Normal flora are found in specific areas of the body and often depends on environmental factors such as pH, oxygen concentration, amount of moisture present, etc. Some sites in which native microbial is the skin in which you often find staphylococci, streptococci, diptheriod bacilli, yeast and fungi. You often find staphylococci, streptococci, diotheriod, spirochetes, and members of the genera Branhamella, Neisseria, and Haemophilus in the throat or the upper respiratory tract. In this exercise, we identified microorganisms that normally reside in the throat and skin and compared them using streak plate inoculations.
There are several different types on plates used to identify native flora of the skin and throat. Blood agar contains mammalian blood (usually sheep or horse) and is used to isolate fastidious organisms and detect a-gemolytic acitivity and b-hemolytic activity and is specifically used to determine the presence of staphylococci and streptococci on the skin and throat. A mannitol salt agar plate is used for identifying native skin flora and is inoculated to observe the presence of staphylococci, specifically the pathogenic versus the non-pathogenic. The pathogenic causes yellow coloration of the medium surrounding the growth. A Sabouraud agar plate is also used for identifying native skin flora and detects years and molds. Yeast cells will develop colonies that are elevated, moist and glistening and mold colonies will appear as fuzzy, powdery growths. Materials:
-blood agar plates
-Mannitol salt agar plates
-sabouraud agar plates
-nutrient agar plates
-2, 5mL sterile saline tubes
-sterile cotton swabs
Each student must take a sterile cotton swab and either swabs the back of their throat, their palm, or the bottom of their foot. After swabbing for approximately 10-15 seconds we mixed the swab in the solution of sterile saline tubes. Then we each had our own nutrient agar plate, blood agar, mannitol salt, and sabouraud, so we labeled each and steaked them. Then we inoculated the plates and sit for approximately two days. Then we observed and recorded out findings. We noted number of colonies.
CultureThroat SpecimenSkin Specimen
Blood agarclear circles, many coloniesWhite, smooth colonies, many Mannitol salt No colonies, medium was red (+) small round colonies, few SabouraudNo colonies(-), few colonies, few Nutrient broth Round/globular, few Small circular, smooth
For most of the agar plates including the mannitoal salt agar, sabouraud agar and the nutrient agar there wasn’t many microorganisms growing. We did find that microorganisms seemed to grow best on the blood agar. On the blood agar, the throat specimen appeared to have many clear colonies while the skin specimen had larder white colonies. There were no yellow colonies indicating that there was no pathogenic microbe.
When looking at the other plates, we observed more colonies present when examining the skin specimen in comparison to the throat specimen. All of the colonies on the sabouraud, mannitol and nutrient agar were small, white colonies. The reason we may have observed more colonies on the skin specimen in comparison to the throat specimen could be due to the fact that the person that swabbed their throat (me) did not do it for a long enough period of time and therefore, did not observe bacteria growing on the cultures. It could also be because the agars were not the specific environment necessary for those microorganisms to survive.
It would be interesting to make slides of these microorganisms to get a closer look at what they look like and be able to differentiate between them on a microscopic level.
Courtney from Study Moose
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