Histopathological evaluation of brain tissue from rat pups. Five-day-old rat pups were infected by the IP route with wtRS218, RS218compl, RS218cured, E. coli DH5α or PBS. Pups that survived were euthanized 24 hrs post-infection, and the brains were excised, embedded in formalin, sectioned in paraffin, and stained with haematoxylin and eosin. A-F: meningitic lesions observed in pups infected with wtRS218 (A and B) or RS218compl
(C, D, E, and F). Arrows indicate rod-shaped bacteria in meninges and brain tissue (black), neutrophilic infiltration/neutrophilia (blue), and cerebral edema (orange). G to I: normal histology of brain tissue from pups inoculated with RS218cured
(G), PBS (H) or DH5α (I).