Question

Blood agar lab
Please help to interpreting the results of each one, was five students. Start from the top then go to the right . and what type discussion I can have in relation with this results. Also help me to answer those questions.

Answer 1

Interpretation and Questions

1. Streptococcus pyrogens will causes strep throat and the hemolysis will differ from normal throat flora that remain present, which exhibits alpha or gamma hemolysis. Streptococcus pyrogens exhibits beta type of hemolysis, Media will look fluorescent.

2.. S. sanguis produce media will look like chocolate(chocolte agar) and cause alpha hemolysis.

3.. Enterococcus faecalis color remains same, has gamma type hemolysis .Non -hemolytic colonies.

4.Patient A's sample looks fluorescent yellow that is a color characteristic of beta type hemolysis.

1. Blood agar is a differential media because it has additives that will change color upon growth of certain bacteria.

It contains human blood thus only those bacteria which possess enxymes to break down blood cells only those will grow on it. Not all bacteria will grow on it.

Generally used in microbiology to differentiate bacteria present in different samples such as sputum, throat.

It is not selective in nature but it is nutrient rich media whoch allow variety of bacteria to grow on it. The bacteria which releases exotoxins will break the RBC, results in hemolysis.

2)

Beta type hemolysis exhibited by patient A, media color looks yellow and fluorescent.

Based on this one an say that the patient may be infected by S.pyrogen infection.

Based on the pattern of hemolysis one can distinguish between different bacterial strain and types.

Hemolysis pattern are of various types namely $\alpha \beta \gamma$ (alpha, beta ,gamma).

Beta type occurs when complete breakdown of RBCs occurs in presence of bacterial exotoxin.Clear holes appear on the media around bacterial colonies.(yellow and transparent).

Alpha type- partial digestion of RBC occurs due to bacterial generated chemicals. It leads to production of brownish discoloration around the colony. Looks greenish due to oxidation of iron.

Gamma type- no hemolysis occurs. bacteria does not cause any effect thus color of media remains the same.