Prevalence of QnrA Gene in Phenotypic ESBL-Producing Acinetobacter baumannii from high vaginal swabs in selected wards of a Nigerian tertiary hospital

Background: Acinetobacter baumannii has emerged as a significant opportunistic pathogen associated with healthcare-associated infections, particularly in resource-limited settings. The increasing prevalence of extended-spectrum beta-lactamase (ESBL) production coupled with plasmid-mediated quinolone resistance (PMQR) genes poses therapeutic challenges. This study investigated the prevalence of the QnrA gene among all phenotypic ESBL-producing A. baumannii isolated from high vaginal swabs (HVS) in selected wards of a Nigerian tertiary hospital.
Methods: A total of 130 high vaginal swab samples were collected from patients attending the Female Medical Ward (F/MED), Gynecology Ward (GYNED), and General Outpatient Department (GOPD) at Alex Ekwueme Federal University Teaching Hospital, Abakaliki, Nigeria. Acinetobacter baumannii was identified using standard microbiological methods. ESBL production was phenotypically confirmed using the double disk synergy test (DDST). All 20 phenotypic ESBL-producing A. baumannii isolates were subjected to genotypic detection of the QnrA gene by polymerase chain reaction (PCR) using specific primers. Antibiotic susceptibility testing was conducted using the Kirby-Bauer disk diffusion method.
Results: Out of 130 HVS samples, 22 (16.9 %) A. baumannii isolates were recovered, with the highest frequency in F/MED 13 (33.3 %), followed by GYNED 7 (10.3 %), and GOPD 2 (8.7 %). ESBL production was detected in 20 (90.9 %) isolates overall: 11(84.6 %) from F/MED, 7(100 %) from GYNED, and 2(100 %) from GOPD. PCR analysis revealed that 18 out of 20 ESBL-producing isolates (90 %) harbored the QnrA gene. The distribution of QnrA-positive isolates across wards was: 10 (90.9 %) from F/MED, 6 (85.7 %) from GYNED, and 2(100 %) from GOPD. All isolates carrying QnrA showed high-level resistance to ciprofloxacin (94.4 %). Gentamicin (100 % susceptible) and piperacillin-tazobactam (85 % susceptible) remained the most effective antibiotics.
Conclusion: This study reports an alarmingly high prevalence (90 %) of the QnrA gene among all ESBL-producing A. baumannii from high vaginal swabs in a Nigerian tertiary hospital. The co-occurrence of ESBL phenotypes and plasmid-mediated quinolone resistance severely limits therapeutic options and underscores the urgent need for enhanced antimicrobial stewardship and routine molecular surveillance in resource-limited settings.