Fig. 3

Intracellular growth of M. abscessus strains by flow cytometry. Internalization of strain CRM0019 or ATCC 19977 in epithelial (A549) and macrophage (RAW) cell lines was detected by flow cytometry after 6, 24, 48 and 72 h of infection. Intracellular growth was evaluated by calculating fluorescence ratio (a) or with histograms of GFP fluorescence (b). Cells infected with wild-type bacteria and uninfected cells were used as negative controls for GFP fluorescence. Statistical differences were calculated between 6 h, the first period of infection, and 24, and 72 h of infection. *p < 0.05 **p < 0.01 ***p < 0.001. Data represent mean +/− SD from 3 independents experiments