Fig. 1.

Uptake of Mycobacterium avium complex (MAC) incubated in the elemental mixture by macrophages. (A) MAC was incubated in Middlebrook 7H9 broth, the 1-h elemental mixture, and the 24-h elemental mixture for 1 h and 24 h, respectively, and then used to infect Raw 264.7 macrophages. The values (indicated by the bars) are the ratios of the number of bacteria inside cells divided by inocula from three repetitions. Bacteria that were incubated in either elemental mixture infected macrophages more efficiently than bacteria grown in Middlebrook 7H9 broth. Values that were significantly different (P < 0.05) from the control value (Middlebrook 7H9 broth) are indicated by an asterisk. (B) Raw 264.7 macrophages were incubated in the indicated solution for 1 h, washed, and then infected with MAC. Incubation of macrophages prior to infection had no effect on the rate of bacterial uptake. The assay was repeated three times.