Abstract
INTRODUCTION: Carbapenem-resistant Enterobacterales (CRE) strains carrying bla (NDM) variants pose a significant threat to the health of infected patients worldwide. METHODS: This study isolated a carbapenem-resistant Escherichia coli (E. coli) strain carrying bla (NDM-80) from a patient in an intensive care unit in China. Antimicrobial susceptibility testing, whole-genome sequencing (WGS), plasmid transformation assay, cloning experiment, and steady-state kinetic determinations were performed to investigate antimicrobial susceptibility, the characteristics of the genetic environment, the mechanism of resistance gene transmission, resistance gene function, and antibiotic hydrolysis ability. RESULTS: The results indicated that E. coli carrying bla (NDM-80) showed significant resistance to all β-lactam antibiotics except for aztreonam, aztreonam-avibactam, and cefiderocol. WGS analysis revealed that the strain belonged to sequence type (ST) 155 and the O4:H51 serotype. The bla (NDM-80) was carried by an unconjugated plasmid, and its complete genetic structure was found to be IS5-bla (NDM-80)-ble-trpF-dsbD-IS26-nmuD-ISKox3. The bla (NDM-80) had single amino acid substitutions such as V88L, D130N, and M154L compared to bla (NDM-1), whereas it only had the D130N mutation compared to bla (NDM-5). The bla (NDM-80) and bla (NDM-5) had similar antimicrobial resistance profiles. However, in the absence of the native promoter, the minimum inhibitory concentrations (MICs) of bla (NDM-80) for imipenem, meropenem, cefepime, and cefiderocol were twice as high as those of bla (NDM-1). Steady-state kinetic determinations revealed that NDM-80 likely had higher hydrolytic activity against imipenem, meropenem, cefepime, and cefiderocol than NDM-1. DISCUSSION: This study is the first to report on the emergence of the bla (NDM-80) variant, shedding light on its functional mechanism. Our findings enrich the repertoire of NDM resistance genes and highlight the need for increased surveillance of pathogens harboring bla (NDM) variants.