Antibiotics

Antibiotics have saved large numbers of human lives and contributed greatly to public health worldwide during the 20th century. But now antibiotic resistance is becoming an increasingly serious threat to human health. Medical experts, including Swann et al 1969 and the Advisory Committee on the Microbial Safety of Food (ACMSF), are concerned that existing antibiotics are becoming less effective against bacteria and that too few new antibiotics are being discovered and developed.

Use of antibiotics in intensive farming

It’s estimated that at least half of all the antibiotics sold in the world are used for farmed animals. Factory farming has been overusing antibiotics for decades to keep animals productive although they are living in crowded and often unhygienic conditions. In many cases, factory farmers use low doses of antibiotics in the animals’ feed to keep down infection and make the animals grow faster. Overuse of antibiotics in factory farming has made a large contribution to the global development of antibiotic resistance and has caused so much concern that the EU has made it illegal from 2006. By law, farmers are usually required to stop antibiotic treatment at a fixed ‘withdrawal’ time before the animal is slaughtered and eaten, which is intended to protect consumers from eating residues of the antibiotics.

Antibiotics in the environment

People can acquire antibiotic-resistant bacteria from food, from contact with the animals, from working in slaughterhouses, or from antibiotics that are spread into the soil and water in the neighbourhood of factory farms. Workers in farms and slaughterhouses can transfer the resistant bacteria to their family and friends, and bring the bacteria home on their shoes. Pets and wild animals can also transfer antibiotic resistant bacteria from factory farms to the wider community. Studies have shown that workers and people living in the neighbourhood of factory farms that use routine antibiotics are more likely than others to carry antibiotic- resistant bacteria.

Antibiotics that have been put into animal feed can contaminate the environment via waste feed and animal excreta, encouraging the spread of antibiotic resistance to bacteria in the environment. In the US it has been estimated that over 6 million kilograms (13.5 million pounds) of antibiotics are excreted annually in animal wastes as a result of antibiotics in animal feed, which is nearly half the total amount that is fed to the animals in their feed or water.

Antibiotic resistance

When antibiotics are used to keep down the infections in the animals on factory farms (such as Salmonella, Campylobacter and E. coli) the bacteria quite quickly become more resistant to those antibiotics. Usually, human infections are treated with antibiotics that are quite similar to, or very similar to, the antibiotics used in farming. The result is that when the resistant Salmonella or Campylobacter bacteria are passed to people in contaminated meat or other food and people need antibiotic treatment, the treatment does not work. Most foodborne infections do not need antibiotic treatment, but if the infection becomes serious it is essential to have effective antibiotic treatment straight away. Studies have shown that antibiotic-resistant infections are costly in human suffering and in medical resources, for example due to:

• Failure of initial antibiotic treatment
• More severe illnesses and higher death rate
• Increased likelihood of infection
• Reduction in drugs available for use and use of
• less desirable drugs
• Increased risk to children and to people who
• have existing illnesses
• Costs to healthcare system
• Infection with antibiotic-resistant bacteria results
• in longer illness and more hospitalisations compared
• to infection with bacteria that are not resistant

Also, antibiotic resistance causes more infections to occur. People who are prescribed an antibiotic for one illness can find that they then become infected with another type of bacterium that is resistant to that antibiotic.

Multiple resistance and superbugs

As well as becoming resistant to more and more antibiotics, bacteria can pass on their antibiotic resistance genes to other strains and types of bacteria. ‘Superbugs’ have been linked to the overuse of antibiotics in chicken and pig farming. An increasingly common strain of Salmonella (known as DT104) is resistant to at least five well-known antibiotics. Enterococci are bacteria usually found in people’s guts which can cause serious infections in hospitals. The superbugs known as Vancomycin-resistant Enterococci (VRE) are resistant even to the ‘antibiotic of last resort’ Vancomycin, which has been used to treat infections that are resistant to all other antibiotics. The rise of VRE has been linked by scientists to the use of a related antibiotic named avoparcin, that is used to make chickens grow faster in factory farms.

Resistant bacteria in people and farm animals around the world

The resistance of many common bacteria to antibiotics has been growing around the world. Factory farming has been implicated in this growth on numerous occasions.

USA: Antibiotics that have caused most concern are the fluoroquinolones, in particular Cipro, which is used to treat severe Salmonella and Campylobacter infections. In some countries, a similar antibiotic, enrofloxacin, is used to control infection in chickens and there is good evidence that the use of enrofloxacin has contributed to increasing resistance to Cipro. Because of this, the US Food and Drug Administration has announced a ban on the use of enrofloxacin in farming.

UK: The Food Standards Agency found that 23 per cent of the Salmonella samples from chicken meat were resistant to four or more antibiotics and over 10 per cent of the Campylobacter samples were resistant to Cipro, the drug of choice for treating human infections. The UK’s Health Protection Agency recorded more than 400 cases of E. coli infections that were drug-resistant over 12 months in 2003-2004. This was a very large increase compared to previous years, when there had been only a few drug-resistant cases.

Brazil: 70 per cent of the strains of E. coli infecting children showed multiple antibiotic resistance. 18.2 per cent of one Campylobacter strain in children with diarrhoea were resistant to fluoroquinolone antibiotics and an even higher proportion of the same bacteria isolated from animals were resistant to the same drugs. The children had never been treated with these drugs before, so it was concluded they had acquired the resistance from food animals.

Netherlands: A study examined the antibiotic resistance of E. coli in the faeces of chickens, turkeys, and people who were poultry farmers and poultry slaughterers. They found that 23 per cent of the E. coli from chickens, 22 per cent of the E. coli from chicken farmers and 10 per cent of the E. coli from chicken slaughterers were resistant to five or more common antibiotics, strongly suggesting that the resistance has passed from chickens to people.

Turkey: The first fluroquinolone resistance of Campylobacters was found in animals and people in 1992, around two years after the licensing of enrofloxacin, which is used for farm animals. By 2000, around 20 per cent of Campylobacter strains were resistant to both enrofloxacin and ciprofloxacin, due to the use of fluoroquinolones for disease control on farms.

Success stories: Alternatives to overuse of antibiotics

Factory farmers overuse antibiotics so that the animals can survive in crowded and stressful conditions. But there are alternatives to intensively farmed food. Animals reared in free-range and organic farms are much less likely to have antibiotic-resistant bacteria and so are safer for the consumer. Because of fears about antibiotic resistance, the use of antibiotics to speed up animal growth was banned in the EU in early 2006. Increasing numbers of supermarkets and food companies have also banned their suppliers from routinely using antibiotics as growth promoters.

Denmark: A ban on the use of antibiotics just to make animals grow faster resulted in a reduction in the prevalence of Vancomycin– resistant Enterococci (VRE) in chickens from 80% of the chickens down to 10%. In pigs, the prevalence of antibiotic resistant bacteria was reduced from 65% to 25%.

Philippines: A commercially successful free-range poultry farmer stopped all use of antibiotics but keeps his chickens free of infection and parasites by the use of medicinal herbs such as chilli, oregano, paminta and ginger.