Released just in time for World Health Day, we’ve a fresh study that appears in The Lancet authored by Timothy Walsh, Janis Weeks , David M Livermore, and Mark A Toleman that looked for – and found – bacteria carrying the NDM-1 enzyme in New Delhi's drinking water supply.
NDM-1, or New Delhi metallo-ß-lactamase-1, is an enzyme that can confer resistance to certain gram negative bacteria like E.coli and Klebsiella against a class of antibiotics called carbapenems.
Carbapenems are newer generation beta-lactam antibiotics (a class that includes penicillins, cephalosporins, cephamycins, and carbapenems) that are usually reserved as an antibiotic of last resort.
Up until recently, Carbapenems have been generally resistant to Beta-lactamases - enzymes bacteria use to breakup the ring structure of “beta-lactam” antibiotics - that renders them ineffective.
But in recent years a new enzyme has been spreading in India, Bangladesh, and Pakistan that helps certain types of bacteria to defeat Carbapenem antibiotics; NDM-1.
Although the NDM-1 enzyme has been around since about 2008, it made headlines last August when a Lancet Infectious Diseases article was published on its growing prevalence on the Indian sub-continent and its recent importation into the UK, US, and other countries.
Professor Timothy Walsh, along with two of the co-authors of today’s report (David M Livermore , Mark A Toleman) were among the authors of this original Lancet study.
The Lancet Infectious Diseases, Early Online Publication, 11 August 2010
doi:10.1016/S1473-3099(10)70143-2Cite or Link Using DOI
Since that time the NDM-1 gene has been the subject of much scientific scrutiny and enhanced surveillance, particularly since it often carried on a plasmid – a snippet of DNA - that has the potential to jump to other strains of bacteria.
Although most cases reported in Europe and North America have travel links to Southeast Asia, that can’t be said for all of them.
We’ve a press release on today’s study, issued by Cardiff University, that gives the highlights of the study, but the `money quote’ (emphasis mine) buried about halfway down is:
Resistant bacteria were found in 4 per cent of the water supplies and 30 per cent of the seepage sites. The researchers identified 11 new species of bacteria carrying the NDM-1 gene, including strains which cause cholera and dysentery.
The spread of the NDM-1 gene to 11 new strains of bacteria is particularly ominous news.
In an interview for Reuters today, co-author Mark Toleman of Britain’s Cardiff University School of Medicine stated that as many as 500,000 residents of New Dehli may be carrying the NDM-1 resistance gene in their gut flora.
Disease-causing bacteria carrying the new genetic resistance to antibiotics, NDM-1, have been discovered in New Delhi's drinking water supply.
A Cardiff University-led team found new strains of resistant bacteria in the Indian capital, including species which cause cholera and dysentery. The findings are the first evidence of the environmental spread of NDM-1, which had previously only been found in hospitals.
The scientists are calling for urgent action by health authorities worldwide to tackle the new strains and prevent their global spread. The Cardiff scientists also highlight the all-round benefits of preventative measures such as better sanitation and appropriate drinking water.
Cardiff scientists were the first to identify the NDM-1 gene which makes bacteria resistant to a large range of antibiotics. Moreover, the NDM-1 gene is carried on mobile DNA called plasmids which can carry up to 13 other antibiotic resistance genes. While most patients with the bacteria have recently been hospitalised in India, some cases have occurred there without recent hospital treatment, prompting the team to test the wider environment.
Samples were taken in New Delhi from public water taps and from waste seepage, such as water pools in the street. Resistant bacteria were found in 4 per cent of the water supplies and 30 per cent of the seepage sites. The researchers identified 11 new species of bacteria carrying the NDM-1 gene, 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. Worryingly, the identified Shigella isolate, which can carry dysentery, is resistant to all appropriate antibiotics.
Study leader Professor Tim Walsh, of Cardiff University's School of Medicine, said: "These are extremely worrying results. 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."
Below is a link to the Lancet study, which you can read in its entirety (a free registration is required).
The Lancet Infectious Diseases, Early Online Publication, 7 April 2011
doi:10.1016/S1473-3099(11)70059-7Cite or Link Using DOI
Dissemination of NDM-1 positive bacteria in the New Delhi environment and its implications for human health: an environmental point prevalence study
Prof Timothy R Walsh PhD , Janis Weeks BS, David M Livermore PhD , Mark A Toleman PhD
The presence of NDM-1 β-lactamase-producing bacteria in environmental samples in New Delhi has important implications for people living in the city who are reliant on public water and sanitation facilities. International surveillance of resistance, incorporating environmental sampling as well as examination of clinical isolates, needs to be established as a priority.
Antibiotics have often been called the miracle drugs of the 20th century, but almost from their inception bacteria have been evolving and finding ways to evade them.
In 1940, even before penicillin could be rolled out for clinical use, the first β-lactamase (Penicillinase) was identified by researchers in a sample of Gram-negative E. coli.
Over the next two decades this penicillinase resistance spread to other bacteria, which required the creation of newer generations of penicillin (such as Methicillin in 1959), that were resistant to these enzymes.
Methicillin is no longer used (replaced by newer generation antibiotics), although we retain its name in the term MRSA (Methicillin-resistant Staphylococcus aureus), which was identified in the UK just two years after Methicillin was introduced.
Today, we are seeing an ever expanding array of antimicrobial resistant bacteria and a worrying lack of new drugs in the development pipeline to deal with them.
Which is why the World Health Organization has declared that the focus on this year’s World Health Day (April 7th) to be on this growing threat.
You can read more on this global observance in my blog World Health Day 2011.