The comparative in-vitro activity of roxithromycin and other antibiotics against Bordetella pertussis

In spite of vaccination programmes, whooping cough epidemics continue to occur. The disease affects all age groups, although its severity is greatest in the young, with infants being particularly vulnerable. Erythromycin is generally accepted as the drug of choice both for treatment and for prophylaxis during epidemics. Roxithromycin is a macrolide with pharmacokinetic advantages over erythromycin; it is well absorbed, produces high serum concentrations, has a long half-life and penetrates respiratory secretions well. There are no accepted standards for testing the sensitivity of Bordetella pertussis to antibiotics, and reports of the activity of roxithromycin and erythromycin are variable. Using Isosensitest agar supplemented with 5% horse blood and an inoculum of 10(4) cfu, 88 strains of B. pertussis were tested for their sensitivity to roxithromycin, erythromycin, rifampicin and trimethoprim/sulphamethoxazole. The range of MICs was 0.12-0.5 mg/L for both roxithromycin and erythromycin. Roxithromycin was bactericidal, with an MBC of 1 mg/L (as compared with 0.5 mg/L for erythromycin). Since roxithromycin is well tolerated by children when used for respiratory tract infections, the good in-vitro activity against B. pertussis, combined with its favourable pharmacokinetics, suggest it may be a good candidate for use in the treatment and prophylaxis of whooping cough.