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E. N. Hoskins, J. Keenan, T. Lietman, V. Cevallos, N. R. Acharya; Topical Fluoroquinolone Use as a Risk-Factor for In-Vitro Fluoroquinolone Resistance in Ocular Cultures. Invest. Ophthalmol. Vis. Sci. 2009;50(13):2662.
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To determine whether recent use of topical fluoroquinolones (FQ) is a risk-factor for in-vitro FQ resistance in bacterial cultures from ocular sources.
Institutional review board approval was obtained for this retrospective chart review. All positive bacterial cultures isolated from ocular sources at the Proctor Foundation microbiology laboratory since January 1, 2005 were identified. Disk diffusion susceptibility testing for ciprofloxacin, moxifloxacin and gatifloxacin was performed for all cultures. Culture results from the four most common bacterial isolates were included. The medical records of patients with positive cultures were reviewed to determine topical or systemic FQ use within the three months prior to culture. Patients could contribute multiple positive cultures to the study, but only the patients’ first positive culture in any three-month time period was included. Fisher's exact test was used to compare the proportion of patients who used topical FQ in the past 3 months among FQ sensitive and resistant cases.
The four bacterial species included were S. aureus, S. pneumoniae, P. aeruginosa, and H. influenzae. Due to the small number of resistant organisms in the other three categories, the chart review was focused on S. aureus. Of 200 S. aureus cultures, 41(20.5%) were resistant to FQ. 32(16%) were MRSA. 100% of MRSA cultures were resistant to ciprofloxacin, moxifloxacin and gatifloxacin. 10 (5%) of the positive cultures were from the conjunctiva alone, 96 (48%) were from conjunctiva and lids, 80 (40%) were from lids alone, and 14 (7%) were from cornea. 142 (83%) of 171 patients with no prior FQ use were sensitive to all three FQ’s tested, and 29 (17%) of 171 were resistant. 17 (58.6%) of 29 patients with prior topical FQ use in the 3 months preceding culture were sensitive to FQs tested, and 12 (41.4%) of 29 were resistant, P=0.005.
Recent topical FQ use is significantly associated with FQ resistance in S. aureus isolates from ocular cultures. To our knowledge, this is the first report using ocular isolates that demonstrates a correlation between antibiotic use and resistance to FQs.
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