Microbiological Profile and Antimicrobial Resistance Patterns of Endotracheal Aspirates in a Tertiary Care Hospital

Background Antimicrobial resistance among Gram-negative bacilli has emerged as a major challenge in hospitalized patients, particularly in respiratory infections associated with prolonged hospitalization and invasive airway devices. Continuous surveillance of respiratory isolates and their antimicrobial susceptibility patterns is essential for guiding empirical therapy and strengthening antimicrobial stewardship practices. Objective This study aimed to determine the bacterial profile, antimicrobial susceptibility patterns, and multidrug resistance prevalence among clinical endotracheal aspirate isolates. Methods This prospective observational study was conducted in the Department of Microbiology of a tertiary care hospital. Endotracheal aspirate samples received during the study period were processed using standard microbiological techniques. Identification and antimicrobial susceptibility testing of isolates were performed using the VITEK automated system (bioMérieux, Marcy-l'Étoile, France), and results were interpreted according to the Clinical and Laboratory Standards Institute (CLSI) guidelines. Resistance phenotypes including extended-spectrum β-lactamase (ESBL)-associated resistance patterns and carbapenem non-susceptibility among Enterobacterales were analyzed. Results Of 428 endotracheal aspirate samples processed, 133 (31.1%) yielded significant bacterial growth. Among the culture-positive isolates (n=133), Acinetobacter baumannii was the most frequently isolated organism, 48 (36%), followed by Klebsiella pneumoniae, 37 (28%), and Pseudomonas aeruginosa, 28 (21%). Acinetobacter baumannii exhibited extensive multidrug resistance, with amikacin demonstrating the highest susceptibility, 36 (75%), while susceptibility to carbapenems, fluoroquinolones, ceftazidime, and piperacillin-tazobactam remained low. Pseudomonas aeruginosa demonstrated moderate susceptibility to amikacin, 19 (67.8%), ciprofloxacin, 13 (46.4%), meropenem, 12 (42.8%), piperacillin-tazobactam, 12 (42.8%), and ceftazidime and imipenem, 11 (39.3%). Among Enterobacterales, 35 (74.5%) demonstrated ESBL-associated resistance patterns, and 37 (78.7%) showed carbapenem non-susceptibility. Colistin retained activity against all Enterobacterales isolates tested. Conclusion The present study demonstrates a high prevalence of multidrug-resistant Gram-negative bacilli among respiratory isolates obtained from endotracheal aspirate samples, with markedly reduced susceptibility to several routinely used antimicrobial agents. These findings highlight the importance of continuous local antimicrobial surveillance, institution-specific antibiograms, robust infection prevention practices, and strengthened antimicrobial stewardship programs to optimize empirical therapy and limit the emergence of antimicrobial resistance in hospitalized patients.