Abstract
The purpose of this study was to analyze the metallo-β-lactamases (MBLs) genotype and oprD mutations of the β-lactam antibiotic-resistant Pseudomonas aeruginosa (PA) strains isolated from southern China. We collected 110 strains of β-lactam antibiotic-resistant PA from 2 hospitals during January 2016–December 2017 from Dongguan, South China. MBLs were detected, amplified, and typed using EDTA disc synergy test, PCR, and Sanger gene sequencing. The mutations and expression levels of oprD were detected using Sanger gene sequencing and qPCR. A total of 16.36% (18/110) β-lactam antibiotic-resistant PA strains produced MBLs, and the main genotypes of MBLs were IMP-25, VIM-2, and SIM-2. Sanger gene sequencing results showed that 107 of the 110 strains harbored mutations in oprD sequence, while 3 strains were negative for oprD amplification (2.73%). Among the 107 strains with positive amplification (97.27%), the rate of intentional mutations (including deletions, insertions, and premature stop codons) was 93.46% (100/107) and that of no disrupted mutation was 6.54% (7/107). qPCR analysis confirmed that the expression level of the OprD protein in the 7 strains of no disrupted mutation was significantly reduced. Among the β-lactam antibiotic-resistant PA strains in southern China, 16.36% were positive for MBLs. The loss rate of oprD was 2.73%, and almost all PA strains showed oprD amplification variation or transcription downregulation. Thus, impaired oprD expression and MBLs production may be some of the mechanisms of β-lactam antibiotic-resistance of PA strains in southern China.
Highlights
Pseudomonas aeruginosa (PA) is a common opportunistic pathogen that can cause infections in immunocompromised patients or in patients with burns
The 110 strains of PA isolated from Dongguan were resistant to β-lactams, fluoroquinolones, tetracyclines, and sulfonamides
100%, 100%, 98.18%, 97.27%, and 96.36% of the isolates were resistant to imipenem, ampicillin, nitrofurantoin, compound sulfamethoxazole, and cefazolin, respectively
Summary
Pseudomonas aeruginosa (PA) is a common opportunistic pathogen that can cause infections in immunocompromised patients or in patients with burns. Since the 1990s, the incidence of clinical isolates of PA has increased [1]. Β-lactam antibiotics are one of the most commonly used antibiotics for treatment of PA infections. The use of antibiotics for a long time may increase the drug. MBLs can effectively hydrolyze β-lactams, including carbapenems, and aminoglycosides, and other antibiotics such as quinolones [5]. Various types of MBLs have been identified in PA, including IMP, VIM, SPM-1, GIM-1, SIM-1, NDM-1, and FIM-1. Outer membrane porins, like OprD, that uptake amino acids, peptides, and carbapenems undergo insertion, frameshift, and mutation-mediated gene inactivation or expression suppression, which can increase carbapenem resistance in PA [8,9,10,11]
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