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Deana L. Choi, Mark Slabaugh, Jennifer Yu; Predictive Factors for Culture Positivity for Microbial Keratitis. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5853.
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To evaluate patient demographics, risk factors and causative organisms of microbial keratitis and their correlation to culture positivity.
We analyzed a retrospective case series of patients over a seven year period with a diagnosis of corneal ulcer that were cultured. Medical records were reviewed to obtain clinical and microbiology data. Corneal ulcers caused by HSV and VZV were excluded. Associations between risk factors and clinical presentations of microbial keratitis with rate of culture positivity were analyzed.
92 eyes of 88 patients who had cultures taken at the time of presentation for microbial keratitis were identified and included. 40 patients (45.5%) were female and 48 (54.5%) were male. Average age was 46.8 +/- 20.1 years. 30 patients had vision of hand motions or worse at presentation and the remaining 62 eyes had average Va of 0.809 +/- 0.681 (logMAR). 55 of 92 (60%) scrapings were culture positive. Of the positive cultures, 34 (62%) were gram positive bacteria, 18 (33%) were gram negative bacteria and 3 (5%) were fungal. Most common primary isolates were coagulase negative staphylococcus (29%), Pseudomonas (22%) and alpha hemolytic streptococcus (13%). History of intraocular surgery (p=0.044) and surface disease (p=0.023) were associated with negative cultures. Central location of infiltrates (p=0.097) and initial poor vision (p=0.065) approached, but did not reach statistical significance with positive cultures.
In this series of patients from the Pacific Northwest, culture positive infectious corneal ulcers were predominantly due to gram positive bacteria; the most common organisms cultured were coagulase negative staphylococcus, Pseudomonas and alpha-hemolytic streptococcus. The clinical characteristics of patients with microbial keratitis were not significantly predictive for positive laboratory culture. A history of intraocular surgery and surface disease were significantly associated with negative cultures.
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