In vitro activity of new rifamycins aganst rifampicin-resistant M. tuberculosis and MAIS-complex mycobacteria

Comparisons were made of the in vitro activity of rifampicin, and the rifamycin derivatives, rifapentine, rifabutin, CGP 29861, CGP 7040 and CGP 27557, against rifampicin-sensitive and rifampicin-resistant strains of Mycobacterium tuberculosis and against the Mycobacterium avium/intracellulare/scrofulaceum (MAIS) complex. The new rifamycins had MICs four to eight times lower than those of rifampicin against sensitive M. tuberculosis strains. Of the 35 rifampicin-resistant strains of M. tuberculosis 31% were sensitive to rifabutin but only 3–11% to the other rifamycins. The proportions of the MAIS strains found to be sensitive were 35% for rifapentine and rifabutin and 85–92% for CGP 29861 and CGP 7040. L'auteur a comparé l'activité in vitro de la rifampicine et des dérivés de la rifamycine-rifapentine, rifabutine, CGP 29 861, CGP 7040 et CGP 27 55-vis-à-vis des souches de Mycobacterium tuberculosis sensibles à la rifampicine et résistantes à la rifampicine et vis-à-vis du complexe Mycobacterium avium/intracellulare/scrofulaceum (MAIS). Les nouvelles rifamycines avient des CIM 4 à 8 fois plus basses que celle de la rifampicine vis-à-vis des souches sensibles de M. tuberculosis. Parmi 35 souches de M. tuberculosis resistantes a la rifampicine, 31% étaient sensibles à la rifabutine, mais seulement 3 à 11% aux autres rifamycines. Les proportions des souches du complexe MAIS trouvées sensibles ont été de 35 en ce qui concernait larifampicine, 50–69% pour CPG 27 557, rifapentine et rifabutine et 85–92 % pour CGP 29 861 et CGP 7040. Se comparó la actividad in vitro de la rifampicina y de derivados de la rifamicina — rifapentina, rifabutina, CGP 29861, CGP 7040 y CGP 27557- contra cepas de Mycobacterium tuberculosis resistentes a la rifampicina y sensibles a la rifampicina y contra el complejo Mycobacterium aviuml/intracellulare/scrofuleceum (MAIS). Las nueuvas rifamicinas tertian MICs 4 a 8 veces más bajas que la de la rifampicina contra cepas sensibles de M. tuberculosis. De un total de 35 cepas resistentes a la rifampicina de M. tuberculosis el 31% eran sensibles a la rifabutina, pero sólo 3–11% a las otras rifamicinas. Las proporciones de cepas de MAIS que resultaron sensibles fueron: 35% para la rifampicina, 50–60% para CGP 27557, rifapentina y rifabutina y 85–92% para CGP 29861 y CGP 7040.