Resistance of Klebsiella pneumoniae Strains Carrying bla NDM-1 Gene and the Genetic Environment of bla NDM-1

Tianxin Xiang; Chuanhui Chen; Jiangxiong Wen; Yang Liu; Qi Zhang; Na Cheng; Xiaoping Wu; Wei Zhang

doi:10.3389/fmicb.2020.00700

Resistance of Klebsiella pneumoniae Strains Carrying bla _NDM-1 Gene and the Genetic Environment of bla _NDM-1

Front Microbiol. 2020 Apr 30:11:700. doi: 10.3389/fmicb.2020.00700. eCollection 2020.

Authors

Tianxin Xiang¹, Chuanhui Chen², Jiangxiong Wen³, Yang Liu¹, Qi Zhang¹, Na Cheng³, Xiaoping Wu³, Wei Zhang²

Affiliations

¹ Department of Hospital Infection Control, The First Affiliated Hospital of Nanchang University, Nanchang, China.
² Department of Respiratory and Critical Care, The First Affiliated Hospital of Nanchang University, Nanchang, China.
³ Department of Infectious Disease, The First Affiliated Hospital of Nanchang University, Nanchang, China.

Abstract

Objective: Regional dissemination is the major cause of the widespread prevalence of a plasmid-encoding NDM-1 enzyme. We investigated the drug resistance, joint efficiency, and gene environment of a Klebsiella pneumoniae strain carrying bla _NDM-1 gene.

Materials and methods: Carbapenem-non-susceptible strains were analyzed using the VITEK 2 Compact. Strains carrying bla _NDM-1 were identified using polymerase chain reaction and sequencing. Antimicrobial susceptibility testing and plasmid conjugation experiments were then conducted. Strains carrying bla _NDM-1 were subjected to Southern blot analysis. After the gene mapping of bla _NDM-1, library construction, and sequencing, plasmids were subsequently spliced and genotyped using the software Glimmer 3.0, and then analyzed using Mauve software.

Results: Among 1735 carbapenem-non-susceptible strains, 54 strains of bla _NDM-1-positive bacteria were identified, which consisted of 44 strains of K. pneumoniae, 8 strains of Acinetobacter baumannii and 2 strains of Escherichia coli. Strains carrying bla _NDM-1 had a resistance rate of more than 50% in most antibiotics. Plasmid conjugation between strains carrying bla _NDM-1 and E. coli strain J53 had a success rate of 50%. Southern blot analysis indicated that each strain had multiple plasmids containing bla _NDM-1. Among the five plasmids containing bla _NDM-1 in K. pneumoniae for sequencing, two plasmids with complete sequences were obtained. The findings were as follows: (i) The p11106 and p12 plasmids were highly similar to pNDM-BTR; (ii) the p11106 and p12 plasmids showed differences in the 20-30 kb region (orf00032-orf00043) from the other six plasmids; and (iii) bla _NDM-1 was located at orf00037, while ble was found at orf00038. Two tnpA genes were located in the upstream region, and orf00052 (tnpA) in the 36 kb region was in the downstream sequence.

Conclusion: bla _NDM-1-containing bacteria exhibit multidrug resistance, which rapidly spreads and is transferred through efficient plasmid conjugation; the multidrug resistance of these bacteria may be determined by analyzing their drug-resistant plasmids. The presence of ble and tnpA genes suggests a possible hypothesis that bla _NDM-1 originates from A. baumannii, which is retained in K. pneumoniae over a long period by transposition of mobile elements.

Keywords: Klebsiella pneumoniae; NDM-1; carbapenem resistance; genetic characteristics; plasmid.