FIG. 2.

C. burnetii loads in macrophages from C57BL/6, BALB/c, and A/J mice. Macrophages were infected for 24 h with approximately 100 infective bacteria/cell. At different times, the cultures were processed to determine the relative bacterial loads. (A) Relative amounts of viable bacteria recovered from cultures infected for 2, 4, or 6 days were determined as previously described (18). FFU, focus-forming units. (B) Relative bacterial loads in LRVs from cells infected for 4 or 6 days were determined as previously described (16). Gray bars, BALB/c; black bars, A/J; open bars, C57BL/6. Asterisks indicate statistically significant differences between infective bacteria recovered from C57BL/6 macrophages and those from A/J and BALB/c macrophages (P < 0.05). The experiments were performed in triplicate sets of wells; the values shown are averages of triplicates from one representative experiment out of three performed. Int. pixel., integrated pixel value (16).