A simple and inexpensive method for maintaining a defined flora mouse colony.

The use of autoclaved cages, feed, bedding, water, and filter caps combined with aseptic techniques of animal husbandry in an existing mouse colony was ineffective in maintaining a defined flora colony. The addition of a laminar air flow bench equipped with a high efficiency particulate air filter provided a sterile environment in which to manipulate mice when the filter caps were removed. The installation of a duct to direct all air entering the room through the bench filter reduced the airborne bacterial counts in the room. This modification combined with the culling or marking of infected cages so that no future breeders would be taken from these cages eliminated a number of bacterial contaminants (Staphylococcus aureus, S epidermidis, and streptococci) from the colony.