Mechanism of polymyxin resistance related to lipopolysaccharide modification in carbapenem-resistant Klebsiella pneumoniae
10.3760/cma.j.cn112309-20230106-00007
- VernacularTitle:耐碳青霉烯类肺炎克雷伯菌脂多糖修饰相关的多黏菌素耐药机制研究
- Author:
Xindi ZHANG
1
;
Yan DU
;
Min NIU
Author Information
1. 昆明医科大学第一附属医院医学检验科，云南省检验医学重点实验室，云南省医学检验临床医学研究中心，昆明 650032
- Keywords:
Carbapenem-resistant Klebsiella pneumoniae;
Polymyxin;
Drug resistance mechanism;
Lipopolysaccharide;
Two-component regulatory system
- From:
Chinese Journal of Microbiology and Immunology
2023;43(6):442-450
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To investigate the mechanism of polymyxin resistance related to lipopolysaccharide modification in carbapenem-resistant Klebsiella pneumoniae (CRKP). Methods:Plasmid-mediated drug resistance genes in seven CRKP strains were detected by conjugation assay and mcr gene detection. The expression of polymyxin resistance-related genes was measured using quantitative real-time PCR. The complete genomes of CRKP strains were sequenced. Silver staining and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS) were performed to analyze the changes in lipopolysaccharide (LPS). Results:The seven CRKP strains were negative for mcr genes and the results of conjugation assay were also negative. Moreover, no mobile genetic elements related to drug resistance were detected. Compared with wild-type strain, all seven CRKP strains that were resistant to polymyxin showed increased expression of pmrA, pmrB and pmrC genes at the transcriptional level; six showed increased expression of phoP/ phoQ genes; three showed decreased expression of crrA/ crrB genes; four showed decreased expression of mgrB gene. The missense mutation sites in drug-resistant strains were mainly in KPHS_09430, KPHS_35900, KPHS_39520 and KPHS_52420. IS Kpn14 insertion sequence was detected in CRKP-6 strain. MALDI-TOF-MS reveals the modification of natural lipid A with L-Ara4N in CRKP LPS. Conclusions:LPS modification induced by chromosome-mediated mutation in the two-component regulatory system was the main molecular mechanism of polymyxin resistance in CRKP isolates in this study. Effects of the mutation in the two-component system on polymyxin resistance varied in different strains.
