• Comparative Study of Antibiotic Resistance Patterns in Acinetobacter baumannii Isolates from Intensive Care Unit and Non-Intensive Care Unit Wards in a Hospital in Tehran, 2025
  • Mahboobeh Nazarpoor,1,* Sara Minaeian,2 sara saeidifar,3
    1. Antimicrobial Resistance Research Center, Institute of Immunology and Infectious Diseases, Iran University of Medical Sciences, Tehran, iran
    2. Antimicrobial Resistance Research Center, Institute of Immunology and Infectious Diseases, Iran University of Medical Sciences, Tehran, iran
    3. Antimicrobial Resistance Research Center, Institute of Immunology and Infectious Diseases, Iran University of Medical Sciences, Tehran, iran


  • Introduction: Acinetobacter baumannii is an important cause of nosocomial infections and a higher burden of resistant cases, especially carbapenem-resistant (CRAB) infections, is reported in intensive care units (ICUs) [1,2]. Clinical evidence from Iran also shows that carbapenem-resistant cases in ICUs are associated with more adverse outcomes, including increased mortality [2]. On the other hand, global systematic reviews have reported that colistin resistance is lower on average worldwide, but heterogeneity between countries is high and high levels are seen in some regions [3]; also, the trend of increasing resistance to carbapenems has been confirmed over the past two decades [4]. The aim of this study is to report descriptively the pattern of drug resistance in A. baumannii isolates and compare it between ICU and non-ICU samples.
  • Methods: This descriptive cross-sectional study was conducted on 40 non-duplicate isolates of A. baumannii (ICU = 31; 77.5% and non-ICU = 9; 22.5%). Bacterial identification and antimicrobial susceptibility testing were performed by disk diffusion (antibiogram) according to the Kirby–Bauer method. Thirteen antibiotics were evaluated: colistin; piperacillin–tazobactam (TZP); tetracycline (TET); cefepime (FEP); amikacin (AMK); ceftazidime (CAZ); cefotaxime (CTX); trimethoprim–sulfamethoxazole (TMP-SMX); ampicillin–sulbactam (SAM); doxycycline (DOX); gentamicin (GEN); imipenem (IPM); and ciprofloxacin (CIP). Owing to the limited number of non-ICU cases, between-ward comparisons were reported solely in descriptive form, and inferential statistical testing was omitted.
  • Results: In the total of 40 isolates, resistance across several antimicrobial classes was very high: for TZP, TET, FEP, CAZ, CTX, IPM, and CIP, resistance was 97.5% (39/40) each. Resistance rates were AMK = 87.5% (35/40), TMP-SMX = 92.5% (37/40), SAM = 95% (38/40), GEN = 95% (38/40), and DOX = 82.5% (33/40). Colistin showed the lowest resistance: 42.5% (17/40). Given that 77.5% of the samples were obtained from the ICU, the overall picture indicates a narrowing of therapeutic options in the ICU and the limited effectiveness of many first-/second-line agents. This pattern is consistent with reports from Iran (higher risk in the ICU and worse outcomes in CRAB) and with global reviews (heterogeneity in colistin resistance and an increasing trend in carbapenem resistance) [2–4].
  • Conclusion: This study showed that A. baumannii isolates were predominantly recovered from the ICU and exhibited very high resistance to most antimicrobial classes; only resistance to colistin was relatively lower, although even this level is clinically important. Based on the available evidence, three practical recommendations are proposed: 1. strengthen infection control in the ICU (effective isolation, strict hand hygiene, and careful management of invasive devices); 2. implement antibiotic stewardship grounded in the hospital’s own resistance profile (antibiogram) and avoid prescribing agents that have shown low effectiveness [1]; 3. regularly monitor susceptibility patterns—especially for carbapenems and colistin—and update treatment protocols periodically. Due to the small size of the non-ICU group, future studies should conduct statistical comparisons with more balanced sampling.
  • Keywords: Acinetobacter baumannii; β-lactam antibiotics; antibiotic resistance; Drug Resistance, Multiple