Profiles of expression of the antimicrobial activities of LVFX, KRM-1648 (KRM), and CAM against M. tuberculosis (MTB) and M. avium complex (MAC) residing in MONO-MAC-6 human macrophage like cells (MM6-M phi s) and A-549 human type II alveolar pneumocyte cells (A-549 cells) were determined. First, the antimicrobial activities of LVFX, KRM, and CAM against intracellular organisms of MTB Kurono and MAC N-444 strains were examined under conditions in which infected MM6-M phi s and A-549 cells were cultured for up to 7 days or longer in medium containing the antimicrobials at their Cmaxs in the blood, achievable after oral administration of clinical dosages of these drugs. The antimicrobial effects of LVFX and KRM against respectively MTB and MAC within A-549 cells were significantly less than the activities they displayed against the same organisms residing in MM6-M phi s. Notably, it was also found that KRM had a markedly larger MIC (0.25 microgram/ml) for MAC N-444 within A-549 cells than its MIC (0.008 microgram/ml) for the same strain residing in MM6-M phi s. Thus, the profiles of LVFX- and KRM-mediated killing or inhibition of intracellular MTB or MAC organisms in A-549 cells were markedly different from those observed for the organisms residing in MM6-M phi s. Second, invasive and multiplicative phenotypes of MTB and MAC organisms, which had been adapted to either an extracellular or intracellular environment (designated as E- and I-type organisms, respectively), were studied. In the case of MTB, I-type organisms (retrieved from infected MM6-M phi s after bacterial growth within the M phi s during 5-day cultivation) were less efficient than E-type organisms (prepared by cultivating the organisms in 7H9 medium) in entering MM6-M phi s, whereas I-type organisms were more efficient than E-type organisms in invading A-549 cells. On the other hand, in the case of MAC, infectivity of I-type organisms not only in MM6-M phi s but also in A-549 cells was larger than that of E-type organisms. Next, while I-type organisms of MTB and MAC displayed more vigorous replication within MM6-M phi s than E-type organisms, the growth rate of E-type organisms within A-549 cells was more rapid than that of I-type organisms residing in A-549 cells. These findings indicate that there are significant differences between E- and I-type organisms of MTB or MAC in ability to invade and multiply within M phi s (professional phagocytes) and alveolar epithelial cells (nonprofessional phagocytic cells).