Urinary tract infections (UTIs) are usually treated with antibiotics, however a new study has found that these drugs may be ineffective when used on children, as antibiotic resistance is high among this population.

The discovery and development of effective antibiotics in the 1940s and 1950s meant that many serious infections such as pneumonia, meningitis and tuberculosis were no longer seen as potential killers. These drugs are also used to treat common infections, such as UTIs.

However, gross overuse has led to the problem of antibiotic resistance, whereby bacteria change and build up a resistance to drugs that have been used over a long period of time and in great numbers. The World Health Organization describes antibiotic resistance as a ‘major threat to public health'.

Children are frequent users of antibiotics, however little research has been carried out into antibiotic resistance among this group. UK researchers decided to investigate this further.

They assessed the prevalence of antibiotic resistance in UTIs caused by Escherichia coli (E.coli), a bacterium that is responsible for more than 80% of all UTIs in children.

The researchers also looked at the link between previous exposure to antibiotics and subsequent resistance in children.

Over 77,000 E. coli samples from 58 studies in 26 countries were reviewed.

The researchers found that globally, the prevalence of resistance to some of the most commonly prescribed antibiotics was high. Within OECD countries, of which Ireland is a member, half of all samples were resistant to amoxicillin - a commonly used antibiotic in this country.

A further one in four was resistant to trimethoprim, another well-known antibiotic here.

Meanwhile, antibiotic resistance in non-OECD countries was even higher. The researchers suggested that a reason for this may be due to the availability of antibiotics in those countries over the counter.

"The results also suggest previous antibiotic use increased the subsequent risk of E. coli resistance to that particular antibiotic, for up to six months after treatment," the researchers noted.

Details of these findings are published in the British Medical Journal.