Brainscape's Knowledge GenomeTM

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


See full index

Semester 2-Infection > Session 6-Streptococci > Flashcards

Session 6-Streptococci Flashcards

1
Q

Describe the gram stain of streptococci

A

Gram positive cocci chains

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

What are the classifications of streptococci by haemolysis?

A

1) alpha haemolysis
2) beta haemolysis
3) gamma haemolysis (non-haemolytic)

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

Give an example of an alpha haemolytic streptococci

A

Viridans streptococci eg. Streptococcus pneumoniae

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

Give an example of a beta haemolytic streptococci

A

Streptococcus pyogenes

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

Give an example of a non-haemolytic streptococcus

A

Enterococcus faecalis

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

Why do alpha haemolytic streptococci look wet?

A

Due to capsule - makes bacteria more virulent because protects bacteria against antibody attack

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the difference between alpha and beta haemolytic streptococci?

A

Alpha - partial breakdown of RBCs

Beta - complete breakdown of RBCs so clear zone around colony

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

What is the:
1) Lancefield antigen
2) Sherman group
Of Streptococci pyogenes?

A

1) A (beta)

2) pyogenic

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the:
1) Lancefield antigen
2) Sherman group
Of Streptococci agalactiae?

A

1) B (beta, gamma)

2) pyogenic

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

What is the:
1) Lancefield antigen
2) Sherman group
Of Streptococci dysgalactiae?

A

1) C, G (beta)

2) pyogenic

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

What is the:
1) Lancefield antigen
2) Sherman group
Of Streptococci pneumoniae?

A

1) NA (alpha)

2) viridans but can be pyogenic

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

What are the virulence factors of streptococcus pyogenes? (8)

A

1) hyaluronic acid capsule
2) M protein
3) adhesins
4) streptolysins O and S
5) DNAses A, B, C and D
6) hyaluronidase
7) streptokinase
8) streptococcal pyrogenic exotoxins

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

What are the actions of the hyaluronic acid capsule of streptococcus pyogenes?

A
  • Inhibits phagocytosis by neutrophils and macrophages

- Poor immunogen because of similarity to human connective tissue hyaluronate

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

What is the action of the M protein of streptococcus pyogenes?

A

-resistance to phagocytosis by inhibiting activation of alternative complement pathway on bacterial cell surface

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the action of streptolysins O and S?

A

Lysis of erythrocytes, neutrophils and platelets

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the action of DNAses?

A

Degradation of DNA, inactivating phagocytosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the action of hyaluronidase?

A

Degradation of hyaluronic acid in CT

18
Q

What is the action of streptokinase?

A

Dissolution of clots through conversion of plasminogen to plasmin

19
Q

What is the action of streptococcal pyrogenic exotoxins?

A

Cleaves IgG bound to group A strep

20
Q

How is streptococcal pharyngitis spread?

A

Thorough droplets - coughing in close range

21
Q

What do untreated patients with streptococcal pharyngitis develop?

A

M protein specific antibody

22
Q

What are the clinical features of streptococcal pharyngitis?

A
  • Abrupt onset sore throat
  • Fever
  • Headache
  • Lymphoid hyperplasia
  • Tonsillopharyngeal exudates
23
Q

How can streptococcal pharyngitis lead to scarlet fever?

A

Infection with streptococcal pyrogenic exotoxins strain of streptococcus pyogenes which is very virulent

24
Q

What are the signs of scarlet fever?

A
  • High fever
  • Sepsis
  • Arthritis
  • Jaundice
25
Q

What are the suppurative complications of streptococcal pharyngitis?

A

1) peritonsillar cellulitis/abscess
2) retropharyngeal abscess
3) mastoiditis, sinusitis
4) meningitis, brain abscess

26
Q

True or false: acute rheumatic fever can follow on from any streptococcal infection

A

FALSE - only from pharyngitis, acute post-streptococcal glomerulonephritis can follow on from any strep infection

27
Q

What is acute rheumatic fever?

A

Inflammation of heart, joints and CNS

28
Q

How can acute rheumatic fever lead to an increased risk of endocarditis?

A

Inflammation of heart valves -> rheumatic heart disease/rheumatic valvular damage -> increased risk of endocarditis

29
Q

What are the possible mechanisms of acute rheumatic fever?

A
  • auto-immune
  • serum sickness (reaction to antigen-antibody complexes)
  • binding of M protein to collagen (provokes immune response because foreign protein)
  • streptolycins O and S induced tissue injury
30
Q

What is acute post-streptococcal glomerulonephritis?

A

Acute inflammation of renal glomerulus

31
Q

Which skin infections can streptococcus pyogenes cause? (4)

A

1) impetigo
2) erysipelas
3) cellulitis
4) necrotising fasciitis

32
Q

What is the most common cause of glomerulonephritis?

A

Impetigo

33
Q

What is erysipelas?

A

Dermis infection with lymphatic involvement on face and lower limbs

34
Q

What is cellulitis?

A

Skin and subcutaneous tissue infection

35
Q

What are the risk factors of cellulitis?

A
  • Impaired lymphatic drainage

- Illicit injecting drug use

36
Q

What is necrotising fasciitis?

A

Infection of deeper subcutaneous tissues and fascia

37
Q

How can necrotising fasciitis be treated?

A
  • surgery to cut away the necrotic tissue

- high dose of IV immunoglobulin, which is full of antibodies which neutralise the strep toxins

38
Q

What is streptococcal toxic shock syndrome?

A
  • deep tissue infection with strep pyogenes
  • bacteraemia
  • vascular collapse (septic shock)
  • organ failure
39
Q

What causes streptococcal toxic shock syndrome?

A

Entry of group A strep into deeper tissues and bloodstream

40
Q

How do streptococcal pyogenic exotoxins cause toxic shock syndrome?

A

Stimulate T cells through binding to MHC class II antigen-presenting cells and V-beta region of T cell receptor, inducing monocyte cytokines and lymphokines

Semester 2-Infection (15 decks)

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