Etiological agents and risk factors of microbial keratitis in Hong Kong: a preliminary report on the first 50 cases

Abstract

Aim: The aim of the study was to determine locally the etiology and risk factors of microbial keratitis, which might be different from those reported in Western countries, because of different climatic, cultural and environmental conditions.

Materials and methods: We prospectively recruited all cases of presumed microbial keratitis from the Hong Kong Eye Hospital and Prince of Wales Hospital from March 1997 to September 1997. Clinical diagnosis of microbial keratitis was established when the corneal infiltration was at least 1 mm in diameter. Corneal scrapings were performed and cultured in all cases. Correlation between risk factors, clinical presentations and culture results were examined.

Results: Fifty consecutive patients were studied. The important risk factors included contact lens wear, ocular injury, ocular surface disease and previous application of steroid.  Fifty-four percent of the cases had positive microbial cultures from corneal scrapings. The culture positive rate was significantly related to the presence of anterior chamber activity. Neither the size nor the position of infiltration was associated with a positive culture. Among patients without a history of contact lens wear, Pseudomonas aeruginosa, the commonest pathogen, was recovered in scrapings from nine patients and Staphylococcus aureus from another three patients. Acanthamoeba and Pseudomonas aeruginosa were the commonest isolates from contact lens wearers.

Conclusion: Contact lens wearing was the most important risk factor of microbial keratitis in Hong Kong. Particular attention should be paid to patients presenting with anterior chamber activity. The first-line antibiotic treatment should be effective against Pseudomonas aeruginosa and Staphylococcus aureus, the two commonest bacteria associated with microbial keratitis in Hong Kong.