Current Microbiological Status of Laboratory Mice and Rats in Experimental Facilities in Japan

On the basis of our 2011 microbiological monitoring tests, we report here the current microbiological status of mice and rats housed in experimental facilities in Japan. We tested more than 14,000 mice, 6,000 serum samples, 500 fecal or cecal samples, and 200 lung samples from 3,549 mouse facilities within Japanese universities and institutes (U/I), pharmaceutical companies and contract research organizations (P/C). We also tested more than 1,500 rats, 1,600 serum samples, and 20 fecal or cecal samples from 772 U/I and P/C rat facilities. Bacterial cultures, serology, microscopy, PCR, and DNA analysis using DNA chips were performed. Staphylococcus aureus (18.8% in mouse facilities, 58.6% in rat facilities) was the most prevalent agent in both the mouse and rat facilities. The next most prevalent agents in the mouse facilities were murine norovirus (11.97%), intestinal protozoa (0.05-8.49%, from various species), Pasteurella pneumotropica (5.32%), and Helicobacter hepaticus (3.17%), while intestinal protozoa (0.74-6.84% from various species), Syphacia muris (6.20%), Pseudomonas aeruginosa (3.61%), and Pasteurella pneumotropica (3.05%) were the subsequent most prevalent agents in the rat facilities. These results suggest that the currently prevalent microbes in laboratory mice and rats in Japan are mainly opportunistic pathogens, intestinal protozoa, and microbes with low pathogenicity.