Characterization of blaCTX-M-27/F1:A2:B20 plasmids spreading among elderly Japanese

Escherichia coli harboring CTX-M-type extended-spectrum beta-lactamase (ESBL) genes have become a global health concern in clinical and community settings. Particularly, the prevalence of ST131 C1/H30R with blaCTX-M-27 has increased not only in Japanese clinical settings and long-term care facility but also in healthy individuals in some European countries. Although the ST131 C1/H30R harboring blaCTX-M-27 has rapidly disseminated worldwide, its plasmid distribution is unclear. This study was conducted to characterize plasmids harboring blaCTX-M-27 obtained from healthy individuals and LTCF residents living in non-acute care settings using next-generation sequencing (NGS) and determine the complete nucleotide sequence of a representative plasmid. Some plasmids co-express several genes conferring resistance to aminoglycosides, macrolides, tetracycline, and trimethoprim. However, we also identified F1:A2:B20 plasmids harboring only blaCTX-M-27 as a resistance gene. Although these plasmids lacked genes encoding some transposases, as well as antimicrobial resistance genes, the fundamental structures of the plasmids were similar to that of blaCTX-M-27/F1:A2:B20 plasmids isolated worldwide. Our findings demonstrate that blaCTX-M-27/F1:A2:B20 plasmids isolated outside of Japan have already disseminated among elderly Japanese living in non-acute care settings. These results suggest that public health problems can arise from the worldwide dissemination of this plasmid type; however, further studies are necessary to clarify the process of blaCTX-M-27/F1:A2:B20 plasmid dissemination.