Eat Shit and...Ride

I can't count how many times I have said that understanding the mysteries of the microbiome will unlock the secrets to many physiological and pathophysiological process. The latest example of the microbiome's explanatory power regards the athletic prowess of elite cyclists. In a new unpublished study, that is getting a crapload of press, the microbiomes of elite and amateur cyclists were compared and, not surprisingly, differences were found. Particularly intriguing was the presence of the anaerobic bacteria Prevotella in half of the elite cyclists and none of the amateurs. An archae (Methanobrevibacter archaea) -- a disparate branch of life from eukaryotes (us) and prokayrotes (bacteria) was also more likely to be present.

This study is thought provoking and has many implications and it will be important for this to be thoroughly vetted through the peer-review process -- as studies on rugby players have. It will also be essential to untangle this correlation to try and determine causation -- is the microbiome difference related to the enhanced performance of athlete or the result of their diet, their exercise regimen, their genetics, or some other factor. If the microbiome is causative, poop doping could become a real phenomenon for enhancing athletic prowess (it already has promise in weight management and treatment of Clostridium difficile infection).

Though it's not quite time to follow athletes into the port-a-John, the promise of microbiome research is definitely making poop exponentially more appetizing each day.

Is Your Microbiome Giving You a Hangover?

Hangovers are multifactorial events induced by alcohol consumption. The causes include dehydration and hypoglycemia. However,  in light of the results of a fascinating new research study, I wonder if hangovers (like almost everything else) are partly an infectious disease.

What Bala and colleagues at the University of Louisville discovered is that when healthy adults binge drink, they have transiently increased levels of endotoxin--a bacterial product--in their blood. This result is likely due to the effect alcohol has on the barrier functions of the gut which normally keep bacteria from translocating into the blood stream. When these products enter the bloodstream, they set off an inflammatory cascade. 

I wonder what role this inflammation has in the physical symptoms experienced during a hangover. Maybe the oft-reached for ibuprofen and naproxen may actually be dampening the inflammation.

The general lesson I draw is, since we are compromised of more bacterial cells than human, any perturbation of the homeostasis achieved with our microbiome  is likely to have repercussions for our overall health status.

How's Your Microbiome?

Increasingly, awareness of a person's microbiome--the total population of bacteria that live within an individual, and their genetic material--has shaped how disease is approached. Not only are treatments that disrupt the microbiome beginning to be viewed as harmful, but also the idea that one's microbiome can be associated with specific conditions.

In the January issue of the Mayo Clinic Proceedings, an excellent review article provides a concise summary of the role of the microbiome in clinical diseases including:

  • Clostridium difficile: probably the most paradigmatic example of microbiome alteration
  • Irritable Bowel Syndrome
  • Inflammatory Bowel Disease
  • Obesity: a really fascinating phenomenon that will definitely be the focus of more research
  • Allergic Disease
  • Neuropsychiatric Diseases

The fact that in a human body the number of bacterial cells outnumber human cells (by a factor of 10) is impressive and will condition the current and future treatment of infectious diseases (as well as other illnesses).

A Bacterium Fit for a Cadaver

Most of the time when I get consulted on a person with a bloodstream infection, the culprit organism is something totally ordinary like Staphylococcus aureusE.coliStreptococcus, etc. 

Sometimes, however, an unexpected organism is isolated (usually in an immunocompromised patient). A few days ago, one such rare organism reared its head in one of my patients.

The patient I saw had a history of recurrent pancreatic cancer and had developed a liver abscess. Blood cultures were also positive and revealed...Clostridium cadaveris. Interestingly, it wasn't found in the abscess fluid.

Judging by its name, it's clear that this organism has some connection with death. In fact, it is one of the most prominent bacteria involved in the decomposition of human bodies after death--not exactly something you want to have in your bloodstream while you're alive. However, this bacteria is not usually a pathogen and lives symbiotically as part of the normal resident flora of the intestine.

Reports of true infections with this bacteria involve immunocompromised patients (pancreatic cancer certainly qualified my patient for that designation) but cases have occurred in the immunocompetent as well. Given the context of my patient's overall condition, this has to be treated as a true infection.

In a way, the practice of infectious disease can be thought of as managing the delicate balance in the human body between peaceful co-existence with its microbial flora (the microbiome) and preventing a microbial insurgency from occurring. During the 2008 IDSA meeting, the visionary Dr. Arturo Casadevall describe infectious disease physicians of the future as microbiome management experts who "protect the symbiont" (see his piece from 1996).