Dissemination of [bla.sub.NDM-5] Driven by Horizontal Transfer of IncFIA Plasmid Between Escherichia coli and Klebsiella pneumoniae Co-Isolated from a Patient's Ascitic Fluid

Purpose: Understanding the horizontal transfer of resistance genes, such as [bla.sub.NDM-5], is pivotal in developing strategies to control the spread of resistance. In this study, we isolated two bacterial strains, Escherichia coli (designated GYB01) and Klebsiella pneumoniae (designated GYB02), from a single patient. The aim of our research is to explore the biological characteristics of these strains and to investigate the interspecies horizontal transfer of [bla.sub.NDM-5]. Materials and Methods: Strain identification and antimicrobial susceptibility testing were conducted using the Vitek 2 system. Both GYB01 and GYB02 were sequenced with the Illumina HiSeq platform. Bioinformatics analysis tools, including multilocus sequence typing, PlasmidFinder, ResFinder, and others, were utilized to analyze the strains. Additionally, conjugation assays and Galleria mellonella infection assays were employed to assess the strains. Results: The isolates exhibited similar antimicrobial resistance profiles and both harbored the [bla.sub.NDM-5] gene within the IncFIA plasmids (pGYB01-2, 165.8 kb and pGYB02-2, 211.6 kb, respectively). These plasmids (pGYB01-2 and pGYB02-2) shared over 99% homology, suggesting a common ancestral origin. Conjugation experiments confirmed the transferability of the [bla.sub.NDM-5] carrying IncFIA plasmids among Enterobacteriaceae. GYB02 possessed an iucACD-iutA gene cluster, exhibited high virulence, and tested positive in the string test. Conclusion: Our findings provide direct evidence of potential in vivo interspecies transfer of a multidrug-resistant plasmid, thus enriching our understanding of the mechanisms driving multidrug resistance (MDR) and aiding in the formulation of containment and treatment strategies. Keywords: CRE, NDM-5 carbapenemase, IncFIA plasmid, interspecies horizontal transfer