Community Sources of <i>Clostridium difficile</i>

Peter L. Salgo, MD: Do the risk factors in the community differ from the risk factors that we see in the hospital? You were mentioning that there are people in the community who get Clostridium difficile with no antibiotics. How does that figure into all of this?

Erik Dubberke, MD: You’ve got those people that had a recent hospitalization that get Clostridium difficile outside in the community, and that’s what Dale was talking about—where it’s the same population as the hospital, but we’re pushing them out the door a little quicker, so it’s community onset.

The risk factors for those people are the same as people who are in the hospital. You have someone with diarrhea who’s recently been hospitalized. They should be treated and tested as if they were still in the hospital, even up to 3 months after discharge. But, those people that are truly in the community have not been hospitalized in the last 3 months. The studies have shown that the prevalence of antibiotic exposure amongst those people is about 70% or so, versus with a hospital onset. For those people recently being discharged from the hospital, it’s more in the 90% to 95% or more range.

Some of the reason is that there probably is a lower prevalence of antibiotic exposure, but sometimes there might be some recall bias. All the studies depended on the person saying yes when they were asked if they were on an antibiotic. And they had to know that they were on an antibiotic.

I always recall a story that Stuart Johnson, MD, told me once—I think it was when he was a fellow or junior faculty member up at the University of Minnesota. An elderly person came in with bad Clostridium difficile, was admitted to the hospital, and was denied antibiotic exposures. But, he recently had pulled his back or something, so he took some pain medicines that his wife had in the cabinet. So, Dr. Johnson asked the wife to bring the pain medicine in. Do you want to know what the name of the pain medicine was? Amoxicillin.

So, some of it is that there’s some recall bias. But, I think the other thing is that Clostridium difficile is actually a ubiquitous organism. Again, Dale said that Clostridium difficile is all over the hospital. It’s not all over the hospital. It’s all over the entire planet. It’s in the soil. It’s been cultured from animals. It’s been cultured from food. You’re just as likely to culture Clostridium difficile from the home of someone who is otherwise healthy as you are from a hospital room that does not have a patient with Clostridium difficile in it.

Peter L. Salgo, MD: Is there such a thing as an asymptomatic carrier—someone who’s shedding Clostridium difficile at a higher rate than somebody else, and in whose presence you would be more likely to get this disease?

Yoav Golan, MD, MS: Well, we would think that there are probably more asymptomatic carriers than people who are sick. There’s some work that actually shows that there’s a good correlation. Maybe Dale should talk about this work of admissions, and being in a hospital, and being an asymptomatic carrier?

Dale N. Gerding, MD: The biggest risk group would be infants who are under the age of 2 years old. They have a very high frequency of asymptomatic carriage of Clostridium difficile, and there has actually been an association in community disease with having an infant in your household.

Peter L. Salgo, MD: Is that because their flora changes as they grow older?

Dale N. Gerding, MD: They are developing their microbiota, and so they’re sampling everything around them. They bring in these organisms, check them out, and they colonize their gut for a month or so. And then, they boot them out if they don’t like them.

Presumably, they don’t like Clostridium difficile because they keep changing organisms and they don’t get sick—which is still somewhat of a mystery. The best theory is that they have not gotten mature receptors for the toxins yet.

Lawrence J. Brandt, MD: That’s not been studied, though, has it?

Dale N. Gerding, MD: That’s been done in rabbits, but not in children.

Lawrence J. Brandt, MD: It’s been shown in rabbits?

Dale N. Gerding, MD: Yes, it’s been shown that they lack the receptor maturity, but that’s as far as we’ve gotten. Others are asymptomatic carriers as well—especially in the hospital where far more patients pick up Clostridium difficile in the hospital and are asymptomatic than those who actually get sick with it.

Lawrence J. Brandt, MD: And isn’t it true that if you treat an asymptomatic carrier with antibiotics, you actually increase their shedding rate of the organism and may precipitate clinical disease?

Dale N. Gerding, MD: You can do that, but we tried it. We thought that it might be a good idea to stop them from being carriers, or asymptomatic colonized patients. We tried metronidazole. We tried vancomycin. And we tried a placebo.

Metronidazole and the placebo were both completely ineffective, largely because metronidazole is so well absorbed in the absence of diarrhea that nothing gets in the stool. Vancomycin did knock out the Clostridium difficile, and it went away. But, all those vancomycin patients, essentially, got re-colonized again following treatment. And one of them had a non-toxigenic strain in his stool, lost it, and picked up a toxigenic strain and became sick. So, we thought that it was a really bad idea to do this, and we’ve not done it anymore since.

Peter L. Salgo, MD: And what about foodborne strengths?

Dale N. Gerding, MD: Well, foodborne illness has never been documented for Clostridium difficile, although the contamination of food is certainly there at low levels. So, root vegetables, lettuce, and meats of a variety of kinds all have low levels spore contamination.

Lawrence J. Brandt, MD: The contamination, if I’m not mistaken, for certain foods like chorizo is about 40%. The food that is the highest of all is a food called “braunschweiger,” which is a type of pork sausage that is spreadable. It’s liver.

Yoav Golan, MD, MS: I must say that the food connection is interesting. We talked about exposure to antibiotics, so I’m taking us, just a for a second, a step backward. You can document exposure to antibiotics, but no exposure to antibiotics is not something you can document. And it is important to remember that a lot of the chicken and meat that we consume receive antibiotics, particularly here in this country. And what the concentrations are is debatable, as well as what the effect is in the flora. But, we seem to be exposed to antibiotics on a constant