Distinguish between pathogen and virulence
pathogen- a disease-causing organism
virulence- the degree of pathogenicity of a microorganism
Indicate two factors that contribute to the virulence of a microbe
invasiveness- ease of entry and spread through the host
toxigenicity- the capacity to produce toxins
Indicate two factors that contribute to the invasiveness of a microbes.
Portal of entry-a place through which an organism enters: mucous membranes, resp. tract, GI tract, UG tract.
Dose- appropriate number of m/o needed to cause disease. Often quantified experimentally as: ID50- dose necessary to cause infection in (about) 50
Define portal of entry and identify the principal portals of entry.
portal of entry- a pace through which an organism enters. mucous membranes, resp. tract, GI tract, UG tract, skin, parenteral route- damaged skin, injection, bite of mosquito, cut
Using examples explain how bacteria adhere to host cells.
bacteria adhere to host cells by surface projections- fimbriae viral spikes, biofilms (glycocalyx- adhere to surface of cell better
Explain how capsules and cell wall components contribute to pathogenicity.
capsules- sugar coating biofilm production resists phagocytosis. Helps pathogens stick to surface. Impairs phagocytosis by WBC
Explain how microbial chemicals contribute to the spread of a m/o throughout the body.
capsules- glycocalyx coating around the cell wall
helps pathogens stick to surfaces
impairs phagocytosis by WBC
enzymes- chemicals made by cells that are secreted and contribute to spread
Define toxin and distinguish between an exotoxin and an endotoxin.
toxin- any poisonous substance produced by an organism
exotoxins- are produced inside mostly gram-positive bacteria as part of their growth and metabolism. They are then released into the surrounding medium. (neurotoxins, enterotoxins, cytotoxins)
endotox
compare pathogenicity a with virulence?
the ability of a microorganism to produce a disease is called pathogenicity. The degree of pathogenicity is virulence
How are capsules and cell wall components related to pathogenicity. Give specific examples.
encapsulated bacteria can resist phagocytosis and continue growing. Streptococcus pneumonia and Klebsiella pneumonia produce capsules that are related to their virulence. M protein found in the cell walls of Streptococcus pyogenes and A protein in the cel
how can viruses and protozoa avoid being killed by the host's immune response?
viruses avoid the hosts immune response by growing inside host cells; some can remain latent in a host cell for prolonged periods. Some protozoa avoid the immune response by mutations that change their antigens.
the removal of plasmids reduces virulence in which of the following organisms?
a) Clostridium tetani
b) Escherichia coli
c) Staphylococcus aureus
d) Streptococcus mutans
e) Clostridium botulinum
e
Define ID50 and LD50
ID50= dose necessary to cause infection in (about) 50% of subjects
LD50= dose necessary to kill (about) 50% of subjects
which of the following is not a portal of entry for pathogens?
a) mucous membranes of the resp tract
b) mucous membranes of the GI tract
c) skin
d) blood
e) parenteral route
d
All of the following can occur during bacterial infection. Which would prevent all of the others?
a) vaccination against fimbriae
b) phagocytosis
c) inhibition of phagocytic digestion
d) destruction of adhesins
e) alteration of cytoskeleton
d
The ID50 for Campylobacter sp. is 500 cells; the ID50 for Cryptosporidium sp. is 100 cells. Which of the following statements is not true?
a) both microbes are pathogens
b) both microbes produce infections in 50% of the inoculated hosts
c) Cryptosporidium
c
An encapsulated bacterium can be virulent because the capsule
a) resists phagocytosis
b) is an endotoxin
c) destroys hosts tissues
d) interferes with physiological processes
e) has no effect; because many pathogens do not have capsules, capsules do not co
a
the earliest smallpox vaccines were infected tissues rubbed into the skin of a healthy person. The recipient of such vaccine usually developed a mild case of smallpox, recovered, and was immune thereafter. What is the most likely reason this vaccine did n
a
which of the following statements is true?
a) the primary goal of a pathogen is to kill its host
b) evolution selects for the most virulent pathogens
c)a successful pathogen doesnt kill its host before it is transmitted
d) a successful pathogen never kill
c
Why are incidences of E. coli seasonal?
during the months of june and july the weather is warmer allowing the bacteria to grow more rapidly. People are also outside more children are playing in the water and going to the bathroom in it allowing the E. coli to travel outside of the intestines an