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"New superbug" 3 years old, but not so horrible

08-18-2010 12:10 BJT

by Xinhua writer Huang Kun

LONDON, Aug. 17 (Xinhua) -- The NDM-1 bacteria, which are resistant to almost all antibiotics and described as "a new horrible superbug" by many media in recent days, is already three years old and may not be as horrible as feared, according to a scientist of the team discovering the bacteria.

"Our first isolate was on Jan. 9, 2008 ... Other isolates are from 2007," said Dr. Mark Toleman, a coauthor of a paper published in The Lancet Infectious Diseases last week.

The paper immediately caught worldwide attention since some of the isolates are proved to be resistant to all existent antibiotics. "Isolate" is a term used by scientists that means sample.

Toleman told Xinhua their first paper about the NDM-1 bacteria was published in 2009, but that was "nearly two years after the isolate started to be investigated" because the research work and publication took time, he said.

That means the NDM-1 bacteria's appearance could go back to three years ago, and researchers have got some experience of dealing with the bacteria, which aren't such a new threat.

Dr. David Livermore, director of antibiotic resistance monitoring at the British Health Protection Agency (HPA), also confirmed this by telling Xinhua "the first cases of infections with bacteria with NDM-1 enzyme in the UK and Europe occurred in 2008," and "there is evidence that this type of resistance was circulating in India in 2007."

But the paper issued last week, which was the second paper about the NDM-1 bacteria from Toleman's group, emphasized the epidemic evidence of the bacteria.

It says there are already 37 cases of the bacteria inside Britain and more than 100 cases in India, Pakistan and Bangladesh. The spreading of the bacteria, especially its emergence in Britain, has come under the spotlight of British media and soon got worldwide attention.

Indian authorities formally protested against the superbug being named NDM-1, short for New Delhi metallo-Beta-lactamase 1, which means it originated from the Indian capital of New Delhi.

It's understandable why NDM-1 has become such a focus.

First of all, this superbug is resistant to almost all antibiotics including carbapenems, a group of antibiotics generally reserved for emergencies and the treatment of infections caused by multi-resistant bacteria.

And it is proved that only two antibiotics, namely tigecycline and colistin, are effective to some NDM-1 samples. But colistin is "an old, rather toxic, antibiotic" and tigecycline "can only be used in some, not all, types of infection," said Livermore, adding "neither of which is ideal for general use."

In some cases, isolates are resistant to all antibiotics.

What's worse, NDM-1 is actually the name of a gene which is transferable between different bacteria, such as Klebsiella pneumoniae and Escherichia coli. It travels on a DNA molecule named plasmid from one bacterium to another, and spreads the drug resistance.

"In summary this gene is exceptionally moveable - one of the most mobile genes that I have come across," said Toleman.

That means we are not facing just one species of the drug-resistant superbug, but a bunch of them, which are infecting different organs. The Escherichia coli are famous for causing intestinal diseases and Klebsiella pneumoniae could cause pneumonia as showed by its name.

"The rapid emergence of these multi-drug resistant NDM-1 producing bacteria and their potential worldwide spread could herald a period, in which antibiotics become redundant and demands very close international monitoring and surveillance," said Professor Tim Walsh at Cardiff University, who has led the production of the Lancet Infectious Diseases paper.

Authorities like the World Health Organization still have not sent a strong alert over the bacteria, as it issued the pandemic alert over the A/H1N1 influenza virus, which was just called off on Aug. 10. That day was only one day before the NDM-1 bacteria became the new international focus.

"Although some bacteria are very resistant, they are not necessarily very pathogenic," Toleman explained.

He said we all carry E. coli in our intestines and 40 percent of people carry Klebsiella in their intestines without suffering any diseases or problems. So being infected with one of the NDM-1 bacteria is unlikely to cause any problem for a normal healthy individual, he added.

However, the problem is that if the same person were to get a urinary tract infection or blood stream infection, the person would be in a very difficult situation. Similarly, immunocompromised individuals such as people undergoing chemotherapy, transplant patients, the very young and the very old, are also high-risk groups.

So the NDM-1 bacteria are not as horrible as feared by many people in the first few days after the news coverage.

Actually, the British National Health Service (NHS) said on its website just after the media frenzy on Aug. 11 that "the public should not be alarmed by this news," and "regular hand-washing will also help to prevent infections in the first place."

Toleman said "hand-washing is very good advice as these bacteria are spread through the oral-faecal route."

As for the HPA, which is the authorities in charge of dealing with the bacteria in Britain, Livermore said "our advice is primarily for healthcare professionals, to make them aware of this emerging type of resistance."

For the general public, Livermore mentioned the possible danger of having "medical tourism" to the Indian subcontinent, where most of the known cases were found.

Speaking of the Indian government's refutation of the origination and name of the NDM-1 bacteria. Toleman said there is "very strong evidence that the UK isolates originated from India."

And Livermore said it is common to name a new type of beta-lactamase after the place where it is first identified -- an enzyme circulating in Brazil is named SPM, or Sao Paulo Metallo, and another is VIM, or Verona Imipenemase etc.

Whatever it is named, the great attention to the new superbug is partly driven by deeper economic reasons, observers say.

The so-called "medical tourism" brings a lot of revenues to India and now it may ebb. And in China, the share prices of some pharmaceutical companies have soared in the stock market over the past few days partly due to the emerging of the new bacteria.

 

Editor:Zhang Pengfei |Source: Xinhua

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