MICROBIOLOGICAL PROFILE AND ANTIBIOTIC SUSCEPTIBILITY PATTERN OF VENTILATORASSOCIATED PNEUMONIA IN A TERTIARY CARE HOSPITAL ICU

ABSTRACTBackground: Ventilator-associated pneumonia (VAP) is the most frequent device-associated infection in intensive care units(ICUs) and is increasingly caused by multidrug-resistant (MDR) organisms. Because empirical therapy must be started beforeculture results are available, unit-specific microbiological and susceptibility data are essential for rational prescribing. Theobjective is to determine the bacteriological profile of VAP, to characterise the antibiotic susceptibility and resistancephenotypes of the isolated organisms, and to describe clinical outcomes in a tertiary care hospital ICU. Materials andMethods: A prospective observational study was conducted in the Department of Microbiology, Netaji Subhas MedicalCollege & Hospital, Bihta, Patna, from March 2025 to February 2026. One hundred consecutive adults who developedpneumonia after more than 48 hours of mechanical ventilation and had a Clinical Pulmonary Infection Score (CPIS) greaterthan 6 were enrolled. Endotracheal aspirate or bronchoalveolar lavage was processed by semi-quantitative and quantitativeculture. Isolates were identified by conventional methods with automated identification, and antimicrobial susceptibilitytesting was performed and interpreted according to Clinical and Laboratory Standards Institute (CLSI) M100 criteria.Multidrug resistance was defined using Magiorakos criteria. Data were analysed using the chi-square test, Fisher exact testand independent-samples t test, with a P value below 0.05 taken as significant. Results: Of 100 patients (mean age 54.6 ± 16.2years; 72% male), 76% had late-onset VAP. Cultures were positive in 92 patients (92%), of whom 13 (14.1%) werepolymicrobial, yielding 105 isolates. Gram-negative bacilli accounted for 94 isolates (89.5%). The commonest organisms wereAcinetobacter baumannii (30; 28.6%), Klebsiella pneumoniae (24; 22.9%), Pseudomonas aeruginosa (18; 17.1%) andEscherichia coli (10; 9.5%). Overall, 88 of 105 isolates (83.8%) were multidrug-resistant; carbapenem-resistant A. baumannii(21), extended-spectrum beta-lactamase producers (21) and carbapenem-resistant Enterobacterales (11) predominated.Susceptibility of A. baumannii was 23.3% to meropenem, 40.0% to amikacin, 70.0% to minocycline, 90.0% to tigecycline and93.3% to colistin. K. pneumoniae was 54.2% susceptible to meropenem and 95.8% to colistin and tigecycline. AllStaphylococcus aureus isolates were susceptible to vancomycin and linezolid; six of nine (66.7%) were methicillin-resistant.Twenty-eight-day mortality was 30%. Non-survivors were significantly older (60.1 ± 15.2 vs 52.2 ± 16.2 years; P = 0.023),and K. pneumoniae as the primary pathogen was associated with higher mortality (54.5% vs 25.7%; P = 0.018). Conclusion:VAP in this ICU was overwhelmingly caused by multidrug-resistant Gram-negative bacilli, with A. baumannii predominatingand carbapenem activity substantially eroded. Colistin, tigecycline and minocycline retained the highest in vitro activity againstGram-negative isolates, and glycopeptides and oxazolidinones against staphylococci. Periodic unit-