Flashcards
Microbiology Lab Practical III
Cards in this deck (26)
- 1What are the hemolysis results of A, B, & C?A: Beta hemolysis
B: Alpha hemolysis
C: Gamma hemolysis - 2What test is this? What are the results? What organism gives positive test?PEA test
Left: + test
Right: - test
S. aureus
- 3What test is this? What are the results? What organism gives positive test?Bile esculin test
Left tube: - test
Right tube: + test
S. bovis
- 4What test is this?Kirby Bauer Test
- 5What test is this? What are the results? What organism gives positive test?MSA plate
Left side: Fermentation of mannitol (positive test), salt tolerent
Right side: No fermentation of mannitol, no growth, not tolerant of salt
+ test: S. aureus
- 6What test is this? What are the results? What organism gives positive test?Catalase test
A. Catalase negative
B. Catalase +
+ test: S. epidermidis
- 71. What is the toxin some gram-positive cocci produce which shows their hemolytic activity? 2. Which media you use to differentiate gram-positive bacteria based on their hemolytic character? 3. What is it composed of?1. Hemolysins
2. Blood Agar Plate
3. Sheep blood and agarose - 8What are the 3 main types of hemolysis? Define each one briefly.Alpha hemolysis: partial hemolysis- will look greenish
Beta hemolysis: complete hemolysis- area around growth will be transparent
Gamma hemolysis: no hemolysis - 9Name one organism that produces beta hemolysis, one that produces gamma and one that produces alpha hemolysis.Beta: S. pyrogenes, S. aureus
Gamma: S. bovis, E. faecalis
Alpha: S. pneumoniae, S. sarguinis - 10Define halophiles and extreme halophiles. Name a gram-positive coccus that can grow in the presence of high salt concentration.HALOPHILES are microorganisms that can grow in salt concentration up to 15%. EXTREME HALOPHILES are microogranims that can grow in salt concentration up to 35% or higher.
S. aureus can grow in high salt concentration. - 11MSA medium is selective for which organism and why?Mannitol Salt Agar (MSA) is selective for S. aureus. It is the only organism that can survive high salt concentration & ferment mannitol.
- 12How do you interpret the results of an Optochin test? Name an organism that gives you a positive optochin test.A test is positive when the ZOI is 14mm+. S. pneumoniae is a positive optochin test.
- 13What is Bacitracin? What is its mechanism of action? How do you interpret the result of Bacitracin test?Bacitran is a peptide antibiotic that acts on the c. wall of a bacteria causing lysis of the cell. When the ZOI is 10mm+ around disc, it is a positive test.
- 14What are the possible results in a MSA plate and how do you interpret those?There will be Gram + bacteria growth, but no Gram - growth. If there is growth but no discoloration or orange color formation then it may be E. faecalis or S. epidermidis, but S. aureus will produce a color because of mannitol fermentation.
- 15Give the name of two gram positive bacteria that give gamma hemolysis in the Blood Agar plate. How do you differentiate them?E. faecalis & S. bovis
You can differentiate by doing a 6.5% salt agar test; E. faecalis will grow, S. bovis won't. - 16How does a positive Bile-esculin test look like? Give the name of two organisms that give positive test.A positive test has a black color.
E. faecalis & S. bovis - 17What is PEA agar medium selective for? What is the mechanism of action of PEA?PEA agar is selective for Gram + organisms.
MOA: Inhibits DNA growth in Gram - organisms. - 18What is the function of bile in a bile-esculin medium? What does Ferric citrate do in a bile-esculin medium? Name an organism that gives positive bile-esculin test.Bile will inhibit growth of many organisms, in the presence of bile some bacteria can convert from esculin to esculatin. Ferric citrate is the pH indicator/color indicator in bile esculin. S. bovis is a positive bile esculin test.
- 19What is the main use of coagulase test? Describe the mechanism of action of bound coagulase.It is used to identify S. aureus because out of all the staph's S. aureus is the only one that will give you a positive coagulase test.
MOA: causes clotting of fibrinogen - 201. What is the other name for Kirby-Bauer test? 2. What is its most important use? 3. What do you measure to determine the sensitivity of an organism to a specific antibiotic?1. Antimicrobial Susceptibility Test
2. It detects sensitivity of different organisms to different antimicrobial agents.
3. ZOI, examine the diameter - 21What does UV light do to kill bacterial cells? Why UV light is considered to have limited efficiency?It causes pyrimidine dimers, when formed DNA becomes dysfunctional and bacteria die. UV light has limited efficiency because it cannot penetrate some things such as paper or plastic and some bacteria produce the enzyme photolyase which fixes broken DNA.
- 22What happens if a plate inoculated with E.coli is exposed to sunlight after it is exposed to UV light for 30 seconds and why?E. coli will have some damage from UV light, once in sunlight that DNA will be repaired because photolyase will be produced.
- 231. What do you test in a catalase test? 2. When do you say the test to be positive 3. Name two organisms that give positive catalase test.1. You test for catalase enzyme which breaks down hydrogen peroxide to produce oxygen.
2. When gas bubbles are produced it is positive.
3. S. aureus & S. epidermidis - 24Name an organism that is catalase positive, coagulase negative and appear as purple color spheres in gram staining.S. epidermidis
- 25Name an organism that is catalase negative, alpha-hemolytic and sensitive to optochin.S. pneumoniae
- 26Name an organism that is a beta hemolytic streptococcus and does not respond to Bacitracin.S. agalactiae
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- Microbiology Flashcards on Microbiology Lab Practical III, created by Davonte' Allen on 20/07/2017.
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