Multidrug-Resistant Strains of Acinetobacter baumannii from Intensive Care Unit Patients Show Genetic Diversity and Distribution of Genes Associated with Aminoglycoside Resistance

Background and Objective: As a significant cause of nosocomial infections, Acinetobacter baumannii has been linked to opportunistic infections. The assessment of clonal relatedness of A. baumannii isolates using typing methods like ERIC-PCR is beneficial for controlling conditions due to these resistant isolates. This research aims to study Acinetobacter baumannii resistant isolates to multidrug using typing methods like ERIC-PCR in clinics of Zanjan city. Materials and Methods: In all, one hundred immunocompromised patients in ICU were included in the study and isolates of A. baumannii were extracted from their samples, and molecular typing using ERIC-PCR was performed on patients who were positive for aminoglycoside resistance-related genes (aph(2'')-Id, ant(4'')-Ia, ant(3'')-I, aac(6'')-Ib, aac(3)-I, aph(3'')-I, aph(2'')-Ib and aph (2'')-Ic). 67% of isolates had gentamicin resistance, and 63% had tobramycin resistance. Results: The isolates tested positive for multidrug resistance (MDR) were all labeled as MDR strains. Furthermore, all antibiotics tested were ineffective against 32% of the isolates, while 91% could be deemed extensively drug-resistant (XDR). The aminoglycoside resistance gene aac(6′)-Ib accounted for 79% of the cases, followed by ant(3'')-I and aph(2'')-Id (47%). Sixty-four percent of the isolates carried three or more aminoglycoside resistance genes simultaneously. A total of six types and 20 subtypes of patterns were obtained from ERIC-PCR. Conclusion: In this study, aminoglycoside-resistant A. baumannii was found in a high percentage of ICU patients, mainly with the enzyme-modified aminoglycosides like aac(6′)-Ib, aph(2'')-Id and ant(3'')-I. ERIC-PCR has also shown an increased level of diversity in A. baumannii isolates. Therefore, genetic diversity or clonal relatedness of A. baumannii isolates in clinical settings can be assessed using ERIC-PCR.