Carbapenem-Resistant Klebsiella Pneumoniae  in Southwest China: Molecular Characterizations and Risk Factors Caused by NDM and KPC Producers

Background: Klebsiella pneumoniae is one of the most common Enterobacteriaceae . In recent years, carbapenem-resistant Klebsiella pneumoniae (CRKP) has become one of the most important carbapenem-resistant Enterobacteriaceae . CRKP are usually resistant to antibiotics. Up to this day, the emergence of carbapenemase-producing K. pneumoniae has been a challenge for treatment of clinical infection. Methods: : (i) 66 non-repetitive clinical CRKP isolates were identified by matrix-assisted laser analytical ionization time-of-flight mass spectrometer (MALDI-TOF-MS) and drug sensitivity analysis was performed by Vitek2 Compact. EDTA-synergy test and mCIM / eCIM test were used to detect drug-resistant phenotypes. (ii) Carbapenemase genes, extended-spectrum β-lactamase genes (ESBLs), cephalosporinase gene (AmpC), virulence genes, integron and resistance gene cassettes were amplified by PCR. (iii) Plasmid typing was performed by plasmid conjugation assay and PCR-based replicon typing (PBRT) method. (iv) The genetic environments of KPC-2 and NDM-1 were analyzed by using overlapping PCR. (v) MLST was used to analyze the molecular epidemiological characteristics of CRKP. (vi) Risk factors of CRKP infection by logistic regression model. Results: : Our study revealed that 42 of the 66 CRKP isolates obtained from patients were identified as bla KPC-2 , 24 bla NDM-1 -positive strains were identified (20 bla NDM-1 and 4 bla NDM-5 ), of which 18 were from the neonatal departments. And CRKP strains were ESBL (extended-spectrum β-lactamases) and AmpC enzymes producer, Notably, we found two CR-hvKp (carbapenem-resistant hypervirulent klebsiella pneumoniae ) strains, which contains bla KPC-2 gene and other resistant genes. Two of the 42 KPC-2-producing CRKP strains were positive for transconjugants, and the plasmid typing was the IncFII type. And two NDM-producing CRKP strains tested positive for transconjugants, which belonged to the lncX3 plasmid. Analysis of the genetic environment of these two genes has revealed that the highly conserved regions ( tnpA - tnpR -IS kpn8 - bla KPC-2 ) and conserved regions ( bla NDM−1 - ble MBL -trpF - tat ) are associated with the dissemination of KPC-2 and NDM-1. Intl1 carrying drug resistance gene cassettes were widely distributed in CRKP. According to the MLST results, a total of 13 ST types were measured in 66 CRKP strains, ST11 and ST4495 were the main ST types, and the latter was the newly discovered ST type. Hematological disease, tracheal cannula and prior use of β-lactams and β-lactamase inhibitor combination were identified as independent risk factors for CRKP infections. Conclusion: These findings manifested the need for intensive surveillance and precautions to monitor the further spread of KPC and NDM in southwest China.