Scientists have announced that hospital 'superbugs', bacteria resistant to antibiotics, have been dealt a blow by the decoding of the genomes of two of the most feared of the bugs.

Japanese researchers from Juntendo University in Tokyo have decoded the DNA sequence of two antibiotic-resistant strains of the bacteria staphylococcus aureus. One of these strains, methicillin-resistant Staphylococcus aureus (MRSA), infects patients who have had operations and has become endemic in hospitals. The other, vancomycin-resistant Staphylococcus aureus (VRSA) has developed a resistance to what is known as the 'last resort' antibiotic vancomycin, which was, until recently, an effective treatment against MRSA.

It is hoped that the complete DNA sequences of the two bugs will help show why they can cause such devastation and lead to the design of therapies or vaccines. The scientists have discovered 70 new genes which could affect the virulence of the bugs and which could be targets for new drugs.

The research also shows that the genes of Staphylococcus aureus have been partly acquired from other organisms, ranging from bacteria to human beings. It is this characteristic, combined with the repeated duplication of harmful genes, that gives the bug its 'super' power. It has also been discovered that the antibiotic-resistant genes exist along mobile lengths of DNA known as plasmids. These have the ability to spread across strains of staphylococcus aureus, as well as across species.