Group A Streptococci

Question 1

GAS is also known as s. Pyogens.

T/F

Answer 1

True.

Question 2

What are the pyogenic infections of GAS?

Answer 2

Pharyngitis.
Cellulitis.
Necrotizing fascitis.

Question 3

What is the toxin mediated infection caused by GAS?

Answer 3

Scarlet fever.

Question 4

What is the immunological infection caused by GAS?

Answer 4

Glomerulonephritis.

Question 5

What is the epidemiology of GAS?

Answer 5

It’s a URT commensal in 3-5% adults and 10% children.
Transmission is by respiratory droplet spread.

Question 6

What are the risk factors for GAS?

Answer 6

People >65yrs old.
Those with recent VZD infection
HIV+ individuals
Those with diabetes
Heart disease
Cancer
Injection drug use
Those on high dose steroid.

Question 7

In the virulence factors of GAS, what are the somatic constituents?

Answer 7

Hyaluronic capsule
Lipothechoic acid
Fibronectin binding proteins
M proteins
Serum opacity factor

Question 8

Regarding virulence factors of GAS, what are the extracellular products?

Answer 8

Streptolysin O and S
Dnases A-D
Hyaluronidase
Streptokinase
C5a peptidase
Streptococcal superantigens.
Streptococcal pyrogenic exotoxins

Question 9

What is the function of Hyaluronidase?

Answer 9

Facilitates spread through tissues

Question 10

What is the function of Streptokinase in GAS?

Answer 10

Activation of plasminogen to plasmin.

Question 11

Streptococci pyrogenic exotoxins are grouped into?

Answer 11

SpeA, SpeB, speC, speF (superantigen that induces fever).

Question 12

What are the clinical manifestations of GAS?

Answer 12

Pharyngitis-commonest infection.
Scarlet fever.
Rheumatic fever.
Skin manifestations.
Post streptococcal glomerulonephritis
Bacteriemia
Streptococcal TSS

Question 13

What are the examples of skin manifestations in GAS?

Answer 13

Impetigo.
Cellulitis.
Necrotising fascitis.
Eresipelas.
Pyomyositis.

Question 14

What are the suppurative conditions in the clinical manifestation of GAS?

Answer 14

Tonsillitis
Mastoiditis
Retropharyengeal abscess
Peritonsilar abscess
Otitis media
Mastoiditis
Suppurative cervical lymphadenitis
Sinusitis

Question 15

Rheumatoid fever occurs 1-3 weeks after pharyngitis.
True/false

Answer 15

False. 1-5wks

Question 16

Diagnosis of GAS?

Answer 16

Facultative anaerobic, non sporing, non capsulated, catalase negative, gram positive cocci that form long chains when observed on gram stains.

Culture on blood agar produces smooth, circular colonies, usually beta hemolytic.

Sensitive to bacitracin.

Serology is used to diagnose immunological complications.

Question 17

ASOT means?

Answer 17

Anti streptolysin O titre.

Question 18

ASOT and anti Dnase B are used in which dxs?

Answer 18

Throat associated dx and pyoderma associated dx respectively.

Question 19

What is the treatment of GAS?

Answer 19

PO phenyloxymethyl penicillin in mild cases and IV benzyl penicillin in severe cases.

In penicillin allergic pts, use azythromycin, erythromycin or clindamycin.

For Bacteriemia, use IV penicillin and clindamycin.

For necrotizing fascitis, surgical debridement.