Superbug 'beating' new antibiotic

Staphylococcus aureus can develop resistance (picture: Pfizer)

Bacteria are already showing signs of resistance to one of the latest antibiotics to reach the hospital wards.

Linezolid is a recent addition to the armoury of doctors struggling to keep up with dangerous bugs which constantly mutate to beat the drugs used against them.

It is a very tough organism that a lot of antibiotics have stubbed their toe against

Dr John Quinn

However, while it has proved highly effective against many so-called "superbugs" in the US, one hospital has reported that a linezolid-resistant strain of the enterococcus bacterium has emerged.

In all, five patients there given the drug were found to be carrying strains which were resistant, a study published in the Lancet medical journal revealed.

UK public health experts say that bacteria move fast to overcome the threat from any new antibiotic.

Genetic makeup

As strains which are vulnerable to the new drug are destroyed, those which have mutated into resistant forms are preserved to breed and spread.

A spokesman for the Public Health Laboratory Service (PHLS) said that while enterococcus was known to have a genetic makeup which gave it a higher chance of mutating to beat linezolid, one of the other big threats in UK hospitals - methycillin resistant staphylococcus aureus (MRSA) - was not genetically primed to do this.

So it was unlikely that MRSA would become resistant to linezolid quite as easily.

Dr John Quinn, one of the report's authors, told BBC Radio 4's Today programme that further studies would be necessary.

He insisted: "This is not unexpected - it is a very tough organism that a lot of antibiotics have stubbed their toe against.

Sickest patients

"It has happened rather quickly but our patients had resistant organisms recorded anywhere between 21-40 days into treatment.

"Normally you would only get the drug for 10 days.

"It is the sickest patients with the worst infections getting the drug for the longest period who appear to be at maximal risk for resistance."

There hasn't been an antibiotic introduced into clinical practice where resistance hasn't developed

Dr Brian Duerden
PHLS

Dr Brian Duerden, medical director at the PHLS, said the antibiotic would still be useful.

Dr Duerden said: "It is a matter of concern that a new drug has been shown to fail in treatment in this way but it is not unexpected.

"The bacteria population is huge with 500 billion in each of us, replicating rapidly and mutating with the chances of becoming resistant so much greater.

Wide use

"The bacteria will become resistant as they are exposed to the antibiotic - there hasn't been an antibiotic introduced into clinical practice where resistance hasn't developed.

Dr Duerden agreed that prescription of antibiotics had become more selective.

"Antibiotics have been very widely used without the thought we give to other important drugs - we are learning much more that we have to be prudent."

The UK government is continuing a crackdown on poor hygiene in hospitals after listing 10 which had failed to meet basic standards.