Laboratory diagnosis in ulcerative keratitis

To identify the common bacterial and fungal isolates from corneal ulcers and to determine the antimicrobial susceptibility patterns of bacterial isolates to commonly used antibiotics at B.P. Koirala Institute of Health Sciences (BPKIHS), eastern Nepal. Culture and direct microscopic correlation and reliability were also compared.

All patients with suspected corneal ulceration presenting to the Ophthalmology Department of BPKIHS from 1st August 1998 to 31st July 2001 were evaluated. Corneal scraping was performed and processed for direct microscopy and culture for bacterial and fungal isolates. Bacterial isolates were subjected to antimicrobial susceptibility testing.

Of 447 specimens examined direct microscopy was positive in 216 (48%) specimens. Culture positivity could be correlated with direct microscopy in 179 (83%) of specimens. Growth of etiologic agents was found in 303 (67.8%) samples. Of these 145 (47.8%) had pure fungal growth, 103 (34%) had pure bacterial growth and 55 (18.2%) had mixed fungal and bacterial infection. The commonest fungal pathogen was Aspergillus spp.in 78 (38.4%) followed by Fusarium spp. in 45 (22%). Aureobasidium sp. was isolated in 25 (12.3%) samples. Staphylococcus aureus (93, 56.7%) dominated the scene as the commonest bacterial agent. Streptococcus pneumoniae (33, 20%) was second in the list. Most of the bacterial isolates were sensitive to commonly used antibiotics.

This study emphasizes the importance and need of the continued surveillance of the agents and their antimicrobial susceptibility for the prevention and management of corneal ulcers and their complications.