Antibiotic Resistance Patterns of Gram-Negative Bacilli Isolated from Inpatients Admitted to Various Wards of a Tertiary Hospital in Tehran, Iran

Background: Hospital-acquired infections (HAIs), specifically those caused by gram-negative bacteria, are a significant public health concern with high mortality rates among patients worldwide, especially in developing countries. Objectives: This survey aimed to determine the prevalence and antibiotic resistance patterns of gram-negative nosocomial infections among patients admitted to different wards of a tertiary hospital in Iran. Methods: This cross-sectional study was conducted using samples collected from patients admitted to coronary care unit (CCU), intensive care unit (ICU), neonatal intensive care unit (NICU), general, and surgery wards of Yas Hospital, Tehran, Iran, from October 1st, 2022, to February 28th, 2023. After the detection of bacteria, antibiotic susceptibility tests were performed using the Kirby-Bauer disk diffusion method by the guidelines of the clinical and laboratory standards institute (CLSI) for gentamycin (GM), ciprofloxacin (CIP), cefepime (FEP), ceftazidime (CAZ), cefotaxime (CTX), imipenem (IPM), meropenem (MR), and piperacillin-tazobactam (TZP), and the results were analyzed using SPSS v22 software. Results: Two hundred and sixty isolates were collected from clinical specimens, most of which were isolated from the ICU ward (53.8%). Among the collected specimens, 98 (37.7%) were isolated from urine, 92 (35.4%) from sputum, 45 (17.3%) from blood, 17 (6.5%) from surgical wounds, and 8 (3.1%) belonged to other specimen types. Among detected bacteria, Klebsiella pneumoniae and Escherichia coli were found to be responsible for 78% of total infections. Based on the Kirby-Bauer disk diffusion results, Acinetobacter baumannii demonstrated the highest resistance to the antibiotics tested, with a resistance rate ranging from 92% to 97%. This was followed by K. pneumoniae, which demonstrated resistance rates between 70% and 85% across all classes of tested antibiotics. Conclusions: The study highlights a high prevalence of nosocomial infections in the ICU, with significant antibiotic resistance, particularly from A. baumannii. It emphasizes strict hospital monitoring, infection control, and responsible antibiotic use.