2. Gamma-hemolysis on a blood agar plate would likely appear: Select one: a. As

Question

2.

Gamma-hemolysis on a blood agar plate would likely appear:

Select one:

a. As no change in the medium

b. Blue

c. Yellow

d. Green

e. As a clearing

3.

Identification of Gram-positive cocci: You perform a gram stain and notice that each spherical cell is isolated from other cells (i.e. not in clusters, chains, etc.). Which genus would you NOT expect your unknown bacteria to be (rarely found as single cells)?

Select one:

a. Streptococcus

b. Micrococcus

c. Enterococcus

d. Staphylococcus

4.

Which one of the following is NOT true about hemolysin?

Select one:

a. They often cause fevers

b. They are common in Streptococci and Enterococci bacteria

c. They are exotoxins

d. They can cause anemia

5.

The main difference between between type O and type S streptolysins is that type O:

Select one:

a. Expresses optimally under aerobic conditions

b. Expresses optimally under anaerobic conditions

c. Is not affected by oxygen

d. Can be destroyed by oxygen

6.

Identification of Gram-positive cocci: You have isolated a catalase-negative bacterium that doesn't grow well in 6.5% NaCl medium. Which test would you expect to give you a presumptive identification? (i.e. The first tests tell you the genus, which test would identify a species of that genus)

Select one:

a. PYR Test

b. Novobiocin Sensitivity Test

c. Coagulase Tube Test

d. CAMP Test

7,

Why was it important to grow both types of bacteria on the same plate for this susceptibility experiment?

Select one:

a. The bacitracin disks talk nicely to each other

b. To confuse students

c. To avoid wasting resources

d. To prevent for fluccuations in grown from media differences

Explanation / Answer

2) There are three types of hemolysis: alpha, beta and gamma.

Alpha hemolysis represents partial decomposition of the hemoglobin of red blood cells. The agar medium appears greenish and is seen in Streptococcus pneumoniae.

Beta hemolysis is the complete breakdown of hemoglobin of red blood cells. There is clearing of agar around the colony. Beta hemolysis is seen in Streptococcus pyogenes.

Gamma hemolysis is the lack of hemolysis around the bacterial colony. The agar plate appears brownish as this is a normal reaction if the blood to microbial growth. This gamma hemolysis is seen in Enterococcus faecalis. There is no change in the medium.

So, the answer for this question is option A.

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