Antimicrobial Resistance Patterns Among Gram-Negative Bacterial Isolates Recovered from Tracheal Aspirate Cultures in Türkiye: A Systematic Review and Meta-Analysis

Background: This systematic review and meta-analysis aimed to evaluate antimicrobial resistance patterns among selected Gram-negative bacterial isolates recovered from tracheal aspirate cultures in Türkiye. Methods: The systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. Electronic databases were systematically searched to identify eligible studies reporting antimicrobial resistance patterns among selected Gram-negative bacterial isolates from tracheal aspirate cultures in Türkiye. Random-effects meta-analyses of study-level resistance proportions were performed using the number of resistant and tested isolates reported by each study. Between-study heterogeneity was assessed using Cochran’s Q test and the I2 statistic. Sensitivity analyses and exploratory univariable meta-regression analyses were also performed. Results: Eighteen studies comprising 5436 isolates belonging to five selected Gram-negative bacterial groups recovered from tracheal aspirate cultures were included. The pooled meropenem resistance rates were 93.21% for A. baumannii, 37.7% for P. aeruginosa, 29.3% for K. pneumoniae, and 4.3% for E. coli. Pseudomonas aeruginosa showed a higher pooled meropenem resistance estimate than K. pneumoniae, while both species exhibited substantial resistance to several other commonly used antimicrobial agents. Exploratory meta-regression indicated an increase in meropenem resistance across more recent study periods for K. pneumoniae, whereas no significant temporal trend was observed for A. baumannii or P. aeruginosa. Conclusions: Multidrug-resistant Gram-negative bacteria continue to represent a major problem in tracheal aspirate cultures in Türkiye. In particular, the high prevalence of carbapenem resistance in A. baumannii highlights the need for continuous national surveillance, standardized microbiological methods, strengthened antimicrobial stewardship, and effective infection prevention and control measures.