Need help assisting with my Microbiology paper on staphylococcus aureus

Angela K. Gregory

Microbiology 233

Dr. Ryan Manow

April 6, 2019

Staphylococcus aureus Lab Report

Introduction:

Gram-positive, cocci-shaped, and cluster-forming, Staphylococcus aureus is an opportunistic, pathogenic bacteria commonly found on the skin of healthy humans and other mammals (Foster, 1996). About 20% of the general population are persistent nasal carriers of S. aureus (Foster & Geoghegan, 2015). However, S. aureus is also known to colonize other parts of the body, such as the pharynx, chest, armpits, hands, abdomen and perineum (Otto, 2010). Although the pathogenic threat of these colonies is often minimized in healthy individuals, S. aureus has been linked to numerous conditions and illnesses, which can be exacerbated by a weakened immune system.

The discovery of S. aureus is attributed to two scientists in the late 1800s: Alexander Ogston (1844-1929) and Anton J. Rosenbach (1842-1943). Ogston, a Scottish surgeon, examined a smear of pus from a patient’s abscess under a microscope. He observed clustered cocci among the pus cells and debris and, in 1882, named it “Staphylococci”—from the Greek word staphyle, translated to mean “bunch of grapes.” Two years later in 1884, a German surgeon, Rosenbach, isolated colonies of the bacteria and added the name aureus from the Latin word aurum, for its golden color. And so in 1884, it was birthed the name Staphylococcus aureus (Orenstein, 2010) .

S. aureus has been linked to a variety of chronic and acute illnesses. S. aureus has been found in the chronic skin lesions of over 90% of patients with atopic dermatitis. The bacteria produce toxins which act as superantigens, provoking our immune response and T-cell activation; this, in turn, leads to amplified inflammation and eczema lesions (Bieber & Jagobi, 2013). In addition, pneumonia is one of the most prominent acute infections mediated by S. aureus, with an estimated 50,000 cases of S. aureus pneumonia per year in the United States alone. An S. aureus coinfection of the lungs paired with the influenza virus has proven to be a deadly combination, with mortality rates at about 50% (Ragle, Karginov, & Wardenburg, 2009).

MSSA (methicillin-sensitive Staphylococcus aureus) and MRSA (methicillin-resistant Staphylococcus aureus) are also among the more severe S. aureus infections now more commonly being treated in hospitals across the U.S. The difference between the two strains is rooted in the fact that MRSA is a carrier of the mecA gene—which encodes for an alternative penicillin-binding protein PBP 2A—making it resistant to multiple antibiotics such as methicillin and penicillin. Whereas MSSA is not a carrier of the mecA gene, and therefore it does not exhibit the same antibiotic resistance (Wielders, Fluit, Brisse, Verhoef, & Schmitz, 2002). MRSA is therefore an S. aureus strain that is more complex and more expensive to treat. In fact, MRSA has surprisingly been estimated to result in more deaths per year than HIV/AIDS (Otto, 2010).

All such examples demonstrate the varying degrees to which S. aureus infections can manifest—from relatively mild to severely life-threatening. It is for this reason that S. aureus infections are a major concern within the medical community. With S. aureus being an opportunistic human pathogen, it is imperative to take precaution in the care of immunocompromised individuals. Not only does this include testing for and treating S. aureus among healthcare workers, but also expanding that protocol to include S. aureus testing and treatment of patients. With up to 85% of Staph infections resulting from bacterial colonies inhabiting the patients’ own bodies, it is absolutely crucial to implement such measures with the goal of significantly reducing this statistic (Ross, 2013).

In order to determine if we are S. aureus carriers ourselves, we each performed a swabbing of our nostrils and ears onto a Mannitol Salt Agar plate and allowed our plates to incubate for 48 hours at human body temperature, 98.6 degrees Fahrenheit (37 degrees Celsius).

Materials:

· Mannitol Salt Agar (MSA) plate, containing:

· 7.5% Sodium Chloride -- a selective agent to encourage the growth of mostly only Staphylococcus bacteria evolved to withstand its salty environment

· Mannitol sugar -- a differential agent in which S. aureus is one of the few bacteria that can consume it

· Phenol Red – a pH indicator used to determine if the mannitol was consumed and if acids were produced; red indicates neutral and yellow indicates acidic

· Wax Pencil

· For labeling the plate

· Sterile Cotton Swabs (2)

· For swabbing of the nostril, and the other for swabbing of the ear

· Parafilm

· For sealing of MSA plate to prevent potential infection

Methods:

1. Flip the MSA plate so that the bottom is facing up. Using the wax pencil, draw a line on the back of the plate, dividing it into halves. Label one side “nostril” and the other side “ear.”

2. Return the plate to lid side facing up and remove the lid. Tear open the wrapping of the sterile cotton swab, careful not to touch the cotton end. Holding it by the opposite end, gently swab the first inch of the interior of your nostril. Then carefully smear the cotton swab on the side of the plate labeled “nostril.” Dispose of the cotton swab in the biohazard waste compartment.

3. Tear open the wrapping of the second sterile cotton swab, again being careful not to touch the cotton end. Holding it by the opposite end, gently swab the ear. Be sure to swab behind the ear, the outer ear and also the inner ear canal. Be careful not to pierce the ear drum. Then carefully smear the cotton swab on the side of the plate labeled “ear.” Again, dispose the cotton swab in the biohazard waste compartment.

4. Replace the lid on top of the plate. Then wrap the parafilm around the edge to seal it.

5. Incubate for 48 hours at 98.6 degrees Fahrenheit (37 degrees Celsius) for similar temperature conditions of the human body.

Results:

My MSA plates:

Before Chlorhexidine: After Chlorhexidine:

ear | nostril right nostril | left nostril

I originally tested positive for being a nasal S. aureus carrier, as shown in the first plate. The white colonies indicate growth of a Staphylococcus bacteria; however, the red color indicates no acid was produced. I interpreted this as a positive test result for the growth of Staphylococcus epidermidis colonies in both my ear and nostril. The colonies of bacteria surrounded by the yellow color demonstrate that the mannitol sugar was consumed and acids were produced, indicating a positive test result for S. aureus in my nostril only. However, as shown in the second plate, after only two treatments with Hibiclens chlorhexidine, I was able to totally eliminate S. aureus from both nostrils. You can see growth of S. epidermidis colonies in both nostrils, but no growth of S. aureus colonies. I emphasize that I was able to completely eradicate S. aureus from my nostrils after only two swabbings with Hibiclens.

Class Data:

Our Microbiology Class	Positive	Negative	Percent Positive for S. aureus
Colonized by S. aureus	13	12	52%
Colonized by S. aureus in the Nostrils	9	16	36%
Colonized by S. aureus in the Ears	10	15	40%

Conclusion & Discussion:

It is estimated that about a third of the general population are carriers of S. aureus. However, within our small class sample, slightly more than half at 52% tested positive as S. aureus carriers: 12% of which were only nostril carriers, 16% of which were only ear carriers, and 24% of which were carriers in both nostrils and ears. I actually fell into the smallest group, being one of the three nostril-only carriers in the class. However, that is no longer the case, as I have now eliminated S. aureus from my nostrils with Hibiclens.

I was not surprised to learn that I was a nasal S. aureus carrier, as I do—from time to time—experience cases of folliculitis around my lips and on my chin. I also suffer from sinus allergies and eczema lesions all year long. S. aureus can be spread from direct contact and I suspect I acquired it while growing up from my father. My father, as a young man, experienced years of severe cystic acne all over his face. Luckily, I have only had to endure an occasional pimple or two. However, I have had eczema on different parts of my body for as long as I can remember. I am hopeful that perhaps if I begin using Hibiclens as a body wash, that I may be able to at least improve my eczema lesions.

In addition to chlorhexidine, other methods of S. aureus body colonization removal are: rubbing alcohol, povidone-iodine, and bleach baths. For Staph infections, over-the-counter triple antibiotics ointment, prescription oral antibiotics, and IV antibiotics are also available. Examples include cephalosporins, nafcillin, sulfa drugs, and vancomycin. With only about 10% of Staph infections today being cured with penicillin, many strains of Staph bacteria are proving to be more resistant to traditional antibiotics. Therefore, intravenously-administered vancomycin is becoming increasingly necessary to treat serious hospital Staph infections (Mayo Clinic, 2017).

With this knowledge, it is important to educate others and do our best to eliminate S. aureus colonies from our bodies while we are healthy, so that these colonies do not pose a threat to us in the future—if we, or a loved one, are ever unfortunate enough to become immunocompromised. We already know that Staph infections paired with other diseases can spell death. Furthermore, as S. aureus strains are increasingly exhibiting signs of antibiotic-resistance, we must do what we can in order to prevent Staph infections in the first place—for ourselves and each other.

References:

Bieber, T., & Jagobi, C. (2013). Atopic and Contact Dermatitis. Retrieved 6 April, 2019, from https://www.sciencedirect.com/topics/medicine-and-dentistry/staphylococcus-aureus

Foster, T. (c1996). Staphylococcus. Retrieved 6 April, 2019, from https://www.ncbi.nlm.nih.gov/books/NBK8448/

Foster, T.J., & Geoghegan, J.A. (2015). Staphylococcus aureus. Retrieved 6 April, 2019, from https://www.sciencedirect.com/topics/medicine-and-dentistry/staphylococcus-aureus

Mayo Clinic. (2017). Staph Infections. Retrieved 7 April, 2019, from https://www.mayoclinic.org/diseases-conditions/staph-infections/diagnosis-treatment/drc-20356227

Orenstein, A. (c2010). The Discovery and Naming of Staphylococcus aureus. Retrieved 9 April, 2019, from http://antimicrobe.org/h04c.files/history/S-aureus.pdf

Otto, M. (2010). Staphylococcus colonization of the skin and antimicrobial peptides. Retrieved 6 April, 2019, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2867359/

Ragle, B.E., Karginov, V.A., & Wardenburg, J.B. (2009). Prevention and Treatment of Staphylococcus aureus Pneumonia with a β-Cyclodextrin Derivative. Retrieved 6 April, 2019, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2798498/

Ross, H.K. (2013). Protection From MRSA? Stick It Up Your Nose. Retrieved 6 April, 2019, from https://www.healthline.com/health-news/policy-simple-steps-before-surgery-can-drastically-reduce-mrsa-infections-061813#1

Wielders, C.L.C., Fluit, A.C., Brisse, S., Verhoef, J., & Schmitz, F.J. (2002). MecA Gene Is Widely Disseminated in Staphylococcus aureus Population. Retrieved 6 April, 2019, from https://www.ncbi.nlm.nih.gov/pmc/articles/PMC139644/

Colonized by S. aureus

S. aureus

Positive Negative 13 12

S. aureus Carriers

S. aureus Carriers

Nostril Carriers Ear Carriers 0.36 0.4

Summary of Class REsults

S. aureus Carriers?

[CATEGORY NAME] (in the Nostrils or Ears) [PERCENTAGE]

Non-Carriers Nostril Carriers Only Ear Carriers Only Both Nostril and Ear Carriers 0.48 0.12 0.16 0.24

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