14.8: Procedures for Case Study #1

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Case Study #1

Choose either unknown #1 or unknown #2 as your unknown for Case Study #1.

A 21 year old male complains of a sore throat and painful swallowing. A physical exam of the throat shows tonsillopharyngeal edema and erythema, a patchy exudate, petechiae on the soft palate, and a red, swollen uvula. He has a temperature of 101.6 °F. He doesn't have a cough or a noticeably runny nose.

Assume that your unknown is a transport medium from a swab of this person's throat.

Caution

TREAT EACH UNKNOWN AS A PATHOGEN!. Inform your instructor of any spills or accidents. WASH AND SANITIZE YOUR HANDS WELL before leaving the lab.

MATERIALS

1 plate of blood agar,
1 Taxo A ® disc,
1 sterile swab,
inoculating loop

PROCEDURE (to be done in groups of 3)

Note

Videos reviewing techniques used in this lab:

1. On the bottom of the petri plate, divide the plate into thirds with your wax marker and label as shown below. Before you streak your plate draw an "X" on the bottom of the blood agar plate in sector 2 to indicate where you will eventually place the Taxo A disk as indicated in Fig. \(\PageIndex{1}\), step 1

Illustration of how to label your blood agar plate for inoculation. — Figure \(\PageIndex{1}\): **Inoculating a Blood Agar Plate with your Unknown, Step** 1. (Copyright; Gary E. Kaiser, Ph.D. The Community College of Baltimore County, Catonsville Campus CC-BY-3.0)

2. Using a sterile inoculating loop, streak your unknown for isolation on a blood agar plate so as to get single, isolated colonies (see Fig. \(\PageIndex{17}\), step 2, Fig. \(\PageIndex{1}\), step 3, and Fig. \(\PageIndex{17}\), step 4).

Fig \(\PageIndex{1}\): Inoculating a Blood Agar Plate with your Unknown, Step 2	Fig. \(\PageIndex{1}\): Inoculating a Blood Agar Plate with your Unknown, Step 3	Fig. \(\PageIndex{1}\): Inoculating a Blood Agar Plate with your Unknown, Step 4

Using a sterile inoculating loop, streak one-third of the blood agar plate with your unknown. Flame the loop and let it cool.	Rotate the plate counterclockwise so sector 1 is at 9:00. Using a sterile inoculating loop, spread out some of the bacteria in area 1 over area 2. Flame the loop and let it cool.
Copyright; Gary E. Kaiser, Ph.D. The Community College of Baltimore County, Catonsville Campus CC-BY-3.0

3. Using your inoculating loop, stab the agar 2-3 times in each of the growth areas in order to detect oxygen-sensitive hemolysins (see Fig. \(\PageIndex{1}\), step 5).

Illustration showing how to stab your blood agar plate. — Figure \(\PageIndex{1}\): **Inoculating a Blood Agar Plate with your Unknown, Step** 5. (Copyright; Gary E. Kaiser, Ph.D. The Community College of Baltimore County, Catonsville Campus CC-BY-3.0)

4. Place a Taxo A ® disk containing bacitracin where you drew the "X" in sector 2. (see Fig. \(\PageIndex{17}\), step 6). Tap it lightly with your loop so that the disk sticks to the agar.

Illustration showing how to place a Taxo A disk containing bacitracin on a blood agar plate. — Figure \(\PageIndex{1}\): **Inoculating a Blood Agar Plate with your Unknown, Step** 6. (Copyright; Gary E. Kaiser, Ph.D. The Community College of Baltimore County, Catonsville Campus CC-BY-3.0)

5. Incubate the blood agar plate upside down and stacked in the petri plate holder on the shelf of the 37°C incubator corresponding to your lab section until the next lab period.

Contributors and Attributions

Dr. Gary Kaiser (COMMUNITY COLLEGE OF BALTIMORE COUNTY, CATONSVILLE CAMPUS)