Prevalence of carbapenem-resistant Enterobacterales with bla IMP-6 predominance in hospitals from 2018 to 2021 in Nara, Japan.

Objectives: Despite the global health risk of carbapenem-resistant Enterobacterales (CRE), especially carbapenemase-producing Enterobacterales (CPE), Japan reports a significantly low frequency of CRE with a predominance of IMP-type carbapenemases. This study aimed to investigate the prevalence and characteristics of CRE isolated from hospitals in the city of Nara, Japan.

Methods: We obtained 171 CRE isolates from 16 791 Enterobacterales isolated at 23 hospitals in Nara between January 2018 and December 2021. Isolates of CPE were characterized through antimicrobial susceptibility testing, the carbapenem inactivation method, PCR and DNA sequencing. Genotypic diversity of carbapenemase-producing Escherichia coli and Klebsiella pneumoniae was determined via MLST and PFGE.

Results: The prevalence of CRE between 2018 and 2021 was 1.02%, gradually decreasing from 1.13% to 0.74%. Ninety-nine isolates were identified as CPE, representing six species. Ninety-seven CPE isolates harboured bla _IMP-6, while the remaining two carried either bla _IMP-1 or bla _IMP-19. Genotype analysis identified ST131 as the dominant genotype for E. coli, but none for K. pneumoniae. PFGE results suggested clonal spread of CPE in Hospital A, where CRE was isolated in high numbers (n = 44).

Conclusions: In this study, CRE prevalence was marginally higher than previously reported in Japan, but still low in frequency. A predominance of Enterobacterales harbouring bla _IMP-6 was confirmed in Nara. The spread of CPE at Hospital A suggested the possibility of a nosocomial outbreak due to bla _IMP-6 transmission via plasmids or clonal spread. Continued monitoring is crucial for effective management of CRE prevalence in the region.