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Quiz 3 Microbiology > streptococcus, pneumococci, listeria, anthrax > Flashcards

streptococcus, pneumococci, listeria, anthrax Flashcards

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Biology 101 flashcards
1
Q

What is the meaning of beta, alpha and gamma hemolysis?

A

Beta hemolysis: complete hemolysis
alpha hemolysis: partial hemolysis
gamma hemolysis: no hemolysis

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2
Q

What is another name for group A strep? (GAS)

A

streptococcus pyogenes

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3
Q

How would you distinguish between group A and group b strep?

A

Group A strep is sensitive to bacitracin while group B strep is not.

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4
Q

What does the CAMP test identify? How does it work?

A

Identifies group B strep. Camp factor damages the RBC, which when combined with the enzyme secreted by S. aureus, creates a zone of hemolysis.

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5
Q

What is another test to differentiate GBS?

A

Hippurate hydrolysis.

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6
Q

What kind of hemolysis would you see with group A/B strep?

A

Group A and B strep both show alpha hemolysis. However, the field of clearance is larger with group A strep

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7
Q

If strep tests positive for hydrolysis of esculin in bile salts, what species would you suspect?

A

Group D strep: Enterococcus faecalis will hydrolyze and turn the tube brown.

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8
Q

Name all the species within Groups A, B, and D streptococci

A

Group A strep: streptococcus pyogenes
Group B strep: streptococcus agalactiae
Group D strep: 1. Enterococcus: E faecalis
2. Non-enterococcus: streptococcus bovis

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9
Q

What are the main differences between enterococcus and non-enterococcus strep?

A 
Enterococcus: Growth in high salt medium
Resistant to antibiotics
Causes UTI, bacteremia, and endocarditis
Non-enterococcus: Lack of growth in high salt medium
Sensitive to penicillin
Causes endocarditis
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10
Q

What are the nontypeable streptococci species?

A

Strep pneumoniae

Strep viridans

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11
Q

What is unique about the morphology of S. pneumoniae?

A

lancet-shaped diplococci

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12
Q

What are two methods of distinguishing S. pneumoniae from S. viridans?

A
  1. Strep pneumoniae is sensitive to optochin

2. Strep pneumoniae is lysed by bile

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13
Q

Where is each species of strep localized to, normally?

A 
group A strep: oral flora (less common) 
group B strep: vaginal flora (less common)
group D strep: colonic flora
S. pneumoniae: oral flora (less common)
S. viridans: oral flora
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14
Q

What is the morphology of most strep species?

A

Gram + cocci in chains (exception is strep pneumoniae)

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15
Q

Are most streptococci catalase positive or negative?

A

Catalase negative

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16
Q

What kind of hemolysis will you observe with group A strep?

A

beta hemolysis

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17
Q

What is the significance of the M protein for S pygenes?

A

Antiphagocytic molecule. Specific types cause rheumatic fever/glomerulonephritis

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18
Q

Does Group A strep have a capsule? a pilus?

A

Yes, has a capsule composed of hyluronic acid

Also has a pilus for adhesion to pharyngeal cells

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19
Q

What are the three types of diseases caused by GAS?

A
  1. Pyogenic diseases
  2. Toxigenic diseases
  3. immunologic diseases
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20
Q

Give an example of pyogenic diseases caused by GAS

A

pharyngitis
impetigo and cellulitis
necrotizing fasciitis
pneumonia,meningitis

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21
Q

Give examples of toxigenic diseases caused by GAS

A

scarlet fever

toxic shock syndrome

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22
Q

Which proteins in GAS help with adhesion to host cells?

A

M protein
Protein F
lipoteichoic acid

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23
Q

Which proteins help with evasion of host defenses?

A

capsule, M protein

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24
Q

Which toxins released by GAS are related to pyogenic inflammation?

A 
hyaluronidase
streptokinase
streptodornase
streptolysin O
streptolysin S
exotoxin B
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25
Q

Which toxins released by GAS are related to toxigenic disease?

A 
erythrogenic toxin (scarlet fever)
pyrogenic exotoxin (TSS)
These are both superantigens
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26
Q

Does isolation of group A strep in a nontoxic individual indicate infection?

A

No

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27
Q

What does scarlet fever look like?

A

sandpaper like rash all over

Pastia’s lines (red lines at the axillary and inguinal regions)

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28
Q

How soon after a GAS pharyngeal infection would you see rheumatic fever?

A

2 weeks

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29
Q

What is the cause of Rheumatic fever?

A

streptococcal M proteins react with antigens in the joint, heart, and brain tissues

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30
Q

How can you prevent rheumatic fever?

A

By treating GAS within 8 days of onset.

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31
Q

How soon after a GAS skin infection would you expect to see acute glomerulonephritis?

A

2-3 weeks

32
Q

What is the point of the ASO titer?

A

Confirmat previous/recent streptococcal infection

33
Q

What are the symptoms of acute glomerulonephritis?

A

hypertension, edema, smoky urine

34
Q

What are the four ways in which you could diagnose GAS?

A
  1. culture skin/pharynx, grow, check for beta hemolysis and inhibition by bacitracin
  2. rapid strep test
  3. culture invasive tissue
  4. elevated ASO titer
35
Q

How do you treat group A strep?

A

penicillin G or erythromycin

36
Q

What are the symptoms of GBS?

A
  1. neonatal sepsis/meningitis

2. postpartum endometritis/wound infection in adults

37
Q

How do you treat GBS?

A

penicillin or ampicillin

38
Q

What kind of hemolysis do you see with group D strep?

A

alpha or gamma hemolysis

39
Q

Where are Group D streptococci found? What unique property do they have that allows them to grow there?

A

Colonic bacterial flora

Has the ability to grow in bile

40
Q

How do you treat group D strep?

A

If enterococci: use vancomycin + aminoglycoside

If S. bovis, use penicillin

41
Q

You observe strep species that is lysed by bile and inhibited by optochin. What do you suspect? What kind of hemolysis would you expect?

A

Strep pneumoniae. Alpha hemolytic colonies.

42
Q

What kind of hemolysis does strep pneumoniae have?

A

alpha hemolysis

43
Q

What is the quellung reaction?

A

Rxn where antibody binds to bacterial capsule and allows the capsule to be visualized.
Basis for typing reaction. If there is no quellung rxn, means bacteria has no capsule

44
Q

What are the pathogenic factors of S. pneumoniae?

A

lipoteichoic acid
pneumolysin (alpha hemolysis)
IgA protease (cleaves mucosal igA for better colonization)

45
Q

How do you treat S. pneumoniae?

A

Otitis media: amoxicillin
pneumonia: fluoroquinolone and amox
Meningitis: vancomycin + ceftriaxone

46
Q

What are the two pneumococcal vaccines? Which is more effective for whom?

A

Pneumococcal polyvalent: (T cell independent) better for elderly

Pneumococcal conjugate: (T cell dependent): better for children under 2

47
Q

What kind of hemolysis does strep viridans produce?

A

alpha hemolysis

48
Q

What is the response of strep viridans to bile/optochin?

A

Not lysed by bile. Resistant to optochin

49
Q

What are the important species within strep viridans?

A

S. sanguis
S. mutans
S. mitis

50
Q

We know that strep viridans is an important part of the oral flora. What is it clinically relevant?

A

It can enter the blood stream after dental surgery to cause endocarditis

Can also cause oral abscess that can lead to sinus/brain abscess after dental surgery

51
Q

How do you treat strep viridans?

A

Penicillin for abscess. Penicillin/vancomycin for endocarditis.

52
Q

What is the morphology of Bacillis anthracis?

A

Large gram positive rods, spore-forming, aerobic

53
Q

What would happen if the anthrax colonies were plated on blood agar?

A

no hemolysis

54
Q

What is unique about the anthrax capsule?

A

Made up of poly-glutamic acid

55
Q

What is a risk factor for developing anthrax?

A

Exposure to grazing animals or their products: hides

56
Q

What is unique about anthrax spores?

A

They are centrally located

57
Q

What are the important factors in the pathogenesis of anthrax?

A
  1. Protective antigen: Forms pores in macrophages
  2. Edema factor: Causes edema in association with PA adenylate cyclase
  3. Lethal factor: Lethal in association with PA phosphokinase of MAPK pathway
58
Q

What are the clinical syndromes of anthrax?

A
  1. cutaneous anthrax
  2. inhalation anthrax
  3. gastrointestinal anthrax
59
Q

How would you treat and prevent anthrax?

A
  1. Cipro/doxycycline

2. There is also a vaccine, which is not commonly used

60
Q

What are the properties of listeria monocytogenes?

A

Small aerobic gram + rod. Non spore forming

61
Q

Where is listeria monocytogenes commonly found?

A

animals, plants, unpasteurized milk and cheese. Commonly found in refridgerated foods because it grows well at low temperature.

62
Q

Is listeria motile?

A

Yes. tumbles!

63
Q

What happens if you plate listeria on a blood agar plate?

A

narrow zone of beta hemolysis

64
Q

Describe the pathogenesis of listeria

A

Invades mononuclear phagocytic cells (macrophage)

  • Grows intracellularly
  • Evades endosomes through listeriolysin O
65
Q

What are the clinical symptoms of listeria?

A

Neonatal sepsis and meningitis

or in immunocompromised host

66
Q

How do you treat listeria?

A

Ampicillin

trimethoprim-sulfamethoxazole

67
Q

What is the most important virulence factor of group A strep?

A

M protein. It determines whether the pt will later have rheumatic fever vs glomerulonephritis because it is an important antigen.

68
Q

What does steptolysin O do?

A

hemolysin it is oxygen-labile and an important antigen

69
Q

What is streptolysin S?

A

Oxygen stable hemolysin. NOT antigenic

70
Q

pyrogenic exotoxin A

A

Toxin responsible for streptococcal toxic shock syndrome. Similar to staphylococcal TSST. Also a superantigen

71
Q

Exotoxin B

A

Responsible for Strep A’s “flesh eating behavior”

72
Q

What is the most common cause of bacterial pharyngitis?

A

Streptococcus pyogenes

73
Q

What bacteria can form impetigo–honey colored crusted lesions of the skin?

A

Either Staph aureus or GAS

74
Q

What is the most common cause of endocarditis?

A

Viridans strep. Common after dental surgery

75
Q

A patient has endocarditis. What are the possible organisms that could be responsible?

A
  1. Strep viridans (think oral surgery)
  2. Staphylococcus aureus
  3. Staphylococcus epidermidis
  4. Enterococcus
  5. Group A strep

Evidence of endocarditis=splinter hemorrhage and enlarged spleen

Quiz 3 Microbiology (4 decks)

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