Streptococci

Question 1

What type of bacteria are streptococci?

Answer 1

Gram positive cocci

Question 2

How can streptococci be classified?

Answer 2

Haemolysis
Lancefield
Sherman

Question 3

How is streptococci classified by haemolysis?

Answer 3

Alpha haemolysis
Beta haemolysis
Non-haemolytic

Question 4

What is an example of an alpha haemolytic streptococcus?

Answer 4

Strep pneumoniae

Question 5

What is an example of a beta haemolytic streptococcus?

Answer 5

Strep pyogenes

Question 6

What is an example of a non-haemolytic streptococcus?

Answer 6

Enterococcus faecalis

Question 7

What is the Lancefield classification?

Answer 7

Serological classification of beta haemolytic streptococci based on cell wall antigens

Question 8

What is the Sherman classification?

Answer 8

Split into viridans and pyogenic

Question 9

What is strep pyogenes?

Answer 9

Lancefield group A beta-haemolytic streptococcus

Question 10

What are the virulence factors of strep pyogenes?

Answer 10

Hyaluronic acid capsule 
M protein 
Adhesins 
Streptolysins O+S
DNAses A, B, C, D
Hyaluronidase
Streptokinase

Question 11

What is the action of Hyaluronic acid capsule?

Answer 11

Inhibits phagocytosis by neutrophils and macrophages

Question 12

What is the action of M protein?

Answer 12

Resistance to phagocytosis by inhibiting activation alternative complement pathway

Question 13

What is the action of adhesins?

Answer 13

Aid adherence

Question 14

What is the action of streptolysins?

Answer 14

Lysis of RBCs, neutrophils and platelets

Question 15

What is the action of DNAses?

Answer 15

Degradation of DNA

Question 16

What is the action of hyaluronidase?

Answer 16

Degradation of hyaluronic acid

Question 17

What is the action of streptokinase?

Answer 17

Dissolution of clots through conversion of plasminogen to plasmin

Question 18

What condition is caused by strep pyogenes?

Answer 18

Streptococcal pharyngitis

Question 19

How is strep pharyngitis spread?

Answer 19

Droplet spread

Question 20

What are the clinical features of strep pharyngitis?

Answer 20

Abrupt onset sore throat
Maliase
Fever
Exudate on tonsils

Question 21

What are complications of strep pharyngitis?

Answer 21

Scarlet fever 
Peritonsillar abscess
Retropharngeal abscess 
Mastoiditis 
Meningitis
Acute rheumatic fever
Acute post-strep GN

Question 22

What is scarlet fever?

Answer 22

Infection with streptococcal pyrogenic exotoxin strain of strep pyogenes

Question 23

What are the clincal features of scarlet fever?

Answer 23

High fever
Widespread rash
Sepsis

Question 24

What is acute rheumatic fever?

Answer 24

Inflammation of the heart, joints and CNS

Question 25

What is post strep GN?

Answer 25

Acute inflammation of the glomerulus

Question 26

What skin infections are caused by strep pyogenes?

Answer 26

Impetigo Erysipelas Cellulitis Necrotising fasciitis

Question 27

What is impetigo?

Answer 27

Childhood infection

Question 28

What is erysipelas?

Answer 28

Dermis infection with lymphatic involvement Affects face and lower limbs

Question 29

What is cellulitis?

Answer 29

Skin and subcutaneous tissue infection

Question 30

What is necrotising fasciitis?

Answer 30

Infection of deeper subcutaneous tissue and fascia

Question 31

What is streptococcal toxic shock syndrome?

Answer 31

``` Deep tissue infection - strep pyogenes + Bactaraemia + Vascular collapse + Organ failure ```