Scientists have opened up the possibility of a new treatment for asthma after trials showed that an antibiotic could shorten the recovery time after a bad attack from eight days to five.

Severe asthma attacks have previously been linked with viral infections, and therefore thought resistant to antibiotics. But the discovery suggests bacteria may also play a part in some attacks.

At hospitals around the world 278 people were involved in a trial within 24 hours of having a severe attack. Half of the group was given the antibiotic Telithromycin and the other half a placebo.

Those on the drug recovered in five days compared with the placebo group's eight days. The improvements in symptoms and lung function were twice as great in those on the antibiotic.

Sebastian Johnston, a professor at Imperial College London, who led the study, published today in the New England Journal of Medicine, said they were not sure what caused the antibiotic to be effective but the study indicated it was beneficial. There was still some way to go before treatment might be available for asthma sufferers; the drug is not yet licensed for use in the UK for asthma.

In the UK 5.2 million people suffer from asthma and there are 72,000 emergency admissions to hospital a year following attacks. Most of the acute asthma attacks are thought to be linked to viral infection.

The researchers said the apparent success of the antibiotic could arise from its impact on the bacteria Chlamydophila pneumoniae and Mycoplasma pneumoniae. In the trial 61% of the patients tested positive for one of these bacteria. The scientists also believe the anti-inflammatory properties of Telithromycin may play a part in shortening recovery time.