A New Variant of the aadE-sat4-aphA-3 Gene Cluster Found in a Conjugative Plasmid from a MDR Campylobacter jejuni Isolate

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.

Automated summary

This study describes the presence of a plasmid and its transferability in a multi-drug resistant strain of Campylobacter jejuni. The plasmid not only carries tetracycline resistance genes, but also a gene cluster that provides resistance to kanamycin and gentamycin. Additionally, the study suggests the possibility of genetic exchange between Campylobacter and distantly related G-positive bacterial genera.