Differentiation of etiologic agents of bacterial keratitis from presentation characteristics
Presenting characteristics of bacterial corneal ulcers may suggest particular causative organisms, helping to guide treatment decisions before cultures become available. In this study, we analyze the association between presentation demographic and clinical characteristics, using data collected as part of a randomized, controlled clinical trial. Data for this study were collected as part of the Steroids for Corneal Ulcers Trial, a randomized, placebo-controlled, double-masked trial. All patients had a culture-proven bacterial corneal ulcer. Patient history, clinical examination, and photography were performed in a standardized fashion at enrollment. Analysis of variance or Fisher’s exact test was used to compare characteristics by organism. Univariate logistic regression was used to analyze predictors of the most common organisms. Five hundred patients were enrolled in the trial, of whom 488 were included in this analysis. The most common organism was Streptococcus pneumoniae (N = 248, 51 %) followed by Pseudomonas aeruginosa (N = 110, 23 %). Compared to other organisms, P. aeruginosa was significantly associated with a larger baseline infiltrate/scar size [odds ratio (OR) 1.6, 95 % confidence interval (CI) 1.4–1.8] and deeper infiltrate (OR 2.4, 95 % CI 1.5–3.8). S. pneumoniae was significantly associated with a smaller baseline infiltrate/scar size (OR 0.8, 95 % CI 0.7–0.9) and dacryocystitis (OR 7.3, 95 % CI 4.1–13.3). Nocardia spp. were significantly associated with longer duration of symptoms prior to presentation (OR 1.4, 95 % CI 1.2–1.6), more shallow infiltrate (OR 0.3, 95 % CI 0.2–0.5), and better baseline visual acuity (OR 0.4, 95 % CI 0.2–0.65). Staphylococcus spp. were less likely to be central in location (OR 0.16, 95 % CI 0.08–0.3). Baseline characteristics of bacterial ulcers may suggest the likely etiology and guide early management.
KeywordsBacteria Keratitis Pseudomonas Risk factors
We would like to thank the patients who enrolled in the SCUT trial and their families, as well as the research staff at each of the trial sites. We are also grateful for the invaluable guidance and advice of the SCUT data and safety monitoring board: Marian Fisher, Ph.D. (chair), Anthony Aldave, M.D., Donald Everett, M.A., Jacqueline Glover, Ph.D., K. Ananda Kannan, M.D., Steven Kymes, Ph.D., G.V.S. Murthy, M.D., and Ivan Schwab, M.D. Funding for the SCUT was from the National Eye Institute, U10 EY015114. Dr. Acharya is supported by a National Eye Institute K23EY017897 grant and a Research to Prevent Blindness Award. The Department of Ophthalmology at UCSF is supported by a core grant from the National Eye Institute, EY02162, an unrestricted grant from Research to Prevent Blindness, New York, NY, and That Man May See, Inc., San Francisco, CA, USA.
Conflicts of interest
None of the authors has any conflicts of interest to declare.
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