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Microbiology > Chapter 2: Streptococci > Flashcards

Chapter 2: Streptococci Flashcards

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Biology 101 flashcards
1
Q

Streptococci is:

A 
gram-positive
non-motile
catalase negative
aerotolerant anaerobes (grow fermentatively even in the presence of oxygen)
culture on blood enriched medium
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2
Q

All the followings are true exept:
a. α-Hemolytic streptococci cause complete hemolysis of red cells in blood agar, resulting in the appearance of a red pigment that forms a ring around the colony

b. β-Hemolytic streptococci cause gross complete hemolysis of red blood cells, resulting in a clear ring around the colony.
c. γ-Hemolytic no color change or hemolysis in blood agar

A

a:
α-Hemolytic streptococci cause partial hemolysis of red cells in blood agar, resulting in the appearance of a green pigment that forms a ring around the colony

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3
Q

1st step in the classification of streptococci:

A

Hemolysis pattern

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4
Q

True or False:
Many species of staphylococci have a polysaccharide in their cell walls known as C-antigen, which is antigenic and easily extractable with dilute base or Boiling.

A

False:
Many species of streptococci have a polysaccharide in their cell walls known as C-antigen, which is antigenic and easily extractable with dilute acid or Boiling.

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5
Q

The Lancefield scheme classifies primarily ……….. into groups A to H and K to U on the basis of their ……

A

β-hemolytic streptococci, C-antigen

there are 20 C-antigen

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6
Q

Match the following β-hemolytic streptococci with their names:
β-hemolytic streptococci A strep.bovis
β-hemolytic streptococci B strep. agalactiae
β-hemolytic streptococci D strep. pyogenes

A

β-hemolytic streptococci A => strep. pyogenes
β-hemolytic streptococci B => strep. agalactiae
β-hemolytic streptococci D => strep.bovis

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7
Q

Some strains of S. pyogenes cause postinfectious sequelae, including:

A
  • rheumatic fever and

- acute glomerulonephritis.

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8
Q

Structural features involved in the pathology or identification of group A streptococci include:

A
  1. Capsule: Hyaluronic acid identical to human, non-immunogenic, anti-phagocytic
  2. Cell wall
  3. Extracellular products: exotoxins
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9
Q 
Which of the following is not a component of S.pyogens cell wall:
M protein
Hyaluronic acid
Group A-specific C-antigen:
Protein F (fibronectin-binding protein)
A

Hyaluronic acid

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10
Q

M protein:

A
  • S. Pyogenes is not infectious in the absence of M protein.
  • highly variable, especially the N-terminal regions, resulting in over 80 different antigenic types.
  • individuals may have many S. pyogenes infections throughout their lives as they encounter new M protein types
  • anti-phagocytic and they form a coat that interferes with complement binding.
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11
Q

Group A-specific C-antigen is composed of:

A
  • rhamnose and

- N-acetylglucosamine.

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12
Q

All of the followings mediate the attachment of fibronectin in the pharyngeal epithelium except:

a. Protein F
b. Group A-specific C-antigen
c. lipoteichoic acids
d. M proteins

A

b. Group A-specific C-antigen

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13
Q

True or False:
S.pyogenes may simply replicate sufficiently with causing injury in which case the patient is then considered colonized (carrier).

A

False:

it may simply replicate sufficiently without causing injury

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14
Q

True or False:
However, direct inoculation of skin from another person’s infection can lead to:
- streptococcal skin infection and
- soft tissue infection.

A

True

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15
Q

Syndromes caused by pyogenes:

A
  1. Acute pharyngitis or pharyngotonsilitis:
  2. Impetigo
  3. Erysipelas
  4. Puerperal sepsis:
  5. Invasive group A streptococcal disease: Cellulitis or
    “flesh-eating bacteria
  6. Streptococcal toxic shock syndrome:
  7. Post-streptococcal sequelae: a. Acute rheumatic fever. b. Acute glomerulonephritis
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16
Q

Which of the following statements is wrong:

a. S. Pyogenes is a major cause of cellulitis.
b. Pharyngitis is the most common type of S. pyogenes infection.
c. Many strep throats are severe, and many sore throats caused by viruses are mild.

A

c:

Many strep throats are mild, and many sore throats caused by viruses are severe.

17
Q

Treatment of impetigo:
topically
systemically

A
  • topical agent: mupirocin
  • systemically with
    - penicillin or a
    - first-generation cephalosporin: cephalexin,
18
Q

Puerperal sepsis:

A
  • starts during, or soon after, the delivery of a newborn.
  • caused by:
    1) exogenous transmission (by nasal droplets from an infected carrier or from contaminated instruments) or
    2) endogenously (mother’s vaginal flora)
  • a disease of the uterine endometrium in which patients experience a purulent vaginal discharge and are systemically ill.
19
Q

Symptoms of invasive GAS disease:

fhm st

A
  • toxic shock–like syndrome,
  • fever,
  • hypotension,
  • multi-organ involvement,
  • a sunburn like rash
  • or a combination of these symptoms
20
Q

Patients with streptococcal TSS may initially present with:

fn sar

A

flulike symptoms
followed shortly by necrotizing soft tissue infection, shock,
acute respiratory distress syndrome,
and renal failure.

21
Q

Treatment of streptococcal TSS:

A

high-dose of: penicillin G plus clindamycin.

22
Q

Acute rheumatic fever

A
  • autoimmune disease
  • 2 to 3 weeks after start of pharyngitis.
  • caused by cross-reactions
  • fever, rash, carditis, and arthritis, Sydenham’s chorea(uncontrolled movement, loss of fine motor control)
  • preventable if the patient is treated within the first 10 days
23
Q

Acute glomerulonephritis

A
  • 1 week after impetigo or pharyngitis
  • due to a few nephritogenic strains of grp 1 strep
  • Antigen-antibody complexes on the basement membrane of the glomerulus initiate the disease.
  • no evidence that penicillin treatment can prevent it
24
Q

True or False:

Rapid latex antigen kits tests have high specificity but variable sensitivity compared with culture techniques.

A

True

25
Q

specimens for laboratory analysis for strep:

A 
throat swabs, 
pus and 
lesion samples, 
sputum, 
blood, or 
spinal fluid
26
Q

Hemolysis of the blood cells is caused by:

A

steptolysin S

27
Q

True or False:

Group B streptococci are β hemolytic, with larger colonies and less hemolysis than group A

A

True

Microbiology (4 decks)

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