Spreading Patterns of NDM-Producing Enterobacteriaceae in Clinical and Environmental Settings in Yangon, Myanmar

The spread of carbapenemase-producing Enterobacteriaceae (CPE), contributing to widespread carbapenem resistance, has become a global concern. However, the specific dissemination patterns of carbapenemase genes have not been intensively investigated in developing countries, including Myanmar, where NDM-type carbapenemases are spreading in clinical settings. In the present study, we phenotypically and genetically characterized 91 CPE isolates obtained from clinical (n = 77) and environmental (n = 14) samples in Yangon, Myanmar. We determined the dissemination of plasmids harboring genes encoding NDM-1 and its variants using whole-genome sequencing and plasmid analysis. IncFII plasmids harboring bla(NDM-5) and IncX3 plasmids harboring bla(NDM-4) or bla(NDM-7) were the most prevalent plasmid types identified among the isolates. The IncFII plasmids were predominantly carried by clinical isolates of Escherichia coli, and their clonal expansion was observed within the same ward of a hospital. In contrast, the IncX3 plasmids were found in phylogenetically divergent isolates from clinical and environmental samples classified into nine species, suggesting widespread dissemination of plasmids via horizontal transfer. Half of the environmental isolates were found to possess IncX3 plasmids, and this type of plasmid was confirmed to transfer more effectively to recipient organisms at a relatively low temperature (25 degrees C) compared to the IncFII plasmid. Moreover, various other plasmid types were identified harboring bla(NDM-1), including Inc-FIB, IncFII, IncL/M, and IncA/C-2, among clinical isolates of Klebsiella pneumoniae or Enterobacter cloacae complex. Overall, our results highlight three distinct patterns of the dissemination of bla(NDM)-harboring plasmids among CPE isolates in Myanmar, contributing to a better understanding of their molecular epidemiology and dissemination in a setting of endemicity.