[Dapsone inhibition of the bactericidal action of rifampicin on Mycobacterium leprae in mice]

In the experimental infection of mice by Mycobacterium leprae, the bactericidal effect of 4 weekly doses of rifampicin (RMP) is completely suppressed if this administration is preceded by a daily treatment of dapsone (DDS) during one month then continued in conjunction with rifampicin. The application of this methodology: the delayed adding of rifampicin clearly shows the bacillary persistence induced by dapsone (DDS). The rifampicin appears to be less effective on Mycobacterium leprae when its metabolism is inhibited either by the action of a drug such as dapsone (DDS), or spontaneously. The highlighting of this late-appearing antagonism between rifampicin and dapsone in mice, should not at present lead to the questioning of the therapeutic procedures recommended by the WHO, because of the limits of this experimental model, namely the small size of bacillary populations studied over relatively short periods of time.