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17-01-2013 | General practice | Article

Fluoroquinolone use may predispose to antibiotic resistance


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medwireNews: People who have taken fluoroquinolone antibiotics may be at increased risk for antibiotic resistance, clinical trial data indicate.

Post-hoc analysis of data from The Steroids for Corneal Ulcers Trial suggest that fluoroquinolone use caused the minimum inhibitory concentration (MIC) to increase by up to 3.5 times.

"Further studies may reveal whether this is de novo or acquired resistance," write Thomas Lietman (University of California, San Francisco, USA) and co-authors in JAMA Ophthalmology.

Lietman et al studied 480 people who had participated in a randomized, double-blind, placebo-controlled trial of adjunctive topical corticosteroids for bacterial keratitis.

The most prevalent causative organisms were Streptococcus pneumonia (51.5%), Pseudomonas aeruginosa (22.7%), and Nocardia species (11.5%).

At presentation, 92 (19.2%) patients reported having used topical fluoroquinolones. This subset of patients did not differ from the rest of the cohort with regard to gender distribution or age, but were less likely to have systemic immune or inflammatory disease.

All participants had bacterial culture isolates assessed for MICs against moxifloxacin. Isolates from patients who were pretreated with fluoroquinolones had a 2.01-fold higher MIC, report Lietman and co-authors.

This discrepancy was even more pronounced in patients who had received fourth-generation fluoroquinolones such as gatifloxacin and moxifloxacin; these individuals had 3.48-fold-higher MICs than those who did not report pretreatment.

Furthermore, in linear regression analysis, adding fluoroquinolone generations as predictors led to a significant improvement in model fit.

Noting that topical fluoroquinolones have been shown to select for resistant conjunctival isolates in previous studies, the researchers state that isolates pretreated with the newer fluoroquinolones appear to be driving the higher MICs in the present study.

"This is not surprising because bacterial isolates were tested for susceptibility to moxifloxacin," they write. "Regardless, these results suggest that an increase in topical antibiotic therapy before presentation may contribute to increasing observed resistance."

By Joanna Lyford, Senior medwireNews Reporter

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