Etiological diagnosis of microbial keratitis

To identify the different microbial pathogens in infective corneal ulcers.

Observational study.

Department of Ophthalmology Unit I, Eye Hospital, Liaquat University of Medical and Health Sciences, Hyderabad, Sindh, from April 2006 to September 2008.

Patients above 15 years of age with suspected infective corneal ulcers were studied. After detailed history every patient underwent a comprehensive ophthalmic slit lamp bio-microscopical examination, for characteristics of the ulcer to locate the site, size, depth of ulcer and anterior chamber inflammation. After a detailed ocular examination corneal scrapings were collected under aseptic conditions under magnification of slit lamp or operating microscope. The scraping material obtained from leading edge and base of each ulcer was spread onto labeled slides for staining. Another portion was inoculated on to the surface of solid and the liquid culture medias. The inoculated medias were incubated at appropriate temperature for appropriate time.

Of the 328 patients; 192 (64.99%) were male with age ranging from 15 to 80 years, and majority from rural population (64.99%). Majority i.e. 201 (61.28%) were previously treated. Out of 328 patients, 161 cultured (49.10%) for bacteria, 87 (26.52%) for fungi, and 12 were found positive culture for both bacteria and fungi. The rest of 68 (20.73%) were culture-negative corneal ulcers. Of the 173 bacterial isolates, 119 (68.79%) had Gram positive cocci, most common isolated being Staphylococcus aureus in 82 (47.40%); fungal pathogens were isolated from 99 corneal ulcers. The commonest organism isolated was Candida albicans in 75.76%, followed by Aspergillus flavus in 11.11% of the total fungal isolates.

Staphylococcus aureus, Candida albicans and Aspergillus flavus were common causes of microbial infective keratitis in this series.