Experts in Britain say virulent bugs such as MRSA (methicillin resistant Staphylococcus aureus) are now spreading beyond hospitals and into the wider community and may put lives at risk.
The experts, gathered at a conference in Cardiff, Wales are particularly concerned about a potentially lethal form of MRSA which can infect the lungs, and may strike young people in particular; MRSA is not usually a threat to young people.
They say certain strains of community-acquired MRSA such as Panton Valentine leukocidin (PVL) can cause a condition called necrotizing pneumonia, which destroys lung tissue and while it only affects a minority of those infected, it can be deadly.
The strain produces a potent toxin which causes recurrent boils and abscesses, but if it enters into the bloodstream it can lead to necrotising pneumonia.
Even with the strongest antibiotics, more than 60% of otherwise healthy, young and fit people who contract the infection die and it can easily be misdiagnosed by GPs because the symptoms appear relatively harmless.
The experts say the emergence of community MRSA highlights just how efficient the bacteria are at evolving and presenting new and difficult problems to be dealt with.
Dr. Marina Morgan, of the Royal Devon and Exeter Foundation NHS Trust says community-acquired MRSA is spread outside of hospitals by skin-to-skin contact and appears as sores which look like insect bites.
The bacteria appear to be able to stick to damaged skin and airways better than the hospital MRSA strains, and can also multiply at a faster rate; in the very worst case scenario Dr. Morgan says they can kill in a day.
In the United States 12% of all MRSA cases are already community-acquired and the UK also has an increasing number of cases.
It is suspected that children are at particular risk because they have more cuts and abrasions than older people and have more contact with other people.
According to the Health Protection Agency, in 2005, the first year it had figures for PVL infection, there were 130 cases; last year 150 new infections were recorded.