Superbug in Delhi water, says Brit study (Times of India 07 April 2011)

NEW DELHI: A superbug immune to almost all known antibiotics has been found in Delhi's water. British scientists said they have found the New Delhi metallo-beta-lactamase (NDM) 1 gene that makes bacteria highly resistant to all known drugs in the capital's public water supply used for drinking, washing and cooking.

In August last year, after announcing the existence of this superbug created by the NDM1 gene, scientists had said it was hospital-acquired.

"Now, we know it is not present in hospital ICUs but is actually freely circulating in Delhi's environment, both in the water people drink and those that lay stagnant," Dr Mark Toleman from Cardiff university told TOI.

"Drinking contaminated water will help the superbug enter our bodies. However, we still don't know how many in the population are already carrying the superbug," Toleman said.

The most worrying factor was that the NDM1 gene had already spread to the bacteria that causes cholera and dysentery in India, the scientists said. Their findings were published in British medical journal 'The Lancet Infectious Diseases' on Thursday.

This means when people carrying the superbug, especially children, suffer from a bout of cholera and dysentery, it would be nearly impossible to treat them with available antibiotics.

The researchers made another important finding. The rate at which the NDM-1 gene is copied and transferred between different bacteria was highest at 30°C — a temperature common in Delhi for almost seven months in a year, from April to October.

"This will lead to faster transfer of the NDM1 gene between bacteria, making them drug resistant. This also includes the monsoon season, when floods and drain overflows are most likely, which disseminates resistant bacteria," Dr Toleman said.

In the study, scientists investigated how common NDM-1-producing bacteria were in community waste seepage (water pools in streets or rivulets) and tap water in urban New Delhi. The researchers collected 171 swabs of seepage water and 50 public tap water samples from sites within a 12km radius of central New Delhi between September and October 2010.

These included areas like Connaught Place, Greater Kailash, Kalkaji, Nehru Place, Paharganj, Daryaganj, Kidwai Nagar, Friends Colony, Okhla, Asian Games Villages Complex, Civil Lines and Shahadara.

Samples were tested for the presence of the NDM-1 gene using polymerase chain reaction (PCR) and DNA probing. All bacteria isolated from the water samples were also tested for antibiotic susceptibility and examined for NDM-1 by PCR and sequencing. NDM-1 bacterial transfer frequency was also examined at three different temperatures relevant to the Indian environment: 25°C, 30°C, and 37°C.

"The NDM-1 gene was found in 2 of the 50 drinking-water samples and 51 of 171 seepage samples. Importantly, the gene was found in 20 bacterial isolates comprising 14 different species including 11 species in which NDM-1 has not been previously reported. Worryingly, the gene has spread to pathogenic species including Shigella boydii and Vibrio cholerae, which cause dysentery and cholera, respectively," the study said.

The two positive water samples were from district of Ramesh Nagar and south of the Red Fort. The NDM1 positive seepage samples were collected from close to Connaught Place, Gole Market and Ganga Ram hospital area.

According to Mohd Shahid from Jawaharlal Nehru Medical College and Hospital, Uttar Pradesh, "The potential for wider international spread of plasmids encoding NDM-1 is real and should not be ignored. A coordinated and collective effort is needed to limit their spread. To add to these, we are working on similar studies by collecting environmental and fecal samples from a city close to New Delhi, to explore the severity of the situation."

Scientists say that oral-faecal transmission of drug resistant bacteria is a problem worldwide, but its potential risk varies with the standards of sanitation. "In India, this transmission represents a serious problem as 650 million citizens do not have access to a flush toilet and even more probably do not have access to clean water," the study said.

The Lancet in August 2010 published a multi-centre study warning how a new superbug NDM1 had emerged from India and had spread across the world which made bacteria highly resistant to almost all antibiotics, including the most powerful class called carbapenems.