‘Superbug’ found in Pennsylvania patient highlights dangers of antibiotic resistance


May 31, 2016 — A “superbug” that is resistant to colistin—the antibiotic of last resort—was recently found in a U.S. patient with a urinary tract infection. Sarah Fortune, professor of immunology and infectious diseases at Harvard Chan School, discusses the danger posed by pan-resistant bacteria and how best to fight it.

Just how big a problem is this new “superbug”?

The media makes it sound catastrophic, but this particular case of antibiotic resistance—which was found in a woman who has now recovered—is probably not quite as new as some news reports have suggested. The U.S. actually has seen some colistin-resistant organisms over the past ten years. However, this is the first appearance of what is called plasma-mediated colistin resistance—which means that a gene called mcr-1, which enables bacteria to be resistant to colistin, is carried on a piece of DNA called a plasmid that can be rapidly exchanged between organisms, so that other bacteria can become resistant.

Although this particular case of antibiotic resistance may not be as acute as the media makes it sound, in general these increasingly high-level resistances are an enormous problem. We should be scared enough that we do something about it while we still have antibiotics that work. I think it is easy to take for granted having an arsenal of really effective antibiotics—we have about 100 or so right now. But bacteria are going to evolve resistances to them, and we must be mindful of that.

Already, resistance has emerged among several classes of incredibly effective antibiotics, such as penicillins. The genie is out of the bottle.

Now, is the world going to end tomorrow? No, but healthy people are dying of infections that would have been unthinkable 15 years ago.

Who is most at risk from colistin-resistant bacteria?

One of the most affected groups would be cancer patients undergoing chemotherapy. Their white cells go away, so they routinely get infections with bacteria from their gut or their skin. Those patients are at real risk. And the risk-benefit to cancer chemotherapy really changes if you might die because your immune system is compromised.

As for the general public, it’s not like you would go out into the street and cough and transmit completely drug-resistant bacteria. The most likely scenario is that these resistant strains will begin to appear in greater numbers in hospitals and chronic care facilities where people are already taking a lot of antibiotics. You could have an entire ICU affected. In that sort of situation, these strains can kill a whole lot of people.

What is being done—and what should be done—to protect people from the dangers of these deadly bugs?

Hospitals are really heavily engaged in surveillance and active management of infection control. They have really stepped up their efforts to quickly identify high-level drug resistances and respond to them so that their patients aren’t put at risk.

The most important thing, however, is to invest in the development of new antibiotics. Unfortunately, there are not enough new antibiotics in development. It costs upwards of a billion dollars to develop one new drug. Because antibiotics have traditionally been cheap and you don’t take them for a very long time, there’s no economic incentive for the drug companies.

In addition, in an effort to use our antibiotics wisely, we as an infectious disease community have limited the use of a lot of antibiotics, both to preserve them for drug resistance, but also because of cost—and this has also made antibiotics unattractive to drug makers.

But we need pharmaceutical companies on board and engaged in developing new antibiotics. We can limit the rate at which these highly antibiotic-resistant strains emerge, but they have evolved and they’re not going to go away. So it’s imperative that we invest in developing new tools for our arsenal.

Karen Feldscher

Learn more

Listen to an excerpt from the June 3 edition of Harvard Chan’s “This Week in Health” podcast: William Hanage, associate professor of epidemiology, discusses the problem of superbugs and antibiotic resistance (clip runs from 0:35–4:00)