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F. N. Kazi, H. Hsu, L. Tseng; Contemporary Ocular Bacterial Flora and Their Antibiotic Resistance Patterns - A Prospective Study of Patients Undergoing Cataract Extraction. Invest. Ophthalmol. Vis. Sci. 2008;49(13):2373.
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To investigate the spectrum of conjunctival microbial flora and their antibiotic resistance patterns of patients undergoing cataract surgery in hopes of better understanding local resistance patterns and guiding antibiotic use.
Twenty eyes from twenty patients scheduled for routine cataract extraction and intraocular lens implantation by one of two anterior segment ophthalmology staff were cultured. Patient of all genders, ethnic backgrounds, health status and ages over 18 were recruited. The day of surgery subjects answered a brief questionnaire regarding recent hospitalization, antibiotic usage, health care field employment, and institutional housing status. Prior to surgery and before drops were instilled, a routine conjunctival swab was collected using a cotton tip applicator following administration of tetracaine.
Out of the 20 eyes studied, 31 isolates were recovered from 17 eyes. Three eyes had negative cultures. Only 2 of the isolates were gram negative species (6.45%), 2 were fungi (6.45%) and the remaining 27 were gram positive species (87%). The most commonly isolated organisms were S. epidermidis and methicillin resistant coagulase negative Staphylococci. Of the gram positive organisms, 9 (33%) were resistant to methicillin. The largest group of isolates resistant to methicillin was the coagulase negative staphylococci. Seven coagulase negative staphylococci were isolated and of these 4 were methicillin resistant (4/7; 57%). However all were sensitive to the fluoroquinolones. Only 3 (11%) of the gram positive organisms and 1 of 2 gram negative organisms were resistant to fluoroquinolones. Of the 3 out of 20 patients exposed to a hospital setting, only one grew isolates resistant to fluoroquinolones. Of the remaining 17 patients not exposed to a hospital setting, 2 had isolates resistant to fluoroquinolones.
There are a larger number of methicillin-resistant coagulase negative staphylococci than recognized in previous studies. However, there is not a larger percentage of fluoroquinolone resistance among the conjunctival flora isolated. It is difficult to make conclusions regarding fluoroquinolone resistance in patients exposed to hospital settings due to the small number of patients.
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