The concept of the GMC, on the one hand being part of an integrated research network and on the other hand harboring mice with varying hygienic status and thereby representing a challenging experimental animal unit, is based on a working compromise. This takes into account the basic specific research requirements. These include, from the scientist's point of view a modular design with mouse rooms and laboratories adjacent to each other, simultaneous handling and analysis of mice from different hygienic sources, unrestricted transfer of mice between the modules, frequent access of numerous users from different facilities, and a shared infrastructure. From the hygienic point of view, mice and personnel from different areas/facilities/institutions, the use of a shared infrastructure and continuous flow of mice between the different modules require standardised measures and efficient means to avoid cross infections and development of disease during the phenotyping workflow. The measures for husbandry, barrier- and import regulations and acceptance of mice only with certified pathogens have been implemented in order to prevent spreading of pathogens from infected to non-infected colonies and to minimize the risk of carry-over and dissemination of infections in the GMC.

To improve the knowledge of the actual hygienic status, a custom-tailored sentinel monitoring program was implemented, which uses sentinel mice standardised according to strain, age and gender, thereby avoiding the use of valuable mutant animals. To account for monitoring of mice in IVC racks, use of the newly developed Bioscreen TM integrated in the IVC racks facilitates combined testing of soiled bedding and soiled air. In case of detection of new pathogens the GMC database allows to trace back suspicious animals and the origin of infection.

Despite available state-of-the-art equipment and standardised operating procedures in the mouse rooms and laboratories, residual risks arising from specific scientific needs of this unique research facility remain unresolved. These include the handling of mice in the phenotyping instruments outside the IVCs or changing stations, the fluctuation and individual discipline of the personnel, unknown susceptibility of mutant mice to pathogens and an unpredictable influence of the stress exerted on the mice due to the fast workflow within the phenotypical screens.