Follow up on the Kirby-Bauer Test:
Today we checked the results of the antibiotic test by measuring the effects of the antibodies on our unknown bacteria. Using a ruler with millimeters we measured each disc of the antibiotic.
1. The penicillin had no effect on our bacteria and therefore is resistant (this is because our bacteria is a gram negative and has a small cell wall, so the penicillin that acts on the cell wall is not effective in killing our bacteria
2. Tetracyclin did work and measured 18mm, meaning it was in the intermediate range, our bacteria was not completely resistant but it was definitely sensitive.
3. Neomysin was also effective and measured 17mm and was also intermediate.
*Both Neomysin and Tetracyclin work against the protein synthesis of our bacteria
4. Cinnamon was effective against the bacteria and measured 19mm
5. Lemon had no effect and the bacteria is resistant
6. The Augmentin was resistant and only measures 10mm, it did not effectively work against our bacteria
The Differential plates:
Urine Sample-
EMB plate was used to detect a strong, weak or nonlactose fermenter in coliforms. The small colony growth and pinkish tinge indicated that our sample was a weak lactose fermenter and a positive test. Our test actually was a positive due to contamination from skin bacteria, we actually learned about in class today. Although the sample was contaminated we learned the direct effects that everyday microflora living on our skin can have on samples. The colony count was 4 per the 50 microliters so for every liter there would be 800 colonies. A real positive test of a weak fermenter would have determined it was a staphylococcus. ( a strong fermenter would have meant an E. coli) Lesson of the day: Aseptic technique is essential to microbial testing!!
Nose Sample:
For this we used a Mannitol plate to detect pH and halophiles in the nose sample. This plate also differentiates between the halophile staphylococcus aurelis (fermenter) and epididimis (nonfermentor). If MRSA was present the plate would have turned a yellow due to the pH change. Our test results were negative.
Throat Swab:
For the throat swab we used a Blood agar plate to look for Strephtolococcus pyrogenes or Strephtolococcus alactica. The results of the trhaot sample were gamma hemolysis, meaning there was no lyses of the red blood cells and our test is negative. If we had a positive result of beta-hemolysis we could have further tested for Strephylococcus pyrogenes with Bacitracin and the other groups went onto test their beta hemolysis results. If their bacteria is sensitive to Bacitracin it will signify a positive test for S. pyrogenes
PCR – Polymerase Chain Reaction
We learned about the polymerase chain reaction test used to amplify a specific region of a DNA strand (the DNA target) for detecting antibodies and antigens and therefore a bacteria or virus. The PCR carries out this reaction using several small tubes and a thermal cycler to heat and cool the liquid during the different stages of the test. The heating breaks apart the DNA of the bacteria or virus and adds a new complimentary substrate or strand. Then after another series of cooling and heating and adding an enzyme, the DNA begins to replicate the new strand and the virus or bacteria can now be detected using software and graphs showing the antigens and antibodies of the DNA.
Antibody-Antigen Reaction in Agar and Food Purity
This process was to study the technique of immunology and apply it in a test for food purity. First we made four wells in the agar after placing it over the diagram II of our handout. We made the hole using a droping pipet. Then in each hole we placed a drop of diferent solution in each hole- Bovine Albumin, Goat Anti-horse, Anti-bovine and Anti-swine Albumin.
Then we made four more holes using template III and this time in each hole we placed a solution of either Hamburger extract, Goat Anti-horse, Anti-bovine and Anti-swine Albumin. This is to test the purity of the hamburger extract.
Finally we placed the agar plate in our very own draw and will see the results tomorrow.
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