[Antibiogram of mycobacteria for erythromycin, tetracycline and cotrimoxazole]

Disc method checks the bacterial susceptibility to erythromycin, tetracycline and cotrimoxazole, while the percentage method determines the MIC and the proportion of resistant bacilli at a critical concentration. The mycobacteria include 113 strains representing 12 species. Both methods show that cotrimoxazole is more active on germs than the other substances. Nevertheless, the sensitivity varies with the species, according to the technique. As the proportion method is a more reliable test to establish the susceptibility of mycobacteria, we have only used this technique to determine the activity spectrum of the various drugs. Specifically, M. marinum, M. scrofulaceum and M. szulgai are inhibited by the three substances, while M. kansasii, M. ulcerans and M. xenopi are especially sensitive to cotrimoxazole and erythromycin. M. fortuitum and M. haemophilum are particularly sensitive to cotrimoxazole, while they are resistant to erythromycin and tetracycline. It is the contrary with M. chelonei. M. avium and M. tuberculosis are sensitive to erythromycin and cotrimoxazole, but to a lower degree, while M. bovis does not respond to any drugs.