TB and the Question of Evolution

I recently attended a national meeting of biologists, gathered in dismay over the way we teach medicine in the United States, at least regarding basics of biology. At the top of their list was the failure of medical schools to adequately teach principles of evolution. They blamed such ignorance for what we all face now -- an unwanted and dangerous experiment in microbe evolution.

I'm talking, of course, about the rise of antibiotic resistant bacteria. The "superbugs" are once again in the news following this week's travel fiasco, involving a Georgia man, who against the advice of his doctors, decided to fly to Europe for his honeymoon, although he was infected with tuberculosis. In fact, by the time he arrived in Italy, doctors realized that he was carrying a worst-case form of the disease called XDR TB, which is highly infectious, usually fatal, and resistant to almost all available treatment.

The man has since been hustled into quarantine in Atlanta, where the U.S. Centers for Disease Control is headquartered. The agency has stationed an armed guard outside his room. CDC is also conducting TB tests on airline personnel from his Air France flight to Europe and his Czech Air flight back to North America, in addition to trying to track down and test passengers seated near the infected passenger.

It would be easy enough to speculate at this point about human stupidity and its causes. But I don't want to dwell on the passenger in question. I want to dwell on the mycobacterium responsible for tuberculosis and why it shape-shifted into a form so potentially deadly that CDC issued its first quarantine order since 1963. (That order involved a suspected case of smallpox.)

And that, of course, brings us back to medical schools and the question of evolution. Today most doctors prescribe antibiotics sparingly but, even 10 years ago, medications were given for
infection the way water is given for thirst. The result was to create a richly antibiotic-laced world, one that presented bacteria with a challenging new environment. And microbes responded by adapting, evolving to meet its pressure. The problem (for us) was not the bacteria that died, but the ones that contained mutations that allowed them to survive. The survivors reproduced. Challenged by another drug, they died back except for a few resistant to both chemical agents. And that scenario repeated itself to create our current problem. To use TB as an example, there are now more than half a million people infected with multiple-drug resistant tuberculosis.

I am somewhat overstating the doctor's responsibility here because the problem was -- as is -- complicated by patient compliance -- which simply means that people don't take the drugs as ordered, cut back too soon, allow the bacteria population to bounce back, newly energized and more resistant.

But it's impossible to overstate the evidence for evolution at work in this dilemma. If we were half as good as bacteria at evolving to meet challenges, we'd probably now rule the universe. In fact,
bacteria are such wonderfully adaptive creatures that biologists are now conducting "experimental evolution" tests with common species such Escherichia coli -- commonly referred to as e. coli - which thrive in the human gut. The editor of Physiological and Biochemical Zoology, which plans to publish those studies this summer, exults that "Now, we can study evolutionary change as it is happening."

So for all of you who don't believe in the principles of evolution, who don't get the idea that evolution is, among other things, a foundation of smart medicine, I suggest you visit Grady Memorial Hospital in Atlanta and check out the room with the armed guards. Maybe you'll learn something.