ARCHIVE: Surveillance and control of antimicrobial resistance in bacteria associated with animals
The guiding principle of Defra’s policy, with respect to antimicrobial resistance, is to seek to reduce the impact of antimicrobial resistance in organisms associated with animals on public health and animal health in a proportionate way, in conjunction with partners and in accordance with the Animal Health and Welfare Strategy.
Links to other information sources and specific issues regarding antimicrobial resistance in bacteria associated with animals, including Meticillin-Resistant Staphylococcus aureus (MRSA) and Extended-Spectrum Beta-Lactamase (ESBL) producing Escherichia coli, can be found at the bottom of this page.
29 July 2009 - News release: 2nd International Conference on Meticillin-Resistant Staphylococcus aureus (MRSA) in animals taking place 22-25 September 2009, London.
12 July 2007 - News release: First overarching report on antimicrobial usage and bacterial resistance published.
The use of antimicrobials in human and veterinary medicine
Antimicrobials are chemicals that kill tiny organisms known as microbes, or prevent them growing or multiplying. Antimicrobials produced naturally by some species of fungi and plants were discovered in the late 1920s. Since then, many naturally occurring and man-made antimicrobials have been developed for use in human and veterinary medicine. The term ‘microbes’ is used to refer to microscopic fungi, bacteria, viruses and protozoans. Microbes that are capable of causing disease in humans, animals or plants are known as pathogens.
Doctors and veterinarians prescribe antimicrobials to treat diseases and remove infections that are caused by pathogens. Sometimes people or animals with no signs of disease are given antimicrobials to prevent disease developing. This is known as prophylactic treatment. The use of antimicrobials in medicine led to a revolution in the treatment of infections and has saved countless lives.
Some antimicrobials, when used in low concentrations, can increase the growth rate of animals. They are then known as growth promoters. The European Union has issued legislation banning the use of antimicrobials as growth promoters from the 1st of January 2006.
What is antimicrobial resistance?
Antimicrobial resistance is the ability of a microbe to withstand an
antimicrobial. This may be due to the basic nature of the microbe and
is called intrinsic or inherent resistance. This means that the organism
in question is never susceptible to that particular antimicrobial. In
other cases, strains of microbes which were previously sensitive to a
particular antimicrobial develop resistance to it. This is called acquired
Microbes that are resistant to one type of antimicrobial may still be affected by other types. Sometimes a strain of microbe may become resistant to many different antimicrobials. Multiple antimicrobial resistance is commonly defined as resistance to four or more unrelated antimicrobials.
Resistant pathogens do not necessarily cause more severe disease than sensitive ones, but of course the disease is more difficult to treat, because a reduced range of antimicrobial drugs will be effective. Even though some strains of a microbe have developed resistance to a particular antimicrobial, there may still be other strains of the organism that remain sensitive to the same antimicrobial.
Development of antimicrobial resistance
The development of acquired resistance occurs through ‘natural selection’. For most species of plants and animals, the process of evolution through natural selection occurs over periods of thousands of years. However, since microbes can reproduce very rapidly (bacteria can grow and reproduce in as little as twenty minutes), and since there are such enormous numbers of microbes in the environment, the development of antimicrobial resistance in microbes can occur relatively quickly.
- spontaneously from a random mutation in the microbe’s genetic
material that makes that particular microbe resistant to a certain kind
of antimicrobial. As a result, when in the presence of that antimicrobial,
normal (sensitive) cells will not grow whereas resistant ‘mutants’
grow and multiply and may be transmitted to other animals or people.
This process is illustrated in figure
- by obtaining resistance genes directly from other microbes. The microbe which passes on the resistance gene may not itself be a pathogen. So a harmless organism may develop resistance and then pass it on to a harmful one. This is particularly important in bacteria. These resistance genes are present on pieces of DNA that can be transferred between different bacteria and are known collectively as mobile genetic elements. This process is shown in figure 2. These mobile genetic elements often contain clusters of genes that enable recipient bacteria to become resistant to several antimicrobial drugs all at once. The ability of mobile genetic elements to transfer multiple antimicrobial resistances between bacteria is a very important reason why the development of antimicrobial resistance has become a problem.
Why is antimicrobial resistance a problem?
When people or animals are infected with resistant pathogens, treatment with antimicrobials may no longer work. This can result in prolonged or more severe illness or in some cases, death.
Use of antimicrobial compounds in animals and man can increase the levels of resistance in the bacterial population. This can sometimes cause problems if people later become infected with these resistant bacteria. The extent to which antibiotics given to animals contribute to the overall problem of antibiotic resistance in people is still uncertain. It is clear that there are types of bacterial resistance in people with no link to treatment of animals. The emergence and spread of multi-drug resistant tuberculosis is one example.
Concerns over this issue have led to a European Union ban on the use of antimicrobials as growth promoters.
Surveillance for antimicrobial resistance in the UK
Surveillance for AMR in animal-associated bacteria in the UK is carried out in a number of ways by several public funded bodies in partnership with private laboratories, veterinarians and animal owners. Collecting, analysing and sharing this information allows us to:
- monitor trends in patterns of resistance
- detect new and emerging AMR organisms
- identify the risk factors that lead to the development of AMR.
Vets and farmers use this information to treat sick animals in a way that reduces the risk of AMR developing. It also guides Government policy and is used to assess the effectiveness of control measures.
The measurement of AMR presents those involved with some unique challenges. In particular, ensuring that results can be compared within and between different measuring and recording systems is difficult. In the UK, a great deal of effort and co-operation has been put into developing a process by which AMR results from human and veterinary bacterial isolates can be compared in a truly meaningful way. Steps are being taken to extend this approach internationally so that trends in the development and persistence of AMR between different countries can be better monitored and risks to public health identified sooner.
The annual UK Zoonoses Trends and Sources Report contains information on trends and sources of zoonoses and zoonotic agents in United Kingdom. The information covers the occurrence of these diseases and agents in humans, animals, foodstuffs and in some cases also in feedingstuffs. In addition the report includes data on antimicrobial resistance in some zoonotic agents and commensal bacteria as well as information on epidemiological investigations of foodborne outbreaks. Complementary data on susceptible animal populations in the country is also given.
What are the most important AMR problems associated with animals in the UK?
AMR in animals restricts the types of antimicrobial that can be used for treatment of those animals. Human health concerns have been raised with antimicrobial resistant organisms such as campylobacter and salmonella and there is also concern about the passage of antimicrobial resistance from animal types (or strains) of enterococci and Escherichia coli to strains of these organisms that can cause human disease.
- Zoonoses pages on the Defra website
- Defra’s Strategy for Developing and Implementing a Programme of Surveillance for Antimicrobial Resistance in Animals in England and Wales (PDF 144 KB)
- 2005 VLA Report on Antimicrobial Sensitivity (PDF 260 KB)
- Defra Antimicrobial Resistance Coordination (DARC) Group
- Information regarding Extended-Spectrum
Beta-Lactamase (ESBL) and Defra's Position.
Information about Meticillin-Resistant Staphylococcus aureus (MRSA) in Animals.
- Other websites - These sites may be useful if you are interested in further information about AMR in the UK. Please note that Defra does not necessarily endorse the content, information or opinions of these sites.
The Office for Science and Innovation, as part of their review of the way Government departments identify their science requirements and commission, quality assure and use science and scientific advice, has recently published a review of science in Defra.
As part of this review, antimicrobial resistance was selected as one of five case-studies to provide evidence of how science is managed and contributes to Defra's business. The annex of the report (PDF 186 KB), specifically dealing with the antimicrobial resistance case study is available.
Page last modified:
18 January, 2010
Page last reviewed: 13 December 2007