Microbiological profile of bacterial and fungal corneal ulcers at a national institute of ophthalmology in Perú.

Objective: To describe the microbiological profile of bacterial and fungal corneal ulcers, as well as the antibiotic susceptibility profile of the most frequent pathogenic species.

Methods: A retrospective descriptive study was conducted using the recorded data of corneal ulcer scrapings from the ocular microbiology laboratory of the National Institute of Ophthalmology. Laboratory data from 2015 to 2022 were collected and included for all corneal ulcer scrapings.

Results: After excluding repeated, non-cultured, and duplicate results, a total of 3,470 corneal samples were analyzed. Positive samples accounted for 88.1% of all scraps. Of these, 2,816 (81.2%), 904 (26.2%), and 662 (19.1%) showed bacterial, fungal, and mixed growth, respectively. Coagulase-negative Staphylococci (2,257; 69.8%) were the most frequent bacteria, with Staphylococcus epidermidis (1,677; 51.9%) being the most isolated organism, followed by Pseudomonas aeruginosa (275; 8.5%) and Staphylococcus aureus (274; 8.5%). Fusarium spp. was the most common fungus. Less than 60% of S. epidermidis isolates showed susceptibility to Oxacillin, Cefazolin, Moxifloxacin, and Gentamicin, while more than 90% of isolates were susceptible to Gatifloxacin. P. aeruginosa showed less than 80% susceptibility only to Imipenem.

Conclusion: Gram-positive bacteria were the most isolated, with S. epidermidis being the most frequent pathogen, followed by P. aeruginosa. S. epidermidis exhibited alarmingly low susceptibility to commonly used antibiotics.