Corneal ulcers in two institutions in Singapore: analysis of causative factors, organisms and antibiotic resistance.

The aim of this study was to determine the causative factors, organisms and antibiotic resistance in patients with bacterial keratitis in Singapore. We analysed retrospectively 103 cases of bacterial keratitis admitted to the Singapore General Hospital or the Singapore National Eye Centre during a 21-month period from March 1992 to December 1993. Contact lens wear represented the largest single predisposing factor (35 eyes, 34.0%), followed by ocular trauma (28 eyes, 27.2%) and pre-existing ocular disease (28 eyes, 27.2%). Thirteen of the twenty-eight cases of trauma-related keratitis were work-related injuries. Gram-negative organisms formed the largest group (41 cultures, 80.4%), with Pseudomonas aeruginosa being the most common organism identified (30 eyes). Pseudomonas was also responsible for 78.6% of all contact lens ulcers (11 out of 14 eyes). Resistance to gentamicin was only encountered in 1 case of Proteus mirabilis keratitis. All cases of Pseudomonas infection and 3 of the 10 Gram-positive cases were also resistant to chloramphenicol. All Gram-positive cases were sensitive to cephalosporins. Contact lens wear and ocular trauma are the major preventable risk factors for bacterial keratitis in young sighted eyes in Singapore. Gentamicin continues to be the antibiotic of choice for Gram-negative corneal infections in view of the low incidence of resistance. The routine use of chloramphenicol as the topical antibiotic of choice for corneal infection is not recommended due to the high resistance in Gram-positive and Gram-negative organisms locally.