Previous studies have shown an association between increased antibiotic use and increased resistance. This study recruited healthy individuals aged 18 or older who had not had any antibiotics in the preceding three months (n=224). Entrants were randomised to treatment with azithromycin, clarithromycin or placebo. Throat swabs were taken before the treatment (day 0) and at regular intervals after administration of the trial medication (8, 14, 28, 42 and 180 days).
The proportion of streptococci that were resistant to macrolide antibiotics was assessed from each swab. Bacterial resistance was higher in both antibiotic arms of the study when compared to placebo:
- Azithromycin group - mean increase 53.4% [95% CI 43.4-63.5; p<0.0001]
- Clarithromycin group - mean increase 50.0% [95% CI 41.7-58.2; p<0.0001]
Peaks in resistance occurred at day 4 for azithromycin and day 8 for clarithromycin although resistance was statistically increased at all points of the study. The authors conclude that, "physicians prescribing antibiotics should take into account the striking ecological side-effects of such antibiotics".
Action: All clinicians should already be aware of the long-term risks posed by antibiotic resistance and adopt strategies to minimise unnecessary use of antibiotics.
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