Citrobacter rodentium

Prevalence
Citrobacter rodentium affects mice and (one publication in 1999) mongolian gerbils. It is a gram negative, non-motile bacterial rod that causes “transmissible murine colonic hyperplasia” (TMCH). It rarely occurs in barrier facilities.
 
Diagnosis
Bacterial culture onto Horse Blood/MacConkey agar. Confirmation by PCR.
 
Disease
Pathological lesions include, hyperplasia of the colonic mucosa, diarrhoea and colitis accompanied by clinical signs of weight loss, rectal prolapse, runting and even death. Initial colonisation of the surface of the lymphoid tissue in the caecum within a few hours. After 2-3 days bacteria are seen in the distal colon. Depending on the strain of mouse peak proliferation of the organism occurs at day 5-14 post infection (pi) with clearance of the caecum and then colon by day 21-28 pi.
 
Strains
All strains of mice affected, however the majority (C57Bl/6, Swiss, Balb/c) show little or no mortality with C.rodentium. But C2H/HeJ is exquisitely sensitive with high mortality by day 10 pi.
 
Screening
Microbial testing of faecal contents involves the screening of C. rodentium with confirmation by PCR.
 
Transmission
Faecal-Oral route.
 
Duration
Once the pathogen gains entry into the gastrointestinal tract, it attaches to the caecal patch causing gross lesions which include thickening of the colonic walls, a shrunken caecum and abnormalities in the stool of the animal. The progressive nature of the pathogen induces a profound hyperplasia of the colonic mucosa which occurs 2-3 weeks after infection.
 
Durability
When the infection reaches its’ maximum pathological hyperplasia, it is no longer possible to isolate the organism from the intestines.  Two months post-infection the colonic mucosa appears normal.
 
Significance
As a non-spore forming organism, the rate of infection of C. rodentium is slow among infected colonies.
 
Control
Pathogen exclusion by rederivation through caesarean section or embryo transfer onto/into pathogen free dams is recommended.
 
Reading
  • The Mouse in Biomedical research, Vol. 2: Diseases Fox and Barthold. Second Edn. Elsevier, Inc. 2007.
  • Cellular Microbiology (2005) 7(12):1697-1706, Citobacter rodentium of mice and man. Mundy R et al.
  • Pathology of Laboratory Rodents and Rabbits, 3rd Edn., Dean H Percy & Stephen W Barthold, 2007.
  • Infectious Diseases of Mice and Rats National Research Council 1991.