Page last updated at 12:24 GMT, Wednesday, 10 May 2006 13:24 UK

Scientists target threat of MRSA

By Rami Tzabar
Producer, Frontiers, Radio 4

Powerful strains of MRSA are beginning to break out of hospitals into the community.

With the superbug also becoming more resistant to antibiotics, researchers are in a race for new ways to counter it.

Microbe USA300 has already swept through more than 25 different states in the USA, infecting children, college students, and even athletes.

One incident involved several members of the St Louis' Ram's Football team.

The infection is easily spread, highly resistant to drugs and much more virulent than ordinary MRSA as it can cause the victim to suffer a nasty flesh-eating condition called necrotizing fasciitis.

According to the Centre for Disease Control in Atlanta, USA300 is fast becoming the dominant form of MRSA in the community.

"USA 300 is unique because it is capable of acquiring multi-drug resistance" said Dr Binh Diep, part of a team at the University of California at San Francisco, who sequenced the genome of USA300 earlier this year.

"This particular clone that we sequenced carried resistance to four different classes of antibiotic."

Flexible strategy

Dr Diep's team think they have discovered how this particular strain or clone of MRSA has become so adept at resisting antibiotics.

The real doomsday scenario now is that you have an increasing number of young fit people with Community MRSA, you have a flu epidemic that makes the lungs more susceptible to infection and then the MRSA will actually kill people very quickly
Professor Richard James

Its DNA contains what Dr Diep calls "a mobile genetic element" - a part of its genome whose job it is to acquire DNA from other microbes including those that already live benignly on human skin.

It is hoped that working back through the genetic changes which have turned ordinary MRSA into USA300 might yield a treatment in the future.

But what do we do in the meantime?

In his microbiology lab at Nottingham University, Dr Paul Williams talks casually about experimenting on his favourite microbes - plague, dysentery, E. coli and MRSA to name a few.

"The kind of work we do here in Nottingham is to try to turn a nasty pathogenic bug into a nice happy microbe who doesn't cause any harm."

The secret, explains Dr Williams is to unlock the mysterious process known as quorum sensing.

It was a term coined about 15 years ago in Nottingham by a late colleague of Dr Williams, and refers to the way bacterium, once thought of as individuals rather than a community of organisms, can communicate with one another and make a decision.

"As the bacteria begin to grow they produce low levels of a signal molecule.

"As that concentration of the molecule accumulates, it allows more and more cells to sense there are more bacteria present.

"When that reaches a critical threshold concentration then bang! The bacteria say: 'OK there is a enough of us here, we can really make a difference and cause some trouble'."

Boardroom analogy

This phenomenon has been called 'quorum sensing' with the idea very much in the context of a board of directors where the company have to make a decision and can only do it when the board is quorate - when there are enough of them there to make that decision binding.

The important thing is we're not trying to kill the micro-organism, we're trying to reform it
Dr Paul Williams

Dr Williams said: "It is the same in the bacterial world - you need enough cells there to make a decision that is binding."

The idea is to interfere with this communication process, prevent a decision and turn a nasty pathogen into a friendly well-behaved microbe that doesn't cause disease.

"We can either destroy the signal molecule or the receptor that senses the presence of signal molecule - then we have a new set of [treatment] targets but the important thing is we're not trying to kill the micro-organism, we're trying to reform it - turning off that bad behaviour, a little bit like a bacterial ASBO."

Once an obscure corridor of microbiology, quorum sensing is now centre stage with research teams across both Europe and the US.

But researchers hoping to exploit the secrets of bacterial communication say it could take a decade.

Immediate threat

The threat of MRSA in the community is more immediate.

Right now, the Health Protection Agency aren't overly concerned.

Last year there were only about 100 official cases of community MRSA registered in the UK with the HPA.

But the most worrying scenario according to Professor Richard James, also at Nottingham's Centre for Biomolecular Sciences is an outbreak of Community MRSA off the back of a flu epidemic.

Already about 30% to 40% of the general population carry the MRSA bug in their noses, without any ill effects.

It is only when there is a vulnerability - a wound, a graze - some way for the microbe to get into the body, that there is a risk of infection.

Recent research from US investigators in Baltimore, has concluded that there is a strong link between influenza and the risk of falling victim to the most severe form of MRSA.

Professor James said: "The real doomsday scenario now is that you have an increasing number of young fit people with Community MRSA, you have a flu epidemic that makes the lungs more susceptible to infection and then the MRSA will actually kill people very quickly."

  • Radio 4's investigation into the post-antibiotic era can be heard in the first of a new series of Frontiers beginning Wednesday 10 May at 2100BST.

  • SEE ALSO
    Boost for 'superbug' drugs race
    30 Mar 06 |  Norfolk
    MRSA 'superbugs'
    24 Feb 05 |  J-M

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