Molecular Detection of blaOXA and qnrS Resistance Determinants and Clinical Predictors in Multidrug-Resistant Acinetobacter baumannii and Enterobacter cloacae

Abdalkader Saeed  Latif

Authors

Abdalkader Saeed Latif Polymers Research Unit, College of Science, Mustansiriyah University, Baghdad, Iraq

Keywords:

antimicrobial resistance, blaOXA carbapenemase, qnrS, Acinetobacter baumannii, Enterobacter cloacae, molecular epidemiology

Abstract

Background: Carbapenem-resistant Acinetobacter baumannii and quinolone-resistant Enterobacter cloacae are designated critical-priority pathogens by the World Health Organization. Data on the molecular drivers of resistance and their clinical predictors in Iraq remain limited. We determined the prevalence of the blaOXA carbapenemase and qnrS plasmid-mediated quinolone-resistance determinants, their clinical predictors, and their phylogenetic relationship to regional strains. Methods: In this cross-sectional study, 120 non-duplicate clinical isolates (60 A. baumannii, 60 E. cloacae) were collected from 120 patients. Species identification used automated systems and antimicrobial susceptibility testing followed CLSI M100 (36th ed.). The blaOXA and qnrS genes were detected by validated real-time PCR (efficiency 90–110%, R² > 0.99) and confirmed by Sanger sequencing. Independent predictors of gene carriage were identified by multivariable logistic regression. Sequences were compared with regional strains by BLASTn and neighbour-joining phylogenetics. Results: blaOXA predominated in A. baumannii (65% vs 20%; p < 0.001), whereas qnrS predominated in E. cloacae (45% vs 17%; p = 0.002); gene co-existence occurred in 9.2% of isolates. Prior antibiotic use (adjusted OR 3.8, 95% CI 1.9–7.6), ICU stay > 7 days (OR 2.9, 1.4–6.1) and recurrent urinary-tract infection (OR 2.6, 1.2–5.5) were independent predictors of gene carriage. Iraqi sequences clustered tightly with Iranian, Turkish, Jordanian and Egyptian strains (98.4–99.1% nucleotide identity). Conclusions: MDR A. baumannii and E. cloacae in Iraq carry a high burden of blaOXA and qnrS determinants embedded in a regional dissemination network. Modifiable healthcare-associated exposures predict gene carriage, supporting targeted antimicrobial stewardship and molecular surveillance.

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