Map of life expectancy at birth from Global Education Project.

Tuesday, December 20, 2005

Es muy difícil

I've been meaning to say something about Clostridium difficile for a while now, in part because I have personally had the extremely unpleasant experience of C. difficile disease, in connection with emergency abominable -- excuse me, abdominal -- surgery in 1991. Back then, C. difficile (hereinafter known as C) was known as a nosocomial infectious disease -- something hospitalized people get. The disease happened when otherwise debilitated people were given powerful antibiotics, which wiped out the normal symbiotic intestinal flora, allowing C to flourish. The symptoms, if you're lucky, are severe diarhhea. Worst case, it damages the colon permanently (or kills you).

Recently there has been a sudden, sharp rise in incidence in the U.S., from about 35 annual hospital discharges per 100,000 population in 2000, to more than 60 in 2003. Similar rises have been seen in Canada and the UK. For people 65 and older, the incidence is now more neaerly 350 per 100,000. (Per McDonald et al, 14th annual meeting of the Society for Healthcare Epidemiology of America, 2004.) Just as disturbing, the disease has shown up in the community, notably in Toronto earlier this year.

An analysis by Michael Warny of Acambis labs in Cambridge, Massachusetts finds that many cases are associated with a new strain that produces both kinds of toxin associated with C (most produce mostly one or the other). Now, Sandra Dial and colleagues from McGill University report in the new JAMA, based on data from the UK, that people taking proton pump inhibitors -- you know, that purple pill and its cousins which are constantly advertised on TV -- are at higher risk of getting C disease. Of course, widespread use of antibiotics may also be associated with the increasing incidence.

Here are some more dots to connect. Barry J. Marshall and J. Robin Warren won the Nobel Prize in medicine for discovering that the bacterium Helicobacter pylori causes stomach ulcers. Well, not exactly. H. pylori infection used to be nearly ubiquitous among humans, but only a minority got ulcers. So the cause of ulcers must be more complicated. However, it is true that if you eliminate H. pylori from the gut, ulcers heal.

However, it's not only people with ulcers who have had their H. pylori eliminated, it's most of us, because most of us, at one time or another, have taken courses of antibiotics for various reasons, and they happened to kill the H. pylori in the process. That's good news as far as the prevalence of ulcers is concerned, but there are indications now that H. pylori, when it wasn't acting as a necessary condition for ulcers, was suppressing gastric acid production and protecting us against Gastroesophageal Reflux Disease, in which stomach acid damages the esophagus. So that may account for the rise in prevalence of GERD, which caused lots of people to be prescribed proton pump inhibitors, which is now making them susceptible to C. difficile . . .

The fact is that each individual human is a complex ecosystem unto itself, which also interacts complexly with the organisms around it. When we intervene in this system, we are begging for unintended consequences. We need to be as conservative in our interventions. Proton pump inhibitors are heavily marketed, and lots of people take them who don't need them, people who don't have GERD but just plain old indigestion, who can benefit just as well from much cheaper conventional antacids. And of course, those of us who don't have ulcers would probably do well to hang on to our H. pylori, meaning not take antibiotics if we don't really need them, which is a good idea for many other reasons as well.

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