Common Organisms and Their Drug Resistance Patterns in Endotracheal Aspirate Samples of Patients With Ventilator-Associated Pneumonia: A Retrospective Observational Study

Background: Ventilator-associated pneumonia (VAP) is one of the important and serious nosocomial infections among critically ill patients, contributing to significant morbidity, mortality, and healthcare costs, particularly in resource-limited settings.Rising multidrug resistance (MDR) among causative organisms further complicates management and underscores the need for local antimicrobial surveillance.Objective: This study aimed to determine the frequency of bacterial isolates and their antimicrobial susceptibility patterns in patients diagnosed with VAP in a tertiary care intensive care unit (ICU) in Peshawar, Pakistan.Methods: A cross-sectional, retrospective observational study was conducted at the ICU of Northwest General Hospital from January to December 2024.Adult patients (≥18 years) who developed new-onset pneumonia-like symptoms at least 48 hours after endotracheal intubation were included.Endotracheal aspirate samples were cultured, and antimicrobial susceptibility testing was performed using the Kirby-Bauer disk diffusion method and interpreted according to Clinical and Laboratory Standards Institute (CLSI) M100, 34th edition (2024) guidelines.Data were analysed using IBM SPSS Statistics for Windows, Version 29 (Released 2022; IBM Corp., Armonk, New York) for descriptive and inferential statistics, with p < 0.05 considered statistically significant.Results: Of 224 endotracheal aspirate samples analysed, 128 (57.1%) were from male patients, and the predominant age group was 60-74 years (67/224, 29.9%).The most frequently isolated organisms were Acinetobacter species (47/224, 21.0%; 95% CI: 16.2-26.8)and Pseudomonas aeruginosa (46/224, 20.5%; 95% CI: 15.8-26.3),followed by Escherichia coli (36/224, 16.1%; 95% CI: 11.8-21.4)and Enterobacter species (35/224, 15.6%; 95% CI: 11.5-21.0).High resistance rates were observed across several beta-lactam agents, particularly among Acinetobacter, Enterobacter, Klebsiella, and Escherichia coli isolates.Polymyxin demonstrated the highest overall in vitro susceptibility among the tested agents.Descriptive variation in organism distribution was observed across age groups; however, the association was not statistically significant (Pearson's chi-square test of independence: χ²(8) = 7.98, p = 0.435).Conclusion: Acinetobacter species and Pseudomonas aeruginosa were the most prevalent pathogens isolated from patients with VAP and showed high resistance across multiple antimicrobial classes.Polymyxin demonstrated the highest overall in vitro susceptibility and remains one of the most effective therapeutic options for these isolates, although treatment decisions should be guided by local antibiogram data, patient factors, and antimicrobial stewardship principles.These findings emphasise the urgent need for continuous local antibiogram monitoring and robust antibiotic stewardship programs to optimise empirical therapy and limit the spread of MDR organisms in ICU settings.