Antibiotic susceptibility testing of Bordetella pertussis

A tube dilution test to evaluate the effectiveness of antibiotics against Bordetella pertussis is described. Five B. pertussis strains, including a well-characterized research strain and four fresh clinical isolates, were tested with several antibiotics. Erythromycin showed the highest in-vitro activity of the antibiotics tested. A concentration of 0.12 microgram/ml was bacteriostatic for all strains, while 2 microgram/ml was bactericidal. Minimal inhibitory and minimal bactericidal concentrations for ampicillin by tube tests were found to be higher than values previously reported for agar plate tests.