Effect of Rifampin and Minocycline on Meningococcal Carrier Rates

Abstract

Six hundred forty-three military recruits in four companies were treated for five days with either rifampin, minocycline, ampicillin, or a placebo. All three antibiotics significantly reduced the carrier rate during therapy, but among the ampicillin-treated group. the carrier rate returned to pretreatment levels within two weeks. In the groups treated with rifampin and minocycline, the carrier rate remained below 20% during four weeks of observation after antibiotics were discontinued. The only significant difference between rifampin and minocycline in this study was related to the emergence of resistant strains. Seventeen recruits treated with rifampin subsequently carried organisms resistant to the drug while resistance to minocycline was not encountered. Rifampin-resistant isolates fell into two distinct populations. For one, the MIC of rifampin was 2–6 µg/ml, and the other group was inhibited only by 100–200 µg/ ml.