The bacteria are more virulent than the infamous hospital MRSA, can affect otherwise healthy people and are spreading across Britain.
They can be transmitted through skin-to-skin contact and hugging as well as sneezing and coughing.
One strain, called USA300, can lead to blood poisoning or a form of pneumonia that eats away at lung tissue.
The bacteria are usually resistant to several types of antibiotics and can cause large boils on the skin.
Chris Williams, professor of molecular genetics at the University of Birmingham, said: ‘It breaks down tissue. If it gets into your heart, bacteria can get into your bloodstream and take hold of different parts of your body. That could lead to death quite easily.’
The dangers of the ‘community- acquired’ superbugs are raised in a new study, examining the way they spread. Researcher Dr Ruth Massey said USA300 was ‘causing huge problems in America and is being reported here increasingly’.
She added: ‘These community- acquired strains seem to be good at affecting healthy people – they seem to be much better than the hospital ones at causing disease.’
Dr Massey said there were 1,000 cases of so-called PVL-positive community-acquired MRSA in England in the last year, of which 200 were USA300 strains.
Prof Williams added: ‘If you’re on a crowded tube or bus and you sneeze you can spread the bacteria.
‘But your sneeze can also land on a metal surface and when someone else gets up from their seat and steadies themselves on the hand rail they can catch it.’
However, MRSA was also prevalent in the nose and the hair so might be spread by scratching the head and then shaking hands, he said.
The Health Protection Agency said it had been aware of the strains for more than a decade but it was ‘not a major public health issue in this country’.
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Flesh-eating bug that you can catch on the bus or train is spreading in the UK
- Strain of MRSA from the U.S. causes large boils and is resistant to several front-line antibiotics
- Survives on surfaces so can be picked up on public transport
A flesh-eating form of pneumonia that is easily passed between healthy people on public transport is spreading across the UK, experts have warned.
The deadly strain of MRSA called USA300 passes easily through skin-to-skin contact. It can also survive on surfaces and so has the potential to be picked up on crowded buses and tubes.
It was first seen in the U.S but cases are now being reported in the community and not just hospitals in Britain.
USA300: The deadly MRSA strain can cause large boils on the skin
Dr Ruth Massey, from the Department of Biology and Biochemistry at the University of Bath, said extra vigilance was required around this and similar MRSA bugs known as PVL-positive community acquired strains.
USA300 is resistant to treatment by several front-line antibiotics and can cause large boils on the skin. In severe cases, USA300 can lead to fatal blood poisoning or a form of pneumonia that can eat away at lung tissue.
Dr Massey said there were 1,000 cases of PVL-positive community acquired MRSA in England in the last year, of which 200 were USA300 strains.
'These community-acquired strains seem to be good at affecting healthy people - they seem to be much better than the hospital ones at causing disease.
'They don't rely on healthcare workers moving them around, which the hospital ones seem to.'
Dr Massey said USA300 is 'a really big issue in the U.S. and it's starting to emerge here.
'But hopefully because we are aware of it and are working to understand it, it won't become as big of a problem (in the UK).'
In a new research paper published in the Journal of Infectious Diseases, Dr Massey and colleagues analyse the way community-acquired MRSAs are able to adapt and fine tune themselves to spread outside of hospitals.
MRSA bacteria in hospitals has not been able to migrate into the community in the same way.
Dr Massey said: 'Our research found that the composition of the cell wall of the bacteria is critical to the community-acquired bacteria being more toxic.
Different danger: MRSA bacteria in hospitals have a different kind of cell wall to community-acquired MRSA strands which have evolved further
'The ability of the MRSA bacteria to secrete toxins is one of the main ways it causes disease.
'Using a sensing system, it carefully controls when it switches on its ability to do this, so as not to cause disease until it is firmly established within the human.
'Many antibiotics target the cell walls of harmful bacteria, and to resist this, the bacteria have to make changes to their cell wall.'
Community-acquired MRSA strains have cell walls that are different to those seen in hospitals, allowing them to sense their environment and switch toxin expression on at the right time.
Justine Rudkin, a PhD student working on the project, said: 'The community-acquired bacteria has evolved further, and is able to maintain a higher level of toxicity while also resisting treatment from antibiotics, making it a much larger problem.'
She added: 'While we are constantly learning more about MRSA, there is a serious threat posed by this newer strain of bacteria capable of causing disease and even death in perfectly healthy people.
'We need to respond seriously to this threat as it reaches Britain from the United States.'
An HPA spokesman played down the danger of USA 300, saying: 'In England we have seen sporadic cases of this type of MRSA most often causing boils and abscesses, but it has not emerged as a major public health issue'
Chris Thomas, professor of molecular genetics at the University of Birmingham, said: 'The key message is that strains of MRSA that are spreading in the community are better able to infect the young and healthy, precisely because they are not actually trying so hard to be resistant as the bugs that have been encountered in hospitals for many years.'
He said there was now a 'need to worry about community super bugs that are fine tuned to spreading outside of hospitals and we all need to be extra vigilant about hygiene and unnecessary use of antibiotics.'
A spokeswoman for the Health Protection Agency (HPA) said: 'The paper highlights some important observations which helps us understand at the molecular level why hospital strains of MRSA are less virulent than the so-called community MRSA strains.
'We have known about community MRSA for over a decade and, whilst they are responsible for a high burden of disease in North America, this is not the case in the rest of the world.
'In England we have seen sporadic cases of this type of MRSA most often causing boils and abscesses, but it has not emerged as a major public health issue in this country.
'The HPA are carrying out active surveillance of this type of bacteria and advise healthcare professionals on correct infection control procedures to reduce the likelihood of spread.'
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