19. Streptococci

Question 1

Is streptococci gram positive or negative?

Answer 1

Gram positive

Question 2

Is streptococci chains or clusters?

Answer 2

Chains

Question 3

What are the classifications of streptococci by haemolysis?

Answer 3

Alpha haemolysis - partial breakdown (green)
Beta haemolysis - complete breakdown (white)
Gamma haemolysis - non-haemolytic (no change)

Question 4

What is the action of hyaluronic acid capsule virulence factor?

Answer 4

Inhibits phagocytosis by neutrophils and macrophages

Question 5

What is the action of M protein virulence factor?

Answer 5

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

Question 6

How does hyaluronidase virulence factor work?

Answer 6

Degradation of hyaluronic acid in connective tissue

Question 7

What is the action of streptokinase virulence factor?

Answer 7

Dissolution of clots though conversion of plasminogen to plasmin

Question 8

What is streptococcal pharyngitis caused by?

Answer 8

Streptococcus pyogenes

Question 9

How is streptococcal pyogenes transmitted?

Answer 9

Droplet spread

Question 10

What happens in untreated patients with streptococcal pharyngitis?

Answer 10

Develop M protein specific antibody

Question 11

What are the clinical features of streptococcal pharyngitis?

Answer 11

Abrupt onset sore throat
Malaise, fever, headache
Lymphoid hyperplasia
Tonsillipharyngeal exudates

Question 12

What is a possible complication of streptococcal pharyngitis?

Answer 12

Scarlet fever

- due to infection with streptococcal pyrogenic exotoxin strain of S.pyogenes

Question 13

What are the symptoms of scarlet fever?

Answer 13

High fever
Sepsis
Arthritis
Jaundice

Question 14

What are some complications of streptococcal pharyngitis?

Answer 14

Peritonsillar cellulitis/abscess
Retropharyngeal abscess
Mastoiditis, sinusitis, otitis media
Meningitis, brain abscess
Acute rheumatic fever 
Acute post-streptococcal glomerulonephritis

Question 15

What are some of the streptococcus pyogenes skin infections?

Answer 15

Impetigo
Erysipelas
Cellulitis
Necrotising fasciitis

Question 16

What is impetigo?

Answer 16

Childhood infection
Initial skin colonisation, followed by intradermal inoculation
Most common cause of glomerulonephritis

Question 17

What is erysipelas?

Answer 17

Dermis infection with lymphatic involvement
Face, lower limbs
Facial lesions frequently preceded by pharyngitis
Lower limb infection usually secondary to invasion of skin via trauma, skin disease or local fungal infection

Question 18

What is cellulitis?

Answer 18

Skin and subcutaneous tissue infection

Impaired lymphatic drainage and illicit injecting drug use important risk factors

Question 19

What is necrotising fasciitis?

Answer 19

Infection of deeper subcutaneous tissues and fascia
Rapid, extensive necrosis 
Usually secondary to skin break
Severe plain
High fever, high mortality

Question 20

What is streptococcal toxic shock syndrome?

Answer 20

Deep tissue infection with strep pyogenes
AND bacteraemia
AND vascular collapse
AND organ failure