Most commercially raised poultry have campylobacters in their intestinal flora, with 87% of broiler carcasses in the UK found to be contaminated. Recently the type six secretion system (T6SS), which can play a significant role in bacterial pathogenicity, was reported in Campylobacter spp. and a key component of the T6SS is the hcp gene. Because campylobacteriosis is associated with the consumption of infected poultry meat, this study aimed to investigate C. jejuni (n=59) and C. coli (n=57) isolated from retail raw chicken for the presence of the hcp gene, and for other virulence characteristics, and to investigate the association of T6SS with virulence. Multiplex PCR found a significantly higher prevalence of hcp in C. coli isolates (56.1%) than in C. jejuni (28.8%) and AFLP analysis of the isolates showed a high degree of genetic similarity between the isolates carrying the hcp gene. Genome sequencing data showed that 84.3% of the C. coli and 93.7% of the C. jejuni isolates had all 13 T6SS open reading frames. Moreover, the virulence characteristics of hcp+ isolates, including motility and the ability to invade human intestinal epithelial cells in vitro, were significantly greater than in the control strain C. jejuni 12502; a human isolate which is hcp+. Overall, it was discovered that hcp+ C. coli and C. jejuni isolated from retail chicken isolates posses genetic and phenotypic properties associated with enhanced virulence. However, since human infections with C. coli are significantly less frequent than those of C. jejuni, the relationship between virulence factors and pathogenesis requires further study.
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