FIGURE 3.

In a whole blood model, M. catarrhalis is killed through MAC-mediated killing. CFSE-labeled bacteria were added to whole blood previously incubated with 1 μM OmCI, 10 μM cytochalasin D or both. (A,B) M. catarrhalis clinical isolate #473 was picked as more serum resistant than most clinical isolates and the reference strain RH4 (C,D) Staphylococcus aureus JE2 was used as an example of MAC-resistant bacteria (A,C) Survival of bacteria overtime was assessed by collecting a sample at t = 0, 30, 60, and 90 min post-infection, and plating bacteria on agar plates. The number of bacteria is represented as log of CFU/ml. (B,D) Phagocytosis was assessed by detection of CFSE+ cells among granulocytes and monocytes from whole blood. At 1 and 2 h post-infection, a sample was collected, red blood cells were lysed, cells were fixed and stained with anti-CD14, and cells were analyzed using flow cytometry. The percentage of CFSE+ cells was measured in granulocytes and monocytes (gated using Side Scatter and CD14 staining). Mean (±SD) from four (A) or three (B–D) independent experiments are shown. Statistical significance of differences was calculated using two-way ANOVA with Dunnett’s post-test; *p < 0.05; **p < 0.01; and ***p < 0.001.