Adoption of Exhaust Air Dust Testing in SPF Rodent Facilities.

Reliable detection of unwanted microbial agents is essential for meaningful health monitoring in laboratory animal facilities. Most rodents at our institution are housed in IVC rack systems to minimize aerogenic transmission of infectious agents between cages. The most commonly used rodent health monitoring systems expose live sentinel rodents to soiled bedding collected from other rodent cages on IVC racks and subsequently test these soiled-bedding sentinels for evidence of infection with excluded agents. However, infectious agents might go undetected when using this health surveillance method, due to inefficient organism shedding or transmission failure. In 2016, our institution switched the health monitoring methodology for the majority of our SPF rodent colonies to real-time PCR testing of environmental samples collected from the exhaust plenums of IVC racks. Here we describe our rationale for this conversion, describe some interesting health monitoring cases that arose soon after the conversion, and discuss a potential problem with the conversion-residual nucleic acids. We compared cost and implementation effort associated with 2 sampling methods, sticky swabs and in-line collection media. We also compared the ability of these 2 sampling methods to detect 2 prevalent microbes in our facilities, Helicobacter and murine norovirus. Our institution-wide switch to health monitoring by real-time PCR assay of exhaust air dust samples thus far has provided a sensitive, simple, and reliable approach for maintenance of SPF conditions in laboratory rodents and has dramatically reduced the use of live sentinel animals.

Potential for using a hermetically-sealed, positive-pressured isocage system for studies involving germ-free mice outside a flexible-film isolator.

Germ-free mice are used to examine questions about the role of the gut microbiota in development of diseases. Generally these animals are maintained in semi-rigid or flexible-film isolators to ensure their continued sterility or, if colonized with specific microbiota, to ensure that no new species are introduced. Here, we describe the use of a caging system in which individual cages are hermetically sealed and have their own filtered positive airflow. This isopositive caging system requires less space and reduces animal housing costs. By using strict sterile techniques, we kept mice germ-free in this caging system for 12 weeks. We also used this caging system and approach to conduct studies evaluating a) the stability of the microbiome in germ-free mice receiving a fecal transplant and b) the stability of dietary-induced microbiota changes in fecal-transplanted mice. As has been shown in fecal transfer studies in isolators, we found that the transferred microbiota stabilizes as early as 2 weeks post transfer although recipient microbiota did not completely recapitulate those of the donors. Interestingly, we also noted some sex effects in these studies indicating that the sex of recipients or donors may play a role in colonization of microbiota. However, a larger study will be needed to determine what role, if any, sex plays in colonization of microbiota. Based on our studies, an isopositive caging system may be utilized to test multiple donor samples for their effects on phenotypes of mice in both normal and disease states even with limited available space for housing.

Immunocompetent orthotopic isograft mouse model of ovarian cancer for high-intensity focused ultrasound (HIFU) treatment.

Ovarian epithelial carcinoma is the most common form of ovarian cancer, causing more deaths than any other cancer in women with gynecologic malignancies in the United States. The poor outcome for women with late-stage ovarian cancer underscores the need for early detection strategies and for new treatment options to be developed. High-intensity focused ultrasound (HIFU) is a therapeutic modality that is safe and effective against various types of solid tumors, and has the potential to serve as a treatment for ovarian cancer. Use of an appropriate animal model is important in obtaining relevant data for translational research. The purpose of the study reported here was to modify and create an immunocompetent orthotopic tumor isograft model for evaluation of intra-operative HIFU application. This model would resemble the clinical presentation of human patients with late-stage ovarian cancer. We were able to consistently produce a surgical model that presented with a single large, intra-abdominal tumor nodule within the left ovarian bursa, as well as multiple small nodules on the surface of other organs and tissues. This technique may also be used to refine other tumor models, using the ovarian bursa as an implant site for heterotopic tumor isografts.