Group A Streptococci Flashcards
GAS is also known as s. Pyogens.
T/F
True.
What are the pyogenic infections of GAS?
Pharyngitis.
Cellulitis.
Necrotizing fascitis.
What is the toxin mediated infection caused by GAS?
Scarlet fever.
What is the immunological infection caused by GAS?
Glomerulonephritis.
What is the epidemiology of GAS?
It’s a URT commensal in 3-5% adults and 10% children.
Transmission is by respiratory droplet spread.
What are the risk factors for GAS?
People >65yrs old.
Those with recent VZD infection
HIV+ individuals
Those with diabetes
Heart disease
Cancer
Injection drug use
Those on high dose steroid.
In the virulence factors of GAS, what are the somatic constituents?
Hyaluronic capsule
Lipothechoic acid
Fibronectin binding proteins
M proteins
Serum opacity factor
Regarding virulence factors of GAS, what are the extracellular products?
Streptolysin O and S
Dnases A-D
Hyaluronidase
Streptokinase
C5a peptidase
Streptococcal superantigens.
Streptococcal pyrogenic exotoxins
What is the function of Hyaluronidase?
Facilitates spread through tissues
What is the function of Streptokinase in GAS?
Activation of plasminogen to plasmin.
Streptococci pyrogenic exotoxins are grouped into?
SpeA, SpeB, speC, speF (superantigen that induces fever).
What are the clinical manifestations of GAS?
Pharyngitis-commonest infection.
Scarlet fever.
Rheumatic fever.
Skin manifestations.
Post streptococcal glomerulonephritis
Bacteriemia
Streptococcal TSS
What are the examples of skin manifestations in GAS?
Impetigo.
Cellulitis.
Necrotising fascitis.
Eresipelas.
Pyomyositis.
What are the suppurative conditions in the clinical manifestation of GAS?
Tonsillitis
Mastoiditis
Retropharyengeal abscess
Peritonsilar abscess
Otitis media
Mastoiditis
Suppurative cervical lymphadenitis
Sinusitis
Rheumatoid fever occurs 1-3 weeks after pharyngitis.
True/false
False. 1-5wks
Diagnosis of GAS?
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.
ASOT means?
Anti streptolysin O titre.
ASOT and anti Dnase B are used in which dxs?
Throat associated dx and pyoderma associated dx respectively.
What is the treatment of GAS?
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.
