Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

+ MICB 202 Final > Bacteria Chapter 12: Capsule as Virulence Factor > Flashcards

Bacteria Chapter 12: Capsule as Virulence Factor Flashcards

1
Q

What do polysaccharide capsules do?

A
  • prevents phagocytosis — attachment and engulfment by neutrophils or macrophages
  • prevent other host cellular immune responses
  • prevent deposition of antibodies and complements on bacterial surface — avoids complement-mediated killing
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What bacteria uses capsule to avoid phagocytosis by host macrophages?

A

Streptococcus pneumoniae

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What are S. pneumoniae characteristics?

A
  • non-motile
  • non-sporulating
  • Gram-positive
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is S. pneumoniae sensitive to?

A
  • heat
  • cold
  • drying
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How is S. pneumoniae transmitted?

A

close person-to-person contact with respiratory droplets

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are the major virulence factors of S. pneumoniae?

A
  • polysaccharide capsule
  • adhesins
  • pneumolysin
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is pneumolysin?

A

toxin that binds to cholesterol in host cell membrane and disrupts them by forming pores

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What are some diseases caused by S. pneumoniae?

A
  • otitis media (ear infection)
  • pneumonia (inflammation of lungs)
  • bacteremia (bacteria in blood)
  • meningitis (inflammation of membrane surrounding brain and spinal column)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

S. pneumoniae causes more deaths than any other vaccine-preventable disease

A

-

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does S. pneumoniae do as a transient member of microbiota?

A

colonizes nasopharynx of 40% of healthy adults and children with no adverse effects

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What does S. pneumoniae do as an opportunistic pathogen?

A

common bacterial complication of influenza and measles infections

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Why are smokers more at risk of S. pneumoniae infection?

A

cigarette smoke can injure airways and damage cilia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why are alcoholics at increased risk of S. pneumoniae infection?

A

alcohol acts as sedative and can diminish reflexes that trigger coughing and sneezing

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What are the minimum criteria for identification of S. pneumoniae?

A

(observe sputum, blood, or CSF)

  • Gram-positive staining
  • hemolytic activity
  • bile sensitivity
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What are the different types of hemolysis that S. pneumoniae may cause?

A
  • alpha hemolysis
  • beta hemolysis
  • gamma hemolysis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is alpha hemolysis?

A

in aerobic conditions:

partial or greening hemolysis from reduction in RBC hemoglobin

17
Q

What is beta hemolysis?

A

in anaerobic conditions:

complete lysis of RBCs surrounding colony

18
Q

What is gamma hemolysis?

A

lack of hemolysis of RBCs around the colony

19
Q

What problems may arise when diagnosing S. pneumoniae?

A
  • bacteria can be difficult to grow, therefore a negative result does not necessarily rule out pneumonococcal pneumonia
  • positive culture from sputum sample may be the result of contamination from bacteria in the mouth of a colonized patient
20
Q

What is used for treatment of S. pneumoniae?

A
  • penicillin & penicillin-derivatives used to work well, but penicillin-resistant strains are becoming more common
  • erythromycin or tetracycline are alternative treatments, but there’s also resistance to these
21
Q

What does the current vaccine for S. pneumoniae contain?

A

purified, capsular polysaccharide antigens of 23 types of S. pneumoniae

  • cross-reactivity occurs for several of the capsular types
22
Q

What is cross-reactivity?

A

antibody against one serotype will bind to another serotype because of a shared epitope

23
Q

Is the current S. pneumoniae vaccine given to everyone?

A

no — only high-risk individuals

24
Q

Does the current vaccine elicit a strong immune response? Why?

A

no — polysaccharides are less immunogenicity than proteins

especially true in high-risk groups

25
Q

What does the conjugate vaccine for S. pneumoniae consist of?

A

polysaccharide antigens covalently bonded to proteins (to make the vaccine more immunogenic)

covers only 7 capsular types

26
Q

Compare the mechanism of immunogenecity of polysaccharide vaccines (PPV) and polysaccharide-protein conjugate vaccines (PCV).

A

PPV: T cell independent B cell activation

  • B cell → plasma cell →IgM
  • not effective in children < 2 years old
  • no memory effect

PCV: T cell dependent B cell activation

  • APC + T cell interaction + B cell interaction → plasma cell → IgG
  • B cells also become memory B cells
  • effective in children < 2 years old
  • has memory effect
27
Q

Is the capsule of S. pneumoniae toxic?

A

non-toxic and does not induce inflammatory response

28
Q

How can different capsular types be identified?

A

serological testing

  • sample of bacterial colony is mixed with a specific monoclonal antibody
  • positive test is indicated by capsule swelling, which can be viewed under a phase-contrast microscope
29
Q

What is the essential determinant of the virulence of S. pneumoniae? Why?

A

capsule

  • encapsulated = pathogenic
  • mutant without capsule = non-pathogenic
30
Q

What is the primary reason S. pneumoniae can invade and grow?

A

their resistance to host phagocytic responses

  • antibodies and/or complement cannot bind to bacterial cell surface
  • capsule interferes with phagocytosis by preventing C3b opsonization of bacteria and formation of C3 convertase that would normally result in MAC
31
Q

Can S. pneumoniae be part of the microbiota of healthy people?

A

yes

32
Q

The vaccine against S. pneumoniae consists of only 23 of the 90 possible capsule types, yet it induces humoral immunity to more than the 23 capsules types present in the vaccine. How would you explain this observation?

A
  • many of the polysaccharides may share a common structure
  • antibody produced to one specific polysaccharide may cross-react with other polysaccharides that have similar molecular structure
  • binding of these cross-reacting antibodies to bacteria with capsule types not present in the vaccine may not be precise, but is adequate to opsonize bacteria so that phagocytic cells can engulf it

+ MICB 202 Final (20 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions