Are superbugs spreading on food?
Monday 11th August 2008
About half of all antibiotics used in the UK each year are given to farm animals, often to prevent, rather than to treat, disease. (1) The drugs allow livestock and poultry farmers to control the inevitable disease problems which arise when thousands of animals are crowded together indoors.
It is generally accepted that farm antibiotic use contributes to the problem of antibiotic resistance in food poisoning infections, such as salmonella and campylobacter, but Richard Young, organic farmer and policy adviser to the Soil Association, argues in the latest issue of The Food Magazine that over-reliance on antibiotics in farming is also increasing the number of other serious infections in humans which fail to respond to most antibiotics.
An estimated 30,000 people each year in the UK are affected by E. coli infections that are resistant to almost all antibiotics (2) and up to 4,200 of these are thought to die, partly due to treatment failures. (3) The problem is caused by types of antibiotic resistance known as ESBLs (extended-spectrum beta-lactamases), which are spreading both in humans and farm animals. Between 2001 and 2006, the percentage of ESBL blood poisoning caused by E. coli rose from 0 to12%, with those affected with an ESBL strain being more than twice as likely to die.
Antibiotic use is widespread. A survey of 7,120 people by the Department of Health found that almost one third had taken a course of antibiotics within the last year, often unnecessarily for minor ailments, or those which do not even respond to antibiotics. (4) As a result doctors are coming under increased pressure to prescribe antibiotics more sparingly.
Similar pressure has not yet been applied to veterinary surgeons and farmers in the UK or in food-exporting counties, who still give large quantities of antibiotics to farm animals preventatively, as well as to treat specific illnesses, and who are also increasingly using drugs classified as critically important in human medicine.
ESBL E. coli have been found in imported poultry meat (5) and home-produced cattle, (6) and studies in other countries have implicated food in the spread of infections to humans. (7)
A new type of MRSA (methicillin resistant Staphylococcus aureus), has also now arisen in pigs and other farm animals, and is passing to humans. MRSA (ST398) is spreading rapidly across continental Europe and some other countries, in part due the heavy use of antibiotics in pig feed. (8)
In the Netherlands, approximately 40% of pigs and some chickens, calves and dairy cows already carry this strain. The most immediate threat is to those who work with animals. 50% of Dutch pig farmers have been found to be carrying the strain, and several dozen have been hospitalised due to serious MRSA infections. This MRSA strain has also been found at low levels in a high percentage of Dutch pork, poultry and beef. (9)
Luckily, the UK has not imported live pigs from affected countries for some years and MRSA ST398 has not yet been found in British farm animals. However, this strain has now been identified in three humans in the UK with no direct link to farm animals, giving rise to concerns that it could be spreading to the UK on imported meat. (10)
Richard Young said, ‘The use of antibiotics is a cornerstone of intensive livestock production and because this is such an enormous industry there will inevitably be a reluctance to change. No one wants to stop farmers using antibiotics when they are genuinely needed. However, there are a number of very serious problems now developing and the evidence increasingly suggests that food is part of the problem. As such we need an urgent review of the overall situation with clear recommendations to prevent an impending crisis.’
Notes for editors
For further information contact Richard Young on 01386 858235 or RYoung@SoilAssociation.org
Article published in The Food Magazine issue 82, 11th August 2008. The Food Magazine is published by The Food Commission, an independent watchdog which campaigns for healthier, safer, sustainable food in the UK.
In 1998, a Department of Health report, The path of least resistance, stated that, ‘50% of antibiotic use is in man, 50% in animals’ (p29). Latest data gathered by the Veterinary Medicines Directorate shows that, in 2006, 405 tonnes of antibiotics (calculated by weight of the active ingredient) were used in animals, with approximately 8% of this being used in companion animals.
Reported by the Health Protection Agency in a press release ‘Infections caused by ESBL producing E. coli’ on 24/07/08
“Threat from ‘new E. coli’”. Templeton S-K., 2007. The Times.
The public’s attitudes to and compliance with antibiotics. C. McNulty, P. Boyle, T. Nichols, P. Clappison and P. Davey. Journal of Antimicrobial Chemotherapy 2007 60: Suppl. I i63-i68
Imported chicken meat as a potential source of quinolone-resistant Escherichia coli producing extended-spectrum beta-lactamases in the UK. Warren RE, Ensor VM, O'Neill P, Butler V, Taylor J, Nye K, Harvey M, Livermore DM, Woodford N, Hawkey PM. Journal of Antimicrobial Chemotherapy. 2008 March;61(3):504-8.
Extended-Spectrum Beta-Lactamases (ESBL) in bacteria associated with animals. DEFRA, 2007.
Dissemination of extended-spectrum ß-lactamase-producing bacteria: the food-borne outbreak lesson. S. Lavilla, J. J. González-López, E. Miró, A. Domínguez, M. Llagostera, R. M. Bartolomé, B. Mirelis, F. Navarro, and G. Prats. Journal of Antimicrobial Chemotherapy. June 2008; 61: 1244 - 1251.
“Fears grow that MRSA variant has entered food chain”. Hickman, M., 2008. The Independent.
MRSA in farm animals and meat, A new threat to human health, report five in the series 'The use and misuse of antibiotics in UK agriculture'. Nunan, C. Young, R., 2007. Soil Association.
ST398 MRSA infections in Scotland. Health Protection Scotland, HPS Weekly Report. 2008. Volume 42, No. 2008/23