Comparison of rifampin and ampicillin in day care center contacts of Haemophilus influenzae type b disease.

A prospective, randomized, crossover trial was conducted comparing therapy with rifampin to therapy with ampicillin in eradicating Haemophilus influenzae type b carriage. Twenty-eight carriers were identified in a day care center following exposure to a patient with H influenzae type b meningitis; 26 children were randomly assigned to treatment with either ampicillin (100 mg/kg for five days) or rifampin (20 mg/kg for four days). Cultures were repeated two and four days after discontinuing therapy. In the initial trial, 6/17 children (35%) remained culture positive after treatment with ampicillin compared to 0/9 children treated with rifampin (P = .106). The six children who were ampicillin treatment failures had H influenzae type b isolates sensitive to that drug. These children were subsequently treated with rifampin and their cultures became negative. (For both trials, P = .027). Repeat cultures 30 days after therapy in 20 treated children revealed one culture positive for H influenzae type b. No further cases developed in the day care center (four months of follow-up). These data suggest that rifampin may be more effective than ampicillin in chemoprophylaxis of contacts of H influenzae type b disease.