Comparison of CO(2) Generation (BACTEC) and Viable-Count Methods To Determine the Postantibiotic Effect of Antimycobacterial Agents against Mycobacterium avium Complex

The postantibiotic effects (PAEs) of antimycobacterial agents determined with a BACTEC TB-460 instrument (CO(2) production) and by a traditional viable-count method against Mycobacterium avium complex (MAC) were not significantly different (P > 0.05). The longest PAEs following a 2-h exposure to 2× the MIC were induced by amikacin (10.3 h), rifampin (9.7 h), and rifabutin (9.5 h), while the shortest PAEs resulted from clofazimine (1.7 h) and ethambutol (1.1 h) exposure. CO(2) generation is a valid and efficient means of determining in vitro PAEs against MAC.