Last fall, not long after the bloom of news about the “Indian superbug” NDM-1 — a newly identified enzyme that renders common gut bacteria indifferent to almost all antibiotics — I spoke to one of its lead researchers, Timothy Walsh of the University of Cardiff, about next steps in their research.
His work and his collaborators’ had demonstrated that many of the people infected with or carrying bacteria that incorporated the gene had undergone medical treatment in India and Pakistan, sometimes for elective surgery such as medical tourism, sometimes because they had been injured or ill while traveling. But not all, he said — and that was making them wonder whether the spread of NDM-1 had an environmental component. It was a plausible hypothesis given the apparent concentration of NDM-1 in India, a country whose sanitation systems have not kept up with its booming population. A recent UN report estimated that almost half of India’s residents — that would be up to 650 million people — lack treated drinking water and modern toilets. If you sat down to design a system to facilitate the spread of an enzyme carried by bacteria in the gut — that is, in feces — you couldn’t do better than what India already has.
“There has been very little work done or analysis done on the effect that (poor sanitation) would have on the spread of resistance and on carriage of NDM-1 within a normal population,” Walsh told me at the time. “There’s no water sampling for fecal flora or antibiotic-resistant flora.”
Well, now there is: Walsh and his collaborators have done it. And the news, as they suspected, is bad.
They report today on the website of Lancet Infectious Diseases that they collected 50 samples from street taps — sources of drinking, washing and cooking water for entire neighborhoods — and 171 samples of “seepage” (surface water and street puddles) from around New Delhi. They found NDM-1 in two of the drinking-water samples (4 percent) and 51 of the 171 seepage samples (30 percent).
There are two reasons why that finding is so troubling. First, it demonstrates that community conditions could pass bacteria containing NDM-1 to people who have never entered a hospital, have no idea they might be at risk, and might never know that they have become carriers and potential victims of a highly resistant strain. Second, it makes clear that bacteria containing the NDM-1 gene (blaNDM-1) are circulating where many other bacteria are present. Since the gene resides on a plasmid, a mobile piece of DNA, that raises the possibility that NDM-1 could be moving from the bacteria in which it was first identified into other species.
And in fact, that’s what has happened. In the Indian water samples, Walsh and team found NDM-1 in 11 different bacterial species: not only Klebsiella and Citrobacter, which are common hospital-associated infections, but E. coli, the gut bug that is present in the intestines of every warm-blooded being; Shigella, the cause of dysentery, or very serious diarrhea; and Vibrio cholerae. Yes, that’s right: the bacterial cause of cholera, rendered effectively untreatable.
Think about that for a moment.
The researchers say:
The results of this study suggest widespread environmental contamination and are in keeping with the facts that not all of the UK or European patients with
blaNDM-1–positive bacteria who had visited India were admitted to hospital there and that many patients from Chennai who had blaNDM-1–positive clinical isolates had no recent history of hospital admission. Rather than being a purely nosocomial problem, bacteria with this resistance seem to be circulating in the community; thus they may be imported into hospitals with admitted patients and probably enriched within the gut flora when these patients, for whatever reason, receive antibiotic treatment or prophylaxis.
Because NDM-1 can be carried silently, there is no guarantee that its spread can be detected by passive surveillance, that is, by looking for it just in patients whose infections appear resistant. The authors urge — in fact, practically plead — that India and other South Asian countries make it an urgent priority to look for the resistance factor, with financial support from international health authorities:
…International surveillance of resistance needs to be established. Such surveillance must incorporate environmental sampling as well as examination of clinical isolates and cover Pakistan and Bangladesh, because these are also source countries for exported cases. These are pressing needs if the ability to treat severe infections in vulnerable patients is to be maintained. The next step in this analysis should be to sample carriage in south Asia, both in residents and travellers. We would be delighted to advise and help in any capacity to take such studies forward in partnership with Indian, Pakistani, and Bangladeshi scientists, clinicians, and government officials.
NDM-1 was first identified in the West, by Walsh and his collaborators, in 2008 (and by Indian clinicians earlier than that, though no one seems to have listened to them). But when it began to get widespread attention last fall, the Indian government reacted disappointingly, claiming conspiracy theories and Western envy of the medical tourism industry, and refusing to take any significant steps.
It would be nice to say this new news has caused them to perceive the true dimensions of the threat, to South Asia and to the world. The overnight news though is not encouraging. NewsOne, a mobile news channel in India, reported this morning:
The health ministry Thursday said the environmental presence of superbug NDM-1 gene in Delhi does not pose a public health risk. ‘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, told reporters. “Targeting a specific geographical region is totally unscientific as such bacteria is present all over the world.”
Happy World Health Day.
- The Enemy Within: A new superbug, KPC/CRKP
- The “Indian Superbug”: Worse Than We Knew
- NDM-1, the supergene: Further (community?) spread
- NDM-1: More Evidence It Started in India
- NDM-1: Novel, global, complex and a serious threat
Cite: Walsh TS, Weeks J, Livermore DM, Toleman MA. Dissemination of NDM-1 positive bacteria in the New Delhi environment and its implications for human health: an environmental point prevalence study. The Lancet Infectious Diseases, 7 April 2011. DOI: 10.1016/S1473-3099(11)70059-7.