Microbial Medicine

Today Jonathan Eisen makes some good points about probiotics being sold like snake oil miracle cures.

I’ll agree that it’s a growing problem. I often find people on message boards advocating probiotic treatments, despite the lack of evidence-based support for such actions. I always tell them the same thing: Popping some Lactobacillus acidophilus isn’t likely to hurt, but there’s little proof that it will help you, either.

Lactobacillus acidophilus
Lactobacillus acidophilus

Someone was even asking about fecal transplant bacteriotherapy the other day, after reading Carl Zimmer’s excellent article about how it can treat severe Clostridium difficile.

Look, I totally understand why people grasp at straws and search for anything that might help. Living with a chronic condition that has no cure sucks. Wasting your money on treatments that don’t help, though, will only make you lighter in the wallet and still sick. The problem with probiotics in this case are two-fold:

The first problem is that we just don’t understand the composition of the gut well enough to start trying to theraputically change the composition of your microflora. It’s an enormously complex ecosystem, and we’re just now dipping our toes into the water with initiatives like the Human Microbiome Project. Scientists are studying this with a great deal of interest though. In fact, he other day I stumbled across a study showing that by treating rats with antibiotics, then doing fecal transplant, a team could create long-term alterations in the microbiota of rats. This is pretty exciting stuff, but it’s only the first of many advances that will be needed to prove the feasibility of bacteriotherapy. The next steps will be to figure out which microbes we want in our guts, which we don’t, and how we can create a stable environment for those beneficial species. This will undoubtedly take a while.

The other problem with using probiotics to treat gut conditions is that most of these disorders (IBS/IBD/Crohn’s) have both genetic and environmental factors that contribute to the aetiology. I’m most familiar with Crohn’s Disease, which occurs when cells in the intestinal walls aren’t able to keep microbes out properly, so the immune system kicks into overdrive. So far, it hasn’t been linked to any specific species, which seems to make it a poor target for microbial therapy. Add in the fact that there are often systemic inflammatory problems like arthritis and back problems, and it’s not at all clear that we can treat this by just swapping around the microbes in the gut.

So to sum things up, using probiotics to seriously treat disease will have to wait until we better understand both the diseases in question and host/microbe interactions. That said, research into the microbiome is enormously promising, and I do believe that microbial medicine will someday be commonplace. It’s just that we still have a long way to go.

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The Velluvial Matrix

Here’s one physician’s take on increasing complexity in medicine, given as a commencement speech at Stanford. I’ll let you jump over there if you want to find out the details about the “Velluvial matrix”, but it’s really just a device that lets him get at some big-picture ideas about the future of the field:

This is a deeper, more fundamental problem than we acknowledge. The truth is that the volume and complexity of the knowledge that we need to master has grown exponentially beyond our capacity as individuals. Worse, the fear is that the knowledge has grown beyond our capacity as a society. When we talk about the uncontrollable explosion in the costs of health care in America, for instance—about the reality that we in medicine are gradually bankrupting the country—we’re not talking about a problem rooted in economics. We’re talking about a problem rooted in scientific complexity.

This reminds me a bit of the PhD comic, which shows how grad school makes you dumber (a phenomenon closely related to the Dunning–Kruger effect). The more we learn about physiology and medicine, the more specialized each branch has to become, and the more likely that we are to make mistakes when crossing disciplinary boundaries:

Smith told me that to this day he remains deeply grateful to the people who saved him. But they missed one small step. They forgot to give him the vaccines that every patient who has his spleen removed requires, vaccines against three bacteria that the spleen usually fights off. Maybe the surgeons thought the critical-care doctors were going to give the vaccines, and maybe the critical-care doctors thought the primary-care physician was going to give them, and maybe the primary-care physician thought the surgeons already had. Or maybe they all forgot. Whatever the case, two years later, Duane Smith was on a beach vacation when he picked up an ordinary strep infection. Because he hadn’t had those vaccines, the infection spread rapidly throughout his body. He survived—but it cost him all his fingers and all his toes. It was, as he summed it up in his note, the worst vacation ever.

This is absolutely relevant to my last post, about intelligent systems that can make decisions. If designed properly, a machine will never miss a piece of evidence or forget to perform a step. (that’s a big “if”, but one we need to start tackling). Studies have already shown that simple checklists can dramatically reduce complications and deaths during surgery. Now we need to be designing systems that produce those checklists instantly and adapt to the specifics of the patient on the table.

This isn’t as sexy as the type of personalized medicine that relies on genetic screening but it’s probably even more important, in terms of the capacity to save lives in the short-term.

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