Background: Carbapenem-resistant Klebsiella pneumoniae  (CRKP) infection has attracted worldwide concern and became a serious challenge for clinical treatment. The aims of this study were to evaluate the molecular characteristics and risk factors for CRKP infection.
Methods: All the CRKP strains were screened for antimicrobial resistance genes, virulence genes, and integron by polymerase chain reaction (PCR). Plasmid typing was performed by plasmid conjugation assay and PCR-based replicon typing (PBRT). The genetic environments of bla _KPC-2 and bla _NDM-1 were analyzed by using overlapping PCR and molecular typing was performed by multi-locus sequence typing (MLST). Risk factors for CRKP infection were analyzed by logistic regression model.
Results: All the 66 CRKP isolates were multidrug-resistant, but all of them were susceptible to tigecycline and polymyxin B. Among the CRKP isolates, 42 bla _KPC-2-positive strains were identified carrying IncFII plasmids. Meanwhile, 24 bla _NDM-positive strains were found on lncX3 plasmids, including 20 bla _NDM-1 isolates and 4 bla _NDM-5 isolates. Most of CRKP isolates contained several virulence genes and the class I integron (intl1 ). The genetic environments of bla _KPC-2 and bla _NDM-1 revealed that the conserved regions (tnpA-tnpR -ISkpn8-bla _KPC-2) and (bla _NDM-1-ble _MBL-trpF-tat ) were associated with the dissemination of KPC-2 and NDM-1. ST11 was the most common type in this work. Hematological disease, tracheal cannula, and use of β-lactams and β-lactamase inhibitor combination were identified as independent risk factors for CRKP infection.
Conclusion: This study established the resistance pattern, molecular characteristics, clonal relatedness, and risk factors of CRKP infection. The findings of the novel strain that co-harboring bla _NDM-5 and bla _IMP-4, and the novel ST4495 indicated that the brand-new types have spread in Southwest China, emphasizing the prevent and control the further dissemination of CRKP isolates are highly needed.
Keywords: carbapenem-resistant Klebsiella pneumoniae , molecular characteristics, genetic environments, plasmid, risk factors