Neuropathogenesis of Tyzzer's organism in intranasally infected mice.

The neuropathogenesis of Tyzzer's organism was comparatively studied in suckling and weanling mice after intranasal inoculation. In sucklings, suppurative rhinitis was produced in 24 hr postinoculation (p.i.) and organisms were detected in olfactory as well as supporting cells of the nasal mucosa. The lesions later developed to the lamina propria and propagation of organisms was seen within basal and glandular cells. On day 3 p.i., some organisms were found along with the olfactory nerve fibers and within neurons in the olfactory bulbs. Meningoencephalitis was produced with intraneuronal growth of bacteria on day 5 p.i. or later. On day 7 p.i., the brain lesions spread multifocally to the posterior parts and bacterial antigen in the nasal mucosa disappeared. In weanlings, infection was first established in the nasal mucosa and then some necrotized lesions were produced in the olfactory bulbs though much less in severity as compared to those of sucklings. Both suckling and weanling mice had necrotizing hepatitis while hemorrhagic enteritis was seen only in some sucklings.