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20 Cards in this Set
- Front
- Back
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T/F: Streptococci are aerobic |
... trick question. They are faculatively anaerobic |
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Are Streptococci gram positive or gram negative? |
Positive |
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In what pattern do streptococci often occur on a culture? |
Chains or pairs |
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T/F: streptococci are catalase-negative? |
True! |
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What is catalase? Why is it significant in infections? |
An enzyme that catalyzes the decomposition of H2O2 to H2O and O2. When Neutrophils attack pathogens in their phagolysosome and producing H2O2 (and eventually HOCl (bleach)), and these pathogens synthesize catalase, the H2O2 is immediately converted to harmless O2 and H2O. This makes the neutrophils attack ineffective (unless the neutrophils can produce HOCl... but they need myeloperoxidase for this rxn) |
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Streptococci are subdivided into groups by __________ that recognize __________ ____________. These groups may contain one or more species. |
Antibidies; surface antigens |
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Infectious disease is caused by which group? |
A. pneumoniae, mutans, and other so-called viridans streptococci |
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Which species do not posses group antigens? |
pneumoniae, mutans, and other so-called viridans streptococci |
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Alpha, beta, and gamma refer to the types of _________ rxn seen after growth of streptococci on sheep blood agar. |
hemolysis |
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Describe what you see with an Alpha strep. |
Partial hemolysis with a green coloration (from production of an unidentified product of hemoglobin) seen around the colonies. |
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Describe what you see with a Beta strep. |
complete clearing (hemolysis) |
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Describe what you see with a Gamma strep. |
No lysis |
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Which groups of strep are beta hemolytic? |
A and B |
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Which group is usually alpha or gamma? |
D |
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Streptococcus pneumoniae and viridans are ______ hemolytic. |
alpha |
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T/F: the hemolysis rxn is important in grouping streptococci. |
True. This plus one physiologic characteristic is sufficient for a presumptive clinical ID. |
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Group D streps are divided into those that will grow in 6.5% saline (__________), and those that will not (____-___________) |
enterococci, non-enterococci |
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Which group D strep more commonly causes human disease? |
Enterococci |
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Which group D strep is often resistant to penicillin? |
Enterococci |
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Viridans streptococci are either ____________ or ______-__________, and are part of the normal oral flora. |
nonhemolytic; alpha-hemolytic. |
