Emergence of NDM-type metallo-β-lactamase and ArmA 16S rRNA methylase co-producing Morganella morganii in Myanmar

Background: Morganella morganii is intrinsically resistant to a wide range of antibiotics and is increasingly being reported worldwide. Methods: A total of five M. morganii isolates were obtained from five patients at three hospitals in Myanmar between Sept. 2023 and Oct. 2024. Minimum inhibitory concentrations (MICs) were determined using the broth microdilution method. Genomic DNA was extracted and sequenced on the next generation sequencer. Drug-resistant factors were determined and the genetic environments surrounding carbapenemase and 16S rRNA methylase genes were analyzed. A phylogenetic tree was constructed using forty-six M. morganii subsp. morganii genome sequences, including the five isolates from Myanmar. Results: One isolate harbored both bla_NDM−1 and armA. This isolate was resistant to imipenem (MIC: 16 µg/ml) but susceptible to meropenem (MIC: 1 µg/ml). Whole genome sequencing revealed that bla_NDM−1 and armA were located in close proximity on the chromosome of M. morganii strain YGH122, with the genetic region flanked by the two IS26 elements. Twenty-four strains deposited in GenBank carry the identical IS26-flanked genetic structure. Conclusions: This is the first report of a clinical M. morganii isolate co-harboring bla_NDM−1 and armA in Myanmar. These genes located on chromosome with the genetic region flanked by the two IS26 elements. The presence of this structure suggests the possibility of horizontal co-transfer of these resistance genes from other Enterobacterales, such as Escherichia coli and Klebsiella pneumoniae.