial diarrhoeal illness in the developed world. Many cases are thought to be acquired from consumption of undercooked poultry. The aim of this study was to compare the effect of the rate of cooling on the survival, at 4 degrees C and -20 degrees C, of Campylobacter coli and Campylobacter jejuni strains, inoculated on chicken skin from axenic culture or as mixed inoculums. Strains chilled in a domestic refrigerator varied in their tolerance to storage at 4 degrees C. Statistically significant differences between strains applied as axenic or mixed inoculums were observed for specific strain combinations using two-way ANOVA, including the enhanced survival of antibiotic resistant C. coli 99/367 at 4 degrees C. The use of rapid cooling (at -20 degrees C/min) enhanced the survival of all the Campylobacter strains chilled to 4 degrees C compared to standard refrigeration. Freezing to -20 degrees C reduced viable counts by 2.2-2.6 log10 CFU/cm(2) in 24 h. Rapid cooling to -20 degrees C (at -30 degrees C/min) enhanced the survival of C. coli 99/367 compared to freezing in a domestic freezer. Statistically significant interaction terms between specific strains were observed in mixed inoculums chilled to -20 degrees C by freezing in a domestic freezer and by rapid chilling to -20 degrees C. Rapid chilling of poultry, particularly for 4 degrees C storage may enhance survival of Campylobacter and although this is an issue that affects meat quality, it should be considered by poultry processors.
Campylobacter jejuni, the commonest cause of bacterial diarrhoea worldwide, can also induce colonic inflammation. To understand how a previously identified heat stable component contributes to pro-inflammatory responses we used microarray and real-time quantitative PCR to investigate the transcriptional response to a boiled cell extract of Campylobacter jejuni NCTC 11168.
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