December 17, 2010
NDM-1: No Drug Matters
My longtime readers know that I’m not one to panic when the media does. I wasn’t very worried about anthrax in the mail. I didn’t think swine flu was going to be a big deal. (See link below.) And I’m not concerned about the health effects of airport X-ray back-scatter machines.
But there’s plenty of stuff that worries me. Most of it is scary on time scales longer than the typical media attention span. What scares me is stuff that will hurt us decades from now. For example, I’m very worried about stuff like the inevitable but not imminent collapse of Medicare, the fact that world population will peak on about 2075 and then decline, and the unavoidable zombie apocalypse. OK, I’m just kidding about that last one.
This week’s New England Journal of Medicine published a perspective article about a topic that is sure to become an increasingly dangerous problem. As far as I can tell it received no media attention. The article described a new bacterial gene for antibiotic resistance.
The gene is called NDM-1, which stands for New Delhi metallo-beta-lactamase 1. It deserves our concern for two reasons. The first reason is that this gene codes for an enzyme that gives a bacterium resistance to almost all current antibiotics. That’s bad.
To explain the second reason for concern, I first need to explain how genes normally get around. Say you have a really nice gene, the gene for brown eyes as an example. Say that you’d like to give that gene to someone else. The only way for humans to do that naturally is to make another human. You have to find a mate, procreate, and voila! Nine months later you have an offspring with your brown eyes. Genetic engineers have figured out ways to take genes from one living thing and put it into another, but nature typically works by having genes move only from parents to progeny. You can’t give your tall stature to your neighbor or your natural red hair to your friend. You can only transmit your genes to your kids.
Well, bacteria long ago have circumvented this limitation, essentially inventing their own genetic engineers. They have most of their genes on a chromosome that is passed just to the descendents of each bacterium. But some genes are on a tiny loop of DNA called a plasmid that can leave one bacterium and enter another. If a chromosome is like a hard drive of genetic information, a plasmid is like a flash drive – tiny and portable. NDM-1 is coded on a plasmid and has already been identified in several different kinds of disease-causing bacteria. That means it can spread itself to different bacteria species. (The equivalent genetic trick would be giving your brown eyes to your dog.)
To put it all in perspective, these bacteria carrying NDM-1 aren’t more infectious and don’t cause worse diseases than their non-NDM-1 cousins. An E. coli with NDM-1 will cause a bladder or kidney infection that is no worse than a standard E. coli infection. The disaster is that virtually no antibiotics will work for it.
NDM-1 was first discovered in 2008 and for now seems to be concentrated in the Indian subcontinent, though recent travelers to India have been found to be infected with NDM-1 in many other countries.
Is there anything for us to do? Doctors should be constantly reminded about the danger of emerging antibiotic resistance and should be urged to use antibiotics rationally. We should all keep an eye on the story of antibiotic resistance as it unfolds over the next years. It is entirely possible that antibiotics, after serving us for about a century, will become ineffective.
New England Journal Medicine article: NDM-1 — A Cause for Worldwide Concern
My post in 2007 about increasing antibiotic resistance: Serious MRSA Infections More Common
My post from April 2007 when H1N1 flu first made news: Swine Flu: Unlikely to End the World
Important legal mumbo jumbo: