Defiant bacteria found in drinking water

CARDIFF U. (UK) — Antibiotic-resistant bacteria that cause cholera and dysentery have been discovered in the drinking water supply in the India capital of New Delhi.

It is the first evidence of an environmental spread of the NDM-1 gene that had previously only been found in hospital settings.

Not only does NDM-1 make bacteria resistant to antibiotics, it is also carried on mobile DNA called plasmids which carry up to 13 other antibiotics resistant genes.

While most patients testing positive for the bacteria had recently been hospitalized, some occurred without recent hospital treatment, prompting researchers to test the wider environment.

Study findings are published in The Lancet Infectious Diseases.

Samples were taken in New Delhi from public water taps and from other public seepage areas like street water pools. Resistant bacteria were found in 4 percent of the water supplies and 30 percent of the seepage sites.

Eleven new species of bacteria carrying the NDM-1 gene were identified, including strains which cause cholera and dysentry. Antibiotics are used to reduce excretion of bacteria in cholera patients, and to reduce the duration and severity of dysentery. Shigella isolate, which can carry dysentery, is resistant to all appropriate antibiotics.

“These are extremely worrying results,” says Tim Walsh, professor of medicine at Cardiff University. “We found resistant bacteria in public water used for drinking, washing, and food preparation and also in pools and rivulets in heavily-populated areas where children play.

“The spread of resistance to cholera and to a potentially-untreatable strain of dysentery is also a cause for extreme concern.”

A United Nations report shows that 650 million Indian citizens do not have access to a flush toilet and even more probably have no clean water. The New Delhi sewage system itself is reported to be unable to cater for the city’s population. Temperatures and monsoon flooding make the city ideal for the spread of NDM-1.

“This is an urgent matter of public health. We need similar environmental studies in cities throughout India, Pakistan and Bangaldesh to establish how widespread resistant bacteria are,” Walsh says. “If we are to maintain our ability to treat severe infection in vulnerable patients, this action is vital.

“The environmental spread of bacteria is also an international issue. We have discovered patients in the UK and Europe carrying NDM-1 who did not visit hospitals while in India.”

More news from Cardiff University: