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NDM-1: Battling a New Breed of Bugs

MGH’s associate chief of infectious disease, who’s working to find new approaches to fight drug-resistant superbugs, discusses how he treated one of the most notorious: NDM-1.

By Linda Keslar // The MGH Research Issue 2011

Denise Bosco for Proto

Last year a patient at Massachusetts General Hospital was one of three people in the United States treated for an infection with a bacterium producing NDM-1, one of a new breed of antibiotic-resistant infections—“superbugs”—that are threatening public health at a time when few promising drugs are on the horizon. David Hooper, associate chief of infectious diseases and head of infection control at MGH, talks about the problem and how MGH is addressing it.

Q: What is NDM-1? And what makes it so resistant?

A: NDM-1 stands for New Delhi metallo-beta-lactamase, an enzyme that destroys an entire group of penicillinlike antibiotics that we rely on to treat some of the most difficult infections. The gene that’s the source of this enzyme resides on free-floating pieces of DNA within bacterial cells called plasmids. Plasmids often have several antibiotic-resistance genes, and plasmids can transfer themselves from one bacterium to another. That lets a bacterium adapt rapidly when it’s threatened by an antibiotic. And because the plasmids with the NDM-1 gene have so many kinds of resistance, there’s hardly any drug left to treat the infection if it reaches sufficient magnitude.

Q: How does NDM-1 spread?

A: People don’t get it through airborne transmission. Rather, it spreads largely in close contact situations, when someone touches a patient or a patient’s surroundings, which can become contaminated. Most reported cases have happened in hospital and health care settings, because patients often have underlying diseases that make them vulnerable and they may be connected to devices, such as IV catheters, that increase the risk of infection. NDM-1 showed up first in patients who had been treated in India or Pakistan, countries in which sanitation is poor and antibiotics can be obtained easily without a prescription, which increases the risk of overuse and the likelihood that someone will have an abundance of resistant bacteria.

Q: How did the patient at MGH get the bug? And how did you treat it?

A: After being hospitalized for surgery in India, the patient returned to the United States and developed a urinary tract infection caused by a strain of the bacterium Enterobacter that was eventually identified in the lab as carrying NDM-1. Fortunately, it was a mild infection. NDM-1 hadn’t entered the patient’s bloodstream and we didn’t need any special antibiotics.

Q: How should we be responding to the threat of NDM-1 and other superbugs?

A: We need more antibiotics in the pipeline to treat these infections. Researchers are also beginning to experiment with nonantibiotic approaches—for example, by focusing on the proteins that make pathogens toxic—but it can take many years to develop a drug. So it’s crucial to be vigilant. We have to identify these organisms promptly and take appropriate infection-control precautions in addition to the usual hand washing, such as isolating an infected patient in a single room and requiring health workers to wear gowns and gloves to prevent transmission.


Video: Battling a New Breed of Bugs

David Hooper explains the evolving field of infectious disease research.

The War on Superbugs

As medicine battles antibiotic resistance, tougher drugs breed still more deadly bacteria. New approaches could break the cycle.

NDM-1: A New Superbug

In the fight against a burgeoning breed of drug-resistant pathogens, researchers look to add weapons beyond antibiotics.

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