Work

Shifting microbial profiles and antimicrobial susceptibility in infectious keratitis: a 13-year longitudinal analysis at a Brazilian tertiary center

Year: 2026

Type: article

Abstract: Background/Aims Infectious keratitis is a sight-threatening disease often managed with empiric antibiotics. Continuous monitoring of causative agents and resistance patterns is essential to detect shifts in susceptibility and optimize treatment protocols. This study analyzed the etiology and antibiotic susceptibility trends of microbial keratitis at a major tertiary referral center over a 13-year period. Methods Retrospective analysis of corneal scrapings from patients clinically diagnosed with infectious keratitis between January 2013 and December 2025. Cases were divided into two periods (2013–2019 and 2020–2025) to evaluate temporal trends. Statistical analyses included Bonferroni-corrected chi-square/Fisher’s exact tests and the Cochran-Armitage trend test. Results Among 649 corneal scrapings, 343 (52.9%) were culture-positive, yielding 420 isolates (18.1% polymicrobial). Bacteria predominated (88.8%), comprising 56.9% Gram-Positive (GP) and 31.9% Gram-Negative (GN) isolates. Coagulase-negative Staphylococci were the most frequent GP (21.4%), while Pseudomonas aeruginosa (11.4%) was the leading GN. Fungi comprised for 10.2%. Longitudinal analysis revealed significant reductions in Cutibacterium acnes (adjusted p < 0.001) and Serratia marcescens (adjusted p = 0.009), a downward trend in fungal isolation (p trend = 0.010) and a marginal decline in ciprofloxacin susceptibility among GN (p trend = 0.056). All GP isolates demonstrated 100% in vitro susceptibility to vancomycin. Methicillin resistance was identified in 19.4% of S. aureus and 43.1% of coagulase-negative Staphylococci . Conclusion The microbiological profile of infectious keratitis showed significant temporal shifts, including a reduction in C. acnes and a downward trend in fungal isolation. While Gram-positive and Gram-negative organisms maintained high susceptibility to vancomycin and amikacin, respectively, a marginal, non-statistically-significant decline in ciprofloxacin susceptibility among Gram-negative isolates warrants continuous microbiological surveillance.

Source: Clinics

DOI: 10.1016/j.clinsp.2026.101220