Potential mechanism of the antibacterial effect of b-MVs. (A-C) Representative transmission fluorescence microscopy images (of 35 similar ones from 4 experiments) about coincubation of b-MVs with opsonized S aureus at time points 0 (A), 10 minutes (B), and 30 minutes (C). Red marks indicate CD11b-positivity and green marks show GFP-expressing S aureus. (D) Confocal microscopy image of a representative clump (35 areas of interest were investigated from 4 experiments). Z-axis was 1 μm. Red and green marks are the same as described. (E) Statistical analysis of images taken from 4 independent experiments. Means were made on each sample by 3 individual investigators, and averaged. On the x-axis the ratio of bacteria and CD11b-positive, at least 1.5-μm wide aggregates to all CD11b-positive events is presented. Concentration of inhibitors is the same as detailed in Figure 4. Error bars show SEM, n = 4; #P < .05. (F) Relation of growth rate to the ratio of clumped bacteria (bacteria within CD11b-positive environment compared with all bacteria). Error bars represent SEM, n = 4. (G) Graphic representation of the proportion of clumped bacteria, large aggregates, and growth rate of bacteria in the presence of 3 different MV preparations. Error bars represent SEM, n = 4.