Prevalence of Extended-Spectrum Beta-Lactamase and Carbapenemase Genes in Clinical Isolates of Escherichia coli in Myanmar: Dominance of blaNDM-5 and Emergence of blaOXA-181

The increasing trend of Escherichia coli producing extended-spectrum beta-lactamases (ESBLs) and carbapenemases is a global public health concern. In this study, prevalence and molecular characteristics of E. coli harboring ESBL and carbapenemase genes were investigated for 426 isolates derived from various clinical specimens in a teaching hospital in Yangon, Myanmar, for the 1-year period beginning January 2016. A total of 157 isolates (36.9%) were ESBL producers and harbored CTX-M-1 group genes (146 isolates; bla(CTX-M-15), bla(CTX-M55)) or CTX-M-9 group genes (11 isolates; bla(CTX-M-14), bla(CTX-M-27)). Carbapenem resistance was detected in 35 isolates (8.2%), among which 26 isolates had carbapenemase genes encoding NDM-1 (2 isolates), NDM-4 (6 isolates), NDM-5 (14 isolates), NDM-7 (3 isolates), and OXA-181 (2 isolates). bla(NDM-5) was identified in phylogenetic groups A, B1, and D isolates belonging to various genotypes (ST101, ST354, ST405, ST410, ST1196) associated with bla(TEM-1), bla(CTX-M-15), bla(OXA-181), bla(CMY-2), bla(CMY-6), bla(CMY-42), qnrB, qnrS, or aac6-Ib-cr. While two isolates with bla(OXA-181) belonged to phylogenetic group A-ST410, one isolate had also bla(NDM-5), as well as bla(CTX-M-15) and bla(CMY-2), and the other harbored bla(CMY-42) and aac6-Ib-cr, showing different resistance patterns. Phylogenetic group B2 isolates examined were classified into mostly ST131 and had solely bla(CTX-M-15) or bla(CTX-M-27), harboring more virulence factors than other phylogenetic groups. The present study revealed high prevalence of ESBL genes represented by bla(CTX-M-15) and dominance of bla(NDM-5) among NDM genes, disseminating to various E. coli clones. Notably, carbapenemase gene encoding OXA-181 was first identified in Myanmar, suggesting its spread together with NDM genes.