Figure 5. Inoculum size and macrophages regulate bottleneck sizes.

(A) CFU, N_b, and N_r values from mice given a low (~5E6, circles) and high (~2E7, squares) dose of extraintestinal pathogenic Escherichia coli (ExPEC) intravenously (i.v.) 5 days post infection (dpi). Note that all measurements in the spleen were significantly higher in mice inoculated with a higher dose, but only N_r, not CFU, was significantly greater in the liver. Low founding population (FP) values with high CFU indicate that a few clones replicated substantially. Points with the same color and shape are derived from the same animal. (B) CFU, N_b, and N_r values from mice treated with control liposomes (circles) or clodronate-containing liposomes (squares). CFU is significantly increased in the spleen and kidneys, but not the lung and liver. FP is significantly greater after clodronate treatment in the liver. Points with the same shape and color are from the same animal. The two animals with high CFU in the liver result from the expansion of very few clones (high CFU, low FP). Statistical significance for each comparison represents q-values from multiple Mann–Whitney tests.