Our Expert FAQs panel ranges from members of RUMA’s independent Scientific Group to other veterinary specialists in their field. They are on hand to answer your tricky or pointed questions about use of antibiotics in farming.
Just complete the boxes below and we will put the question to our panel as quickly as possible. When they’ve answered, we will let you know and post the answer on our list of Frequently Asked Questions.
Antibiotic resistance occurs when an antibiotic is no longer able to effectively control or kill bacteria. As the bacteria become resistant, they continue to multiply in the presence of antibiotics, which would normally kill them.
Antibiotic resistance is a natural phenomenon. Resistant bacteria are found on and in humans, in our environment, on farms, and on animals. They are all around us because resistance happens naturally as bacteria defend themselves against attack. A paper published in Nature in 2011 found resistant bacteria in the frozen remains of a woolly mammoth, and demonstrated that the genes that confer resistance to antibiotics were present in bacteria 30,000 years ago. Gerald Wright, who led the study, said: “This isn’t surprising, since that type of bacteria is the source of many antibiotics. These bacteria produce probably 80% of the drugs currently used today – they also make anti-cancer agents, they make immune suppressants, they are remarkable little chemists. Scientists don’t yet know why soil bacteria have a tendency to make antibiotics and be resistant to antibiotics, but they speculate it may help them compete with other bacteria in an environment crowded with millions of bacterial species.”
When an antibiotic is used, bacteria that can resist that antibiotic have a greater chance of survival than those that are ‘susceptible’. Those bacteria that survive, can then multiply. Some resistance occurs without human action, as bacteria can produce and use antibiotics against other bacteria, leading to a low-level of natural selection for resistance to antibiotics. However, the current higher-levels of antibiotic-resistant bacteria that are found in both human and veterinary medicine are attributed to the overuse and abuse of antibiotics.
Some bacteria are naturally resistant to certain types of antibiotics. However, some mutate to either produce enzymes that ‘deactivate’ antibiotics, while other mutations change or close the target area on the bacteria that the antibiotic would normally attack. Some even create mechanisms to push the antibiotic back out of the cell when it attacks. Bacteria can acquire antibiotic resistance genes from other bacteria in several ways. They can transfer genetic material through a simple mating process (conjugation), or through plasmid transfer that can ‘reprogramme’ other bacteria to be resistant to antibiotics. They can also pick up stray DNA in their environment or can be infected by viruses, which transmit the resistance gene.
Antibiotic resistance spreads as bacteria themselves move from place to place via direct human contact, for example through coughing or contact with unwashed hands, as well as animal contact, or by contaminated materials and housing and in water, food and even in the wind.
You find resistant bacteria the same places you find bacteria – it’s just some of them are resistant.
No, resistance can happen naturally, but overuse of antibiotics can result in resistant bacteria. Bacterial populations can also move around via introduction of animals from other farms, or through introduction via carrier species. It does not always mean that it is directly attributable to practices on any one farm.
Among humans, human medicine is currently the main source of resistant bacteria. This has been acknowledged by the European Medicines Agency Committee for Medicinal Products for Veterinary
Use (CVMP) in its draft strategy on antimicrobials: “…the greatest driver of AMR in people is the use of antimicrobials in human medicine.” The UK Department of Health also says: “Increasing scientific evidence suggests that the clinical issues with antimicrobial resistance that we face in human medicine are primarily the result of antibiotic use in people, rather than the use of antibiotics in animals. Nevertheless, use of antibiotics in animals (which includes fish, birds, bees and reptiles) is an important factor contributing to the wider pool of resistance which may have long term consequences.” In farming, spread from other farm animals would be the main source of resistant bacteria. The cross-over between the two is very small at the moment, with recent studies confirming farm animal use could be responsible for as few as one in every 370 clinical cases of E coli infections. However, a risk does remain and people should always wash their hands thoroughly after contact with animals. Resistant bacteria can be found on meat, but good kitchen hygiene, washing hands after handling raw meat and thorough cooking of meat will almost completely prevent the transmission of antimicrobial resistance – or indeed bacteria in general – from meat to man.
Reducing , refining and replacing use of antibiotics reduce selection for resistant strains (see What is the role of the antibiotic in creating resistance?). But reducing use also doesn’t necessarily lessen resistance. In some countries, antibiotic use has halved over the past 10 years but levels of resistant bacteria have risen. Bacteria resistant to some medically critically important antibiotics (CIAs) have also been found on farms that have never bought or used that antibiotic.
At the moment, there is lots of confusion over what ‘antibiotic-free’ means and there is no single definition. Remember that antibiotics are used to treat and prevent disease in animals in all countries, but also for growth promotion in some countries where that practice is still permitted. All animal farming must abide by strict withdrawal periods after an animal has been treated with antibiotics for any reason, to ensure medicine residues do not enter the food chain. So in this sense, all food should be ‘antibiotic-free’. However, we have seen the term ‘antibiotic-free’ used (rightly or wrongly) in a number of different situations, for example: where antibiotics have not been used for the purposes of growth promotion in countries where it is still permitted (such as in the USA); where highest priority critically important antibiotics haven’t been used to treat or prevent disease in livestock; and where no antibiotics have been used ever for any purpose in that animal. There is no standard meaning, and labelling one food that way does not mean another food has antibiotics in it. See specific questions about whether meat from animals treated with antibiotics has antibiotics in it.
Any move to reduce antibiotic use sustainably, without impacting animals welfare, should be welcomed. However, there is some concern that ‘antibiotic-free’ labelling could be misleading or confusing, and have ramifications on animal welfare. Reassurance should be given that such labels don’t lead to treatment being delayed or avoided for sick animals, or that livestock in need of nothing more than a short course of medicine to recuperate will not be destroyed rather than treated.
In human medicine, MRSA (Methicillin-resistant Staphylococcus aureus) and E-coli resistant to a number of different antibiotics tend to have the highest profile. But resistance can be found anywhere. For example, a recent report found worryingly high levels of resistance to widely used antibiotics such as ampicillin, which is used to treat urinary tract infections (UTIs) in children.
In human medicine, MRSA (Methicillin-resistant Staphylococcus aureus) and E-coli resistant to a number of different antibiotics tend to have the highest profile.
It is not currently common in the UK, nor a high risk, but it is being monitored closely. A risk assessment published in February 2017 by the Food Standards Agency (FSA) assessed the risk associated with the preparation, handling or consumption of foodstuffs which may be contaminated with MRSA, in particular Livestock-Associated LA-MRSA. It concludes the risk is very low and based on this the FSA’s current advice remains unchanged, i.e. that raw food should be stored appropriately, handled hygienically and cooked thoroughly to ensure any harmful bacteria present are destroyed. LA-MRSA infection is rare in humans in the UK and such organisms are not readily transmitted from person to person. To the FSA’s knowledge, there have been no reported food borne outbreaks of LA-MRSA in humans in either the UK or worldwide. Furthermore, the indication is that prevalence of food contaminated with LA-MRSA is low in the UK. LA-MRSA has been shown to enter the food chain and survive on raw meat up to the point of retail, although thorough heat treatment of raw meat is sufficient to destroy LA-MRSA and other vegetative bacteria.
E coli is a classic marker of faecal contamination in humans and animals. It is likely that exposure to antibiotics from medical or veterinary treatment could give rise to resistance in E coli, and the potential for these organisms to cause UTIs in humans – whether they are originally from human or animal sources – is also not unexpected. As inhabitants of the intestine, this organism can potentially gain access to the urethra and may cause infection – so it is possible. The likelihood and frequency of this occurrence, though, has not been demonstrated.
All antibiotics in the UK require a prescription by a vet and as such are tightly controlled. Online sales of antibiotics are very closely monitored to ensure they are dispensed with a prescription and no fraud is taking place. The Veterinary Medicines Directorate confirms that its enforcement team has succeeded in removing over 824 antibiotic products from the illegal online market since 2014 – this is not counting all the products taken down directly by E-bay (new procedures were put in place by E-bay in 2016).
Therapeutic or curative treatment of a sick animal or group of animals follows the diagnosis of infection and/or clinical disease in those animals. Control treatment (sometimes referred to in veterinary medicine as Metaphylaxis) is the treatment of a group of animals after the diagnosis of infection and/or clinical disease in part of the group, with the aim of preventing the spread of infectious disease to animals in close contact and at considerable risk and which may already be (sub-clinically) infected or incubating the disease. A useful comparison with human medicines would be where a child in a classroom is diagnosed with meningococcal meningitis necessitating urgent treatment of all other in-contact children. Preventive treatment (sometimes referred to as Prophylaxis) is the treatment of an animal or a group of animals, before clinical signs of infectious disease, in order to prevent the occurrence of disease or infection.
RUMA and almost all farming and veterinary organisations in the UK do not support routine preventative treatment, and agree that preventive treatment or prophylaxis with antibiotics:
Thus there sometimes is a strategic or veterinary need for preventative treatment hence preventative treatment should not be banned, but preventative use should not be routine.
Yes. Preventative use of antibiotics (prophylaxis) is the administration of an antibiotic to healthy animals at risk of a specific infection(s) or in a specific situation where a bacteria caused infection or disease is likely to occur if the drug is not administered, with an appropriate dose and for a limited duration. The Veterinary Medicinal Products (VMP) containing antimicrobial agents should only be used on the prescription of a veterinarian. Use of antibiotics for growth promotion is where it is administered with the purpose of increasing the rate of weight gain and/or the efficiency of feed utilisation in animals by other than purely nutritional means. The term does NOT apply to the use of antibiotics for the specific purpose of prophylactic, metaphylactic or therapeutic use, even when an incidental growth response may be obtained. This definition is in line with the definition developed by Codex Alimentarius in CAC/RCP 61-2005.
In the UK, where it is banned, it would be very difficult. For a product to be used at a low, sub-therapeutic dose for the purpose of creating a growth promotion effect would require either the farmer or the vet to breach the rules of use of antibiotics as growth promotion has been banned across the EU since 2006), and this could have a detrimental effect on their careers. It should be noted that for a veterinary medicinal product to be used preventatively, it should be authorised for this indication, as stated in its summary of product characteristics (SPC), thereby limiting which products can be used for this purpose. There is also a shift in the wording of indications listed in SPCs away from prophylactic use to metaphylactic use; which has a defined definition in the EU legislation, thereby providing more of a steer away from using antibiotics unless the consequence of not doing so are detrimental to health and welfare.
In short, no. The use of veterinary medicines – including antibiotics – can sometimes result in low concentrations of the medicine being present within the animal’s system for a period of time. This is usually at a low level – measured in parts per million. Strict withdrawal periods are stipulated for each licensed medicine. These are based on rigorous testing regimes, and give time for medicines to be excreted from the animal or fall to a level that will not cause any adverse reaction in man should they be eaten. This means medicines must have almost entirely left the animal body by the time meat or milk can enter the food chain. In summary, the current debate is not about antibiotics found in food, but whether resistant bacteria are found in food and can they be transmitted to man.