Ege Journal of Medicine

Abstract

Aim: This study aimed to evaluate the distribution of gram-negative bacteria isolated from patients diagnosed with ventilator-associated pneumonia and to assess changes in antimicrobial resistance patterns over a three-year period.
Materials and Methods: Patients diagnosed with ventilator-associated pneumonia in the adult intensive care unit between January 2023 and December 2025 and with growth detected in lower respiratory tract samples were retrospectively analyzed. Identification of isolates and antimicrobial susceptibility testing were performed using the BD Phoenix M50 system, and results were interpreted according to the 2025 criteria of the European Committee on Antimicrobial Susceptibility Testing. Extended-spectrum beta -lactamase positivity in Enterobacterales species and carbapenem resistance in all isolates were examined. Changes over the years were analyzed using the Cochran–Armitage trend test.
Results: A total of 96 patients were included in the study (68.8% male; mean age 74.2 ± 12.6 years). Gram-negative bacteria constituted 88.5% of all isolates over the three-year period. The most common pathogen was Klebsiella pneumoniae (49.4%), followed by Acinetobacter baumannii (23.5%) and Pseudomonas aeruginosa (11.8%). Extended-spectrum beta-lactamase positivity was detected in 90.5% of Klebsiella pneumoniae isolates. Carbapenem resistance was high in Klebsiella pneumoniae (95.2%) and Acinetobacter baumannii (95.0%) and did not show a significant change over the years (p>0,05). Resistance rates in Pseudomonas aeruginosa varied.
Conclusion: Gram-negative bacteria are the predominant pathogens in ventilator-associated pneumonia cases. High extended-spectrum beta-lactamase production and carbapenem resistance in Klebsiella pneumoniae and Acinetobacter baumannii limit empirical treatment choices. Regular monitoring of institution-specific resistance patterns is important for determining appropriate antimicrobial strategies.