Selection of Antibiotic Resistance by Azithromycin and Clarithromycin in the Oral Flora

Impact of Azithromycin and Clarithromycin Therapy on Pharyngeal Carriage of Macrolide-Resistant Streptococci Among Healthy Volunteers: A Randomised, Double-Blind, Placebo-Controlled Trial

Resistance to antibiotics is a major public-health problem and studies linking antibiotic use and resistance have shown an association not a causal effect. Utilizing the newer macrolides, azithromycin and clarithromycin that are commonly prescribed for respiratory infections, we investigated the direct impact of antibiotic exposure on resistance at the individual level.

Resistance to antibiotics is a major public-health problem and studies linking antibiotic use and resistance have shown an association not a causal effect. Utilizing the newer macrolides, azithromycin and clarithromycin that are commonly prescribed for respiratory infections, we investigated the direct impact of antibiotic exposure on resistance at the individual level. 203 healthy cohorts were treated with azithromycin, clarithromycin, or a placebo in a randomised, double-blind trial. Pharyngeal swabs were collected pre- (day 0) and post-antibiotic administration (days 8, 14, 28, 42, 180) and proportions of macrolide-resistant streptococci (MRS) were determined at each time-point.

Inclusion Criteria:

• healthy adults (≥ 18 years of age)
• non-pregnant
• free of any respiratory tract infection
• not having been administered any antibiotic at least in the past three months

Exclusion Criteria:

• <18 years of age
• pregnant
• having a respiratory tract infection
• having been administered any antibiotic at least in the past three months