Microbial keratitis in Sao Paulo, Brazil: a 10-year review of laboratory results, epidemiological features, and risk factors.

Purpose: To study epidemiological data, laboratory results, and risk factors associated with microbial keratitis.

Methods: We conducted a retrospective study of corneal sample cultures from patients with microbial keratitis from January 2010 to December 2019. Results were analyzed according to the etiological diagnosis of bacterial, mycotic, or parasitic infection and were associated with related risk factors.

Results: We analyzed 4810 corneal samples from 4047 patients (mean age 47.79 ± 20.68 years; male 53.27%). The prevalence of bacterial, fungal, and Acanthamoeba infections were 69.80%, 7.31%, and 3.51%, respectively. The most frequently isolated bacteria were coagulase-negative Staphylococcus (CoNS) (45.14%), S. aureus (10.02%), Pseudomonas spp. (8.80%), and Corynebacterium spp. (6.21%). Among CoNS, the main agent was S. epidermidis (n=665). For mycotic keratitis, Fusarium spp. (35.42%) and Candida parapsilosis (16.07%) were the most common agents among filamentous and yeasts isolates, respectively. Contact lens use was associated with a positive culture for Acanthamoeba spp. (OR = 19.04; p < 0.001) and Pseudomonas spp. (OR = 3.20; p < 0.001). Previous ocular trauma was associated with positive fungal cultures (OR = 1.80; p = 0.007), while older age was associated with positive bacterial culture (OR = 1.76; p = 0.001).

Conclusions: Our findings demonstrated a higher positivity of corneal sample cultures for bacteria. Among those, CoNS was the most frequently identified, with S. epidermidis as the main agent. In fungal keratitis, Fusarium spp. was the most commonly isolated. Contact lens wearers had higher risks of positive cultures for Acanthamoeba spp. and Pseudomonas spp. Ocular trauma increased the risk of fungal infection, while older age increased the risk of bacterial infection.