Abstract
An isolated occurrence of multifocal severe granulomatous dermatitis and mastitis accompanied by extensive calcifications is described in 2 female Sprague-Dawley, SPF breeding rats. Poorly growing Staphylococcus aureus of uncertain lysotype (probably lysotype II) was isolated from the lesions of both rats. The source of infection could not be determined. No further cases in the closed barrier maintained breeding colony occurred in the following 7 months. Difficulties in interpreting these findings and the practical consequences relating to the hygienic status of the barrier breeding colony are discussed.