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    Streptococcus

       Hugh B. Fackrell
    Filename:Strept.ppt




                 5/8/2013
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        Streptococcus Outline
     Streptococcus Characteristics
     Streptococcal Diseases




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        Streptococcus: characteristics

     Genus definition
     Growth requirements
     Capsule
     Colonial morphology
     Hemolysis
         Destruction   of RBCs
       Hemolysins
         molecules   that destroy RBCs
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         Streptococcus
         Genus Definition

     Gram +ve cocci, chains or
      pairs
     Catalase -ve facultative
      anaerobes
         some strictly anaerobic
         some capnophilic (CO2)

     Ferment sugars to mixed
      acids and ethanol
     Lancefield group D is motile
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        Fastidious

     Most Streptococci are
      fastidious in their
      growth requirements
     Grow poorly on
      nutrient agar
     Grow well on blood
      agar

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      Capsule

   Made of hyaluronic acid:
     polymer of glucuronic acid &
      N-acetylglucosamine
   Non immunogenic
     hyaluronic   acid intercellular
      cement
   detected only in young(2-4 h)
    broth cultures
     bacteria   produce hyaluronidase
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    Colonial Morphology

 GLOSSY: no capsule,
  colonies small
 MUCOID: capsule,
                        Glossy
  colonies are large,       Mucoid
  glistening, viscous
 MATT:capsule, older
  colonies are dried,
  flatter rougher

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        Two Forms of Hemolysis


                               Alpha Hemolysis
                               Greening “viridans”




             Beta Hemolysis
                Clearing

(Gamma hemolysis = no lysis)
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    Streptococcal Beta Hemolysis

      Two hemolysins
      Both cause clearing
      Both involved in disease




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      Hemolysin S (stable in air)

 Beta hemolysis on blood agar
 Do not develop antibodies
 Induces arthritis
 Two parts
      Carrier
        hemolysin polypeptide
    cell bound hemolysin
      lysesleukocytes and platelets
      stimulates release of lysosomal contents   5/8/2013
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            Hemolysin O

          Oxidized  in air
          oxygen labile (reversible)
          Protein
          Cardiotoxic
          patients develop antibodies        Subsurface colony of
          ASOT                                  Streptococcus
                                             producing Hemolysin 0
          cholesterol labile (irreversible)

        Antistreptolysin O test
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         Streptococcus pyogenes
         Suppurative Diseases
        Pharyngitis           Subacute Bacterial
        Scarlet Fever          Endocardititis
        Erysipalas ( St.      Otitis Media
         Antony’s fire)
        Cellulitis
        Puerperal Fever
        Sepsis
        Meningitis
        Pneumonia
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         Diseases of S. pyogenes

        Pharyngitis:                       Scarlet fever:
            incubation period of 2             all of the above plus
             to 4 days                           red rash and red tongue
            sore throat, fever,            Pyoderma
             malaise, headache                  Non-suppurative,
            Erythema of the                     inflammatory:
             pharynx
            cervical
             lymphadenopathy
            diagnosis -- differential
             -- viral pharyngitis
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     Streptococcal Suppuration




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         Puerperal Fever

        “Childbirth Fever”              S. pyogenes Not
            Semmelweis                   isolated from vagina
        Membranes of genital             of healthy females
         tract ruptured                   before birth
            fulminating septicemia          50-60% from physician
            fatal 24-48 hr                  rest from own nose &
                                              throat
        S. pyogenes 60-75%
         of cases
            Anaerobic streptococci
             20-25%
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     Post vaccination Streptococcal
     Infection




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     Streptococcal Cellulitis




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     Scarlet Fever
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         Scarlet Fever Rash

        Peticial
         hemorrhage
          Pinpoint
          Subcutaneous

        Erythrogenic toxin
          Scarletina toxin
          causes rash
          associated with a
           temperate phage
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     Scarlet Fever




                     Strawberry Tongue


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         Schultz-Charlton test

      Inject 0.1 ml antitoxin subcutaneously
      Rash fades after 6-8 hours (possible delay
       14 h)
      Differentiates from other similar rashes




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          Erysipalas

    Secondary invasion
      minor    original lesion
    Skin reddened thickened
      later   purple
    Bacteria only in advancing
     edge



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         Erysipalas: butterfly rash

        Butterfly rash
          common   near nose
          spreads after 4-6 days

      Septicemia common
       complication
      No toxin
      No immunity
          repeated   attacks
           possible                   5/8/2013
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     Rheumatic Fever

      autoimmune
      acute glomerulonephritis
      Acute, non suppurative
      post streptococcal inflammation
          Joints,heart valves,myocardium,nerves
             chorea- inflammation of nerves




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         Scarred heart valves

      reduced cardiac output
      heart failure
      Mitral valve stenosis
        edema, hypertension, hematuria and
         proteinuria



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     Rheumatic Endocarditis



 Scarred heart valves




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         Rheumatic fever
         latent period
      Latent period 2-4 weeks
      same after repeated infections
            not immunological
        Antibiotics taken during first week of
         pharyngeal infection
          Drop Steptococcal count
          Block rheumatic fever



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         Aschoff Bodies

      Inflammation of myocardium
      Mononuclear cell infiltration
      Granuloma-like nodules
      Characteristc of rheumatic fever




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         Streptococcal Antigens
      Lancefield groups
      M antigens
      T antigens
      R antigens




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     Streptococcus
     Lancefield Groups

      Rebecca Lancefield
      Grouped by presence of distinctive cell wall
       antigens
          Polysacchardies   or glycero teichoic acids
        Antigens labelled A-T
          exclude   I&J
        Group A Streptococci Clinically Important

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         Lancfield Groups

      S. pneumoniae N/A
      S.pyogenes -- Lancefield Group A
      S.agalactiae -- Lancefield Group B
      Enterococcus-Lancefield Group D
      Viridans group




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         Group A Streptococci

        S. pyogenes Group A
          clinically   important
      Lancefield grouping time
       consuming
      Group A correlated with
       sensitivity to bacitracin
         Bacitracin sensitive Beta hemolytic Strept reported
                          as Group A Strept
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         Group D Streptococci

        glycerol teichoic acid -        Disease:
         - associated with the               urinary tract infection
         cytoplasmic                         intra-abdominal
         membrane                             abcesses
            Streptococcus bovis,            wound infection
             Enterococcus faecalis,          Endocarditis
             Enterococcus faecium
            resist bile and high
             concentrations of
             sodium chloride

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         M antigens
        proteins of the pilus
          sensitive to Pepsin & Trypsin
          soluble at pH 2
          50 types

        Involved in rheumatic fever
          5-8types
          Antibodies neutralize streptococcal infections



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         Pathogenesis


      capsule -- non-immunogenic
      M Protein -- antiphagocytic, anticomplementary
      Lipoteichoic acid (LTA):
          mediates   adherence to epithelial cells
        LTA binding protein
          Hostcell membrane:
          Deacylated LTA


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         Enzymes

        Streptokinase A & B:
          lyse   blood clots
        DNA ase:
          depolymerase    DNA in pus
        Hyaluronidase:
          hyaluronic   acid
        DPN ase

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       Lab diagnosis

 Gram stain -- good in cases of pyoderma
 fluorescent antibody
               of antibodies to Streptolysin O ASO
      detection
      3-4 weeks after exposure

    Culture:
      swab the lesion directly
      blood agar plates - hemolysis

    Eliza
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     S. pneumoniae




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         Streptococcus pneumoniae

      Gram positive cocci in pairs, singles, short
       chains
      alpha hemolysis -- aerobic
      beta hemolysis -- anaerobic
      capsule -- immunogenic (84 serotypes)




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         Diseases:

      Pneumonia -- inflammation of the lungs
       with exudation and consolidation
       (solidification)
      Sinusitis
      Meningitis
      Bacteremia




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     Pathogenesis

  virulence factor, capsule -- prevents
   phagocytosis
  Pneumolysin is a temperate and oxygen labile
   hemolysin
  Purpura-producing principal is released during
   cell autolysis
  Neuraminidase -- glycoproteins and glycolipids
  Autolysins, amidases -- autolyse peptidoglycan
   layer                                       5/8/2013
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     Mechanisms of Pathogenicity

      aspiration of S. pneumoniae, an endogenous
       oral organism
      organism colonizes the oropharynx
      epiglottal reflex, coughing is inhibited




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     Lobar Pneumoniae

            multiplication in the alveolar spaces
            viral infection frequently precedes
             bacterial infection
            highly invasive due to capsule
            bacteremia common
            Meningitis -- most often in children
            Treatment:
                Penicillin,   Erythromycin
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         Laboratory Diagnosis

      sputum -- gram+ cocci, lancet
       shaped,capsule, may appear over-
       decolourized
      alpha-hemolytic, optochin sensitive
      Quellung reaction -- specific antiserum to
       capsular polysaccharide
      capsular antigen can be detected by very
       sensitive immunologic tests
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     The End




        5/8/2013

				
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