Molecular Characterization of Aminoglycoside Resistance Genes aphA1, aphA6, and armA in Clinical Isolates of Acinetobacter baumannii

Document Type : New and original researches in the field of Microbiology.

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Department Genetic Engineering, Institute of Genetic Engineering and Biotechnology for Postgraduate Studies, University of Baghdad, Baghdad, Iraq

10.21608/ejmm.2025.379338.1593

Abstract

Background: Acinetobacter baumannii is a major nosocomial pathogen with increasing multidrug resistance, particularly to aminoglycosides. Aminoglycoside resistance in A. baumannii is primarily mediated by genes encoding aminoglycoside-modifying enzymes (AMEs) such as aphA1 and aphA6, as well as 16S rRNA methylases such as armA. Objective This study aimed to determine the prevalence and expression levels of aphA1, aphA6, and armA in A. baumannii clinical isolates and correlate these with aminoglycoside-resistant phenotypes. Methodology: Two hundred clinical samples were collected from diverse sources (sputum, wounds, burns, urine, and blood). Twenty A. baumannii isolates were identified and confirmed by biochemical tests, VITEK-2, and 16S rRNA PCR. Antibiotic susceptibility and minimum inhibitory concentration (MIC) were assessed using the VITEK 2 system. Gene detection was performed using PCR, and RT-qPCR was used to evaluate the expression levels normalized to 16S rRNA. Results: The isolates exhibited high resistance to aminoglycosides amikacin (90%), gentamicin, and tobramycin (85%). All isolates were multidrug-resistant (MDR), with 75% classified as extensively drug-resistant (XDR). gene prevalence was aphA1 (45%), aphA6 (65%), and armA (55%). RT-qPCR revealed significant upregulation (P ≤ 0.01) of these genes in resistant isolates, Conclusion: This study elucidated the critical role of aminoglycoside resistance genes (aphA1, aphA6, and armA) in mediating resistance phenotypes in A. baumannii.

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