Nine-Year Trends in Antibiotic Resistance of Culture-Proven Pseudomonas aeruginosa Keratitis at a Tertiary Eye Center

PURPOSE: The aim of this study was to evaluate the trends in antibiotic resistance among Pseudomonas aeruginosa isolates from microbial keratitis cases over a 9-year period. METHODS: This retrospective observational study included 154 patients with culture-proven Pseudomonas aeruginosa keratitis seen between 2014 and 2022. Antibiotic susceptibility data were reviewed for fluoroquinolones, cephalosporins, beta-lactams, aminoglycosides, and other antibiotic groups. Year-wise resistance patterns were analyzed using the chi-square or Fisher exact test. Cross-sensitivity and cross-resistance between ciprofloxacin and other fluoroquinolones were also assessed. RESULTS: Ciprofloxacin and other older-generation fluoroquinolones maintained high sensitivity (>85%) throughout the study. Moxifloxacin showed a higher resistance rate (23%), with a rising trend from 2014 (16%) to 2022 (36%), although there was a rise and dip in between. Cephalosporins showed poor efficacy, except for ceftazidime, which had a notably lower resistance rate (21%). Beta-lactam resistance was high, except for piperacillin-tazobactam. Aminoglycosides (gentamicin, tobramycin, and amikacin) exhibited the lowest resistance rates (