What\'s the purpose of this lab and the observation and conclusion? LAB 24: ISOL

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What's the purpose of this lab and the observation and conclusion?
LAB 24: ISOLATION AND DENTIFICATION OF Inghin booo STREPTOCOCCI senzyme that can re A. Introduction 1. Streptococci are Gramt, spherical bacteria that are arranged in chains 2. Many species of streptococci cause pneumonia, meningitis, endocarditis, pharyngitis, erysipelas, and glomerulonephritis (infection of kidney tubules) 3. Some strepuococci species are part of normal flora of the pharynx, teeth, saliva, skin, colon, rectum, and vagina 4. In 1919, J.H. Brown proposed that different types of streptococci can be classified based on their ability of hemolysis (rupturing of red blood cells) 5. In 1933, R C. Lancefield further proposed that streptococci species can be divided into Groups A, B, C and D based on their serological test precipitation 6. Now, by combining both methods of classification, there are 7 major groups of streptococci (their physiological differences will be compared later) a) Group A S. pyogenes b) Group B S agalactiae c) Group C S. equi, S. equisimilis d) Group D (enterococci) S faecalis, S. faecium e) Group D (nonenterococci)-S bovis Viridans S mitis, S. salivarius, S mutans Pneumococci S pneumoniae l. This lab is done in a group of 2-3 students 2. a sterile cotton swab, a tongue dep and a blood 3. Your lab partner will use the tongue depresser and hold down your tongue, and quickly use the cotton 4. swab to swap the back wall of your throat (be careful not to touch other parts of the oral cavity) 5. using the swabbed cotton swab, inoculate onto the blood agar plate by quadrant streak Using a sterile inoculating loop, stab areas I and II into the agar 6. write your name on the plate, and place it in the designated rack inverted for incubation 7. in the second lab periode recover your blood agar plate 8, the lid of the plate, and examine hemolysis around the bacterial colonies a) alpha-hemolytic strep shows a green zone around the colony due to the enzyme hemolysin which reduces hemoglobin to methemoglobin b) beta-hemolytic strep shows a clear zone around the colony due to hemolysin rupturing the red blood cells 9. Obtain 2 test tubes of tryptic soy broth CTSB) and transfer the two types of strep into each tube using a 10. sterile inoculating wire (if you only find one type, then perform only one inoculation) Write your name on the tubes, and place them in the designated rack for incubation 11. In the third lab period recover your TSB tubes 13. Perform a Gram staining procedure for each tube in order to confirm the presence of strep For strep, inoculate a loopful into 2 special media and 6.5% Naci

Explanation / Answer

The purpose of this lab is to identify the groups of streptococci. There are 7 different groups of streptococci, which give either beta or alpha haemolytic zone on the blood agar plate, which is the first step of identification of these 7 groups. Groups A, B and C give beta haemolytic zones whereas the other 4 groups, each give alpha haemolytic zones. Depending on the characteristics of each of the groups, the different groups grow in different media, such as Group B growing in Hippurate, Group A growing in the presence of Bacitracin , and group C growing in the presence of SXT. Similarly, the D enterococci grow in 6.5%NaCl and Bile esculin. D nonenter. grow in only bile esculin and SXT and viridans grow only in SXT and Pneumococci grow only in bacitracin presence.

It could be concluded that from this experiment one can easily identify the different groups of Streptococci.

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