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Published on: December 10, 2016
Isolation, Characterization, and Epizootiology of Clostridioides cuniculi from Immunodeficient Mice with Enteric
Amy Funk1, Ashley Crawford2, Kourtney Nickerson3
11Animal Resource Center, St. Jude Children's Research Hospital, Memphis, Tennessee.
Abstract:
Mouse strains deficient in adaptive and innate immune functions, such as NSG, NSG-SGM3, and NBSGW, are highly susceptible to opportunistic infections. Over a period of 7 mo, 1,193 mice from the above 3 strains in an SPF barrier were observed with mild loose stool (LS). Affected mice had minimal weight loss and mortality. Histopathology revealed erosion of the jejunal villi with neutrophilic inflammation and Gram-positive bacterial rods adhering to the cecal mucosa with varying degrees of mucosal hyperplasia, epithelial vacuolation, and apoptosis. Anaerobic culture revealed a clostridial species that could not be speciated using standard biochemical phenotyping. Further, Clostridioides difficle and Clostridioides perfringens ELISA on intestinal contents were negative for toxins. We performed a challenge study by exposing naïve NSG mice to dirty bedding from affected cages; metagenomics on pre- and postchallenge feces identified and associated the etiopathogenesis to Clostridioides cuniculi. Whole genome sequencing and phylogenetic analysis confirmed the identity of C. cuniculi. The isolate was sensitive to trimethoprim-sulfamethoxazole (TMS). TMS was effective in abrogating signs of LS and clearing infection in mice in studies. A probe-based real-time PCR specific for C. cuniculi was established. This assay was used to screen environmental and fomite contamination and potential use in rack-level screening. We traced the source of the outbreak to a NBSGW breeding colony. However, in our observation, spontaneous C. cuniculi-induced disease was only seen in the presence of an irradiated diet in the breeding NBSGW strain and not in the breeding colonies of NSG or NSG-SGM3 strains. Interestingly, we observed that exposure to infected feces from NBSGW-induced LS in both NSG and NSG-SGM3 mice. This investigation provides insights into the etiopathogenesis and probable source of sporadic clostridial infections in immunodeficient mice and lays the groundwork for its prevention and surveillance in immunodeficient mouse colonies.
Insights
Immunodeficient mice experienced mild loose stool due to Clostridioides cuniculi infection. This study identified the pathogen, its source, and an effective treatment, trimethoprim-sulfamethoxazole (TMS), aiding surveillance in mouse colonies.
Area of Science:
- Microbiology
- Immunology
- Veterinary Pathology
Background:
- Immunodeficient mouse models (NSG, NSG-SGM3, NBSGW) are susceptible to opportunistic infections.
- Mild loose stool (LS) and minimal mortality were observed in 1,193 mice over 7 months.
- Histopathology revealed jejunal villi erosion and cecal mucosal changes.
Purpose of the Study:
- To identify the causative agent of sporadic clostridial infections in immunodeficient mice.
- To investigate the etiopathogenesis and source of the infection.
- To establish methods for surveillance and prevention.
Main Methods:
- Anaerobic culture and ELISA for bacterial identification.
- Challenge studies with naive mice exposed to contaminated bedding.
- Metagenomics and whole genome sequencing for pathogen identification.
- Antimicrobial sensitivity testing and real-time PCR development.
Main Results:
- Clostridioides cuniculi was identified as the cause of LS in immunodeficient mice.
- The infection was traced to a NBSGW breeding colony, potentially linked to an irradiated diet.
- Trimethoprim-sulfamethoxazole (TMS) effectively treated the infection.
- A specific real-time PCR assay was developed for C. cuniculi detection.
Conclusions:
- C. cuniculi is a significant pathogen in immunodeficient mouse colonies.
- Early detection and surveillance using specific PCR assays are crucial for prevention.
- Understanding host-pathogen interactions, including diet, is vital for managing infections in these models.
