The role of APH (۳′)-VIa and ANT (۲")-Ia enzymes in increasing the minimum inhibitory concentration of aminoglycosides against clinical isolates of Acinetobacter baumannii

BACKGROUND AND OBJECTIVESAcinetobacter baumannii, is an opportunistic pathogen known for causing a variety of infections in humans. Aminoglycosides are the significant antibiotics to treatment the infections caused by Acinetobacter baumannii. This study aimed to determine the role of genes encoding aminoglycoside-modifying enzymes (AMEs) in increasing the minimum inhibitory concentration of aminoglycosides against clinical isolates of A. baumannii.MATERIALS AND METHODSThis study was performed on A. baumannii isolated from the patients. We collected ۱۰۰ clinical isolates of A. baumannii and identified by microbiological standard tests. The presence of APH (۳′)-VIa (aphA۶) and ANT (۲")-Ia (aadB), AME encoding genes, was detected by PCR method .RESULTS AND DISCUSSIONThe most effective aminoglycosides in this study were netilmicin with ۶۸% resistance rate, while ۹۴% of the isolates were resistant against gentamicin, kanamycin, tobramycin, and streptomycin. Also, ۷۷% and ۷۳% of the A. baumannii clinical isolates in this study were contained the aphA۶ and aadB genes. However, ۳۹ A. baumannii isolates contained simultaneously both aphA۶ and aadB genes. Among them, (۹۷.۴%), (۹۷.۴%), (۸۷.۱%), (۹۴.۸%), (۱۰۰%), (۸۴.۶%), and (۸۲%) isolates were non-susceptible to gentamicin, tobramycin, amikacin, netilmicin, kanamycin, streptomycin, and spectinomycin, respectively. In addition, among ۷۷ isolates containing the aphA۶ gene, (۸۷.۰۱%), (۹۲.۲%), (۷۴.۰۲), (۶۴.۹۳%), (۸۸.۳۱%), (۹۳.۵), and (۷۶.۶۲%) isolates showed a MIC range of ≥ ۲۵۶ μg/ml, respectively. However, among ۷۳ isolates carrying the aadB gene, (۹۵.۸۲%), (۹۳.۱۵%), (۶۵.۷۵%), (۶۵.۷۵%), (۸۷.۶۷%), (۹۴.۵۲%), and (۸۶.۳%) isolates exhibited this MIC range .The analysis of AMEs encoding genes in this study revealed a significant occurrence of aphA۶ and aadB genes, aligning with previous research conducted in Iran.CONCLUSIONHigh-level aminoglycoside MIC ranges in isolates with the simultaneous presence of AME encoding genes indicated the importance of these genes in resistance to aminoglycosides .

کلیدواژه ها:

Acinetobacter baumannii ، Aminoglycoside Modifying Enzymes ، Aminoglycoside resistance.