The emerging superbug
Visa is resistant to just about every antibiotic known to medicine and has been discovered in hospitals from Japan to Scotland - find out where it comes from and why it has got doctors worried.
Staphylococcus aureus - the root of the problem (picture: Pfizer)
The emergence of a superbug - a bacteria resistant to all antibiotics - could herald the end of the era of antibiotics, the biggest medical advance of the twentieth century.
That at least was the view of public health scientists in New York earlier this year when they reported a growing incidence of VISA - vancomycin intermediate-resistant Staphylococcus aureus.
These bacteria have been proving resistant to vancomycin, the most powerful antibiotic in doctors' armoury, although combinations of other antibiotics have been able to halt it.
Vancomycin is seen as the last line of defence against MRSA - Methicillin-resistant Staphylococcus aureus - which is unaffected by most antibiotics and is becoming more common.
All around the world
The emergence of VISA shows that, in doctors' race to keep antibiotics advanced enough to defeat bacteria, the bugs are taking the lead.
VISA has been found in hospitals in Japan, America, France and, more recently, in Scotland.
Although only one person is thought to have died directly from infection with the bug, the fear is that more dangerous bacteria such as those that cause tuberculosis could develop the same characteristics that allow VISA to resist even the most powerful antibiotics.
Were this to happen, doctors would be back where they started before the introduction of penicillin - confronted by a host of diseases caused by bacteria and unable to cure them.
In February, a report in the New England Journal of Medicine recorded three cases of bacteria resisting vancomycin.
In two of them, cocktails of other antibiotics cleared up the infection. In the third, a combination of antibiotics failed and the 79-year-old patient died.
Dr Alexander Tomasz, professor of microbiology at New York's Rockefeller University, said in the journal: "This is the tip of the iceberg. At the moment such strains are very, very rare.
"But they are not as susceptible as they used to be. They have moved up the threshold of resistance. It is a warning."
The reports suggested that it would only take one small mutation for the bacteria to develop full resistance to even the most powerful drugs.
Dr Theresa Smith, of the US Centers for Disease Control and Prevention reported two of the cases in the journal, and said the appearance of such bacteria "threatens to return us to the era before the development of antibiotics".
Optimism in Glasgow
However, when it appeared at the Royal Glasgow Infirmary Dr John Hood, consultant bacteriologist at the hospital's Infection Control Unit, was less alarmed.
He said that while the strain showed increased resistance to traditional antibiotics, it was not yet immune to them and newer drugs were also available to combat it.
But Professor Hugh Pennington, who conducted the inquiry into the 1996 Lanarkshire E. coli infection, described the development as "worrying".
"If it turns out to be the case that this strain proves resistant to Vancomycin, that really is quite bad news and would confirm our fears that these bugs are developing a full house of resistance," he said.
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