Diversity and characteristics of pTet family plasmids revealed by genomic epidemiology of Campylobacter jejuni from human patients in Toyama, Japan from 2015 to 2019

This study investigated 116 clinical isolates of Campylobacter jejuni from Toyama, Japan, which were isolated from 2015 to 2019. Antimicrobial susceptibility testing and whole-genome sequencing were used for phenotypic and genotypic characterization to compare antimicrobial resistance (AMR) profiles and phylogenic linkage. The multilocus sequence typing approach identified 37 sequence types (STs) and 15 clonal complexes (CCs), including 7 novel STs, and the high frequency CCs were CC21 (27.7%), CC48 (10.9%), and CC354 (9.9%). Overall, 58.6% of the isolates were resistant to at least one of the antibiotics and 3.4% were resistant to three or more antibiotic classes. The AMR profiles and related resistant factors were as follows; fluoroquinolones (51.7%), mutation in QRDRs (GyrA T86I), tetracyclines (27.6%), acquisition of tet(O), ampicillin (5.2%), promoter mutation in blaOXA193, aminoglycosides (1.7%), acquisition of ant(6)-Ia and aph(3)-III, chloramphenicol (0.9%), acquisition of cat. The resistance factors of fosfomycin (1 strain), sulfamethoxazole-trimethoprim (2 strain), and linezolid (1 strain) resistant isolates were unknown. The acquired resistance genes, tet(O), ant(6>)-Ia, aph(3)-III, and cat, were located on pTet family plasmids. Furthermore, three pTet family plasmids formed larger plasmids that incorporated additional genes such as the Type IV secretion system. A comparison of pTet family plasmids in Japan has not been reported, and these results imply that the diversity of pTet family plasmids has increased. The prevalence of ST4526, belonging to CC21, in Japan has been reported, and it was also the major ST type (10.9%) in this study, suggesting that the ST4526 prevalence continues in Japan.