Letter to the Editor Study of microbial keratitis in central India

Corneal ulceration is a leading cause of ocular morbidity and blindness worldwide, especially in developing countries such as India. Infection is the major cause of corneal ulceration [1]; therefore, prompt diagnosis and appropriate antimicrobial therapy is the hallmark of preventing corneal scarring and blindness. This study was undertaken in an attempt to identify the possible predisposing factors and etiological agents of corneal ulceration and to compare and correlate between direct microscopy and culture in the detection of etiological agents. The age, sex, occupation and various predisposing factors leading to corneal ulceration were recorded for 74 patients. Clinical examination was performed with the aid of a slit lamp. To localize the ulcer properly, fluorescent stain was applied to the affected eye. Corneal scrapings, which were collected using a sterile Bard Parker blade (No. 15) from the base and advancing margins of the ulcers, were inoculated directly on sheep blood agar, chocolate agar, brain heart infusion broth, Sabouraud's dextrose agar, and 2% agar without any additive nutrients. Smears were prepared for Gram staining and wet mount for 10% potassium hydroxide (KOH) and calcofluor white (CFW) staining (Himedia Laboratories, Mumbai, India). The results showed a male preponderance (67.5%) of cases and that the majority of patients in both sexes were in their sixties. No specific history was observed in 15 (20.3%) cases. Correlation of type of trauma with microbial infection is shown in Table 1. Vegetative matter was found to be the predominant predisposing traumatic factor, and this was statistically significant (p < 0.05). Vegetative matter also caused more fungal (10; 33.3%) than bacterial (8; 26.7%) cases of keratitis, although this was not statistically significant (p  0.05). Infectious etiology was identified in 39 of 74 cases (52.7%). Bacterial infection (20; 27.0%, culture only) was more frequently detected than fungal infection (19; 25.7%, culture and microscopy); however, this was not statistically significant. Among the 20 diagnosed cases of bacterial keratitis, both culture and Gram staining were positive in 12 (60%) individuals, whereas the remaining 8 cases were only culture-positive. Among 19 fungal keratitis cases, sensitivity of microscopy was 100% (KOH and/or CFW) and that of culture 78.9% (15 cases). The 100% sensitivity of microscopy could be attributed to the CFW stain, as KOH alone detected only 11 cases (52.9%). The higher positivity of CFW in detecting the fungal elements over KOH was statistically significant (p  0.05). Bacterial and fungal pathogens isolated are …