Suboptimal ability of dirty-bedding sentinels to detect Spironucleus muris in a colony of mice with genetic manipulations of the adaptive immune system.

Spironucleus muris is an unacceptable infectious agent for most rodent colonies. Exposure of sentinel mice to dirty bedding and examination of sentinel intestinal smears was not sufficient for identification of the extent of spironucleosis within 1 mouse room. Clinical abnormalities were not reported in the animals housed in the room despite extensive breeding and a preponderance of mice genetically engineered to have nonfunctional T and B cells. In addition, researchers reported that the infection had not altered their research data. During investigation of the outbreak, direct intestinal smears performed on related animals (conspecifics, offspring, or siblings) revealed that immunodeficient mice often tested negative whereas the immunocompetent cohort tested positive. In this study, we used culled colony animals and compared direct intestinal exam test results with histologic results. The comparison showed the extent of false negatives that may occur when direct intestinal exam alone is used to detect this protozoon. Sensitivity of the direct intestinal exam for detection of S. muris was calculated to be 71%, while histology sensitivity was 91%. In light of the study results and an extensive literature review, we revised our health surveillance plan so that the age and duration of exposure to dirty bedding among sentinel mice is varied at the time of testing.

Detection of Spironucleus muris in unpreserved mouse tissue and fecal samples by using a PCR assay.

The purpose of this study was to develop a rapid DNA isolation method and a sensitive and specific PCR assay for detecting Spironucleus muris in mouse tissue and fecal samples. A PCR assay based on the carboxy terminus of the elongation factor 1a gene was developed; the PCR product was confirmed by nucleic acid sequencing and nested PCR. The new PCR assay then was used to test feces from animals that had been screened for S. muris by using direct intestinal examination and histology. The PCR assay was determined to be a more sensitive test than either direct intestinal examination or intestinal histology. To our knowledge, this assay represents the first use of a PCR-based diagnostic screening method to confirm the presence of S. muris in murine tissue and fecal samples.