Infections caused by ESBL-producing E. coli

In light of increased media and public interest in ESBL-producing E. coli, the UK's Health Protection Agency felt it would be helpful to provide some background about these infections and the work that is being carried out in this area.

ESBL (Extended-Spectrum Beta-Lactamase)-producing E. coli are antibiotic-resistant strains of E. coli. E. coli are very common bacteria that normally live harmlessly in the gut. ESBL-producing strains produce an enzyme called extended-spectrum beta lactamase, which makes them more resistant to cephalosporin antibiotics. Many ESBL-producing strains are also resistant to antibiotics belonging to other classes. This makes the infections harder to treat.

The kinds of infections that ESBL-producing E. coli can cause range from urinary tract infections, to – at the more serious end of the spectrum – cases where they enter the bloodstream and cause blood poisoning. Infections with ESBL-producing E. coli are most common amongst the elderly, or those who have recently been in hospital or received antibiotic treatment. ESBL-producing E. coli are extremely rare in simple cystitis.

Infections caused by ESBL-producing E. coli are a growing worldwide phenomenon and are not unique to the UK . The Health Protection Agency is one of the leading institutions worldwide in terms of research into this area and has been providing advice about these infections for many years and, in particular, produced a report on the increasing frequency of these infections in 2005.

Since 2003 the Agency has been working with NHS hospital microbiologists to ensure they are aware of these infections and are able to advise and provide information to their local GPs and hospitals about the diagnosis and treatment of these infections. The Agency has also published a lot of information in scientific journals and issued advice directly to GPs via its website and leaflets. It also continues to review the activity of new antibiotics against bacteria with these enzymes.

A lot of research still needs to be carried out into the origin of the strains of E. coli that cause infections. Imported chicken has been suggested as a possible route for their introduction into the UK . However recent HPA research shows that the particular strains of E. coli and the particular ESBLs that they produce are significantly different from those so far found in chickens, so this link remains unproven. This research detected E. coli with the ESBLs CTX-M-1; CTX-M-2 and CTX-M-14 in imported chicken meat; however most of the ESBL-producing E.coli from human infections have the CTX-M-15 ESBL which was not found in any chicken samples.

A second theory for the origin of these infections, which also requires more research, is that migration could be a source. More research is needed on other aspects too, such as the number of people who carry ESBL-producing E. coli in their gut, though it should be stressed that most of these will be carrying it harmlessly, and it will not cause them any illness.

The figure being quoted in the media of 30,000 cases of infection due to ESBL-producing E. coli each year in the UK is an estimate. This estimate takes into account all cases, whether they cause urinary tract infections or blood poisoning; however this estimate still needs to be verified.

The Agency's monitoring shows that around 20,000 people a year in the UK (excluding Scotland ) are affected by blood poisoning caused by E. coli . Of these, around 2,000 cases are caused by ESBL-producing E. coli (these figures cover blood poisoning only and not urinary tract infections). The Agency will be widening this surveillance system shortly and its eight regional laboratories will be carrying out surveillance of ESBLs in other types of infection (e.g. urinary infections) so that a more complete picture of numbers and trends can be established. Any introduction of mandatory surveillance, as we currently have for MRSA or C difficile, would be the responsibility of the Department of Health.

For further information about ESBL-producing E.coli go to: http://www.hpa.org.uk/infections/topics_az/esbl/