Construction and pathogenicity analysis of Klebsiella pneumoniae vgrG-deficient strain
10.3760/cma.j.cn112309-20240715-00261
- VernacularTitle:肺炎克雷伯菌 vgrG基因缺失株的构建及其致病性分析
- Author:
Shuangyi XU
1
;
Xiaowei ZHANG
;
Yujia HAN
;
Xiaomei LI
;
Gang XU
Author Information
1. 扬州大学附属苏北人民医院/江苏省苏北人民医院整形烧伤外科，扬州 225001
- Publication Type:Journal Article
- Keywords:
Klebsiella pneumoniae;
Type Ⅵ secretion system;
Structural protein;
Pathogenicity
- From:
Chinese Journal of Microbiology and Immunology
2025;45(8):643-648
- CountryChina
- Language:Chinese
-
Abstract:
Objective:To investigate the role of the structural gene vgrG of the type Ⅵ secretion system (T6SS) of Klebsiella pneumoniae ( Kpn), and evaluate the growth ability in vitro and pathogenicity of the bacteria after vgrG was deleted. Methods:Using sequences published by the National Center for Biotechnology Information (NCBI), primers were designed to amplify the upstream and downstream homology arms of vgrG via PCR. These fragments were cloned into the vector pKO3-Km after overlapping, the recombinant vector pKO3-Km- vgrG was transferred into Kpn competent cells, and the vgrG deletion strain Δ vgrG was obtained through homologous recombination. The vgrG promoter with the complete gene fragment was amplify by PCR and cloned into the pBAD33 vector. The pBAD33- vgrG was then transferred into Δ vgrG competent cells to obtain the complemented strain CΔ vgrG. The wild-type strain (WT), Δ vgrG strain and CΔ vgrG strain were cultured in LB (Luria-Bertani) liquid medium to compare growth rates. Adhesion to human lung epithelial A549 cells and intracellular survival in macrophages Raw264.7 cells were assessed. In vivo experiments included mouse survival analysis ( n=10) and lung bacterial load quantification ( n=6). Statistical comparisons were performed using the Student t-test. Results:The Δ vgrG strain was obtained through homologous recombination. It was identified by specific primers that compared with the WT strain, the complete vgrG fragment (2 487 bp) was deleted. On this basis, the CΔ vgrG strain was obtained. Deletion of vgrG did not significantly affect Kpn growth in vitro growth ability of bacteria before on after Kpn deleted vgrG [(1.40±0.10) vs (1.20±0.30), t=0.63, P>0.05]. The viscosity of WT strain was significantly higher than that of the Δ vgrG strain [(0.96±0.04) vs (0.38±0.05), t=9.72, P<0.05], the viscosity of the CΔ vgrG strain was also significantly higher than that of the Δ vgrG strain ( P<0.05). At the cellular level, the amount of adherent bacteria of the WT strain to A549 cells was significantly greater than that of the Δ vgrG strain [(5 367.00±318.00) CFU vs (4 067.00±88.19) CFU, t=3.94, P<0.05], the amount of adherent bacteria of CΔ vgrG strain was also significantly higher than that of Δ vgrG strain ( P<0.05). After 12 h infection, the WT strain survival rate in macrophages was significantly higher than that of the Δ vgrG strain[(69.00±1.00)% vs (47.50±2.50)%, t=7.99, P<0.05]. At the animal level, the survival rate of WT strain group after lethal dose infection of mice was significantly lower than that of Δ vgrG strain group [(16.67±8.82)% vs (53.33±6.67)%, t=3.32, P<0.05]; mice infected with semi-lethal dose and the number of bacteria load in the lungs of WT strain group was significantly higher than that of the Δ vgrG strain group[ (4.97±0.06) lg CFU/g vs (4.05 ±0.04) lg CFU/g, t=12.27, P<0.01], the amount of bacteria in the lungs of mice in CΔ vgrG strain group was also significantly higher than that in Δ vgrG strain group ( P<0.01). Conclusions:The vgrG gene does not affect the growth of Kpn in vitro, but it is involved in the adhesion of Kpn to epithelial cells, resistance to macrophage killing and pathogenicity to mice.
