Microorganisms and Disease
Type III secretion systems are used to inject "effector" proteins directly into a host cell. Salmonella uses a type III secretion system to help the pathogen to

activate T cells to proliferate and secrete cytokines
survive within macrophages
survive the acid pH of the stomach
secrete LT (heat labile toxin) and ST (heat stable toxin) into the lumen of the intestine

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Microorganisms and Disease
A major difference between EHEC and EPEC is

EPEC rearranges host cell actin and EHEC does not
EHEC secretes a Shiga-like toxin and EPEC does not
EPEC passes through the placenta to infect the fetus and EHEC does not
EHEC possesses a type III secretion system and EPEC does not

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Microorganisms and Disease
The "A" subunit of diphtheria toxin

lysis macrophages with the release of cytokines
forms cAMP that leads to fluid accumulation
binds host cell receptors found on heart cells
cause ADP ribosylation of a factor involved in protein synthesis

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Microorganisms and Disease
The influenza vaccine is administered each year because

mutations in the viral hemagglutinin may allow the virus to evade the immune response elicited by previous vaccines
it is a polysaccharide vaccine that does not confer long-term protection
None of these
the vaccine is sufficiently toxic to make it necessary to administer only a small amount at any one time

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