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Michael C. Chen, Catherine E. Oldenburg, Muthiah Srinivasan, Jeena Mascarenhas, Prajna Lalitha, Kathryn J. Ray, Michael E. Zegans, Stephen D. McLeod, Nisha R. Acharya, Thomas M. Lietman; Clinical Differentiation of Organisms in Bacterial Keratitis. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5848.
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To determine if certain demographic factors and clinical characteristics are associated with the type of organism in bacterial keratitis.
Baseline demographic factors and clinical characteristics of culture-proven bacterial keratitis, collected as part of the Steroids for Corneal Ulcers Trial, were analyzed. Cases that involved multiple or unspeciable organisms were excluded. Characteristics included age, gender, duration of symptoms, visual acuity, infiltrate/scar size, depth of ulceration, presence of hypopyon, size of hypopyon, ulcer location, and concurrent dacryocystitis. Analysis of variance and logistic regression were employed. Categories with a significance of P<0.05 were further analyzed by pair-wise comparisons.
Of the 500 subjects enrolled in the study, 488 cases of bacterial keratitis were included for analysis. The most commonly isolated organisms were Streptococcus pneumoniae (n=248; 51%), Pseudomonas aeruginosa (n=110; 23%), and Nocardia spp. (n=55; 11%). Significantly different characteristics across species of bacteria include age (P=0.009), gender (P=0.020), duration of symptoms (P=0.015), infiltrate/scar size (P=0.004), depth of ulceration (P<0.001), ulcer location (P=0.006), and concurrent dacryocystitis (P<0.001). S. pneumoniae was associated with older age (OR 1.5, 95% CI, 1.3 to 1.7, P<0.001), female gender (OR 1.6, 95% CI 1.1 to 2.3, P=0.01), and dacryocystitis (OR 7.4, 95% CI 4.1 to 13.3, P<0.0001). P. aeruginosa was associated with larger infiltrate/scar size (OR 1.6, 95% CI 1.4 to 1.8, P<0.001), and deeper ulceration (OR 2.4, 95% CI 1.5 to 3.8, P<0.001). Nocardia spp. was associated with longer duration of symptoms prior to presentation (OR 1.38, 95% CI 1.2 to 1.6, P<0.001) and more superficial ulceration (OR 0.3, 95% CI 0.2 to 0.5, P<0.001).
Certain demographic factors and clinical characteristics can aid in the differentiation of organisms in bacterial keratitis. P. aeruginosa appeared to be associated with more severe ulcers at presentation. Dacryocystitis had a 7.4-fold odds of being associated with S. pneumoniae.
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