Experimental production of brain abscess in rats

This study was aimed at establishing a single step method for production of brain abscess in the rat utilizing Staphylococcus aureus inoculum, prepared from a clinical specimen. Adult Wistar rats were stereotactically inoculated with 1 ul of multidrug resistant Methicillin sensitive Staphylococcus aureus inoculum. A dilute non-standardized inoculum and a standardized inoculum containing 1 million organisms/ul were utilized. Rats were sequentially sacrificed from 24 hours to 24 days. Gross and histopathologic studies with H & E, avidin biotin conjugate (ABC) immunoperoxidase technique using monoclonal anti glial fibrillary acidic proteins (GFAP) antibody and Gram's stain were performed. No abscess was formed with the dilute non-standardized inoculum. The overall success rate was 32.14 percent. Cerebritis was evident in the 24 hour specimen. An acute abscess was seen by day 4, and although fibroblasts were noticed on day 10 a well defined capsule was seen only by day 16 when gliosis became evident.Clusters of Gram positive cocci were demonstrable in all specimens. Cultures from abscess specimens yielded pure Staphylococcus aureus growth with a similar drug sensitivity as the parent inoculum.