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.

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.

'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 USA300 is 'a really big issue in the U.S. and it's starting to emerge here.

'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.'

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.'