Campylobacter spp. is a significant and prevalent public health hazard globally. Campylobacter jejuni is the most frequently recovered species from human cases and poultry are considered the most important reservoir for its transmission to humans. In this study, 30 Campylobacter jejuni isolates were selected from clinical (n = 15) and broiler (n = 15) sources from a larger cohort, based on source, virulence, and antimicrobial resistance profiles. The objective of this study was to further characterise the genomes of these isolates including MLST types, population structure, pan-genome, as well as virulence and antimicrobial resistance determinants. A total of 18 sequence types and 12 clonal complexes were identified. The most common clonal complex was ST-45, which was found in both clinical and broiler samples. We characterised the biological functions that were associated with the core and accessory genomes of the isolates in this study. No significant difference in the prevalence of virulence or antimicrobial resistance determinants was observed between clinical and broiler isolates, although genes associated with severe illness such as neuABC, wlaN and cstIII were only detected in clinical isolates. The ubiquity of virulence factors associated with motility, invasion and cytolethal distending toxin (CDT) synthesis in both clinical and broiler C. jejuni genomes and genetic similarities between groups of broiler and clinical C. jejuni reaffirm that C. jejuni from poultry remains a significant threat to public health.
Background:Campylobacter is commonly transmitted to humans from chickens. Campylobacter jejuni is the species most frequently associated with human illness, and the most prevalent species recovered from poultry.Objective: The objective of this study was to analyse a sub-population of C. jejuni from two broiler flocks on the farm and at slaughter using whole-genome sequencing to gain insights into the changes in the Campylobacter population during broiler production, including changes in virulence and antimicrobial resistance profiles.Methods: In this study, ten composite faecal samples (n=10), obtained by pooling ten fresh faecal samples (n=10), were collected in the broiler house on two farms on days 14, 21, 28, and 34 (n=80) and ten composite (n=10) caecal samples were collected at the time of slaughter for each flock (n=20). These were tested for C. jejuni using the ISO 10272-2:2016 method. Seven isolates were randomly selected from each of the nine Campylobacter-positive sampling points (n=63) and were subjected to antimicrobial susceptibility tests. Their genomes were sequenced and the data obtained was used to characterise the population structure, virulence, antimicrobial resistance determinants and inter-strain variation.Results: The Farm 1 isolates had three MLST types (ST257-257, ST814-661 and ST48-48) while those on Farm 2 were ST6209-464 and ST9401. Interestingly, only the MLST types positive for most of the virulence genes tested in this study persisted throughout the production cycle, and the detection of antimicrobial resistance determinants (gyrA T86I and tetO) increased after thinning and at slaughter, with the detection of new strains.Conclusion: The persistence of the most virulent strains detected in this study throughout the production cycle has important implications for the risk to consumers and requires further investigation. The detection of new strains within the population corresponding with the time of thinning and transportation reflects previous reports and provides further evidence that these activities pose a risk of introducing new Campylobacter strains to broiler batches.
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