Question

pver the questions first. Go over exercises 5-21. Answer the following questions 1. Is Blood agar a selective media, differential media, and/or an enriched media? Hint: it is more than one of these, but it is not all three. Please explain your answer. 2. Define hemolysins. 3. List the three major types of hemolysis and briefly describe each.

Answer 1

1) BLOOD AGAR is a differential media and a enriched media

• enriched media contain the nutrients required to support the growth of a wide variety of organisms,

Blood agar is a type of growth medium (trypticase soya agar enriched with 5% sheep blood)

type of organism cultured in blood agar are fastidious organism like Haemophilus influenzae, Streptococcus pneumoniae and Neisseria species.

Blood agar is also a differential media because,they help to distinguishes bacterial species by their ability to break down red blood cells. The ability to break down the cells will cause a change in the color of the blood agar.

2) HEMOLYSIN are the lipids or protein substance that causes the dissolution of red blood cells.

3) Alpha hemolysis

    beta hemolysis

   gamma hemolysis

Alpha hemolysis

It is the partial breakdown of Red blood cell by the alpha hemolysin produced by the bacteria like Streptococcus pneumoniae, Streptococcus viridans and form a greenish discoloration around the colony

beta hemolysis

it is complete breakdown of red blood cell by the beta hemolysin produced by the Streptococcus pyogenes, staphylococcus aureus.

gamma hemolysis

is a lack of hemolysis in the area around a bacterial colony. A blood agar plate displaying gamma hemolysis actually appears brownish. bacteria like Enterococcus faecalis shows gamma hemolysis.