Figure 3. In the blood, piliated and RrgA-expressing single cocci, typified by the absence of DivIVA, express more RrgA than do chains and are more prone to penetration of the BBB.

(A) Immunofluorescence staining showing capsule (blue), pilus-1 (green), and DivIVA (red) of pneumococci in brain homogenates. For each strain, 3 mice were analyzed (approximately 300 images per mouse were taken). (B) Immunofluorescence staining of RrgA-expressing pneumococci in blood samples showing capsule (blue), RrgA (green), and RrgBC (red). “Enhanced magnification” panels show the parts within the white-outlined areas at higher magnification (original magnification, ×5). One representative image per strain is shown (×100 objective); in total, approximately 900 bacteria per strain were imaged.