Figure 3: GBS depends on HrtBA expression to colonize host blood-rich organs.

(A) Organ CFU of WT and ΔhrtBA GBS strains at 13 h post-infection. Mice infected as described in Fig. 2B were euthanized at 13 h post-infection. Dissected organs were homogenized and processed for CFU determinations (Methods). Symbols represent data from n = 8 to 10 mice from 3 independent experiments. Two tailed Mann–Whitney was used to determine P values: heart, P = 0.009; kidney, P = 0.029; liver P = 0.067; brain, P = 0.19. *P < 0.05; **P < 0.01; ***P < 0.001; ns, not significant (P > 0.05). (B) Bioluminescence from dissected organs. Indicated organs were imaged with the IVIS 200 (acquisition time, 5 min; binning 8). Representative organs from systematically infected mice sacrificed 13 h following the start of infection as in (B). a, top view; b, cross section of the indicated organs. (C) Growth of WT and ΔhrtBA in mouse blood. Bacteria from an ON preculture were diluted to an OD = 0.01 in 1 ml of freshly collected (<24 h) and heparinized blood of 6 weeks old BALB/c mice (Janvier, Le Genest Saint-Isle, France). At the indicated times, 100 μl of the culture was serially diluted and plated on agar plates for determination of the CFU. Results are representative of three independent experiments.