Phenotypic characteristics and plasmid structure differences between ST11 carbapenem-resistant Klebsiella pneumoniae...

Hypervirulent carbapenem-resistant Klebsiella pneumoniae (HCKP) strains cause infections of extremely high morbidity and mortality, and pose a great threat to public health. The number of reports of HCKP has increased in recent years. However, phenotypic characteristics, and structural features of the resistance and virulence plasmids carried by different geographic strains of HCKP may vary. We collected 18 carbapenem-resistant Klebsiella pneumoniae (CRKP) strains, including nine HCKP and nine non-HCKP (refers to carbapenem-resistant but non-hypervirulent Klebsiella pneumoniae) strains from a tertiary teaching hospital in Yunnan. Antimicrobial susceptibility tests showed that 18 strains exhibited high resistance to common clinical antibiotics. Diverse hypervirulence factors and resistance genes were identified, including iucA, iroN, iutA, entA, entB, fepA, fepB, iroE, irp1, irp2, ybtQ, ybtS, peg-344, rmpA, rmpA2, wcaJ, mrkA, mrkB, fimA, fimB, ureA, uge, wabG, bla _SHV-12, bla _TEM-1, bla _KPC-2, sul1, tet(A) and tet(R). All strains were of the ST11 type. KL64 and KL47 capsular serotypes were identified, with KL64 being the most prevalent type. The siderophore production ability of HCKP was higher than that of non-HCKP. Pulsed field gel electrophoresis (PFGE) separated five PFGE clusters among HCKP strains and seven among non-HCKP strains. Plasmid sequencing showed that the virulence plasmid featured a novel structure, with deletion of the iroBCD but retention of the iroN. The HCKP strain carried 4-6 plasmids, among which the structure of the pLVPK-like and bla _KPC-2-bearing plasmid were relatively conserved, especially the sequences surrounding the hypervirulence and bla _KPC-2 genes. Furthermore, the HCKP strains also harbored a drug-resistant conjugative plasmid with a highly conserved structure. The non-HCKP strains contained 2-4 plasmids, and the structure of the bla _KPC-2-bearing plasmid showed high genetic diversity, with resistance factors flanked by the multiple insertion sequences, transposons and integrons. In the mouse intraperitoneal infection model, it was proved that the representative HCKP-67 strain showed stronger pathogenicity than CRKP-144 indicating that the distinction between HCKP and non-HCKP was correct. The implementation of effective prevention and control measures is urgently required to prevent further dissemination of such organisms.