A paper published this week reminded me to take a fresh look at NDM, the “Indian superbug” — actually a gene and enzyme — that got so much attention, including from me, in 2011. (Most of the posts are here.) Quick reminder: NDM surfaced in 2008 in Sweden, then was found in the United Kingdom, then in the United States and then elsewhere in the world. It had several distinctive qualities. It appeared in gut bacteria such as Klebsiella and E. coli, and caused infections when those bacteria escaped the gut and got elsewhere in the body. It rendered those bacteria not-vulnerable to almost all antibiotics, leaving so few drugs to use against it that medical personnel found it truly alarming. And it had strong links to South Asia: The first known patient was an Indian man living in Sweden who had gone home for a visit and been hospitalized; victims found later either had family links to India and Pakistan or had gotten medical care there, as medical tourists or because they were injured while traveling.
NDM (which stands for New Delhi metallo-beta-lactamase; it was originally NDM-1, but there are now at least seven variants) generated a lot of alarm at the time, with good reason. Its unusual resistance pattern made useless the last category of broad-spectrum, last-resort antibiotics, called carbapenems, that were still working reliably. Physicians treating patients who had infections involving NDM had to hunt among just a few remaining drugs that were still on the shelf because they were toxic or did not work reliably. Plus, because bacteria carrying the NDM resistance factor colonize the gut, the infection could be transported across borders and into hospitals without anyone noticing. With no symptoms showing, few hospitals would bother to check a patient (or a family member), especially since testing for gut bacteria is more complicated and intimate than, for instance, testing someone’s nostrils for MRSA.
By last year, NDM had mostly dropped out of the headlines, even though it was still moving across the globe (this 2013 paper details countries where it has been identified), and had also begun causing hospital outbreaks (for instance, this one in Denver in 2012). So the new paper I mentioned, written by staff from Public Health England and analyzing the first 250 patients with NDM in the UK, is a useful reminder of how formidable a microbiologic foe this can be.