Essay: Antibiotic resistance in human and animals

Introduction
A well-known problem of these days is the antibiotic resistance in human and animals. One of the causes is the use of antibiotics in the animal husbandry. Here the antibiotics are mainly used in production animals to cure or prevent infections. The antibiotic residues can have a direct and/or indirect effect on the health of human and animals. In the first place the antibiotic residues can end up on the meat of the animals. This meat is eaten by humans an can form a direct way to antibiotic resistance. The second (indirect) way is that antibiotic residues can end up in the environment via the feces of the treated animals. The antibiotic residues end up in the ground and can be included by plants that human and animals eat. The antibiotic residues can also be transmitted via farmers or employees of slaughterhouses. For these reasons it is very important that there are strict rules for the use of antibiotics in the animal husbandry, to prevent animals and human from unnecessary contact with antibiotics. In the last few years the rules relevantly to antibiotic use are highly customized by the Dutch government (and European Union), but are these rules sufficient to decrease the antibiotic resistance? And is it possible to use no antibiotics at al?
Discussion/argumentation
As from 1999 the European Union forbids the use of antibiotics in animal feed as a growth promoter step by step. This prohibition had little effect at first, because it led to a doubling of the regular antibiotic use. The government took measures to halve the antibiotic use in 2013 relative to 2009. This aim was already reached in 2012. A small increase in antibiotic resistance was measured in 2013. However, in these days the decrease in antibiotic use is only measurable in cattle. In the poultry sector (chicken and turkey) the antibiotic use is increasing again [1]. To maintain the decrease in antibiotic resistance, it is important to control the antibiotic use in this sector. There are different ways to decrease the antibiotic use. One important aspect to look at is the breading technique of the farmers.
There are research groups that conclude that breading techniques are related to the antibiotic resistance. Cristiana Garofalo et al., 2007 showed that there are many antibiotic resistance (AR) genes on raw pork and chicken meat, consumed by human. These genes are also present in the feces of the animals. The genes tet(K) and erm(B) were found most frequently in meat. tet(M), tet(O), tet(K), erm(A), erm(B), erm(C), vanA, vanB, aac (6′)-Ie aph (2′′)-Ia, and blaZ were found in the feces. The results of this article describe that there are many bacteria with AR genes in the food of the animals. This is a reason why they conclude that the AR contamination is more related to the breading rather than surface contamination, processing or handling in the factory [2].
In these days researchers investigate the effect of possible alternatives for antibiotic, such as probiotics, immune modulating agents and antibacterial vaccines. However, there is a lot more research needed to prove that these alternatives could replace antibiotics [3]. There are a lot of breading techniques that can promote the immune system of the animals, for example the use of probiotics. Probiotics are live bacteria and yeasts that promote the health and mucosal immunity of human and animals. It is know that the use of probiotics in animal feed improves the mucosal immunity of the intestine. It is harder for the pathogens to attach to the mucosa of the intestine. A strong mucosal immunity in the intestine is also important to prevent other infections. If there is an infection in the gut it can also affect other places in the body because the whole mucosal immune system works as one system. For example, if there is an infection in the gut it can also affect the bronchial tract or the mammary gland. So use of probiotics could be one technique to improve the immunity of the animal, decrease the risk of infections and decrease the use of antibiotics. A disadvantage of probiotics use is a lack of standards. Farmers have to work with the right amount of probiotics, because when the amount of probiotics is to high it can cause allergies and diarrhea in the animals. This problem is already reported several times [3]. So, when feeding the right amounts of probiotics, animal health and immunity could be promoted and contribute to an antibiotics free husbandry.
Another way to improve the immune system is decreasing the amount of stress for the animals. If an animal has chronic stress it can affect the immune system. Stressors can activate the CRH production of the hypothalamus and CRH causes a decrease in the ACTH production by the pituitary gland. ACTH causes an increase of cortisol production by the adrenal glands. Cortisol breaks down proteins en transform them into glucose, which increases the blood flow and it causes a shift from the steady state to catabolism. Cortisol also has an inhibitory effect on the hypothalamus; it increases the production of CRH by the hypothalamus. If the cortisol production is chronic, due to stress, the hypothalamus becomes insensitive to cortisol and produces more CRH, because the negative feedback system does not work anymore. In this way high amounts of cortisol are produced and this has a negative effect on the immune system. The animals are more likely to develop infections and wounds will heal slowly compared to non-stressed animals [4].
In the poultry sector the incubation temperature of chicken eggs can also play a role in controlling the health of a chicken. An optimal incubation temperature for chicken eggs is essential for the development of the immune system. Westra et al., 2012 showed that a high incubation temperature has an effect on the sensitivity to pathogens in later life. Chickens from incubated eggs at a high temperate are more sensitive. It is also known that the incubation temperature causes a low spleen and bursa weight, which causes impaired immunological development [4].
In the poultry sector it is common that chicks are fed when they arrive at the farm and not at the place were the eggs hatch. Because not all the eggs hatch at the same day it can happen that some chicks have no food for 72 hours. No food in the first days after hatching has a negative effect on the immune system later in life. Westra et al., 2012 showed that early feeding (immediately after hatch) has a positive effect on the intestinal microbial composition. Early feeding can also be a way to ‘’train’’ the immune system to fight infections in later life, because food-associated (gram negative) bacteria contain LPS. When the immune system of the chick sees the LPS in early life, it is less sensitive to LPS in later life (Kingma, MSc thesis 2007) [4].
Opinion/evaluation
There are many ways to improve the health and immune system of animals. Stress can be reduced, housing of the animals can be optimized, probiotics can be provided, the incubation temperature of eggs can be optimized and early feeding also plays an important role in the development of the immune system. I think that all these techniques can contribute to an antibiotic free husbandry, or at least to a strong decrease of antibiotic use. However, all these breading techniques cost a lot more money and time. This would be the main reason why famers cannot change their breading technique. And I think this problem starts with the government, supermarkets, meat dealers and consumers. If they are willing to pay more money for good quality meat, the farmers could invest in these breading techniques and provide healthier meat, produced without antibiotics.
So I think it could be possible to have an antibiotics free husbandry, based on the breading strategies described in this opinion paper and many other strategies. But it will take a lot of time, it will cost a lot of money and a lot more research is needed. And this is why I think it will be hard to realize an antibiotics free husbandry.