MMI 301-Exam 2-Lecture 12: Streptococci

Card Set Information

Author:
Anonymous
ID:
242871
Filename:
MMI 301-Exam 2-Lecture 12: Streptococci
Updated:
2013-10-25 18:54:28
Tags:
MMI
Folders:

Description:
MMI
Show Answers:

Home > Flashcards > Print Preview

The flashcards below were created by user Anonymous on FreezingBlue Flashcards. What would you like to do?


  1. Significant Streptococcal species
    Pyogenes, agalactiae, and pneumoniae
  2. Doctor who instituted hand cleaning between patients, fought Pyogenes
    Semmelweiss
  3. Historical Classification, Hemolysis Classifications
    • -Separated based on hemolytic activity on blood auger plates
    •      -alpha, beta, or gamma hemolytics       -Alpha:green coloration of surroundings
    • -Beta:Complete lysis, clear surrounding -Gamma:No change
  4. Streptococcal Serology
    • Discovered by Lancefield
    • -Discovered that streptococci possessed unique cell wall carbohydrates
    • -Allowed more specific serotyping
    • -Pyogenes: Group A strep
    • -Agalactiae:Group B
    • -Pneumoniae: Originally classified as
    • Diplococcus, after DNA sequencing went to Streptococcus
  5. Other Strains of Strep
    • -Viridans group: represent oral commensal species
    •     -Cause endocarditis when it gets into blood
    •     -Will attack congenitally abnormal/damaged scarred heart valves
    •            -Stick to valve and multiply
  6. Group A Strep (S. pyogenes)
    • -Capsule, M Protein, lipoteichoic acid, streptolysin O, C5a peptidase, tissue destroying
    • enzymes
  7. Group A Strep (S. pyogenes) M protein
    • -250 different M-protein types
    • -Show differences in repeat regions and binding of host molecules
    • -Binds and inhibits IgA/C4BP to stop classical pathway/IgAmediated phagocytosis
  8. Strep. pyogenes: C5a peptidase/SpeB
    -Destroy C5a/CXC chemokines that serve as signaling molecules
  9. Strep. pyogenes: Cytolytic toxins:
    • -Streptolysin S: is a 2.7 kD modified peptide
    • -Streptolysin O: is a pore-forming toxin (cholesterol-dependent cytolysin)
  10. Strep. pyogenes enzymes: SpeA,
    SpeC, SpeG-M, SmeZ, SSA
    • -Superantigens
    • -Cause release of IL-1, IL-2, IL-6, TNF-alpha, gamma-IFN
  11. Strep pyogenes Epidemiology
    -Group A carried in throat of 15-20% of all children and adults w/o evidence of disease
  12. Strep. pyogenes causes:
    • -Suppurative streptococcal diseases:                                                         
    • -Pharyngitis:Strep_throat                                                           -Scarlet fever: results from erythrogenic toxin
    • -Streptococcal Toxic Shock: fever
    • rash, vomiting, diarrhea, desquamation, renal failure, confusion. Caused by
    • superantigen                                                

    • -Impetigo: pustules around nose and mouth     
    • -Necrotizing fasciitis: Flesh-eating
    • disease. Starts from trauma, excessive pain at site, progresses to blisters on
    • skin/necrosis
  13. Rheumatic Fever
    • -Inflammatory disease of connective tissue, usually manifested on heart valves
    • -Anti-body response to Group A strep antigens leads to cross-reactive antibodies
    •      -attach to connective tissue, leads local complement activation
    •      -destroys tissuse
    •      -seen mostly in 5-15
  14. B. acute Glomerulonephritis (AGN)
    • -Kidneys have filters (glomeruli)
    •      -Attach to small fluid collecting tubes
    •      -Filter blood
    •      -Waste to bladder
    • -Inflammation of glomeruli
    •       -leads to loss of filtration
    •       -Accumulation of waste, kidney failure
    • -Skin or throat Group A is followed by AGN
    •       -Caused by accumulation of Abs-Ags immune complexes in glomeruli
  15. Culture and Identification Group A streptococci
    • -Readily grown on BAP
    • -Beta (occasionally non hemolytic)
    • -Identified (presumptive) with sensitivity to antibiotic bacitracin
    •      -Other betas are resistant
  16. Group B Strep: S. agalactiae Epidemiology
    • Commensal human GI and 10-30% of healthy women
    • Diseases
    • -Neonatal: early onset: Pneumonia from
    • inhaled amniotic fluids/vaginal secretions during birth
    • -Late onset: Intestinal infection,
    • sepsis and meningitis
    • -Postpartum: Mastitis, endometritis,
    • sepsis, meningitis
  17. Lab Identification and Growth
    • -Readily grown overnight on BAP, beta zone
    • -Resistant to bacitracin
    • -Capable of hydrolysis of hippurate, other strep cannot do this
  18. Streptococcus pneumoniae Infections and Disease
    • -Carriage:5-75% depending on time of year/age
    • -Pneumonia:100,000 cases a year, 40,000 deaths
    • -Otitis media:most common cause for visit to pediatrician -Meningitis, sepsis, severe disease
  19. Strept. pneumoniae Capsular polysaccharide
    • -inhibits complement lysis, antibody binding, phagocytosis, > capsule serotypes
    • -Capsular serotype change via cassette type mechanism of genetic recombination
  20. Strep. pneumoniae Pneumococcal surface
    • -PspA: coiled-coil protein
    •     -Bound to choline on bacterial polysaccharides (teichoic/lipoteichoic)
    •     -Inhibits complement lysis
    •     -antibodies to PspA are protective
    •     -many, many serotypes
    • - Other Choline binding proteins (CBPs)
    •     -8-14
    •     -cbpA mutant showed reduced adherence
  21. Strept. pneumoniae virulence mechanism
    • -Pnemolysin
    •      -pore-forming toxin
    •      -Binds Fc of IgG, fixes complement
    •      -Limits inflammatory response
    •      -released by autolysin
    • -IgA protease
    •      -cleaves IgA
    • -Teichoic acid/Lipoteichoic acid:
    •      -Surface polysaccharide carrying phosphorylcholine
    •      -Potentially
    • involved in adherence and invasion
    • -Autolysin
    •      -Division of daughter cells
    •      -Lysis of bacteria in stationary phase
    •      -Release of pneumolysin and possibly other virulence factors
    •      -Autolysin mutants are reduced in virulence in the mouse model
  22. S. pnumoniae Variation: Transformation
    • -Population structure is panmictic (non-clonal)
    • -Pneumococci undergo transformation at high frequency (+95%)
    • -Occurs at late log  phase
    • -Is induced by a secreted peptide (competence factor)
  23. S. pneumoniae: Phase Variation
    • -18% of pneumococcal genes are predicted to phase-vary
    • -Vary between opaque and translucent
    •        -Transparent less virulent
  24. Growth and Laboratory Identification of S. pneumoniae
    • -Readily grown in laboratory
    • -Forms large gooey colonies
    •      -Exhibit alpha hemolysis
    • -Identified by sensitivity to compound Optochin
    • -Serological identification not routine
  25. Most common source of vaccine preventable death in children
    S. pneumoniae
  26. Polysaccharide vaccine for S. pneumoniae
    • -23-valent vaccine available, contains
    • mixture of most common types of capsular polysaccharides
    • -Conjugate vaccine
    •       -2000: 7-valent
    •       -2009: 10-valent
    •       -2010: 13-valent
    • -Implementation of 7-valent vaccine
    • has changed most common serotype to non-7VPCV

What would you like to do?

Home > Flashcards > Print Preview