Microbiological contamination in genetically modified animals and proposals for a microbiological test standard for national universities in Japan

The Biosafety Committee of the Japanese Association of Laboratory Animal Fa cilities of National Universities (JALAN) investigated recent episodes of m icrobiological contamination in genetically modified mice (GMM), and the co untermeasures taken when the contaminated GMM were introduced into animal f acilities, by questionnaires addressed to 53 animal facilities belonging to JALAN and serological tests. Although almost all of the contaminated GMM w ere accepted with conditions such as rederivation after or before reception and housing in designated rooms, contamination with a spectrum of microorg anisms was demonstrated in GMM transferred domestically and from abroad. In serological tests, Mycoplasma pulmonis, mouse parvovirus, and mouse enceph alomyelitis virus were detected in GMM transferred from domestic facilities and from abroad. The present results of the questionnaires and serological tests suggest that GMM are highly and widely contaminated with microorgani sms compared with mice from commercial breeders. Thus, we propose a microbi ological requirement, including microbiological status - excellent, common, and minimum - as a guide for the transfer and procurement of mice and rats in Japan.