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Campylobacter jejuni is a foodborne pathogen causing bacterial gastroenteritis, with the highest incidence reported in Europe. The prevalence of antibiotic resistance in C. jejuni, as well as in many other bacterial pathogens, has increased over the last few years. In this report, we describe the presence of a plasmid in a multi-drug-resistant C. jejuni strain isolated from a gastroenteritis patient. Mating experiments demonstrated the transference of this genetic element (pCjH01) among C. jejuni by plasmid conjugation. The pCjH01 plasmid was sequenced and assembled, revealing high similarity (97% identity) with pTet, a described tetracycline resistance encoding plasmid. pCjH01 (47.7 kb) is a mosaic plasmid composed of a pTet backbone that has acquired two discrete DNA regions. Remarkably, one of the acquired sequences carried an undescribed variant of the aadE-sat4-aphA-3 gene cluster, providing resistance to at least kanamycin and gentamycin. Aside from the antibiotic resistance genes, the cluster also carries genes coding for putative regulators, such as a sigma factor of the RNA polymerase and an antisigma factor. Homology searches suggest that Campylobacter exchanges genetic material with distant G-positive bacterial genera.

Campylobacter jejuni causes campylobacteriosis, a bacterial gastroenteritis with high incidence worldwide. Moreover, C. jejuni infection can trigger the polyneuropathic disorder denominated Guillain-Barré syndrome (GBS). The C. jejuni strains that can elicit GBS carry either wlaN or cgtB, coding both genes for a β-1,3-galactosyltransferase enzyme that is required for the production of sialylated lipooligosaccharide (LOSSIAL). We described a differential prevalence of the genes wlaN and cgtB in C. jejuni isolates from three different ecological niches: humans, broiler chickens, and wild birds. The distribution of both genes, which is similar between broiler chicken and human isolates and distinct when compared to the wild bird isolates, suggests a host-dependent distribution. Moreover, the prevalence of the wlaN and cgtB genes seems to be restricted to some clonal complexes. Gene sequencing identified the presence of new variants of the G- homopolymeric tract within the wlaN gene. Furthermore, we detected two variants of a G rich region within the cgtB gene, suggesting that, similarly to wlaN, the G-tract in the cgtB gene mediates the phase variation control of cgtB expression. Caco-2 cell invasion assays indicate that there is no evident correlation between the production of LOSSIAL and the ability to invade eukaryotic cells.