Antibiotic Resistance and Farm Animals

In this weeks blog I will we be investigating antibiotic resistance and how this is linked to the use of antibiotics in many farm animals. In my microbiology class my teacher briefly discussed why farm animals are given antibiotics, and this sparked my interest, which is why I have decided to make it the topic of this weeks blog post.

Antibiotic Resitance

First off, let me discuss what antibiotic resistance actually is. As described by my microbiology teacher, Dr. Cramer, antibiotic resistance is when a microbe can resist the antibiotic(s) that is meant to treat it. Meaning the antibiotic(s) will have no effect on it and the microbes will continue to grow and infect its host. Many things are causing antibiotic resistance to increase. For example, this can occur because of the use of antibiotics in farm animals or when people take antibiotics incorrectly (meaning they do not complete the full dose or miss/skip doses)

My teacher further went on to explain the 4 general mechanisms of antibiotic resistance. These mechanisms include:

• Antibiotic-inactivating enzymes: Bacteria produce enzymes that chemically modify a specific medication, interfering with its function

•  Alteration in the target molecule: Antimicrobial medications generally act by binding to  specific target molecules in the microorganism, interfering with the target’s function. Mutations that cause minor structural changes in the target that can prevent the medication from binding.

• Decreased Uptake: Changes in the porin proteins (in gram-negative bacteria only) can prevent certain antimicrobials from entering in the cell’s periplasm or cytoplasm

• Increased Elimination : microbes can increase the rate in which antibiotics are removed by making more efflux pumps (a transporter that moves molecules out of the cell)

Now, how do microbes develop one, or multiple, of these mechanisms you may ask? There are two ways in which a microbes can acquire antibiotic resistance. The first, is by spontaneous mutation. This occurs rarely as cells replicate, and 99% of the bacteria that mutate will die. However, those that do survive with an advantageous mutation that makes it resistant to antibiotics will pass it down to its offspring. The second way that a microbe can acquire antibiotic resistance is through horizontal gene transfer. This most commonly occurs by a process called conjugative transfer of the R plasmid. An R plasmid is resistance genes, often carrying resistance to multiple antibiotics, found within a bacterial cell. To put it simply, this process is when a bacteria that contains an R plasmid transfers a copy to a neighboring bacteria. When this occurs successfully that bacteria will now has a copy of the R plasmid and will now be resistant to those antibiotics.

To me, it is quite amazing, but also terrifying, how resilient bacteria are. It is amazing how they have developed these mechanisms to combat the antibiotics that we use and how they can “spread the love” to other bacteria. Yet, this is terrifying to me at the same time because it means that these antibiotics are no longer effective in their treatment, which is bad.

Antibiotic Use in Farm Animals

You are probably wondering, as was I, why are farm animals given antibiotics. Well, there are two main reasons. First, is the more obvious reason, which is to combat disease. According to the CDC, the FDA approves the use of antibiotics on farm animals to: treat disease when infected, to control and contain disease for a group of animals when one or many are sick, or to prevent the animals at risk from becoming infected. Because these animals are in such tight, crowded, unsanitary conditions antibiotics for this purpose are given more often than not. The second reason that antibiotics are given to farm animals is for non-therapeutic purposes. Since the 1940s, antibiotics have been used in livestock feed after some studies proved that these drugs can cause animals to grow faster and put on weight more efficiently. Antibiotics effectively kill off the bacteria in the animals’ guts and make more of the energy in the food available for the animals themselves. The more the farm animals weigh, the more the farmers can sell them for.

According to the FDA, over 20 million pounds of antibiotic drugs were sold for use on livestock farms in 2014, which was estimated to be about 80% of all antibiotics sold that year. This fact blew me away. Well over half of antibiotics made were used on animals! To me that is absurd and shows the lengths farmers will go to in order to make more money. Thankfully, in 2017 the FDA banned the practice of non-therapeutic antibiotic use. This is an amazing win in my opinion because this was one of the factors contributing to the rise in antibiotic resistance. Nonetheless, farmers still administer low doses of antibiotics for  prevent the diseases that result from crowded, unsanitary conditions on factory farms, as mentioned in reason one. And because they are still being given antibiotics, antibiotic resistant bacteria can still occur in these animals and then spread to us.

Antibiotic Resistance and Farm Animals

Now, how exactly can antibiotics given to farm animals lead to antibiotic resistance that affects us so badly? There are many ways in which these antibiotic resistant bacteria can infect us. One avenue is through the farmer or factory workers. When they are processing and handling the animal products they can become infected and then spread it to the community, if not done in a sanitary way. Another way is through the farm animals manure. The manure is often reapplied as fertilizer which can contaminate near by water, via runoff or leach into ground water. Further these resistant microbes can also present in the air, where they travel with dust particles and water droplets that can be inhaled by workers. These are just a couple, and not all of the mechanism for which antibiotic resistant microbes from farm animals can come into contact with us.

So, you’re now probably thinking, like I was at this point in my research, I’ll just buy “antibiotic free” product. Well, there is a catch. For an animal product to be considered “antibiotic free” you must not be able to detect antibiotics in the meat or poultry by the time of sales. Well companies can just take these animals off the antibiotics two weeks prior to their slaughter, so the antibiotics cannot be detected in the blood. So, it is important to note that “antibiotic free” does not mean that the animal has never seen antibiotics per-say, it just means that no antibiotics can be detected at the time of sale. In my opinion, I think that for something to be considered “antibiotic free” it should have never seen an antibiotic in it whole lifecycle. It is very misleading to consumers to label it they way it is now.

In closing, I hope you all enjoyed this weeks blog because I sure did. I really enjoyed researching this topic because I am very interested in my quality of food and also why antibiotic resistance has been rising. It is quite alarming to me how many antibiotics are given to farm animals. I hope that something in the near future is done about this because antibiotic resistance is no joke. My microbiology teacher claimed that we are heading toward a time were we will have no effective antibiotics because all bacteria will become resistant. This means that diseases that are once very easily managed will likely become lethal.

Thank you for reading this weeks blog, and look out for my post next week!