Epidemiology, Relative Invasive Ability, Molecular Characterization, and Competitive Performance of Campylobacter jejuni Strains in the Chicken Gut

One hundred forty-oneCampylobacter jejuni isolates from humans with diarrhea and 100 isolates from retailed poultry meat were differentiated byflaA typing. The bacteria were isolated in a specific geographical area (Dunedin) in New Zealand over a common time period. Twenty nineflaA types were detected, one of which (flaA restriction fragment length polymorphism type 15 [flaA -15]) predominated among isolates from humans (∼30% of isolates). This strain was of low prevalence (5% of isolates) among poultry isolates.flaA -15 strains were five to six times more invasive of HEp2 cells in an in vitro assay than aflaA type (flaA -3) that was commonly encountered on poultry meat (23% of isolates) but was seldom associated with human illness (5%). Competitive-exclusion experiments with chickens, utilizing real-time quantitative PCR to measure the population sizes of specific strains representingflaA -15 (T1016) andflaA -3 (Pstau) in digesta, were carried out. These experiments showed that T1016 always outcompeted Pstau in the chicken intestine. Genomic comparisons of T1016 and Pstau were made using DNA microarrays representing the genome ofC. jejuni NCTC 11168. These comparisons revealed differences between the strains in the gene content of the Cj1417c-to-Cj1442c region of the genome, which is associated with the formation of capsular polysaccharide. The strains differed in Penner type (T1016, O42; Pstau, O53). It was concluded that poultry meat was at least one source of human infection withC. jejuni , that someCampylobacter strains detected in poultry meat are of higher virulence for humans than others, and that bacterial attributes affecting strain virulence and commensal colonization ability may be linked.