Molecular mechanisms of resistance in Morganella morganii with exclusive resistance to imipenem: Whole genome sequencing analysis of 12 clinical isolates.

BACKGROUND

Morganella morganii (M. morganii) is a significant opportunistic pathogen, increasingly linked to infections with high mortality rates.

OBJECTIVE

This study aimed to explore the resistance mechanisms and molecular profiles of 12 clinical M. morganii isolates exclusively resistant to imipenem, employing whole genome sequencing (WGS) to guide infection prevention and control strategies.

METHODS

A retrospective analysis of 12 isolates from a tertiary hospital, collected between May 2014 and March 2023, was conducted, incorporating strain identification and antimicrobial susceptibility testing. Genomic data were acquired via WGS, followed by gene analysis and replicon typing using Abricate. A broader epidemiological assessment of 227 Morganella isolates was performed using Snippy, Gubbins, and FastTree, leading to the construction of a phylogenetic tree to delineate evolutionary relationships.

RESULTS

Three M. morganii isolates were identified as exclusively imipenem-resistant, while remaining susceptible to meropenem and ertapenem, each harboring carbapenemase resistance genes, bla, bla, and bla, respectively. Replicon type analysis revealed that isolate GK07 carried two replicons: IncL/M(pOXA-48)_1_pOXA-48 and IncX8_1.

CONCLUSION

These findings suggest that selective imipenem resistance in M. morganii may be associated with carbapenemase genes and the potential for plasmid-mediated horizontal transmission of resistant clones. The results highlight the need for continuous monitoring of resistance gene dissemination across hosts, targeted interventions to curb resistant clone spread, and sustained vigilance regarding global epidemiological trends.