Plasmid transferability of KPC into a virulent K2 serotype Klebsiella pneumoniae

Background: KPC-producing carbapenem-resistant Klebsiella pneumoniae (CRKP) infections are associated with high mortality; however, their virulence determinants are not well defined. Methods: We investigated the virulence and plasmid transferability among KPC-containing K. pneumoniae isolates. Results: KPC-2 and -3 were successfully conjugated and retained by a virulent K2 K. pneumoniae recipient isolate. Antimicrobial susceptibility testing showed KPC-2 and -3 donor strains were resistant to more than four classes of antibiotics while the K2 isolate was only initially resistant to ampicillin. After conjugation of KPC-2 and -3, the K2 K. pneumoniae transconjugants became resistant to all beta-lactams. Additionally, the KPC K2 K. pneumoniae transconjugants continued to retain its high serum resistance and murine lethality. Conclusions: Conjugation and retainment of KPC by virulent K2 K. pneumoniae and the ability of the tranconjugants to maintain its high serum resistance and murine lethality after conjugation was demonstrated in this study. These findings are concerning for the potential of KPC-like genes to disseminate among virulent K. pneumoniae isolates.