Brent had a small abscess on his right elbow but he wasn’t sure what caused it. He believes it may have been a spider bite although, he doesn’t remember getting bitten or even seeing spiders around his house. His abscess was swollen and painful. He went to the doctor’s office and the doctor swabbed the wound and prescribed antibiotic cream for the infection. After a few days Brent’s abscess was gone.
Kristen recently had surgery on her right knee. A week after the surgery, Kristen started to run a fever and was in a lot of pain due to her knee. The area around the incision was red. She went to her doctor and she was prescribed antibiotics for the infection. Kristen’s symptoms never improved and she continued to have high fevers and had increased lethargy
Both patients, Brent and Kristen, were prescribed antibiotic drug called oxacillin.
What ideas do you have as to why the antibiotic did not work for Kristen?
Since Kristen had surgery in a sterile environment, I believe that she contracted a bacteria that mutated and is no longer affected by antibiotics.
What, if any, diagnoses could you make for Brent and Kristen?
Humans have thousands of bacterium all over our bodies, in our bodies, and on our skin. When our skin in penetrated bacteria can enter and infect the open wound. If the lesion is not properly cleaned it could be a breeding ground for bacteria such as Staphylococcus aureus, a common bacterium that is found on the skin of humans. I believe that Brent was infected with a common strain of Staphylococcus aureus which is why it was easy for his body to accept the antibiotics. I think it is possible that Kristen was infected by an adaptive strand of Staphylococcus aureus. This would explain why Kristen isn’t getting better after taking the prescribed oxacillin
Part II
What do you already know about Staphylococcus aureus?
Staphylococcus aureus is common bacteria found on the skin. They are harmless when they are on the skin however, it is a dangerous pathogen when it enters the body. The bacterium can cause disease when it enters the body, usually at a site where the skin has been penetrated. Symptoms include redness, swelling, and pus surround the lesion. If the Staphylococcus aureus gets into the bloodstream, it may cause pneumonia, fever, chills, and malaise. In more extreme causes it can lead to death.
2. What additional info about S aureus can you find?
MRSA is a type of staph bacteria that is resistant to certain antibiotic classes known as beta lactams
People can carry MRSA without presenting signs and symptoms of infection. An estimated 30% of people carry S aureus (non-harmful) in their noses and two out of 100 people carry MRSA unknowingly.
Hospital Acquired (HA) MRSA can be prevented almost entirely through healthcare workers following CDC guidelines
Community Acquired (CA) MRSA typically affects athletes, daycare workers, military personnel and school students. It is most commonly spread through close contact situations such as sharing of razors and towels, shared athletic equipment
CA (MRSA) can be prevented and/or reduced through proper personal hygiene especially after exercise, proper hand washing etc
It is important to receive treatment as soon as possible if infection is suspected. Prompt treatment prevents further long term complications such as sepsis (bacteremia), respiratory problems and cardiovascular issues
3. List hypotheses that would explain why S aureus was susceptible to antibiotics in Brent’s case but not in Kristen’s?
If the S aureus does not contain the mecA gene then it will be susceptible to antibiotic therapies such as oxacillin, penicillin etc
If S aureus does contain the mecA gene then it will not be susceptible to antibiotic therapies such as oxacillin, penicillin etc
In order to treat S aureus infections that contain mecA gene (MRSA) antibiotic therapy with alternative mechanisms of action must be used against the resistant bacteria
The Staphylococcus aureus that Brent was exposed to was not a resistant nosocomial strain that Kristen was exposed to; and the infections on brent was also mostly on the surface of the skin where Kristen’s infection was deeper due to it being exposed while she was having knee surgery.
Part III
1. Because Brent’s pathogen was not MRSA, it did not contain the mecA gene. Explain why PCR and DNA sequencing provided no results for Brent’s pathogen.
PCR is used to increase the number of copies of a segment of DNA or gene coding region of DNA. PCA and DNA analyzing is designed to be in search of a specific target genes. In this case, the segment of DNA that was copied was unique to MRSA. Therefore, nothing came up for Brent’s pathogen.
2. Does the presence of the mecA gene confirm that Kristen is infected with MRSA? Why?
Yes, the presence of the mecA gene does confirm MARS, however the mecA PCR tests will not detect other resistance mechanisms such as mecC or uncommon phenotypes.MecA gene is the most common gene that mediates resistance in Staphylococcus aureus.
3. What protein does the mecA gene encode for? How does this allow MRSA to be antibiotic resistant?
MRSA is difficult to treat because it is resistant to β-lactams, a class of antibiotics generally prescribed as the first line of defense against normal staph infections. β-lactams, which include drugs like penicillin, oxacillin, and methicillin, kill bacteria by preventing the synthesis of bacterial cell walls–without which bacteria cannot survive. These drugs accomplish this by glomming onto and inactivating penicillin-binding protein (PBP), an enzyme that makes an essential component of bacterial cell walls. MRSA strains, however, are resistant to β-lactam drugs because they carry a gene called mecA. The mecA gene encodes a different form of penicillin-binding protein, PBP2a, which β-lactam drugs cannot inactivate, thus allowing normal cell wall synthesis to occur even in the presence of these drugs.
4. What are some benefits of having a national database for nucleotide sequences and what could you use this site for in the future?
It is important to have a database to have the nucleotide sequences available to the public; and available for research and clinical use. In this case, comparing Kristen’s pathogen to the database revealed that she had MRSA.
Part IV
1. What artificial or selective pressures could influence prevalence of antibiotic resistant microbes?
We as humans need to stop or lessen getting prescribed antibiotics for even the smallest illnesses and if we do, we should finish all of the antibiotic to avoid growing super bacteria that are resistant to antibiotics. With the overuse of antibiotics, antibiotic resistant superbugs are becoming increasingly common.
2. How could MRSA or other “superbugs” become antibiotic resistant?
When the evolve to not be susceptible to antibiotics meaning they learn how to not be affected by them.
3. Read note #5 in your handout about horizontal gene transfer. Discuss how Staphylococcus aureus could have acquired the mecA gene.
Every so often a single tiny piece of pathogen carries the gene to be resistant to the antibiotic. Over time this single pathogen will multiply giving it’s offspring the gene which codes for antibiotic resistance. After a while the only pathogen that is present are the ones that are antibiotic resistant.
4. Is MRSA the result of a fundamentally different process than evolution? Explain.
Evolution takes time with the stronger more resilient species killing off / taking over the other species. In this case, we are “breeding” the bacteria in a short amount of time while killing off the nonresistant types.
5. What can be done to prevent MRSA from becoming more dangerous?
By refraining from taking antibiotics unless you NEED them. Stop the over-prescribing of antibiotics. Finally, take all the antibiotic if you are prescribed it. I mean ALL of it. It will prevent the further growth of the antibiotic resistant bacteria