Medical Archive

H153 Streptococcal Infections

Introduction

Lancefield Group Representative Species Hemolytic Pattern Typical Infections 
A S. pyogenes ? Pharyngitis, impetigo, cellulitis, scarlet fever 
B S. agalactiae ? Neonatal sepsis and meningitis, puerperal infection, urinary tract infection, diabetic ulcer infection, endocarditis 
C, G S. dysgalactiae subsp. equisimilis ? Cellulitis, bacteremia, endocarditis 
D Enterococci a : E. faecalis, E. faecium Usually nonhemolytic Urinary tract infection, nosocomial bacteremia, endocarditis 
Nonenterococci: S. gallolyticus (formerly S. bovis) Usually nonhemolytic Bacteremia, endocarditis 
Variable or nongroupable Viridans streptococci: S. sanguis, S. mitis ? Endocarditis, dental abscess, brain abscess 
Intermedius or milleri group: S. intermedius, S. anginosus, S. constellatus Variable Brain abscess, visceral abscess 
Anaerobic streptococci b : Peptostreptococcus magnus Usually nonhemolytic Sinusitis, pneumonia, empyema, brain abscess, liver abscess 

DDx: by PYR test. (positive if produces �pyrrolidonyl arylamidase�. Group A, D produce.)
Due to not very specific bacitracin test.

Group A streptococci

S.pyogenes

m/c bacterial cause of acute pharyngitis. ASO titer ?
Throat culture?? ??? ??? latex agglutination? ?? ?
Tx: Pc / Benzathin Pc G / Erythromycin / TSS?? IV ?-globuline (Cx, rheumatic fever ??? ? ??)

Pathogenesis

Clinical manifestations

Pharyngitis ???

Rheumatic fever, PSGN ?? ?? 1? benzathine PcG (IM) or PcV (PO)? 10?? ??.

Scarlet fever ???

  • Delayed-type immune response
  • Incubation
    • ?? 3?
  • Triad
    • ??: ???? ????, penicillin ??? ????. (???? ??? ?? ??)
    • ???: ??, ?? ??? ?? ??? ??? ? ??, ??? ??
    • ?? ? ??
  • Rash
    • Triad ? ?????
      • Neck, armpit, groin?? ?? – scarlet spots or blotches
    • 24hr ? ??? ??
      • Sunburn with goose pimples (�sandpaper-like� rash)
      • Blanching – ????? ??? ??
      • ? ?? sparing – circumoral pallor
      • White ? red strawberry tongue
      • Tender, anterior cervical lymphadenopathy
    • 7? ?? ? desquamation start
      • Pronounced in the armpits, groin, and tips of the fingers and toes.
  • Diagnosis
    • Rapid streptococcal antigen test or throat culture.
    • ??? ??? 80%? 3-6? ? ASO titer ?
Treatment
  • Indication: All cases of scarlet�fever�should be treated with�antibiotics, both to prevent complications and to prevent transmission
  • DOC: oral�penicillin V x 10 days (KMLE: amoxicillin x 10 days)
  • Second line: IM benzathine penicillin G
  • Alternative�antibiotics
    • In patients�allergic to�penicillin:�macrolides
    • In cases of recurrence due to�antibiotic�resistance:�cephalosporins
  • After�24 hours�of�antibiotic�treatment, the patient is no longer infectious and may return to day care or school!
??? Cx1? ?AOM
???? Cx2-3?PSGN, rheumatic fever

Skin and soft tissue infections

  • Impetigo(pyoderma)
  • Cellulitis
    • TOC: methicillin/nafcillin/oxacillin.
    • Cefazolin, ampicillin/sulbactam? ?? ??.
  • Deep soft-tissue infections; necrotizing fasciitis
    • ?? ??? anesthesia: ?? ??? infarction – ?? ??? ?? ??.

PSGN? ?? ???? rheumatic fever (-)

Pneumonia and empyema

Bacteremia, puerperal sepsis, and streptococcal toxic shock syndrome

After GAS pharyngitis (P), After GAS skin infections (S)

  • Non-suppurative sequela
    • Acute rheumatic fever (P)
    • PSGN (P)(S)
      • 2 weeks after pharyngitis, impetigo
      • Early antibiotics have not been shown to reduce the risk.
  • Suppurative
    • Cellulitis (S)
    • Streptococcal pyoderma ?. (? PSGN)
    • Necrotizing fascitis, myositis-myonecrosis? deep tissue infection
      • ? ??? ? ???? ??? tenderness, pain ?

Prevention

Streptococci of groups C and G

Group B streptococci

Narrow zone of beta-hemolysis (clear) when plated on blood agar.
Production of CAMP factor, a phospholipid that enhances the activity of beta-hemolysins secreted by certain strains of Staphylococcus aureus.

Infection in neonates

Infection in adults

Nonenterococcal group D streptococci

Enterococci

GIT, GUT? normal flora
Penicillin, AG, All Cefa? intrinsic resistance ? VRE? ?? ??
(E.faecalis? ???, ampicillin? ????? ??)
??? ???, vancomycin ?? ??, Avoparcin? ??? risk factor
Simple colonization? ? no Tx

AG ?? – PenG + Ampicillin
AG, Pen ?? – Vanc + GM

Viridans and other streptococci

Viridans streptococci

S.mutans, S.mitis

Cause dental caries.

S.sanguinis

Makes dextrans that bind to fibrin-platelet aggregates on damaged heart valves, causing subacute bacterial endocarditis.

Abiotrophia and granulicatella species (nutritionally variant streptococci)

Other streptococci