Clinical Molecular and Genomic Epidemiology of Morganella morganii in China

Objectives: Ongoing acquisition of antimicrobial resistance genes has made Morganella morganii a new clinical treatment challenge. Understanding the molecular epidemiology of M. morganii will contribute to clinical treatment and prevention. Methods: We undertook a 6-year clinical molecular epidemiological investigation of M. morganii from three tertiary hospitals in China since 2014. Antimicrobial susceptibility testing was performed using a VITEK-2 system. All isolates were screened for beta-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 all M. morganii isolates (n = 335), forty (11.9%) were recognized as multidrug resistant strains. qnrD1, aac(6')-Ib-cr, bla(TEM-104), and bla(CTX-M-162) were 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 a bla(OXA-181)-carrying IncX3 plasmid and a Proteus genomic island 2 variant carrying bla(CTX-M-3), aac(6')-Ib-cr coexisted in the same multidrug resistant strain zy_m28. Additionally, a bla(IMP-1)-carrying IncP-1 beta type plasmid was found in the strain nx_m63. Conclusion: This study indicates a clade of M. morganii is prone to acquire resistance genes, and multidrug resistant M. morganii are increasing by harboring a variety of MGEs including two newly discovered ones in the species. We should be vigilant that M. morganii may bring more extensive and challenging antimicrobial resistance issue.

Automated summary

The study revealed that a clade of M. morganii is prone to acquiring resistance genes, leading to an increasing number of multidrug resistant strains with a variety of mobile genetic elements (MGEs), including two newly discovered ones in the species. This highlights the potential for M. morganii to pose a more extensive and challenging antimicrobial resistance issue.