Filterable forms of Nocardia: a preferential site of infection in the mouse brain

Filterable forms of Nocardia (i.e., filterable nocardiae) are characterized as spherical structures containing many granules. They fluoresce brilliantly under ultraviolet light when stained with acridine orange and are acid-fast in paraffin-containing broth cultures. An accumulation of acid-fast lipochrome bodies, similar to filterable nocardiae, is observed in glial cells of the midbrain nigral lesions found in Parkinson's disease (PD). Preliminary results from experimental infection with filterable nocardiae revealed a possible site of infection in a region of the nervous system associated with movement disorders. Here we examined the preferential site of filterable nocardiae infection in the brain and investigated the effects of various chemicals and biological substances in relation to this preferential site on nocardiae growth in vitro. Examination of tissue samples immunostained for filterable nocardiae revealed that neurons in the olfactory bulbus and the midbrain periaqueductal gray area were immunopositive for filterable nocardiae. Several erythrocytes within blood vessels of the brain were also immunopositive. In addition, a dose-dependent relationship was observed between the growth of filterable nocardiae and erythrocyte lysates. These results suggest first that the preferential site of infection for filterable nocardiae might be erythrocytes, but could also be neurons in the bulbus olfactorius as well as in the midbrain periaqueductal gray area. Second, filterable nocardiae might grow to be branching cylindrical tubules such as that of mycelial bacteria in the presence of erythrocyte lysates.