Selective and Differential Media

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Lab Session 8: Selective and Differential Media,
Unknown ID (Enzyme Based Tests)
Oct. 25-31st
(To be turned in PRIOR to start of recitation for lab 8)

Name: _____ ________
Objective: Analyze microbes from last week. Understand the use of antibiotics on microorganisms. Gain more knowledge about selective media and differential media. Practice use of the catalase test, coagulase and the oxidase test. Observe microbial flora of the nose.

Significance: Understand the use of Mannitol salt agar, blood agar and MacConkey agar plates which must be used based on the components of the bacteria. The catalase test will be used to understand the difference in facultative anaerobic and groam positive from aero tolerant anaerobes. The coagulase test converts fibrogen to fibrin, causing clotting, and is used to prevent phagocytosis of material. The oxidase test can be used to distinguish bacteria: positive organisms and negative organisms dependent upon the color obtained in the test. In the Nasal swab, we will learn to isolate particular flora.

Procedure: Throat Microbial Flora
1. Analyze the flora from last week and gram stain an isolated colony. 2.Receive TA approval of the gram stain.

Procedure: Disinfectant and Antiseptics
1. Use a ruler to measure the diameter of the zones of inhibition (mm) 2.Record each antibiotic zone size in the chart, determine if it is sensitive, intermediate, or resistant; and report to TA.

Procedure: Selective and Differential Media
1. Label the MacConkey agar plates. Streak the plates for the following organisms: Enterobacter aerogenes, Salmonella enterica, and Staphylococcus aureus, and sterilize the loop after streaking each quadrant. 2.Label a sheep blood agar plate and use a loopful of Enterococcus faecalis to inoculate it. Streak the plate. 3.Repeat step 2 for Streptococcus pyogenes

4.Transfer an A disc with flamed forceps to the cross of first and second quadrant of the Streptococcus...
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