Figure 2

Intracellular growth rate in differentiated THP-1 cells. Cells were infected with 16 Beijing isolates, the control strain H37Rv, and a non-Beijing strain (C). Intracellular growth was expressed as the growth rate (Y Axis), ie, the slope of the function of log₁₀ CFU values during the infection period. CFUs were determined 3 hours after infection and at days 1, 4, and 7. Results are expressed as the mean ± standard error of the three independent experiments per strain. Asterisks indicate isolates with significantly higher intracellular growth rates (P < 0.05).