Field of Science

Resistance is inevitable

Today’s Washington Post has an article by David Brown reporting on an alarming upsurge in the number of cases of tuberculosis that are resistant to some or all known antibiotics. The headline is that 5% of TB cases are now drug resistant, but the substance is much more alarming. In some regions of the former Soviet Union, drug-resistant TB accounts for 20% of cases, and the true rates might be even higher. These TB strains are not only drug resistant, but deadly: as David Brown reports, the death rate in untreated cases is “close to 100 percent.” 100% mortality is truly frightening.

Why should we worry about this? Well, there are (at least) two reasons:
1. Spread is inevitable. The countries of the former Soviet Union, where these new TB strains are spreading, are no longer isolated from the rest of the world. Humans travel freely among all countries now. And tuberculosis doesn’t make everyone sick – some people can carry it without knowing that they have it. A major TB outbreak could pop up anywhere before we even realize that a carrier has been spreading the disease.

2. Resistance is inevitable. The Borg on Star Trek: TNG liked to warn their targets, “resistance is futile.” In the world of infectious diseases, though, we have a different saying, thanks to Mark Crislip of Quackcast: resistance is inevitable. What that means is that whenever we come up with a new drug, the bacteria or viruses will inevitably develop resistance to it. For the bacteria, resistance is not futile – it’s an extremely effective way to survive. Multi-drug resistant (MDR) TB, which is resistant to the two most commonly used drugs, rifampin and isonizid, is spreading rapidly. Even worse, a new strain of “extremely” drug-resistant (XDR) TB is resistant to those two drugs plus two others, leaving basically no effective means of treatment.

I was surprised to read in Brown’s article that Mario Raviglione, the head of the WHO’s tuberculosis department said that the rate of multi-drug resistant infections “wouldn’t go over 10 percent.” I guess he’s much more optimistic than I am. I wouldn't be surprised if the rate went to 50% or even higher. Whenever we get a new drug, we use it – of course. But when we use it, we begin the evolutionary process of selection in favor of drug-resistant strains. Unless you can make sure that every patient is completely cured – an unrealistic goal – then some amount of resistance will begin to emerge.

In the 19th and early 20th centuries, TB was a scourge of all civilized countries. Countless millions, including many famous authors and artists, died of TB (including Balzac, the Bronte sisters, Camus, Kafka, Keats, Thomas Wolfe, and many more). Most of us probably assume that era will never return – but it might. What can we do to prevent it? We need better surveillance of the TB strains now spreading, and even more urgently, we need new drugs. I think that our government(s) should develop these drugs, rather than leaving it to the whims of private companies, but that puts me in a rather small minority here in the U.S. Our best hope for new drugs right now is probably the Gates Foundation, which has made combating TB and malaria its top two priorities. In a much smaller way, everyone can do their part by warning others against the mis-use and overuse of antibiotics. We can’t stop the spread of drug resistance, but at least we can slow it down.

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