Identification of a Chromosomal Integrated DNA Fragment Containing the rmpA2 and iucABCDiutA Virulence Genes in Klebsiella pneumoniae

Klebsiella pneumoniae is increasingly being regarded as a reservoir of diverse antibiotic resistance genes and a pathogen that causes severe infections in both the hospital and the community. In this study, we performed molecular characterization of a carbapenem-resistant and highly virulent K. pneumoniae strain recovered from a hospital patient. The virulence-encoding genes rmpA2 and iucABCDiutA were found to be located in the chromosome and are flanked by IS26 elements. These chromosomally located virulence genes, if not incurring fitness costs, are expected to be much more stable than plasmid-located genes. Detailed analysis of the fragment in which these virulence genes are located showed that the fragment can readily form a circular intermediate that may promote integration of this virulence-encoding fragment into various plasmid backbones and other chromosomal regions. Findings in this work provide new insights into mechanisms of transmission of virulence-encoding genes in K. pneumoniae. IMPORTANCE This study reported for the first time and characterized in detail the genetic features of a mobile virulence-encoding fragment located in the chromosome of a clinical virulent K. pneumoniae strain and revealed the occurrence of a transposition event mediated by IS26. This genetic structure could mediate the transposition of the virulence-encoding fragment into various plasmid backbones and chromosomes through formation of a circular intermediate. Therefore, findings in this work provide important insights into the transmission mechanisms of mobile virulence profiles in K. pneumoniae strains and lay the foundation for devising effective intervention approaches aimed at preventing the dissemination of these virulence-encoding elements.