Figure 1.

Antibiotic killing kinetics in vitro and in cultured macrophages. (A) Time-kill curves of M. abscessus subsp. abscessus (MAB) under aerobic, anaerobic and biofilm conditions and using bactericidal concentrations of amikacin (AMK) and linezolid (LNZ) show viable bacterial colony forming units (CFUs) over 6 days. Antibiotics were added to bacterial culture in 7H9 broth at time zero, and drug treatment groups were compared to MAB growth control. (B) Macrophage invasion assay demonstrates that MAB of biofilm phenotype invaded cells at a higher rate than bacteria of aerobic and anaerobic phenotypes. THP-1 cells were infected as described in the materials and methods, and the percentage of invasion was calculated as the percentage of intracellular bacteria recovered at 2 h infection to initially applied inoculum. (C) MAB survival rates in THP-1 macrophages display bacterial number of the aerobic, anaerobic, or biofilm phenotype recorded over 7 days with and without AMK and LNZ treatments. Antimicrobials were added to culture monolayers at 2 h of infection and then every alternate day. Growth control without drug treatment is also shown.