An estimated 500,000 people in Delhi are carrying bacteria highly resistant to antibiotics acquired from drinking water, say researchers.
Tests on drains and public taps across the city found high levels of contamination with bacteria carrying the NDM 1 gene (New Delhi metallo-beta-lactamase) which confers resistance to almost all known antibiotics.
The discovery highlights the global threat from the spread of untreatable superbugs. An estimated 25,000 people die each year in the European Union from antibiotic resistant bacterial infections. The numbers affected beyond the EU are not known.
Researchers from Cardiff University tested water samples from drains and public taps in Delhi. They found 4 per cent of drinking water samples and 30 per cent of drain samples contaminated with the NDM 1 gene. Further tests showed the gene had spread to bacteria causing cholera and dysentery making them potentially untreatable.
Mark Toleman, an author of the study published in the Lancet Infectious Diseases, said: "Half a million people in New Delhi are carrying NDM 1 bacteria as normal gut flora.
"If we let it go, in the next two or three years we will see the loss of antibiotics in India. We will rapidly get to the stage where those bacteria are untreatable."
Separate research showed that more than 80 per cent of travellers returning from India to Europe carried the NDM gene in their gut. NDM confers resistance to the most powerful antibiotics – carbapanems.
Bacteria testing positive for NDM 1 genes had been isolated from 70 patients in the UK, according to the Health Protection Agency, but there had been no cases of onward transmission.
Dr Toleman said the situation in India and the rest of south-east Asia, which was the largest reservoir of NDM containing bacteria, posed a threat to the world, and international efforts were needed to improve sanitation.
He said the Indian government had expressed concern, but its hidden attitude was one of denial. Researchers investigating contamination of the water supply had been harassed.
At a briefing organised by the World Health Organisation, scientists warned that reckless use of antibiotics was in danger of returning the world to a pre-antibiotic era where infections did not respond to treatment.
David Heymann, chairman of the UK Health Protection Agency said that within two years of Penicillin being discovered, 11 per cent of strains of staphylococcus aureus were resistant and by the late 1990s over 90 per cent of hospital strains were resistant.