Re: Clostridium difficile - can it give false negatives?
Ok, here is my nutshell understanding of C.difficile colitis:
Clostridium difficile is an anaerobic bacteria that is part of the "normal" flora in the intestinal tract of many normal, healthy people. Usually its population is kept in check by the other "good" bacteria that we all have in our gut and the C.diff doesn't cause problems. Sometimes events can throw the balance of "good" bacteria out of whack and allow a more problematic bacteria like the C.diff to increase its population in your GI tract. A typical culprit is antibiotic treatment. An antibiotic can't tell the difference between "bad" bacteria that may be causing for example a sinus infection and the "good" bacteria you need in your gut to help you digest your food. The antibiotic will kill any bacteria in your body that is sensitive to it.
Lets say you have been on an antibiotic and develop diarrhea. There is actually a name for this, its called "antibiotic associated diarrhea" (imagine that!) And this condition is usually cause by the events I just described where too many "good" bacteria were killed off in your gut leaving behind "bad" bacteria in its place. Sometimes the "bad" bacteria is C.diff, but there are others it could be too.
Now, my understanding is there are different strains of C.diff. Some strains are capable of producing a toxin that is directly toxic to your bowel and can produce a life threatening, bloody diarrhea condition called pseudomembranous colitis. The stool test checks for this dangerous toxin, not the bacteria itself I believe. Your father must have had the strain that produced the toxin.
So, finally in answer to your question. I believe you can have C.diff in your stools and can even have diarrhea from it, yet be negative for the more serious and potentially life threatening toxin producing strain.
I'm a big believer in taking probiotic supplements to shore up the populations of "good" gut bacteria for people who are having IBS problems. Look for products that have multiple strains of Lactobacilli, not just a single strain. Modern diets full of preservatives and antibiotic and hormone fed meats, and low in the fiber and other nutrients needed to help maintain healthy gut flora are at the root of digestive troubles for many of us. Base your diet on yogurts (a natural source of lactobacilli,) fruits, veggies, and whole grains, and then supplement with a fiber product and a lactobacilli product and you may find yourself feeling much better.
My condolences regarding your father. Good luck to you in feeling better with your stomach problems!