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3 Cards in this Set
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What is the difference between the strain of Streptococcus pyogenes that causes bacterial pharyngitis and the strain that causes Scarlet fever and sometimes results in rheumatic fever?
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The strain that causes Scarlet fever and rheumatic fever are both sequelas (results) of the S. pyogenes that causes pharyngitis. Scarlet Fever is caused by S. pyogenes being infected by a bacteriophage ( a lysogenic virus that gives it the ability to make erythrogenic toxin) and causes a rash. Rheumatic fever is caused by an autoimmune response where the body's defenses mistake its own heart valve cells for streptococcal M proteins, which causes damage to heart valves (endocarditis).
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What is croup?
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Croup is any acute obstruction of the larynx or epiglottis that produces a characteristic high-pitched barking cough. Can result from viral or bacterial infections of the epiglottis or the larynx and causes breathing difficulties. Associated with children.
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Describe antigenic drift and antigenic shift using the influenza virus as an example.
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Antigenic shift is the process by which two or more different strains of a virus combine to form a new subtype having a mixture of the surface antigens of the 2+ original strains. ... The flu, for example, can combine the bird flu with human flu to produce a new hybrid that can cause a major pandemic flu.
Antigenic drift is a mechanism for variation by viruses that involves the accumulation of mutations within the antibody-binding sites. This means that the resulting viruses cannot be inhibited well by antibodies that fought previous strains. If sufficient drift occurs, an influenza epidemic will follow due to lack of sufficient herd immunity. |
