Subspecies characterization of porcine Campylobacter coli and Campylobacter jejuni by multilocus enzyme electrophoresis typing

Enteropathogenic Campylobacter jejuni, C. coli and C. lari are currently the most common causes of acute infectious diarrhoeal illness in the UK. Many domestic animals, including pigs, act as natural reservoirs of these organisms and infection may occur through the ingestion of contaminated foodstuffs. C. jejuni and C. coli, isolated from the livers of bacon pigs, were examined at subspecies level by multilocus enzyme electrophoresis (MEE) typing with seven enzymic loci. Polymorphological variation was highest with indophenol oxidase, isocitrate dehydrogenase and L-phenylalanyl-L-leucine peptidase giving 5, 5 and 4 alleles at these loci, respectively. The 35 Campylobacter isolates examined in this study (12 C. jejuni and 23 C. coli) represented 30 unique electrophoretic types (ETs). Of these ETs, 8 unique types were detected for the 12 C. jejuni isolates and 19 unique ETs were detected for the 23 C. coli isolates. In addition, 3 types (ETs 2, 5, 10) were shared in common among C. jejuni and C. coli. The average number of alleles per enzyme locus was 3.28. The mean genetic diversity, i.e. arithmetic average over all loci assayed, including monomorphic values, was 0.5573 and 0.5350 for C. jejuni and C. coli, respectively. Alleles were shared by C. jejuni and C. coli, suggesting an exchange of genetic material between the species. MEE analyses of isolates showed that there was a wide range of subspecies types within both C. jejuni and C. coli in porcine livers. In certain cases, up to four phenotypically different strains of C. coli were isolated from one liver, indicating multiple infections.