Antimicrobial Resistance
Antimicrobial resistance is the ability of a microorganism to withstand an antimicrobial such as penicillins or cephalosporins.
Escherichia coli
Extended-Spectrum-Beta- Lactamases (ESBLs) are enzymes that confer the ability to resist a wide range of therapeutic betalactam antimicrobials upon their host organism. One such group of these enzymes is the CTX-M group, which is divided into various 'types' based on their genetic structure. In England and Wales over the last few years, ESBL-producing Escherichia coli have been a significant cause of some urinary tract infections in humans and have seriously affected treatment.
In 2004, VLA reported a CTX-M-14 ESBL in E.coli from calves on a dairy farm in Wales, which was the first time this enzyme had been found in food-producing animals in Great Britain. Further affected herds were identified, as a result of enhanced surveillance and all the ESBL's detected belonged to the CTX-M group. ESBL producing E.coli have also been identified from horses and sheep but this was on a single premises that was being investigated following the detection of resistant organisms in calves at the same location. Multiresistant strains of E.coli, isolated from pigs and poultry have also been examined but no ESBLs have been identified so far.
Discussions between Defra, other Government Departments and Devolved Administrations concluded that current knowledge of the ESBL producing strains of E.coli in the animal and in the farm environment was not sufficient to allow control measures to be introduced to eliminate this resistance from the farm as:
- the organism is likely to be widely disseminated in the environment and other wild animals on an infected farm
- E.coli can survive in the environment for long periods and are naturally present in the gut of most animals
- no vaccines or antimicrobials are available that will specifically deal with this organism
- most strains of ESBL E.coli in animals do not appear to be associated with disease
Collaborative research between VLA and HPA to determine whether any strains of the same type have caused disease in humans in the UK, is also underway.
