Figure 6.

Nicotinamide (NAM) and pyrazinamide (PZA) fail to inhibit Mycobacterium tuberculosis replication within macrophages in the absence of the bacterial nicotinamidase/pyrazinamidase (PncA). Monocyte-derived macrophages were infected (estimated multiplicity of infection, approximately 1) with wild-type (WT) H37Rv or H37Rv-pncAdel for 4 hours in the presence of each drug (1 mmol/L) after which monolayers were washed. Colony-forming units (CFUs) were enumerated after monocyte lysis (0.1% Triton X-100), either immediately (day 0) or after incubation for 3 days in the presence of drug. Mean CFU counts are plotted with standard deviations. No NAM/PZA activity on H37Rv-pncAdel CFU was observed in 2 independent experiments. *P < .05, †P < .01. Abbreviation: NS, not significant (P ≥ .05).