VBS exam 3 questions and answers
graded A+
Describe why most microorganisms do not cause disease. - answerA lot of microbes
cant lives in your body because of your immune system and body temp.
What is the likelihood of developing an infection? What are the 3 factors? -
answer(number of microbes/infectious dose) (virulence of microbe) divided by:
host immunity
Acute infection - answerinfection that develops symptoms very fast and last a short time
Chronic infection - answerinfection that develops slowly but and lasts for months or
years
endotoxin - answerLPS layer of gram negative bacteria
Exotoxin - answertoxic protein produced by microorganism
Infection - answercolonization by a pathogen
Infectious disease - answerinfection that prevents body from functioning normally
latent infection - answerinfection in which the infection agent is present but not causing
symptoms
Why isn't Lyme disease contagious? Can you think of another example of non-
contagious disease? - answer*Lyme disease is not contagious; tick has to be vector
-Malaria is not contagious
Contagious- disease spread person to person
-colds, flu
Exposure to a pathogen does not always result in disease. Why not - answerThere has
to be the correct portal of entry. There are physical and chemical barriers that prevent
disease like lysozyme and mucus. Normal microbiota are also present. The right host
receptor has to be present. Innate and acquired immunity also prevents disease.
What is the difference between symptoms and signs of a disease? - answer*Signs→
Something that you can measure (temperature, BP)
,*Symptoms→ harder to measure (something patient describes to you like headache or
nausea)
How can a primary infection lead to a secondary infection? - answerIn the case of the
flue, the mucocilliatory escalater is damaged which results in secondary infection
because bacteria can travel down to lungs
*primary infection→ Flu virus
*Secondary infection→ streptococcus pneumoniae
When do opportunistic pathogens cause disease? - answer*Primary pathogen→
something that causes disease in healthy people
-influenza, measles, tetanus
*opportunistic pathogen→ disease in weak immune system people
-Can cause disease in healthy people if introduced in wrong location like a cut.
Reduction in your own microbitoa and overgrowth of opportunistic pathogen can cause
disease.
What are virulence factors? What are some examples and how do they increase the
pathogenicity of the microorganism? - answerVirulence factors→ how much they can
cause disease
-toxins-- E coli produce shiga toxin
-adhesions-- HIV bind to receptor on CD4 cells
-bacterial fimbrae
-extracellular enzymes
-capsule or slime layer
-flagella-- salmonella
-conversion to intracellular pathogens-- mycobacterium Terburculosis
How does Mycobacterium tuberculosis evade the immune system? - answerIt is a
facultative intracellular pathogen
-mycobacterium Terburculosis has acid fast cell wall that resists digestion. Bacteria can
multiply within human macrophage cells
How does the prodromal period of disease differ from the symptomatic period -
answer*Symtomatic stage has the sever symptoms whereas in prodromal you feel initial
symptoms like being tired
What is a latent infection? Can someone with a latent infection transmit the infection? -
answer*Infection agent is present in body but person appears to be normal. They can
still transmit the infection
, What are the three types of plague? What type is likely to be most contagious? What is
the vector(s) for plague? What often precedes an outbreak of human plague? - answer-
Bubonic plague→ most common form, contracted when infected rodent bites you,
infects lymphatic system
-septicemic plague→ When the bacteria enter the bloodstream directly and multiply
there, it's known as septicemic plague.
-pneumonic plague→ only form of the plague that can be transmitted from person to
person.
A microorganism may be capable of causing disease if it
A. can grow at body temperature
B. can evade host defenses
C. produce toxins
D. attach to host receptor
E. all of the above - answerE
Strategies for Avoiding immune system - answer1. Antigenic variation→ (antigen means
foreign substance)
-bacteria and viru can change what surface protein they have so they can be different
once you start to build immune response
-example: HIV, Influenza
*Capsule or slime layer
* Facultative intracellular pathogen
2. Leukocidins destroy white blood cells
3. IgA proteases destroy some antibodies (IgA)
-this is the most abundant in the body
4. Elastase inactivates complement proteins
5. Long polysaccharide chains in LPS prevent MAC insertion into membrane
-gram negative bacteria
6. Inhibition of IFN production
-this is for viruses, helps neighboring cells
Phases of infectious disease: - answer1.Incubation period→ 3-7 days where you don't
know you've been infected
2.Prodormal period→ start to feel a little tired
3.Period of illness→ Symptomatic (sore throat, congestion)
4.Convalescent→ non diseased, disability, death
graded A+
Describe why most microorganisms do not cause disease. - answerA lot of microbes
cant lives in your body because of your immune system and body temp.
What is the likelihood of developing an infection? What are the 3 factors? -
answer(number of microbes/infectious dose) (virulence of microbe) divided by:
host immunity
Acute infection - answerinfection that develops symptoms very fast and last a short time
Chronic infection - answerinfection that develops slowly but and lasts for months or
years
endotoxin - answerLPS layer of gram negative bacteria
Exotoxin - answertoxic protein produced by microorganism
Infection - answercolonization by a pathogen
Infectious disease - answerinfection that prevents body from functioning normally
latent infection - answerinfection in which the infection agent is present but not causing
symptoms
Why isn't Lyme disease contagious? Can you think of another example of non-
contagious disease? - answer*Lyme disease is not contagious; tick has to be vector
-Malaria is not contagious
Contagious- disease spread person to person
-colds, flu
Exposure to a pathogen does not always result in disease. Why not - answerThere has
to be the correct portal of entry. There are physical and chemical barriers that prevent
disease like lysozyme and mucus. Normal microbiota are also present. The right host
receptor has to be present. Innate and acquired immunity also prevents disease.
What is the difference between symptoms and signs of a disease? - answer*Signs→
Something that you can measure (temperature, BP)
,*Symptoms→ harder to measure (something patient describes to you like headache or
nausea)
How can a primary infection lead to a secondary infection? - answerIn the case of the
flue, the mucocilliatory escalater is damaged which results in secondary infection
because bacteria can travel down to lungs
*primary infection→ Flu virus
*Secondary infection→ streptococcus pneumoniae
When do opportunistic pathogens cause disease? - answer*Primary pathogen→
something that causes disease in healthy people
-influenza, measles, tetanus
*opportunistic pathogen→ disease in weak immune system people
-Can cause disease in healthy people if introduced in wrong location like a cut.
Reduction in your own microbitoa and overgrowth of opportunistic pathogen can cause
disease.
What are virulence factors? What are some examples and how do they increase the
pathogenicity of the microorganism? - answerVirulence factors→ how much they can
cause disease
-toxins-- E coli produce shiga toxin
-adhesions-- HIV bind to receptor on CD4 cells
-bacterial fimbrae
-extracellular enzymes
-capsule or slime layer
-flagella-- salmonella
-conversion to intracellular pathogens-- mycobacterium Terburculosis
How does Mycobacterium tuberculosis evade the immune system? - answerIt is a
facultative intracellular pathogen
-mycobacterium Terburculosis has acid fast cell wall that resists digestion. Bacteria can
multiply within human macrophage cells
How does the prodromal period of disease differ from the symptomatic period -
answer*Symtomatic stage has the sever symptoms whereas in prodromal you feel initial
symptoms like being tired
What is a latent infection? Can someone with a latent infection transmit the infection? -
answer*Infection agent is present in body but person appears to be normal. They can
still transmit the infection
, What are the three types of plague? What type is likely to be most contagious? What is
the vector(s) for plague? What often precedes an outbreak of human plague? - answer-
Bubonic plague→ most common form, contracted when infected rodent bites you,
infects lymphatic system
-septicemic plague→ When the bacteria enter the bloodstream directly and multiply
there, it's known as septicemic plague.
-pneumonic plague→ only form of the plague that can be transmitted from person to
person.
A microorganism may be capable of causing disease if it
A. can grow at body temperature
B. can evade host defenses
C. produce toxins
D. attach to host receptor
E. all of the above - answerE
Strategies for Avoiding immune system - answer1. Antigenic variation→ (antigen means
foreign substance)
-bacteria and viru can change what surface protein they have so they can be different
once you start to build immune response
-example: HIV, Influenza
*Capsule or slime layer
* Facultative intracellular pathogen
2. Leukocidins destroy white blood cells
3. IgA proteases destroy some antibodies (IgA)
-this is the most abundant in the body
4. Elastase inactivates complement proteins
5. Long polysaccharide chains in LPS prevent MAC insertion into membrane
-gram negative bacteria
6. Inhibition of IFN production
-this is for viruses, helps neighboring cells
Phases of infectious disease: - answer1.Incubation period→ 3-7 days where you don't
know you've been infected
2.Prodormal period→ start to feel a little tired
3.Period of illness→ Symptomatic (sore throat, congestion)
4.Convalescent→ non diseased, disability, death
