Fluoroquinolone resistance conferred by gyrA, parC mutations, and AbaQ efflux pump among Acinetobacter baumannii clinical isolates causing ventilator-associated pneumonia

Area of Science:

• Microbiology
• Infectious Diseases
• Antimicrobial Resistance

Background:

• Acinetobacter baumannii is a critical nosocomial pathogen, frequently implicated in ventilator-associated pneumonia (VAP).
• High rates of antimicrobial resistance in A. baumannii complicate treatment and infection control.
• Understanding resistance mechanisms is crucial for managing VAP caused by this pathogen.

Purpose of the Study:

• To characterize quinolone resistance mechanisms in A. baumannii isolates from VAP patients.
• To investigate the prevalence of the novel abaQ gene in these isolates.
• To identify new mutations conferring quinolone resistance.

Main Methods:

• Genotypic analysis of mutations in gyrA and parC genes.
• Investigation of qnrA, qnrB, qnrS, and abaQ gene presence.
• Phenotypic characterization of drug resistance patterns.

Main Results:

• Twenty-one A. baumannii isolates were analyzed, with 76.2% exhibiting extensively drug-resistance (XDR) and 4.8% pandrug-resistance (PDR).
• All isolates demonstrated high-level ciprofloxacin resistance; qnrA, qnrB, and qnrS genes were absent.
• Co-occurrence of gyrA (Ser81Leu) and parC (Ser84Leu) mutations with the abaQ gene was observed for the first time.
• A novel gyrA mutation (Arg89Cys) was detected in two isolates.

Conclusions:

• The study identified novel quinolone resistance mechanisms in A. baumannii associated with VAP.
• The emergence of XDR and PDR A. baumannii strains poses a significant clinical threat.
• The findings underscore the need for enhanced surveillance and novel therapeutic strategies against resistant A. baumannii.