Genetic instability of Campylobacter coli in the digestive tract of experimentally infected pigs

Campylobacter, a leading cause of food-borne illness worldwide, has a widespread distribution with a broad range of animal hosts and environmental reservoirs. The genetic description of bacterial strains is a powerful tool for epidemiological studies but can be impaired by the high genomic variability of Campylobacter. Our study aimed (i) at investigating the genotypic instability of Campylobacter generated either in vitro by subculturing or after in vivo passage on specific pathogen-free pigs and (ii) at evaluating the suitability of typing methods to detect such variation. Pigs were inoculated per os with three Campylobacter strains (one C. coli originating from pig faeces, one C. jejuni and one C. coli originating from poultry faeces) alone or in mixture and non-inoculated pigs were housed in adjacent pens. Genotypic instability was investigated using both macrorestriction combined with pulsed-field gel electrophoresis analysis (PFGE) and PCR restriction fragment length polymorphism analysis of the flaA gene (flaA PCR-RFLP). No variability in the genetic profile was observed for the three strains maintained through twenty times subculturing events in vitro. Genotypic variability was evidenced in vivo only in pigs inoculated with C. coli of porcine origin, either alone or in a mix, with both genotyping methods. In our study, for one porcine C. coli strain, 13% and 21% of variability were generated in the digestive tract of pigs by PFGE and flaA PCR-RFLP typing methods, respectively. This study is a first approach for a better understanding of the genomic instability of Campylobacter in pig under field conditions.