PULSED-EXPOSURE AND POSTANTIBIOTIC LEUKOCYTE ENHANCEMENT EFFECTS OF AMIKACIN, CLARITHROMYCIN, CLOFAZIMINE, AND RIFAMPIN AGAINST INTRACELLULAR MYCOBACTERIUM-AVIUM

We investigated the postantibiotic effects (PAEs) of four agents again st Mycobacterium avium in a human macrophage model under two different experimental conditions. For postantibiotic leukocyte enhancement (PA LE), bacteria were exposed to antibiotics prior to their phagocytosis, whereas for pulsed exposure (PE), antibiotics were added after phagoc ytosis. In both cases, the drugs were used at their peak concentration s in serum (C-max) for 2 h. The results showed two different patterns: one for the drug for which results under PE and PALE test conditions did not significantly differ (amikacin) and one for drugs for which PA E values were significantly higher under PE test conditions (clarithro mycin, clofazimine, and rifampin). These data suggest that even a brie f exposure of M. avium to peak concentrations of certain drugs in seru m may result in prolonged and persistent suppression of bacterial grow th inside human macrophages.