DETERMINATION OF MICS FOR MYCOBACTERIUM-AVIUM MYCOBACTERIUM-INTRACELLULARE COMPLEX IN LIQUID-MEDIUM BY A COLORIMETRIC METHOD

We investigated the potential of a rapid colorimetric microassay based on the reduction of dimethylthiazol-diphenyltetrazolium bromide (MTT) for determining the growth of Mycobacterium avium-M. intracellulare c omplex (MAC) and MICs of clofazimine, resorcinomycin A, and the quinol one PD 127391 against MAC. The reduction of MTT was directly proportio nal to the number of viable bacteria. A comparison of the MIT reductio n test with the [H-3] glycerol uptake assay show ed the former to poss ess higher analytical sensitivity for detecting MAC growth in microtit er plates. The MTT reduction test avoids the use of radioisotopes and costly material and equipment; it is reliable, reproducible, and conve nient for rapid routine susceptibility testing of MAC.