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Feilin Zhu, Lisa Park, Elisabeth J Cohen; Microbiological study of corneal ulcer patients at Bellevue Hospital Center. Invest. Ophthalmol. Vis. Sci. 2014;55(13):2836.
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To evaluate the cornea ulcer microbiology of patients at an urban city hospital.
Corneal ulcer patients examined and cultured were identified retrospectively. The media and stains submitted were assessed, and the microbiology was analyzed. Gram stains were analyzed and correlated with positive cultures. The use of topical antibiotic and/or topical steroid at time of culture was analyzed to correlate with positive results.
114 corneal ulcers were treated over 10 years (1/2004 to 12/2013). 71/114 (62.3%) ulcers were cultured. 68/71 (95.8%) of the cultures submitted were corneal scrapings plated on blood, chocolate, thioglycolate, sabaround’s, and slides for gram stains. 3 included KOH stains for fungus. 3/71 submissions were corneal swab with gram stain.17/68 (25%) culture submissions from scrapings were incomplete, missing one of the media plates. 9/71(12.7%) submissions did not include a gram stain. 0/3 corneal swabs yielded a positive result. 24/68 (35.3%) of corneal scraping cultures yielded a positive result, including 1 mixed bacterial and 1 fungal. The most common was pseudomonas aeruginosa 8/68 (11.8%), followed by serratia 4/68, coag negative staph 3/68, and stenotrophomonas maltophilia 2/68. There was one positive result each for Bacillus, strep pneumoniae, MRSA, and beta strep group G. One culture grew both bacillus and coag negative staph. One culture grew Aspergillus. At time of culture, 21 patients were on a topical antibiotic (including the patient whose culture grew Aspergillus), 3 were on a topical steroid, and 2 were on both. Compared to positive cultures in patients not on any medications (14/41 or 24%), positive cultures were found in 6/23 (26%) of patients on topical antibiotic with or without steroids (P=0.849), and 2/3 (66%) of patients on steroid alone (P=0.267). 12/62 (19%) gram stains were positive. 5/5 gram stains that showed an organism had corresponding growth in culture. 8/12 (66.7%) of positive gram stains eventually yielded growth of a microorganism compared to 14/50 (28%) of negative gram stains (P=0.012). 0/3 of KOH stains submitted yielded fungal elements.
The majority of ulcers cultured yielded bacteria, with pseudomonas the most common. The use of topical antibiotic or steroid did not statistically affect culture yield. A positive gram stain does correlate with a positive culture yield. However, there is a high frequency of incomplete cultures.
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