The MTb clinical strain CDC1551 was prepared by adding 100 µl of frozen bacteria stock into 10 ml of Middlebrook 7H9 medium (Difco BD, www.bd.com) supplemented with albumin dextrose complex (ADC) and 0.05% Tween 80 (Sigma-Aldrich, www.sigmaaldrich.com). The cultures were grown to an OD650 of 0.4 at 37°C to ensure that they were in the logarithmic growth phase. Bacteria were then plated, washed with PBS, resuspended in PBS, and passed through a 5 µm filter to ensure that the bacteria were in a single cell suspension. Bacterial cell numbers were determined by measurement of OD650 before further dilution with RPMI 1640 medium for cell infection studies at 10∶1 PBMC∶ bacilli or 1∶1 MDM∶ bacilli and THP-1∶bacilli. Colony-forming unit (CFU) analysis was performed and on days 4 and 7 the average CFU counts were 6×103 and 5×104, respectively, confirming that mycobacteria levels increased over the course of infection of primary MDM.