Clinical and Microbiological Analysis of Gram-Positive Bacterial Keratitis, a 15-Year Review

ABSTRACT

PURPOSE: To investigate the shifting trends of pathogenic organisms, antibiotic resistance, and clinical characteristics of patients with Gram-positive bacterial keratitis and to elucidate the prognostic factors. METHODS: We performed a retrospective chart review of 152 isolates in 146 eyes with Gram-positive bacterial keratitis between January 1998 and December 2012. The study was divided into 5 periods for analysis of the bacteriological profiles and in vitro antibiotic resistance. The epidemiological and clinical characteristics were compared according to bacterial isolates. Logistic regression analysis was performed to determine the risk factors. RESULTS: Gram-positive bacterial keratitis tended to decrease and significant change in the distribution of isolates was not observed. Commonly isolated organisms were S. epidermidis (48.7%), S. aureus (25.0%), and S. pneumoniae (7.2%) in order of frequency. The resistance to fluoroquinolone tended to increase (p = 0.104) and resistance to gentamicin was significantly decreased (p = 0.01). S. epidermidis had the shortest corneal epithelium healing time (p = 0.035) and the most favorable visual outcome after treatment (p = 0.035) compared with the other species. Risk factors for poor visual outcomes included a best corrected visual acuity less than 0.1 at initial evaluation and an epithelial healing time greater than 10 days. CONCLUSIONS: Gram-positive bacterial keratitis tended to decrease and S. epidermidis was the most common isolate. The clinical prognosis was most favorable in S. epidermidis. The BCVA less than 0.1 at initial evaluation was an important risk factor for poor visual outcome and surgical treatment in Gram-positive bacterial keratitis.