Bacteriology and risk factors of bacterial keratitis in Ethiopia

Background:  In East Africa, particularly in Ethiopia, bacterial keratitis is a major cause of blindness. The purpose of this study was to identify the spectrum of bacterial aetiology and risk factors of bacterial keratitis and to assess the in-vitro antimicrobial susceptibility of these bacterial isolates at Jimma University Specialized Hospital in Oromia, Southwest Ethiopia.

Methods:  A prospective study was employed from January 2012 to June 2012 from which a total of 24 patients with bacterial keratitis were included in the study. Corneal scrapings collected were transported and microbiologically processed using standard operating procedure.

Results: Four different predisposing factors for bacterial keratitis were identified, of which corneal trauma (38%), blepharitis (29%), herpetic keratitis (20%), and use of contaminated medications (20%). Bilateral corneal infection was found in 21% of the cases. A total of 24 corneal scrapings were collected for microbiological evaluation, of which 20 (83%) had bacterial growth. The isolated bacterial pathogens were Pseudomonas aeruginosa (42%), Staphyloccus aureus (21%), Serratia marcescens (15%), followed by Streptococcus pneumoniae (10%). Antimicrobial susceptibility pattern revealed that 85% of Gram-negative bacilli were susceptible to gentamicin and ciprofloxacin, while 86% of Gram-positive cocci were susceptible to vancomycin and Ciprofloxacin.

Conclusions:  Corneal trauma was the most common risk factor for bacterial keratitis followed by blepharitis. Bacteriological analysis of corneal scrapings also revealed that P. aeruginosa was the most common isolate followed by S. aureus; and the antibiotic with the highest susceptibility was ciprofloxacin. As drug resistance among bacterial pathogens is an evolving process, routine surveillance and monitoring studies should be conducted to provide an update and most effective empirical treatment for bacterial keratitis.

Author(s): Tewelde Tesfaye Gebremariam

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