Mycoplasma pulmonis infection in the brains of rodents.

Mycoplasma pulmonis was frequently present in the brains of both naturally and experimentally infected rats. Recovery of mycoplasmas from the brain was more common than from the lungs, except when there was a mixed respiratory tract infection or when immunodeficient rats were used and they developed chronic respiratory disease. After intranasal infection the mycoplasmas could be recovered from the olfactory lobes before the rest of the brain. Most of the organisms were demonstrated in small groups in the sinuses and blood vessels of the brain, apparently adhering to the epithelium; a few were present in the lumen. The presence of some mycoplasmas outside the blood vessels and attached to cells in tissue showed that the blood-brain barrier can be crossed. Three days after intranasal inoculation, most organisms lined the nasal mucosa, but a few were seen close to neurons, on cells in the olfactory lobes, and in blood vessels.