NDM-1: A New Superbug?

If you thought methicillin-resistant Staphylococcus aureus (MRSA) was bad news for horses and their human connections, there's something even uglier you might want to learn about. There's a new "superbug" in town, and although it hasn't yet infected horses, it isn't to be taken lightly.

New Delhi metallo-beta-lactamase-1 (NDM-1) is an enzyme capable of neutralizing antibiotics. Researchers have found this enzyme can neutralize not only most beta-lactam antibiotics (such as penicillin), but also some "big-gun" antibiotics (such as imipenem), which are sometimes used to treat drug-resistant infections.

Bacteria that produce NDM-1 include members of the Enterobacteriaceae family (such as Escherichia coli). These bacteria produce NDM-1 and therefore are likely resistant to multiple antibiotics, and the NDM-1 gene appears to be easily transferred to other members of the Enterobacteriaceae family.

Since the first human case was diagnosed in 2009, NDM-1-producing Enterobacteriaceae have been found in the United States, Canada, France, Japan, and Australia, among other locations.

"(The) bacteria continue to thwart our best efforts to contain them and destroy them with antibiotics," wrote Robert C. Moellering Jr., MD, from Harvard Medical School and Beth Israel Deaconess Medical Center, both in Boston, Mass.

Although Moellering said "Early experience with NDM-1 has shown all the properties necessary to turn organisms that contain it into superbugs after all," equine infectious disease experts aren't as concerned.

"I'm not too worried about NDM-1 in horses at the moment because it does not seem to have established a good foothold in the general human population," explained Scott Weese, DVM, DVSc, Dipl. ACVIM, an associate professor in the Department of Pathobiology at the University of Guelph's Ontario Veterinary College in Canada. "The big concern is that Enterobacteriacea are so broad and common, if it can establish itself in the gut bacterial population of healthy people or animals, it will be hard to get rid of. Whether that will happen or not isn't yet clear."

The article, "NDM-1--A Cause for Worldwide Concern," was published in December 2010 in the New England Journal of Medicine and can be viewed online.

About the Author

Stacey Oke, DVM, MSc

Stacey Oke, MSc, DVM, is a practicing veterinarian and freelance medical writer and editor. She is interested in both large and small animals, as well as complementary and alternative medicine. Since 2005, she's worked as a research consultant for nutritional supplement companies, assisted physicians and veterinarians in publishing research articles and textbooks, and written for a number of educational magazines and websites.

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