Intracellular replication of 3 isogenic morphotypes of B. pseudomallei in human macrophages. Differentiated U937 cells were incubated for 2 h with B. pseudomallei at a MOI of 25:1, after which non-adherent bacteria were removed by washing and incubation for a further 2 h with kanamycin. At this 4 h time point, fresh medium containing kanamycin was added and incubation continued for a further 4 h. The bacterial count and colony morphology were enumerated at 4, 6 and 8 h by cell lysis and plating onto Ashdown agar. The data shown in Figure 1A represent mean values for each isogenic morphotype derived from 5 B. pseudomallei isolates and is expressed as the bacterial proportion at 6 and 8 h compared with the number at 4 h (which was defined as 100%). Figure 1B-1F shows the number of intracellular bacteria in CFU/ml for individual isolates. Data plots are means ± standard deviations.