Mycobacterium resistance to antimycobacterial reagent

This study was carried out in the tuberculosis laboratory of the Institut National d'Hygiène in Rabat, Morocco, in 1997. The aim was to determine the percentages of drug-resistant strains by using 150 antibiograms. Six antimycobacterial medications were used as tuberculosis treatment: isoniazid (INH), streptomycin (STM), rifampicin (RIF), ethambutol (EMB), kanamycin (KAN) and p-amino-salicylic acid (PAS). The cultures were plated onto a simple agar (Lowenstein-Jensen) plate containing different concentrations of drugs. This test demonstrated the presence of major antimycobacterial (INH, RIF, STM)-resistant strains of Mycobacterium tuberculosis in the following percentages respectively: 34.6 per cent, 33.1 per cent and 26.1 per cent and 80 per cent, 70 per cent and 40 per cent in the case of atypical mycobacteria. The association of INH/RIF showed the highest percentage (27.6 per cent) for Mycobacterium tuberculosis and 70 per cent for atypical strains, whereas, when we associate INH/RIF/STM, the resistance rate becomes 17.69 per cent for Mycobacterium tuberculosis and 25 per cent for atypical mycobacteria. The resistance in question was a secondary or acquired resistance because the tested strains were isolated from patients who had not responded to standard tuberculosis treatment.