Question

I need a help to solve the questions 2, 5,6, 8 and 10.

BACTERIOLOGY LAB PRACTICAL You are welcome to use your lab exercises, class notes or textbook to answer the following questions. Please remember that your isolate is something that we worked with at some point in the semester, so it should look familiar. You are welcome to take this part of the lab practical home to work on, but please have it ready to turn in at the final exam. Day One: 1. Obtain your unknown. Write the number on the tube here: 5 2. Streak for isolation to a sheep's blood and MacConkey agar and place in coffee cans for incubation in ambient air. What is the purpose of performing a streak-for-isolation? Day Two: (When finished with your plates, put your first and last name on them and place them in the designated box, so that I may evaluate your streaking technique also.) 3. Find your the best Evaluate your streak-for-isolation technique here, with 1 being the worst and 4 being What can you determine about your unknown isolate from the growth pattern on these two plates? (Circle one.) 4. Gram Positive Gram Negative f the isolate s growing on Maconkeyf not, go to the If the isolate is growing on MacConkey: 5. What type of fermentation is your unknown displaying? 6. Perform an oxidase on your unknown, using the blood agar. Write the result here: Could this isolate be s member of the Enterobacteriaceae family? 7. 8. Explain your answer to Question No. 7 above. 9. Could this isolate be a stool pathogen? 10. Explain your answer to Question No. 9 above Go-lo quistion½ll on the nect page

Answer 1

ANSWER:-

2. the purpose of streaking for isolation is to produce isolated colonies of an organism on an agar plate. This is useful when you need to separate organisms in a mixed culture or when you need to study the colony morphology of an organism.

5. it may be alpha or beta or no hemolysis based on the unknown which has been taken

6. Hemolysis is the break down of the membrane of red blood cells by a bacterial protein known as hemolysin, which causes the release of hemoglobin from the red blood cell. Many types of bacterial posses hemolytic proteins. These proteins are thought to act by integrating into the membrane of the red blood cell and either punching a hole through the membrane or disrupting the structure of the membrane in some other way. The exact molecular details of hemolysin action is still unresolved.

The blood used in the agar is also treated beforehand to remove a molecule called fibrin, which participates in the clotting of blood. The absence of fibrin ensures that clotting of the blood does not occur in the agar, which could interfere with the visual detection of the hemolytic reactions.

There are three types of hemolysis, designated alpha, beta and gamma. Alpha hemolysis is a greenish discoloration that surrounds a bacterial colony growing on the agar. This type of hemolysis represents a partial decomposition of the hemoglobin of the red blood cells. Alpha hemolysis is characteristic of Streptococcus pneumonia and so can be used as a diagnostic feature in the identification of the bacterial strain.

Beta hemolysis represents a complete breakdown of the hemoglobin of the red blood cells in the vicinity of a bacterial colony. There is a clearing of the agar around a colony. Beta hemolysis is characteristic of Streptococcus pyogenes and some strains ofStaphylococcus aureus.

The third type of hemolysis is actually no hemolysis at all. Gamma hemolysis is a lack of hemolysis in the area around a bacterial colony. A blood agar plate displaying gamma hemolysis actually appears brownish. This is a normal reaction of the blood to the growth conditions used (37° C in the presence of carbon dioxide). Gamma hemolysis is a characteristic of Enterococcus faecalis.

10. ◦ Advantages: fast, doesn't require culturing & incubation
◦ Disadvantages: high rate of false negatives