This bacterium is found in healthy cats, too, but if there’s an overgrowth, problems can occur
Q: I held a cat in September or October 2024 and didn’t know at the time that I had a Clostridium difficile infection. She started having diarrhea, so I took her to my veterinarian, who then referred us to an internist, but we had yet to figure out and treat the cause of her diarrhea.
When I started to have diarrhea, I knew something was wrong. My doctor diagnosed C. diff, which disappeared after 14 days on an antibiotic but returned two weeks later. I then took my cat’s liquid stool to a veterinary microbiologist, who found the C. diff. As it turns out, the cat infected me, and we are both battling irritable bowel syndrome (IBS).
I don’t want to start another round of antibiotics until the C. diff is cleared from my cat’s body. It seems that each antibiotic is less effective than the first one.
What do you recommend to eliminate C. diff in my cat?
A: Thanks for getting in touch, and I am very sorry to hear of the problems that you and your cat are experiencing. While the management of your symptoms will be best addressed by your health-care team, the role that C. diff plays in feline diarrhea (and its potential to serve as a source of infection in people) is enigmatic, and perhaps a few key points regarding this issue would be helpful.
The first thing to realize is that C. diff can be found in clinically healthy cats, and the role that this bacterium plays in feline diarrhea is controversial. While it can be a part of the “good” normal flora of the gastrointestinal (GI) tract of cats, anything that upsets the delicate balance of the populations of the many different species of bacteria in a cat’s GI tract can cause an overgrowth of some species, and if a particular species that overgrows produces toxins or other compounds that negatively impact GI function, this can result in symptoms of disease, including diarrhea.
The overgrowth of C. diff can certainly occur in cats, and the most common cause of this is believed to be the use of antibiotics that decrease the populations of non-C. diff GI bacteria, which can allow C. diff to overgrow. C. diff produces toxins (called enterotoxins) that can cause diarrhea, so if its population is allowed to overgrow, large amounts of these toxins can be produced, resulting in diarrhea in an affected cat.
It’s hard to say whether your respective C. diff infections are related, and it is possible that they are coincidental. Given the fact that there are many different strains of C. diff., one thing to consider in figuring out whether you have infected your cat, your cat has infected you, or neither has occurred would be to have genetic tests run to see if the strains that you and your cat are harboring are the same. If they are not, then your two infections are likely unrelated.
Another thing that you can do to help determine whether C. diff is causing your cat’s diarrhea would be to have your veterinarian (or their lab) perform a microscopic analysis of your cat’s stool to see if there are large numbers of bacteria with morphology that matches C. diff (gram positive spore forming rods), suggesting C. diff overgrowth. If this is the case, genetic tests to verify the suspicion of C. diff overgrowth and enterotoxin assays to test for the presence of the toxins C. diff produces can be performed, although it is important to note that these tests (like all tests) are not 100% sensitive/specific.
Regarding other potential infectious causes of diarrhea in cats, these include intestinal parasites, other bacteria species like Salmonella spp., Campylobacter spp., and Helicobacter spp., viral infections including coronaviruses, feline leukemia, feline immunodeficiency virus, and panleukopenia, and protozoal infections like Tritrichomonas foetus and Giardia. While a full description of the work up of cats with diarrhea is beyond the scope of this column, please discuss ruling out/addressing (if identified) these causes of diarrhea in your cat if this has not already been done.
If, in fact, C. diff is the cause of the diarrhea in your cat, many of these infections respond well to probiotics, such as Enterococcus faecium SF68. In some cases, the addition of antibiotics such as metronidazole, amoxicillin, or ampicillin may be necessary to control clinically significant C. diff infections in cats, but it may very well be best to try the probiotics first.
I hope this is helpful, and please discuss these issues with your veterinary team.
