Epidemiology and medical prediction of microbial keratitis in southeast Brazil

Abstract

Purpose: The goals of the study were the following: 1) to show the epidemiology of microbial keratitis (MK) in the southeast Brazil, 2) to compare the epidemiological differences between fungal (FK) and bacterial keratitis (BK), and 3) to evaluate the frequency which ophthalmologists accurately differentiate bacterial keratitis from fungal keratitis based on clinical diagnosis.

Methods: A retrospective chart analysis of all clinically diagnosed microbial keratitis patients presenting between October, 2003 and September, 2006 was performed. Demographic features, ocular and laboratory findings, and information regarding the risk factors and clinical evolution were recorded.

Results: Among 118 consecutive patients with a clinical diagnosis of microbial keratitis, the positive culture rate was 61%. The predominant bacterial and fungal pathogens isolated were S. epidermidis and Fusarium spp. Prior corneal injury was more frequent among fungal keratitis than bacterial keratitis cases (p<0.0001). Coexisting systemic diseases, ocular diseases, and previous ocular surgery were more frequent among BK cases (p=0.001; p=0.001; p=0.004; respectively). The following clinical findings were more frequent in bacterial keratitis: hypopion, corneal peripheral superficial vascularisation, and ulceration area >20 mm² (p<0.05). The diagnosis was predicted correctly in 81.6% of bacterial keratitis cases and in 48.1% of fungal keratitis cases.

Conclusion: Medical judgment of microbial keratitis agent is possible based on clinical and epidemiological data, but it is more difficult for fungal infection. Thus, such data cannot be the only basis for the diagnosis of suspected microbial keratitis, but oriented clinical suspicion based on these data may be beneficial for guiding antimicrobial treatment and earlier therapy.