Antibiotics are being overused in children of this age group

Report authors writing in BMJ

The parents of the children were asked to keep a log, over a two year period, detailing illnesses, trips to the doctor, and which drugs were prescribed.

Nasal swabs were taken every six months to check for the presence of bacteria.

The likelihood of carrying penicillin-resistant bacteria was doubled in children who had been given penicillin or a similar antibiotic in the previous two months.

Rising chance

In addition, for each additional day of antibiotic use over the previous six months, the chance of finding resistant bacteria was 4% higher.

If resistant bacteria get into a position where they cause infection, they can be much more difficult to treat

Spokesman, PHLS

The researchers, from the National Centre for Epidemiology and Population Health in Canberra, wrote in the British Medical Journal: "Antibiotics are being overused in children of this age group in Australia.

"We found that 47% of all episodes of respiratory symptoms resulted in a visit to the general practitioner, and that up to 48% of children who visited their GP received an antibiotic on their first visit.

"The likelihood that antibiotic use will, in the short term, result in carriage of a resistant organism needs to be built into clinical decision making."

Restraint urged

A spokesman for the UK's Public Health Laboratory Service (PHLS) echoed this.

He said: "This research provides further evidence of just how important it is to ensure that antibiotics are used carefully and appropriately.

Bacteria can swiftly become resistant to drugs

"If resistant bacteria get into a position where they cause infection, they can be much more difficult to treat.

"This work reinforces the message that the more we use antibiotics, the more we promote the development of resistant bacteria."

Campaign started

The UK government launched its own campaign on Thursday to stop patients demanding antibiotics from their doctors - even for viral infections which will not be cured by them.

Deputy Chief Medical Officer Dr Pat Troop said: "Already some antibiotics are becoming less effective at fighting those infections and if we continue to use them inappropriately more bacteria will become resistant to them."

Drug resistant bacteria are a particular problem in hospitals, where it is estimated that they cost the NHS millions annually in extended hospital stays and extra treatment - and contribute to the deaths of thousands more.

Some bacterial strains have developed strong resistant to a whole series of antibiotic types as a result of exposure over long periods.

Resistance develops because the use of antibiotics naturally selects those strains which are best equipped to resist them - by killing the rest.