Single Antibiotic Course Can Lead to Long-Term Resistance

FRIDAY, Feb. 9 (HealthDay News) -- A single course of macrolide antibiotics can lead to macrolide-resistance in oral streptococci that lasts as long as six months, according to study findings published in the Feb. 10 issue of The Lancet.

Herman Goossens, M.D., of University Hospital Antwerp in Belgium, and colleagues randomized 224 healthy adults to placebo or the macrolide antibiotics clarithromycin (500 mg twice a day for seven days) or azithromycin (500 mg once a day for three days). Pharyngeal swabs were taken for six months to assess the resistance of streptococci to macrolides.

The researchers found that both antibiotics significantly increased the proportion of resistant streptococci. The proportion was higher after azithromycin treatment, with a peak difference of 17.4 percent at day 28. Resistance increased by a mean of 50 percent in the clarithromycin group, peaking at day eight, while resistance increased by a mean of 53.4 percent in the azithromycin group, peaking at day four. Clarithromycin selected for the erm(B) gene, conferring high-level macrolide resistance, while azithromycin selected for resistance in the early post-therapy phase.

"The key message is that antibiotic prescribing affects the patient, their environment and all the people that come into contact with that patient or with their environment," Stephanie J. Dancer, M.D., from Southern General Hospital in Glasgow, Scotland, writes in an accompanying editorial. "Doctors who understand this point can influence the risk of antimicrobial resistance, not only for our current patients but also for patients in the future."

Abstract
Full Text (subscription or payment may be required)
Editorial