Organism Isolation in Corneal Ulcer- Utility of Different Techniques

Introduction: Various techniques are available for isolation of microorganism in cases of microbial keratitis including conventional methods of scraping, re-scraping inoculation in different media and corneal biopsy. Methods: This was a cross sectional descriptive study conducted from February 2002 to July 2003. A total of 161 eyes of corneal ulcers were evaluated with scraping inoculation. Re-scraping and corneal biopsy were performed in those cases which did not grow any organism in the first scraping or which did not respond to initial treatment. Results: Microorganisms were isolated in 116 patients (72.04%) after first scraping. S pneumoniae was seen in 50(42%), Fusarium in 21(18%) and Aspergillus in 16(14%) cases. Re-scraping was done in 22 culture negative and non improving cases of which 14 (63.63%) showed isolation of organisms. After re-scraping, Fusarium and Aspergillus were isolated in four patients each (18% each) followed by S. pneumoniae in 3 (14%), S. aureus in 2 (9%), and Penicillium in 1(5%) case.Corneal biopsy was done in 10 cases with isolation of microbial agents in 7 (70%) with Aspergillus and S. aureus in three each, and S. epidermidis in 1(10%). Conclusions: Apart from conventional scraping, other isolation techniques should be considered in the treatment of non-responding and culture negative cases of corneal ulcers. Compared to bacteria, fungi are difficult to isolate in the first scraping and requires more frequent repeat scraping and corneal biopsy. Keywords: Corneal biopsy, corneal scraping, corneal ulcer, microbial keratitis, organismal isolation