Clinical Molecular and Genomic Epidemiology of Morganella morganii in China

Objectives:Ongoing acquisition of antimicrobial resistance genes has madeMorganella morganiia new clinical treatment challenge. Understanding the molecular epidemiology ofM. morganiiwill contribute to clinical treatment and prevention. Methods:We undertook a 6-year clinical molecular epidemiological investigation ofM. morganiifrom three tertiary hospitals in China since 2014. Antimicrobial susceptibility testing was performed using a VITEK-2 system. All isolates were screened for β-lactam and plasmid-mediated quinolone resistance genes by PCR. Isolates carrying carbapenem-resistant genes were subjected to whole-genome sequencing (WGS). The variation and evolution of these mobile genetic elements (MGEs) were then systematically analyzed. Results:Among allM. morganiiisolates (n= 335), forty (11.9%) were recognized as multidrug resistant strains.qnrD1,aac(6′)-Ib-cr,blaTEM–104, andblaCTX–M–162were the top four most prevalent resistance genes. Notably, phylogenomic and population structure analysis suggested clade 1 (rhierBAPS SC3 and SC5) associated with multiple resistance genes seemed to be widely spread. WGS showed ablaOXA–181-carrying IncX3 plasmid and aProteusgenomic island 2 variant carryingblaCTX–M–3,aac(6′)-Ib-crcoexisted in the same multidrug resistant strain zy_m28. Additionally, ablaIMP–1-carrying IncP-1β type plasmid was found in the strain nx_m63. Conclusion:This study indicates a clade ofM. morganiiis prone to acquire resistance genes, and multidrug resistantM. morganiiare increasing by harboring a variety of MGEs including two newly discovered ones in the species. We should be vigilant thatM. morganiimay bring more extensive and challenging antimicrobial resistance issue.