Molecular typing of thermophilic Campylobacter isolates from poultry and human origin

An important source of infection with Campylobacter is considered to be raw poultry meat. The aim of this study was to differentiate isolates of Campylobacter spp. at various stages throughout processing with DNA fingerprinting techniques. To assess the impact of poultry products as vectors for sporadic Campylobacter infections in Germany, additionally the relatedness of Campylobacter spp. strains occurring in a 3-month period within the city of Berlin on retail chicken products and in human campylobacteriosis was analysed by PFGE. Eight poultry flocks from different farms were sampled at different dates. Cloacal swabs were taken at the beginning of the slaughter, and neck skin samples before evisceration were taken from each flock. Crates for living birds were sampled before and after washing, carcasses after scalding and neck skin after air spray chilling in some flocks, additionally. A subset of 154 Campylobacter spp. strains were chosen from each flock at each processing station for ribotyping in a previous study and the same strains were collected for subtyping with pulsed-field gel electrophoresis. A number of genetically distinct Campylobacter strains were isolated at different sampling stations per flock. The populations of C. jejuni and C. coli are extremely diverse and this diversity is reflected in a broad spectrum of subtypes. Distinct flocks could be colonized with different types of Campylobacter. One flock could be colonized by multiple genotypes whereas strains within individual flocks coexisted rather than excluding each other. In addition, more than one strain in each flock may have potential epidemiological importance. Despite the weak clonality of C. spp., 10.6 % of human isolates were genetically identical with isolates found in the same geographical region and time frame in retail chicken products, confirming the importance of poultry products as potential sources for human infections.