To the Editor: In their article describing an outbreak of Bordetella pertussis infection, Spearing and colleagues report an adult contact who was infected with B. pertussis and was treated with roxithromycin.1 In our experience, this is common practice in Australia, where roxithromycin is a frequently used macrolide antibiotic.

We are currently preparing a systematic review (registered with the Cochrane acute infections group) of the effectiveness of antibiotic therapy for treating pertussis. We have found no studies of the effectiveness of roxithromycin for either treatment or contact prophylaxis for pertussis infection. B. pertussis is sensitive in vitro to roxithromycin but 2–4-fold less so than to erythromycin.

While relying on the class effect of macrolides in eradicating B. pertussis and using roxithromycin in preference to erythromycin because of its lower side-effect profile may seem logical, there is no evidence to support this practice. In contrast, there is at least one study showing the efficacy of clarithromycin as an alternative to erythromycin for the treatment of pertussis.2