Modification of results of drug susceptibility tests by coexistence of Mycobacterium avium complex with Mycobacterium tuberculosis in a sputum sample: case report and experimental considerations.

We report on a patient whose sputum contained both Mycobacterium tuberculosis and Mycobacterium avium complex (MAC). The MAC failed to be detected by the PCR-based AMPLICOR test. The unrecognized coexistence of MAC in the sample modified the results of drug susceptibility tests. Experiments revealed that the presence of both M. tuberculosis and MAC was not detected by the AMPLICOR test under certain conditions.