Antibiotic Resistance: Evolution at Work

When Alexander Fleming accidentally discovered penicillin in 1928, the rate of death due to infectious diseases decreased dramatically, especially in developed countries. His discovery led to the development and advancements in antibiotics. These drugs effectively and economically fought off infectious diseases, but the abuse of these “miracle” drugs pressured the bacteria to develop antibiotic resistances.    

This blog will focus on the antibiotics Streptomycin and Methicillin, and how bacteria developed resistance to these drugs. The overall causes and effects of antibiotic resistance will also be discussed.

Streptomycin 

Streptomycin was discovered in 1943 as the cure to Tuberculosis(TB). TB is an infection caused by the bacteria Mycobacterium tuberculosis. This TB bacteria usually attacks the lungs but it can also infect the spine, kidneys and the brain. The first developed antibiotics, Penicillin and sulfonamides, had no effect on this bacteria. Its lipid-rich cell wall was making treatment impossible. Streptomycin’s mode of action was to inhibited bacterial ribosome function. Streptomycin damaged the bacteria by binding to the protein 12S on the 30S ribosome. This inhibition interferes with the binding of formyl-methionyl tRNA to the 30S subunit. It ultimately causes bacterial cell death by preventing proteins from being made. Streptomycin has to be injected in the muscles in order to have any effects. Since 1943 Mycobacterium tuberculosis has evolved genetically to overcome the effects of streptomycin. One way is through changing the amino acids in the S12 protein, so STR cannot bind to it. This new feature has caused cases of incurable TB to occur.

Aside from human use, streptomycin is also used in agriculture. For instance it is used to fight against fire blight in pome, pear and apple orchards. In the spring antibiotic sprays are sometimes used to prevent infection. The Antibiotic is only used when the risk factor for the disease is high. If the plant is already infected, the spray has no effect. Overall, there are a lot of regulations on the use of streptomycin on plants in America. The reason America doesn’t spray annually is because plant resistance arose only five-ten years after its use in agriculture (Stockwell). The rest of the world’s use of streptomycin is unknown due to politics 

Methicillin

Methicillin was developed in the late 1950s to deal with a penicillin resistant Staphylococcus Aureus.  This bacteria would cause lung and skin infections. Early forms of penicillin had been overused by the public which resulted in the antibiotic resistant bacteria. Staphylococcus aureus was able to bypass penicillin’s beta-lactam attack by using an enzyme called beta-lactamase (Penicillinase). This enzyme hydrolyzed the beta-lactam ring in the penicillin making it lose its only effective mode of action. Penicillin cannot destroy the bacteria’s cell wall using beta-lactum.

 In response to this resistance methicillin was made. The mode of action for this antibiotic was to inhibit ribosome function. Inhibiting the ribosome would mean no protein production. Without proteins the cell could not carry out simple functions and would die. This new drug became useless in 1960, when Staphylococcus mutated and became Methicillin resistant. It had gotten a gene that produced proteins that bonded to the antibiotic.This interaction made the antibiotic ineffective. This new strain became known as Methicillin Resistant Staphylococcus aureus (MRSA). This bacteria is still in an issue today but they are drugs that can help cure it. The website MedicineNet.Com says that medical practitioners are being more careful and using these new drugs as last resorts.

This bacteria is still in an issue today but they are drugs that can help cure it. The website MedicineNet.Com says that medical practitioners are being more careful and using these new drugs as last resorts. Even though there are rules in place, Staphylococcus was able to develop resistance to a new drug called vancomycin. It has been dubbed Vancomycin Resistant Staphylococcus aureus (VARS). VARS could be the next superbug, if it becomes widespread. Cases of VARS have increased over the years. 

This is Pamela Oglesby’s mother who had to have her leg amputated because of MRSA. People who have had invasive surgery have higher chance for MRSA infection. This was the case for Pamela’s mom. She had surgery on her ankle and after a couple of weeks the incision sight began to blister and her toes started turning black. After weeks of doctor visits she finally got a culture of her wound. The culture ended up growing MRSA. The doctors prescribed her antibiotics for nine months!! The antibiotics did not work. Amputation was the only option left. 

An article published by Nature.com discusses the appearance of MRSA on pig farms. The antibiotics the pigs are being feed aren’t only used to fight infections, but also to increase the size of the pig. “Studies have found that certain antibiotics can increase pigs' growth rate by 2.5%” (Nature). This extra growth means more profit which means more use of antibiotics. By pumping the environment with antibiotics, we are forcing the bacteria to evolve quicker.

The pigs being feed antibiotics have developed MRSA due to selective pressure. The MRSA thencan be picked up by the farmers handling the pigs. It also manifests itself into our food sources which can become possible ways for us to contract the infection. Uncooked meat or inappropriate handling of the meat can lead to an infection. Another potential source is pig manure being used as fertilizer. A study from the JAMA Internal Medicine found that people who worked with pig manure were 38% more likely to develop MRSA. The bacteria live in the pig’s feces making the farmers more susceptible to the infection.   

Despite the potential danger of antibiotics in agriculture, many meat and agriculture industries are fighting against antibiotic restrictions. Since these industries are wealthy they hold power in the government through what is known as a Super PAC. A Super Pac draws out money from unions and corporations to fund, or advocate against political candidates. They suppress candidates who go against their best interests. The candidates they help elect then go on to pass bills and laws that will benefit the Super PACs that funded them. One agricultural Super Pac is “The Protect the Harvest Political Action Committee”.

There are a few steps people can take to combat the use of antibiotics in agriculture:

1) Support PAMTA (the Preservation of Antibiotics for Medical Treatment Act) and Senator Diane Feinstein of California who is reintroducing the bill.

2)Pressure the FDA to apply Guidance #123. This is a draft that aims to regulate agricultural companies use of antibiotics 

3)The website NCPRIG allows you to send a message to FDA Commissioner Margaret Hamburg. If enough people voice their concerns, the FDA has to act.

4)Donate to NCPRIG. They fund and advertise for candidates whose interests are your interests. They also eek educate other on the issue at hand.

Here are a few links of groups that help educate the general public about this issue:

http://www.psr.org/chapters/student-chapters/resources/stop-antibiotics-use-in-animal-feed.html

 http://www.nrdc.org/food/saving-antibiotics.asp

 http://www.plosmedicine.org/article/info%3Adoi%2F10.1371%2Fjournal.pmed.0020232

 http://www.cdc.gov/features/antibioticresistance/

http://ncpirg.org/

Miscellaneous Facts:

The threat of antibiotic resistance was apparent since the discovery of penicillin. Alexander Fleming saw it and warned the world ahead of time.  

“Eighty percent of antibiotics sold in the U.S. are used for animal agriculture” (PSR)

“Antibiotics are used to offset awful living conditions in factory farms” (One Green Planet). Animals live in cramped places filed with feces. These unsanitary conditions is what gets the animals sick in the first place.

“last year two million Americans suffered from illness and 23,000 died due to antibiotic resistant pathogens”(One Green Planet). 

Bibliography

1) http://pamela99.hubpages.com/hub/Infection-Caused-my-Mothers-Leg-Amputation

2) http://www.cdc.gov/mrsa/tracking/index.html

3)http://www.medicinenet.com/mrsa_infection/page6.htm#what_is_the_treatment_for_a_mrsa_infection

4) http://www.onegreenplanet.org/animalsandnature/5-alarming-facts-about-antibiotic-resistance-and-factory-farming/

5) http://www.cdc.gov/features/antibioticresistance/

6) http://www.cdc.gov/tb/topic/drtb/default.htm

7) http://www.oie.int/doc/ged/D11800.PDF