Maryn McKenna

Journalist and Author

NDM-1: Novel, global, complex and a serious threat

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There’s news today in the journal Lancet Infectious Diseases of the further spread of a troubling new resistance problem that I first talked about in June: Gram-negative bacteria carrying a novel resistance factor that has been dubbed New Delhi metallo-beta-lactamase, or NDM-1.

In writing about resistant bacteria, it’s difficult to avoid overusing superlatives — but this resistance mechanism has spread widely, been transported globally, and brings common bacteria up to the brink of untreatable. It already has been found in India and Pakistan, Sweden, the Netherlands, Australia, Canada and the US, and has been distributed not just by travel but specifically by medical tourism. It has the potential to become an extremely serious global threat.

News break: CDC alert on imported novel resistance

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There’s a troubling item in this afternoon’s issue of the CDC’s Morbidity and Mortality Weekly Report or MMWR: The first report in the United States of a novel resistance mechanism that renders gram-negative bacteria extremely drug-resistant and that has been linked to medical care carried out in India or Pakistan.

The short item describes three isolates (E. coli, Klebsiella pneumoniae and Enterobacter cloacae) found in three patients in three states between January and June of this year. All three isolates produced New Delhi metallo-beta-lactamase (NDM-1), which has never been recorded in the US before. Because of that novel mechanism, the three isolates were resistant to the carbapenems usually used on the most serious gram-negative infections, in fact to all beta-lactam antibiotics (penicillins, cephalosporins, carbapenems, monobactams, etc.) except for one monobactam, aztreonam — and they were also resistant to aztreonam through another mechanism that hasn’t been identified yet. All three of the patients found carrying this novel resistance factor had undergone medical care in South Asia recently.

This may be the first finding of this mechanism in the US, but it’s been causing alarm in Europe for at least two years.

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