The study calls for global monitoring of outbreaks

A string of countries, including the UK, have all in recent years reported cases in the community of ESBL E.coli which are resistant to antibiotics.

Its effects range from cystitis to deadly septicaemia.

Calgary researchers, writing in The Lancet Infectious Diseases, said it was vital to start tracking the strains.

This way, argued the team from the University of Calgary, it could be established which strains were responsible for which infections, and whether there were antibiotics more effective at treating them.

So far, it appears that the elderly are most at risk - particularly those resident in nursing homes.

Food poisoning

E.coli is a very common bacteria found in the gut, and is normally harmless.

Some strains, however, can be very serious, including those linked to food poisoning.

But it is the drug-resistant forms which are particularly worrying public health experts at present: Spain, Israel, Italy, Greece, the UK and Canada have all reported cases of E.coli infection which tended to be resistant to four key antibiotics.

There is a need for sustained research into both the origin of these E.coli strains as well as the number of people who carry ESBL-producing E.coli in their gut Health Protection Agency

Blood poisoning cases caused by E. coli more than doubled in the UK between 1995-2005, and a small but increasing number of those were drug-resistant.

A review of the deaths of 54 people in the county of Shropshire who all had a resistant strain found that the ESBL-producing bug had directly contributed to 20% of the deaths.

The bacterium was also held responsible for a severe outbreak of urinary tract infections between 2003 and 2004.

However, cases are not thought to have increased in the UK in the last two years.

The authors of the paper compared the E.coli threat with that of community-acquired MRSA, which is emerging as a public health problem in many parts of the world.

In the US for instance, this form of MRSA - which is spread outside hospitals via skin-to-skin contact - accounts for 12% of all MRSA cases - and affects the young as well as the old.

ESBL infections "are currently rare, but it is possible, in the near future, clinicians will be confronted with hospital types of bacteria causing infections in patients from the community - a scenario very similar to that of community-acquired MRSA," they wrote.

The UK's Health Protection Agency said it had been investigating these infections for several years and continued "to review the activity of new antibiotics against bacteria with these particular enzymes.

"We agree with the authors that antibiotic resistance is an important issue affecting public health.

"There is a need for sustained research into both the origin of these E.coli strains as well as the number of people who carry ESBL-producing E.coli in their gut, to help gain a better understanding of the risk factors for people acquiring infections; how they are transmitted and to help develop better control measures."

Dr Andrew Berrington, a consultant microbiologist at Sunderland Royal Hospital, said: "It does seem to be true that what was previously regarded as a hospital problem is now being seen in the community as well.