A new superbug, which is fully resistant to one of the most powerful antibiotics in the medical arsenal, has been identified in a 40-year-old hospital patient, increasing fears that science will have trouble keeping ahead of the spread of potentially harmful bacteria.
Staphylococcus aureus is a common bacterium carried in the nose and on the skin of 10% of the population, but it can cause serious blood poisoning when it enters a wound.
It was once treated easily with penicillin, but it has now mutated to the point where it is totally resistant to it. The next defence on the antibiotic ladder has been methicillin, but strains of the bug that are resistant to methicillin have become increasingly common, especially in hospitals. They are known as MRSA (methicillin-resistant Staphylococcus aureus) - dubbed the superbug.
MRSA is treated with the antibiotic vancomycin, which has been regarded as the last established line of defence. There have been a few cases of partial resistance to vancomycin (vancomycin-intermediate Staphylococcus aureus or VISA), but now the first case of a staphylococcus bug that is totally resistant to the antibiotic has been detected in the US.
"This is very disturbing," said David Livermore, director of the public health laboratory service's antimicrobial resistance monitoring and reference laboratory in London.
"Investigations in the US suggest that the organism be came resistant by acquiring a resistance gene from another less serious germ known as an enterococcus, in which vancomycin-resistance is already well established. In effect, the resistance mechanism jumped from the enterococcus to the Staphylococcus aureus. This transfer is something we have feared since vancomycin-resistant enterococci were discovered 16 years ago."
The new bug, vancomycin-resistant Staphyloccocus aureus or VRSA, was identified in a Michigan hospital where a 40-year-old man was being treated for diabetes, chronic kidney failure and problems in the blood supply to his legs. He had received a lot of antibiotic treatment, including vancomycin for MRSA.
It is thought that he developed vancomycin-resistant enterococci in a foot ulcer, and that the resistance gene then transferred to the Staphylococcus aureus bacteria. Fortunately, the bug responded to a combination of two old antibiotics, trimethoprim and sulphamethoxazole, and the man's condition was stabilised. Lab tests also showed it could have been knocked out by several new drugs which have recently been licensed.
But doctors are alarmed at the possibility that vancomycin may be destined to fail, just as penicillin and methicillin have done.Dr Livermore said: "This finding highlights the importance of using all antibiotics carefully to minimise the development of antibiotic resistance, as well as the need for good infection control programmes in hospitals and research into the development of new drugs."
