Figure 4.

GBS exposure to antibiotics. (A) GBS cultures of the ST-17 strain (left) and ST-12 strain (right) were exposed to 5µg/ml ampicillin for 48 hr then 1µg/ml ampicillin for 24 hr. After ampicillin exposure, each culture was resuspended in fresh medium to detect any ampicillin tolerant bacteria. This figure shows representative results from 4 separate experiments (B and C) Phagocytosis (B) and 24 hr survival rate normalized to initial uptake (C) of GBS after cultures were exposed to a sub-inhibitory concentration of ampicillin (0.05µg/ml), penicillin (0.01µg/ml), or erythromycin (0.01µg/ml) during the macrophage infection period. (D) Phagocytosis of BioParticles after 1hr exposure to antibiotics as in B and C. B-D show all data combined from 3 separate experiments done in triplicate. (E) Relative capsule size of GBS after 1hr antibiotic exposure as described in B and C normalized to the media control. Data represents average relative capsule size from 3 separate experiments. (F) Representative images of capsule staining of GBS cultures used for relative capsule size shown in E. Capsule is represented by the clear zone around the cell. RFU: relative fluorescence units; Amp: Ampicillin, Pen: Penicillin; Eryth: Erythromycin (*P < 0.05, **P < 0.01, ****P < 0.0001).