Environmental samples make soiled bedding sentinels dispensable for hygienic monitoring of IVC-reared mouse colonies

Abstract

Accurate knowledge of the health status of experimental animals is pivotal to high scientific and ethical standards in biomedical research. Individually ventilated cages (IVCs) are becoming the predominant system for housing laboratory mice, as they prevent cage-to-cage infections. However, this feature constitutes a major drawback for hygienic monitoring of mouse colonies, as traditional screening programs build on reliable transmission of infectious agents from experimental animals to sentinel mice commonly tested as representatives for the mouse colonies. In recent years, the laboratory animal community has realized that sentinels are ineffectual for screening mouse colonies in IVC systems because infections are often not transmitted to sentinels and therefore remain undetected. Furthermore, sentinel monitoring results in high numbers of used animals. In contrast, environmental monitoring provides a more reliable approach to identify and exclude pathogens in rodent colonies. In recent studies we provided evidence that polymerase chain reaction analysis of exhaust air particles is superior to soiled bedding sentinels for different agents. In this study, we show that testing pooled environmental samples generates more meaningful information compared to soiled bedding sentinels during routine hygienic monitoring in different barriers.

Comparing Mouse Health Monitoring Between Soiled-bedding Sentinel and Exhaust Air Dust Surveillance Programs

“…13 In addition, due to the high sensitivity of exhaust debris PCR surveillance, the potential for detecting contaminant trace DNA material or inactive agents present in the environment has been noted. 27,28 These described drawbacks lead to increased false-positive results, which require costly follow-up tests. In our experience, since implementing EAD health surveillance throughout all facilities at our institution, a total of 4 false positives have been detected over the course of approximately 2 y.…”

“…Although previous research has evaluated the quality of exhaust dust PCR surveillance, 2,5,8,12,17,19,25,[27][28][29]30,39 to our knowledge, our current study is the first to compare immunocompetent SBS and EAD colony surveillance by using sentinel collection media on Allentown IVC racks in a working biomedical research barrier. Other investigators showed similar results from a single 3-mo evaluation using the same collection media and IVC racks; however, sentinel mice were immunocompromised, and MNV status was not evaluated.…”

“…Some agents are not transmitted through the fecal-oral route, including Sendai virus and Filobacterium rodentium (previously cilia-associated respiratory bacillus), or have low prevalence, such as some host-adapted bacteria and parasites, and are not transmitted reliably or at all through soiled bedding. 1,5,8,9,17,23,27,33 Given these known limitations of the use of SBS, other methods of health monitoring have been considered and used to increase the sensitivity of detection of these agents.…”

“…Exhaust debris PCR monitoring of IVC racks has recently been evaluated for its efficacy in detecting several pathogens. 2,5,8,17,19,22,25,[27][28][29]39 Most commonly, the studies found that detection through PCR analysis of exhaust debris was a reliable option or a good adjunct to a health monitoring program. Notably, PCR evaluation of exhaust debris was found to be reliable and in some cases superior in detecting mouse hepatitis virus, Sendai virus, Helicobacter spp., Rodentibacter pneumotropicus and heylii (previously Pasteurella pneumotropica), 3 pinworms, fur mites, and enteric protozoa.…”

Multiplex Immunochromatographic Assay for Serologic Diagnosis of Major Infectious Diseases in Laboratory Mice

“…8 To solve these problems, methods that assess sentinel exposure by surveying the exhaust air of IVC have been reported. 4,6,18,19,26 However, if a pathogenic microbe is detected in animal rooms, sentinels as well as experimental animals must be examined to identify sources of infection or sensitive hosts. In most cases, experimental animals need to Vol 58, No 6 Journal of the American Association for Laboratory Animal Science November 2019 be evaluated without euthanizing them because the number of maintenance strains is increasing and because few animals of each strain are cohoused.…”