New 'superbug' could be immune to treatment

A British scientist has warned of the dangers posed by the appearance of a new strain of superbug in the US that is highly resistant to the last antibiotic in the medical arsenal.

The microbe causes potentially lethal hospital infections and cannot be killed with the drug vancomycin – known as the antibiotic of last resort.

Brian Spratt, a professor of molecular microbiology at Imperial College London, said its sudden emergence in America was a warning "to hospitals in the UK where a similar superbug could lead to the rapid spread of potentially lethal infections".

"One hopes that it has been contained but ultimately a strain like this is going to become established and will spread," Professor Spratt said yesterday.

"It might happen in America, it might happen in any country. These strains can emerge in a clinical setting and they pose a great danger," he said.

American doctors treating a 40-year-old diabetes patient in Michigan found that an ulcer on his foot was infected with a strain of Staphylococcus aureus bacteria that was highly resistant to vancomycin.

Specialists from the US Centres for Disease Control in Atlanta, Georgia, are trying to contact the patient's friends and relatives to test whether the bacteria – normally carried harmlessly in the nose and on the skin – has spread.

S aureus can cause severe wound infections especially in hospital patients with weakened immune systems. Symptoms range from mild skin disease to severe blood poisoning and death. A strain of the bacteria called methicillin-resistant S aureus (MRSA) poses particular problems because it survives treatment with a range of antibiotics, such as penicillin and cephalosporin, leaving vancomycin as the last hope.

The genes that have made the Michigan man's staphylococcus infection resistant to vancomycin could pass into MRSA, rendering the antibiotic of last resort useless against one of the most feared hospital infections, Professor Spratt said.

"If vancomycin-resistant genes become established in S aureus they will move into other strains of MRSA, which are basically resistant to everything we have," he said.

"The crucial thing is to contain these types of organisms. If they do become established it would be very hard to get rid of them. These vancomycin-resistance genes will move into strains that are even more resistant to antibiotics."

Although mild vancomycin-resistance had previously been reported in S aureus in Britain, Japan and the US, this is the first time that a highly resistant strain has been authenticated, Professor Spratt said. Scientists in the US believe that the vancomycin-resistant genes jumped into staphylococcus from another species of bacteria called enterococcus.

"We've always been waiting for this package of genes to move from vancomycin-resistant enterococci into S aureus. It was done experimentally in the laboratory some time ago but it has never happened in nature," Professor Spratt said.

"All of the major hospitals in the UK would at one time or another have problems with these organisms," he said.

David Livermore, the director of the Government's Public Health Laboratory Service in north London, said that the American discovery highlighted "the importance of using all antibiotics carefully in order to try to minimise the development of antibiotic resistance."