Uptake of selected antibacterial agents in Mycobacterium avium.

The antibacterial action of 64 drugs against Mycobacterium avium ATCC 15769 was screened in Middlebrook 7H9 liquid medium. The most active drugs were ansamycin, rifampicin, clofazimine, and pristinamycin. The antibacterial action of the selected drugs was confirmed by testing clinical isolates on Middlebrook 7H10 agar medium. The antibacterial actions were not related with the hydrophobicities and molecular weights of the drugs. However, all the active drugs were highly hydrophobic molecules of low polarity. These drugs dissolved into the lipids forming the outer layers of the bacterial envelope and they appeared to interact with the surface amphiphils.