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Why all the fuss about antibiotic resistance?


The United States Food and Drug Administration approved the use of antibiotics as animal additives without veterinary prescription in 1951, and in the 1950s and 1960s, different European states approved their own national regulations concerning the use of antibiotics in animal feeds.

Overarching European legislation controlling the use of these additives in animal feeds in all member states was published on 14 December 1970 in the Council Directive 70/524. Only those additives named in this Directive could be included in animal feed.  In the years that followed, all the required laws, regulations and administrative provisions were brought into force.

As early as the 1970s, antibiotics from classes which were, or might be, used in human or veterinary medicine were identified and split into two groups according to which category they were used. There were already concerns that the widespread use of antibiotics as feed additives could contribute to the development of bacteria resistant to the drugs used to treat infections. These bacteria posed a potential risk to humans if they were transferred to humans and for this reason the World Health Organization (WHO) (1997) and the Economic and Social Committee of the European Union (1998) concluded that the use of antimicrobials in food animals was a public health issue.

Based on additional scientific information provided by Sweden, Regulation 1831/2003 was published which stated that antibiotics, excluding anticoccidials, could only be used up to 31 December 2005.  After this date, they were no longer authorised as feed additives in Europe.  

During 2007 two federal bills where published in the USA which were aimed at phasing out the use of non-therapeutic antibiotics in US animal production. These bills were not successful. In March 2012 the United States District Court for the Southern District of New York, ruling in an action brought by the Natural Resources Defence Council and others, ordered the FDA to revoke approvals for the use of antibiotics in livestock that violated FDA regulations. On 11 April 2012, the FDA announced a voluntary programme to phase out the unsupervised use of drugs as feed additives and convert approved over-the-counter uses for antibiotics to prescription use only, requiring veterinarian supervision of and a prescription for their use.  In December 2013, the FDA announced a new policy to phase out the use of antibiotics for the purposes of promoting livestock growth.

In response to the consumer concerns about the use of antibiotics in poultry, a number of poultry producers had begun removing all human-use antibiotics from their feeds as early as 2007.  Perdue was one of these companies and, by 2015 52% of the company's chickens were being raised without the use of any type of antibiotic. In March 2015, McDonalds announced that it would be phasing out the use of chicken meat from birds raised with medically important antibiotics. In October 2015, the sandwich restaurant chain, Subway, announced that it intended to stop serving meat and poultry from animals that had been raised with the use of antibiotics at all of its restaurants in the United States. In 2014, Chick-fil-A announced that it would exclusively sell chicken raised without antibiotics within five years. The trend has continued to grow with almost all US poultry producers and food chains having made similar announcements.

In March 2018, Feed Strategy, a division of Watt Global Media, published their annual Poultry Nutrition & Feed Survey. Eighty per cent of the 399 survey respondents worldwide are involved in some level of antibiotic-free poultry production.  Between the 2017 and the 2018 surveys, there was an 8% increase in the number of respondents who practice a 100% antibiotic-free production method. 

Classification of antimicrobials

Since 2005 the World Health Organisation has produced a regularly updated list of all antimicrobials currently used for human medicine, many of which are also used in veterinary medicine. They have grouped them into three categories based on their importance to human medicine. The list is intended to assist in the management of antimicrobial resistance, ensuring that all antimicrobials, especially critically important antimicrobials, are used prudently, both in human and veterinary medicine.

1.   Human & animal antibiotics – shared. Antibiotics that are used in both humans and animals. These should only be used for therapeutic use         under veterinarian guidance.
2.   Human-only antibiotics. These are not approved for use in animals.
3.   Animal-only antibiotics. These antibiotics have been developed to treat animals only and are not used in human medicine.
Is antibiotic resistance just good marketing or just a first-world trend?

A number of poultry producers question whether the concept of antibiotic resistance and the reduction in the use of antibiotics in animal production is something that we should be taking seriously in Africa. 

Antibiotic resistance is the ability of bacteria or other microbes to mutate to be able to resist the effects of an antibiotic. This mutation eliminates the effectiveness of drugs, chemicals or other agents designed to cure or prevent infections and to kill the bacteria that cause disease. The bacteria that are no longer affected by the antibiotic survive and continue to multiply and can no longer be controlled with these drugs.  Scientists from the Kishony Laboratory at Harvard Medical School designed a very simple way to observe how bacteria respond to different levels of an antibiotic. 

Type the following link into your internet explorer to watch this fascinating video.

The experiment was designed to show how bacteria are initially controlled by the presence of an antibiotic at normal dosage levels but that they are able to mutate to become tolerant to the antibiotic even when the dosage level is increased to 1000 times the normal dosage level.

Veterinary laboratories regularly test the efficacy of various antibiotics on the bacteria that they isolate from animals in poultry facilities. Below in Table 1 are the results from a South African veterinary laboratory that isolated three different variants of Escherichia coli from chickens that had been submitted to them.  They tested the ability of seven different antimicrobials to effectively kill these three different E. coli isolates. The results show that none of the antibiotics were able to kill the first isolate at any dosage level.  Only amoxicillin was effective in killing the second isolate at the highest recommended dosage and the third isolate could be killed by six out of the seven antibiotics, but two of them had to be used at the highest recommended dosage levels.  This means that for two of the types of E. coli found in these birds, hardly anything could be done to control them with the antibiotics that are available.

Similar results are also regularly being obtained for bacteria isolated from pigs, cattle and sheep. However, the biggest concern is that they are also being seen in humans.

Table 1: Antibiogram results for three Escherichia coli strains isolated from broilers

R = Resistant.  Antimicrobial cannot be used at any recommended dose

I = Intermediate.  Antimicrobial must be used at the highest recommended dose

S = Sensitive.  Antimicrobial can be used at the recommended dosage

Is this something that we should all be taking seriously? Can it affect me?

To put the problem in perspective, Cancer Research UK reported that 8,2 million people in the world died of cancer in 2012. It is predicted that in 2050, 11,45 million people will die of cancer. In a review commissioned by the WHO and conducted by Tang et al. (2017), it is anticipated that in the same year a further 10 million people will die from antibiotic-resistant bacteria. The review focused on whether the interventions that have been put in place to restrict antibiotic use have been effective in reducing antibiotic resistance. The authors concluded that the interventions applied thus far have been associated with a reduction in resistance in food-producing animals and in human beings who have direct contact with these animals.  The association is not as clear regarding humans in the general population.   These findings will be an important consideration as global policy options are being considered.

With the predicted growth in the human population, we will need to produce 131 billion broilers per year by 2050.  As an industry there are a number of strategies that we can all employ to reduce the problem of antibiotic resistance and these all fall under the banner of ‘Responsible Use’.  We will need to reduce antibiotic use on farms by changing the way that we manage growth and diseases. With the ban on the use of antibiotics in Europe there has been a significant development of products that can be used as alternatives to antibiotics to control the growth of bacteria in the gut. Where antibiotics are indicated, care must be taken to identify the exact organisms causing the disease in an animal or group of animals and then the effective antimicrobial should be prescribed for as short a period as possible. Options to vaccinate will need to be considered.

Feeds for food-producing animals must be designed to maintain a healthy and balanced gut microflora and strategic use can be made of some of the ‘alternative products’ in this regard. Improvements in housing and management will need to be made to improve the environment in which the animals are accommodated.  Management practices will need to be reviewed with the focus on reducing any stress on the animals.  Veterinarians, nutritionists, genetic companies and the producers will have to work much more closely.

As humans we will also need to be much more responsible in our use and prescription of antibiotics. A holistic approach will be required to change the doomsday predictions of Tang and his fellow researchers.