Unveiling Antibiotic Resistance in Ventilator-Associated Pneumonia Patients: A Comprehensive Analysis

Background: Ventilator-associated pneumonia (VAP) remains a major healthcare-associated infection, especially in resource-limited settings where multidrug-resistant organisms are prevalent. This study assessed the bacteriological profile and antimicrobial susceptibility patterns of endotracheal aspirates (ETA) from clinically suspected VAP patients in a tertiary care ICU, and compared microbial distribution between early and late-onset VAP. Methods: A descriptive cross-sectional study was conducted from October 2024 to September 2025 in a tertiary care teaching hospital. Adult patients who were mechanically ventilated for more than 48 hours and met the modified Clinical Pulmonary Infection Score (CPIS) criteria (score >6) were included. ETAs were analyzed using semi-quantitative culture methods, with ≥10⁵ CFU/mL considered significant, and antimicrobial susceptibility testing was performed in accordance with CLSI 2023 guidelines. Demographic variables, risk factors, bacterial isolates, and resistance patterns were analysed using chi-square tests. Results: Among 596 ventilated patients, 195 (incidence proportion 32.7%) had significant culture-positive VAP. The incidence density was 33.6 per 1000 ventilator-days. Early-onset VAP accounted for 57.9% (113/195) and late-onset VAP for 42.1% (82/195). No significant association was observed between VAP onset and age, sex, or indication for intubation. Gram-negative pathogens predominated in both groups (76.1% early vs. 78% late). Acinetobacter baumannii was the most common isolate (35.3% early, 36.2% late), followed by Klebsiella pneumoniae and Pseudomonas aeruginosa. A significant difference was noted in Gram-negative distribution between early and late VAP (p=0.009). Extensive multidrug resistance was observed, with universal susceptibility only to polymyxin B and colistin. Carbapenem susceptibility varied by pathogen, with A. baumannii showing higher sensitivity in late-onset cases. Conclusion: VAP burden in this ICU remains high, with Gram-negative multidrug-resistant organisms, particularly A. baumannii and K. pneumoniae, driving most infections. The findings underscore the urgent need for strengthened antimicrobial stewardship, routine resistance surveillance, and strict adherence to VAP prevention bundles. Early culture-guided de-escalation is crucial to optimize outcomes and curb resistance.