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What genus of bacteria is classified by Lancefield groups?
Streptococcus
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A positive latex agglutination result in Group A would indicate what organism?
Streptococcus Pyogenes
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S.Pyogenes is the causitive agent of what diseases?
Bacterial pharyngitis ("strep throat"), impetigo, scarlet fever, necrotizing fascitis, TSS.
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How are S.Pyogenes infections treated?
Penicillin
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What type of bacteria are identified by the Enterotube test?
Enteric bacteria
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What are some characteristics of enterobacteriacea?
Gram negative, Catalase positive, Oxidase negative, Facultative anerobes.
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What dyes are used in EMB Agar?
Eosin y & Methylene Blue
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True or False:
EMB Agar inhibits the growth of gram negative bacteria
False!
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What is the EMB Agar test used to identify?
Fecal Coliforms
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Why is a Nutrient Agar plate used along with the EMB Agar plate?
To demonstrate a comparison for growth, or to show how well gram positive growth was inhibited.
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What color on EMB would indicate a possible coliform?
Pink
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What color on EMB would indicate a probable coliform?
Dark purple to green or black.
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How is EMB Agar selective?
It inhibits the growth of Gram positive organisms.
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How is EMB Agar differential?
It reacts with lactose fermentors to change the color of the agar.
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Beta Hemolysis
Complete hemolysis of RBC's
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Alpha hemolysis
Partial Hemolysis of RBC's
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Gamma Hemolysis
No hemolysis of RBC's
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A clearing around the colonies would indicate which type of hemolysis?
Beta hemolysis
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A green discoloration of the blood agar would indicate which type of hemolysis?
Alpha hemolysis
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What are hemolysins?
Gram positive cocci toxins that destroy red blood cells.
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Why is the streak-stab technique prefered in Blood Agar?
It provides a favorable enviroment for streptolysins.
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Streptococcus Pyogenes demonstrates what type of hemolysis?
Beta hemolysis
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Streptococcus Pneumoniae demonstrates what type of hemolysis?
Alpha hemolysis
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Streptococcus Pneumoniae is the causitive agent of what diseases?
Cellulitis, brain abcesses, endocarditis, septic arthritis.
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In blood agar, why is it important to cover and tape the plates before incubation?
After incubation, the number of bacteria increase and pose a greater risk of infecting people in the lab.
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Why is the streak plate method preferred over the spot inoculation in blood agar?
Because the sample from the throat is not a pure culture, so isolation is needed to identify the individual colonies.
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What indicator is used in MSA agar? How does it react to changes in PH?
Phenol red; turns yellow in acidic conditions and pink in alkaline conditions.
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How is MSA agar selective?
Its high salt content inhibits the growth of most other bacteria except gram positive staphylococci.
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How is MSA agar differential?
Mannitol provides a substrate for fermentation, the media will change color with acidic conditions.
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MSA is used for isolation and differentation of what staphylococcus organism?
S.aureus
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Why does E.Coli not grow well on MSA?
MSA inhibits the growth of most gram negative bacteria.
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Why is a known catalase positive organism used in the catalase test?
To verify the quality of the peroxide.
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What is the purpose of adding hydrogen peroxide to an uninoculated tube for the catalase test?
It provides a comparison in the case of minimal reaction.
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What blood type is considered a universal donor?
O negative
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What type of blood is considered a universal recipient?
AB positive
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