The activity of amoxicillin plus clavulanic acid against Mycobacterium leprae in mice

The activity of amoxicillin plus clavulanic acid against logarithmically multiplying Mycobacterium leprae was evaluated by treating mice by gavage five times weekly with various amounts of the compound from day 60 to day 150 after footpad infection. At 25, 50, and 100 mg/kg, it was inactive; at 200-600 mg/kg, multiplication of M. leprae was entirely prevented for 6-11 months after drug discontinuation, consistent with observations of bactericidal activity for M. leprae. In a confirmatory study in mice, five-times-weekly intraperitoneal ticarcillin plus clavulanic acid, 1000 mg/kg, was not bactericidal for M. leprae, while amoxicillin plus clavulanic acid, 400 mg/kg five times weekly, was weakly bactericidal (80% +/- 14%). In addition, activity of amoxicillin plus clavulanic acid, 400 mg/kg, was evaluated in combination with previously established active drugs dapsone, 0.0001% (in diet), rifampin, 20 mg/kg monthly (by gavage), and kanamycin, 25 mg/kg five times weekly (intraperitoneally). All three combinations were active, and the combination with kanamycin was more active than either drug alone.