Life with Merlin is going fairly well and the house training has been surprisingly good (so far). He was straining a bit to poop yesterday so I was wondering if diarrhea was on the way. Diarrhea wouldn’t be too surprising since he’s had a pretty good shock to his system with a big lifestyle change and a new diet (gradually transitioned, but a change nonetheless). But, so far, so good.

This morning, I collected a fecal sample from him. I’m getting it checked for parasites, as I mentioned the other day. I also did fecal cytology, out of curiosity and because I can do it easily and quickly in my lab. Fecal cytology is a controversial area for diagnosis of bacterial intestinal disease in dogs. Some people use it to diagnose "clostridial" disease and certain other problems. A common statement is that seeing  more than 5 clostridial organisms per high power field under the microscope is indicative of a problem. However, a recent American College of Veterinary Internal Medicine consensus statement on the diagnosis of bacterial enteropathogens basically said that this "rule" is pretty useless (disclaimer: I was one of the authors). Yet, some people continue to use it.

Why do I think it’s useless?

  • There’s no evidence indicating that it’s accurate. All of the (very few) studies that have looked at this test in dogs have found it to have no usefulness for diagnosis.
  • On a fecal smear, you look at a couple of hundred bacteria. That’s a miniscule percentage of the trillions of bacterial present in the animal, and there’s no assurance that bacteria are equally distributed, so there’s no way to tell if what you see is truly representative of the entire bacterial population (it probably isn’t).
  • There are a few hundred species of Clostridium. Only a few species are known to cause disease. Many of the others are probably important components of the intestinal bacterial population that are important for gut health, so they should be there.
  • You can’t identify a Clostridium species by looking at it under a microscope. It looks like a purple rod when using a typical Gram stain. The "bad" clostridia look no different than the "good" clostridia. Also, there are many other bacteria that have the same appearance. So, finding lots of "clostridia-like" organisms is incredibly non-specific – it really doesn’t tell you much of anything.

Back to Merlin’s poop sample: When I looked under the microscope, I could see lots of clostridia-like organisms. Certainly, there were more than 5 per high power field. Yet, he’s bright, alert, eating well, and has formed stool. Yes, something could be brewing but I don’t see any real sign of that. Some people would treat him with an antibiotic such as metronidazole based on this cytology finding alone. I think that’s a bad idea because he’s not sick, I doubt he’s getting sick, I have no evidence that he has an intestinal bacterial disruption that needs to be treated and the last thing i want to do is mess up his developing intestinal bacterial population with an antibiotic. That’s just asking for trouble.

So, no antibiotics for Merlin. Dewormer… that’s another story.