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Scientists have discovered a dangerous pathogen lurking in the drinking water in Delhi. It’s not a superbug per se, but a supergene — a genetic mutation that can be acquired by a variety of bacteria to make them impervious to powerful antibiotics of last resort.

The gene mutation, New Delhi metallo-beta-lactamase 1 (or NDM-1), was identified in 11 distinct bacterial species, including those that cause cholera and dysentery, researchers from the University of Cardiff reported Thursday in the journal The Lancet Infectious Diseases. “This is an urgent matter of public health,” said the study’s principle investigator, Dr. Timothy Walsh, who was the first to identify the NDM-1 mutation in 2008. (More on Time.com: Q&A With a Superbug Expert: How Dangerous Is CRKP?)

In September and October 2010, Walsh’s research team collected 50 samples from public drinking water taps in New Delhi and 171 samples from “seepage,” standing water that had pooled near public areas, both of which are used by residents for drinking, washing and/or other household functions. The scientists found bacterial strains with the NDM-1 mutation in two of the drinking water samples and in 51 of the seepage samples. For comparison, they collected 70 samples from Cardiff’s water supply and found no evidence of bacteria with NDM-1 mutations.

While the bacteria that cause cholera (Vibrio cholerae), dysentery and diarrhea (Shigella) and other diseases may be commonly found in water samples in New Delhi, the researchers were dismayed to discover bacteria with the NDM-1 gene mutation — which means that these infections may potentially be untreatable with drugs.

Previously, the mutation has been confined to hospital settings. It has been identified in the hospital-associated bug Klebsiella, which causes pneumonia; Citrobacter, which causes urinary tract infections and sepsis; and the intestinal bacteria E. coli. (More on Time.com: Can We Protect Ourselves from the ‘Superbug’ MRSA?)

Last summer, reports of patients with NDM-1 infections began surfacing in Japan, the U.K., the U.S., Australia and other South Asian countries — many but not all of the patients had received medical treatment in India, prompting researchers to wonder whether the mutation was circulating in the environment. The current findings suggest that it is and that it is possibly being transmitted through the fecal-oral route. “Our data would suggest that possibly about 10% of the people in New Delhi carry NDM-1 in normal flora” in their guts, Walsh told Nature News.

The new study coincided with the World Health Organization’s (WHO) World Health Day dedicated to antibiotic resistance. “The world is on the brink of losing these miracle cures,” said WHO Director-General Dr. Margaret Chan in a statement. “In the absence of urgent corrective and protective actions, the world is heading towards a post-antibiotic era, in which many common infections will no longer have a cure and, once again, kill unabated.”

The lack of development of new antibiotics is emerging as a major problem for public health and infectious disease experts. Just two weeks ago, Los Angeles County reported infections of carbapenem-resistant Klebsiella pneumoniae (CRKP), which had previously not reached the region. Like CRKP, bacteria with the NDM-1 mutation are immune to the last-resort antibiotics called carbapenems, which are used to treat drug-resistant infections. NDM-1 allows bacteria to generate an enzyme that can consume any drug in its path. (More on Time.com: Why You Need to Worry About NDM-1: Not a ‘Superbug,’ But Still a Threat)

And if there were an ideal environment for NDM-1 to spread, India would be it. As Scientific American reported:

The researchers also found that the NDM-1 genes were much more prone to swap (by as much as 1 million times) between bacterial species at 30 degrees Celsius (86 degrees Fahrenheit) than at 25 C or 37 C (which is body temperature). This temperature happens to be within the daily reach for much of the year in New Delhi — including monsoon season, “when floods and drain overflows are most likely, which potentially disseminates resistant bacteria,” the authors explained. And the fact that the gene transfer happens more easily at ambient temperatures suggests that the bacteria have found environmental mixing “more important than in the gut.” India has all of the ingredients to further the spread of these resistance genes, Patrice Nordmann, of La Kremlin-Bicetre in France, explained at the 2010 American Society for Microbiology meeting in Boston. The overuse of antibiotics, dense population and poor sanitation “may fuel these resistance bugs,” he said, which can then “spread worldwide just by plane and by transfer of population.” It’s been estimated that in the Indian subcontinent, where some 1.3 billion people live, about 650 million people do not have access to flushable toilets. And in New Delhi, the municipal sewage system only serves about 60 percent of residents.

The Indian Health Ministry dismissed Walsh’s results. “The environmental presence of NDM-1 gene carrying bacteria is not a significant finding since there is no clinical or epidemiological linkage of this finding in the study area,” V.M. Katoch, director of the Indian Council of Medical Research, said to the press. “Targeting a specific geographical region is totally unscientific as such bacteria is present all over the world.”

That’s precisely the problem.