Abstract
An attempt was made to isolate Clostridium dijficile from a total of 565 mice from nine different conventional mouse colonies and six different specified-pathogen-free mouse colonies. C. difficile was isolated from all the conventional colonies but from none of the specified-pathogen-free colonies. Ampicillin injected intraperitoneally increased the isolation rate of C. difficile from mouse faeces to 63·6% compared with 19·4% from untreated mice.