Evaluation of Drug Resistance Pattern and Molecular Detection of ISAba1 and ISAba2 in Acinetobacter baumannii Strains Isolated from Hospitalized Patients

Background and purpose: Acinetobacter species have emerged as major causes of nosocomial infections. Acinetobacter baumannii, the most common clinical subspecies, can cause a wide range of nosocomial infections, including pneumonia, bloodstream infections, and wound infections. These infections are often associated with high mortality rates due to the increasing prevalence of drug resistance among these bacteria. The production of β-lactamases is a significant mechanism of resistance to β-lactams. The transcription of these β-lactamase genes is enhanced by various insertion sequences (ISs) located nearby. The insertion sequences most commonly associated with carbapenem genes in multidrug-resistant Acinetobacter baumannii isolates are ISAba1, ISAba2, ISAba3, ISAba4, and IS18. This study aimed to evaluate the drug resistance patterns and molecular detection of ISAba1 and ISAba2 insertion sequences in A. baumannii isolates recovered from hospitalized patients in Sari teaching hospitals. Materials and methods: This study was conducted over six months, from March 2022 to August 2022, in Sari teaching hospitals. Ninety A. baumannii isolates were collected from various clinical specimens of hospitalized patients. To confirm the species of A. baumannii, various phenotypic tests such as TSI, oxidase, MR/VP, OF, urea, citrate, and SIM were employed. The antibiotic susceptibility pattern of the isolates was evaluated using the disk diffusion method according to the CLSI 2021 guidelines. The minimum inhibitory concentration (MIC) of colistin was determined using the micro broth method. To evaluate the presence of ISAba1 and ISAba2 genes, the Polymerase Chain Reaction (PCR) method was performed using specific primers. Data were analyzed using SPSS version 22 software. The chi-square test was used to determine significant differences, with a P-value less than or equal to 0.05 considered statistically significant. Results: The results of this study showed that A. baumannii isolates had a high level of resistance to several antibiotics, including ciprofloxacin, imipenem, doripenem, cefepime, ceftazidime, piperacillin/tazobactam, and piperacillin, with all isolates (100%) being resistant to these antibiotics. However, the highest susceptibility was observed for the antibiotic colistin (98.8%). Additionally, the frequencies of ISAba1 and ISAba2 genes among the isolates were 95.5% and 81.1%, respectively, indicating a high prevalence of these genetic elements among the study isolates. Conclusion: The results of this study indicate a high susceptibility of isolates to the antibiotic colistin, but due to the risk of resistance development and nephrotoxicity, it should be used with caution. The findings suggest that the presence of insertion elements such as ISAba1 and ISAba2 plays a significant role in increasing the expression of drug-resistance genes and their transfer in Acinetobacter baumannii. This can help explain the high prevalence of drug resistance in these bacteria and highlights the importance of detecting and controlling these factors to reduce nosocomial infections. Therefore, identifying and controlling these factors can be an effective step in improving prevention and treatment methods for infections caused by A. baumannii.