37718007 Streptococci

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    StreptococciStreptococci

    Characters of StreptococciCharacters of Streptococci

    Gram positive cocciGram positive cocci

    11m in diameterm in diameter

    Chains or pairsChains or pairs Usually capsulatedUsually capsulated

    Non motileNon motile

    Non spore formingNon spore forming Facultative anaerobesFacultative anaerobes

    FastidiousFastidious

    Catalase negativeCatalase negative (Staphylococci are catalase positive)(Staphylococci are catalase positive)

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    Classification of StreptococciClassification of Streptococci

    Streptococci can be classified according to:Streptococci can be classified according to:

    Oxygen requirementsOxygen requirements

    Anaerobic (Anaerobic (PeptostreptococcusPeptostreptococcus))

    Aerobic or facultative anaerobic (Aerobic or facultative anaerobic (StreptococcusStreptococcus))

    Serology (Lanciefield Classification)Serology (Lanciefield Classification)

    Hemolysis on Blood Agar (BA)Hemolysis on Blood Agar (BA)

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    Serology: Lanciefield ClassificationSerology: Lanciefield Classification

    Streptococci classified into many groups from AStreptococci classified into many groups from A--K & HK & H--VVOne or more species per groupOne or more species per group

    Classification based on CClassification based on C-- carbohydrate antigen of cell wallcarbohydrate antigen of cell wall Groupable streptococciGroupable streptococci

    A, B and D (more frequent)A, B and D (more frequent)

    C, G and F (Less frequent)C, G and F (Less frequent)

    NonNon--groupable streptococcigroupable streptococci

    S. pneumoniaeS. pneumoniae(pneumonia)(pneumonia)

    viridans streptococciviridans streptococci e.g.e.g. S. mutansS. mutans

    Causing dental carriesCausing dental carries

    Streptococci

    Group AS. pyogenes

    Group BS. agalactiae

    Group CS. equisimitis

    Group DEnterococcus

    Lanciefield classification

    Other groups

    (E-U)

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    Classification of StreptococciClassification of StreptococciBased on Hemolysis on Blood AgarBased on Hemolysis on Blood Agar

    Hemolysis on BAHemolysis on BA EE--hemolysishemolysis

    Partial hemolysisPartial hemolysis

    Green discoloration around the coloniesGreen discoloration around the colonies

    e.g. none.g. non--groupable streptococci (groupable streptococci (S. pneumoniaeS. pneumoniae&& S. viridansS. viridans))

    FF--hemolysishemolysis

    Complete hemolysisComplete hemolysis

    Clear zone of hemolysis around the coloniesClear zone of hemolysis around the colonies

    e.g.e.g. Group A & B (Group A & B (S. pyogenesS. pyogenes&& S. agalactiaeS. agalactiae))

    KK--hemolysishemolysis

    No lysisNo lysise.g. Group D (e.g. Group D (Enterococcus sppEnterococcus spp))

    Streptococci

    E-hemolysis F-hemolysis K-hemolysis

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    Hemolysis on Blood agarHemolysis on Blood agar

    F-hemolysis

    E-hemolysis

    K-hemolysis

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    Group A streptococciGroup A streptococci

    Include onlyInclude only S. pyogenesS. pyogenes

    Group A streptococcal infections affect all ages peakGroup A streptococcal infections affect all ages peak

    incidence atincidence at 55--1515 years of ageyears of age9090% of cases of pharyngitis% of cases of pharyngitis

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    Pathogenesis and Virulence FactorsPathogenesis and Virulence Factors

    Structural componentsStructural components M protein M, which interferes with opsonization and lysis of theM protein M, which interferes with opsonization and lysis of the

    bacteriabacteria

    Lipoteichoic acid & F protein adhesionLipoteichoic acid & F protein adhesion Hyaluronic acid capsule, which acts to camouflage the bacteriaHyaluronic acid capsule, which acts to camouflage the bacteria

    EnzymesEnzymes StreptokinasesStreptokinases

    DeoxynucleasesDeoxynucleases CC55a peptidasea peptidase

    Pyrogenic toxinsPyrogenic toxins that stimulate macrophages and helperthat stimulate macrophages and helperT cells to release cytokinesT cells to release cytokinesStreptolysinsStreptolysins Streptolysin OStreptolysin O lyse red blood cells, white blood cells, andlyse red blood cells, white blood cells, and

    plateletsplatelets Streptolysin SStreptolysin S

    facilitate the spread of streptococci through tissuesfacilitate the spread of streptococci through tissues

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    Disease caused byDisease caused by S. pyogenesS. pyogenes

    SuppurativeSuppurative

    NonNon--InvasiveInvasivePharyngitis (Pharyngitis (strep throatstrep throat))--inflammation of the pharynxinflammation of the pharynxSkin infection, ImpetigoSkin infection, Impetigo

    InvasiveInvasiveScarlet feverScarlet fever--rash that begins on the chest and spreads acrossrash that begins on the chest and spreads across

    the bodythe bodyPyodermaPyoderma--confined, pusconfined, pus--producing lesion that usually occursproducing lesion that usually occurson the face, arms, or legson the face, arms, or legs

    Necrotizing fasciitisNecrotizing fasciitis--toxin production destroys tissues andtoxin production destroys tissues andeventually muscle and fat tissueeventually muscle and fat tissue

    Non SuppurativeNon Suppurative Rheumatic fever: Life threatening inflammatory diseaseRheumatic fever: Life threatening inflammatory disease

    that leads to damage of heart valves musclethat leads to damage of heart valves muscle GlomerulonephrititsGlomerulonephritits

    Immune complex disease of kidneyImmune complex disease of kidneyinflammation of the glomeruli and nephrons which obstructinflammation of the glomeruli and nephrons which obstruct

    blood flow through the kidneysblood flow through the kidneys

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    Differentiation betweenDifferentiation between FF--hemolytichemolytic

    streptococcistreptococci

    The following tests can be used to differentiateThe following tests can be used to differentiate

    betweenbetween FF--hemolytic streptococcihemolytic streptococci

    Lanciefield ClassificationLanciefield Classification

    Bacitracin susceptibility TestBacitracin susceptibility Test

    Specific forSpecific for S. pyogenesS. pyogenes(Group A)(Group A)

    CAMP testCAMP testSpecific forSpecific for S. agalactiaeS. agalactiae(Group B)(Group B)

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    Bacitracin sensitivityBacitracin sensitivity

    Principle:Principle: Bacitracin test is used for presumptiveBacitracin test is used for presumptive

    identification of group Aidentification of group A To distinguish betweenTo distinguish between S. pyogenesS. pyogenes

    (susceptible to B) & non group A such as(susceptible to B) & non group A such as

    S. agalactiaeS. agalactiae(Resistant to B)(Resistant to B) Bacitracin will inhibit the growth of gp ABacitracin will inhibit the growth of gp A

    Strep. pyogenesStrep. pyogenesgiving zone of inhibitiongiving zone of inhibitionaround the diskaround the disk

    Procedure:Procedure: Inoculate BAP with heavy suspension ofInoculate BAP with heavy suspension of

    tested organismtested organism Bacitracin disk (Bacitracin disk (00..0404 U) is applied toU) is applied to

    inoculated BAPinoculated BAP After incubation, any zone of inhibitionAfter incubation, any zone of inhibition

    around the disk is considered asaround the disk is considered assusceptiblesusceptible

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    CAMP testCAMP test

    Principle:Principle:

    Group B streptococci produce extracellular protein (CAMP factor)Group B streptococci produce extracellular protein (CAMP factor)

    CAMP act synergistically with staph.CAMP act synergistically with staph. FF--lysin to cause lysis of RBCslysin to cause lysis of RBCs

    Procedure:Procedure: Single streak ofSingle streak of StreptococcusStreptococcusto be tested and ato be tested and a Staph. aureusStaph. aureusareare

    made perpendicular to each othermade perpendicular to each other

    33--55 mm distance was left between two streaksmm distance was left between two streaks

    After incubation, a positive result appear as an arrowhead shapedAfter incubation, a positive result appear as an arrowhead shapedzone of complete hemolysiszone of complete hemolysis

    S. agalactiaeS. agalactiaeis CAMP test positive while non gp B streptococci areis CAMP test positive while non gp B streptococci are

    negativenegative

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    CAMP testCAMP test

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    Differentiation betweenDifferentiation between EE--hemolytichemolytic

    streptococcistreptococci

    The following definitive tests used to differentiateThe following definitive tests used to differentiatebetweenbetween S. pneumoniae &S. pneumoniae & viridans streptococciviridans streptococci

    Optochin TestOptochin Test Bile Solubility TestBile Solubility Test Inulin FermentationInulin Fermentation

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    Optochin Susceptibility TestOptochin Susceptibility Test

    Principle:Principle: Optochin (OP) test is presumptive test that is used to identifyOptochin (OP) test is presumptive test that is used to identify

    S. pneumoniaeS. pneumoniae

    S. pneumoniaeis inhibited by Optochin reagent (

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    Optochin Susceptibility TestOptochin Susceptibility Test

    Optochin susceptibleS. pneumoniae

    Optochin resistantS. viridans

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    Bile Solubility testBile Solubility test

    Principle:Principle:S. pneumoniaeproduce a self-lysing enzyme to

    inhibit the growth

    The presence of bile salt accelerate this process

    Procedure:Procedure: Add ten parts (Add ten parts (1010 ml) of the broth culture of the organism to beml) of the broth culture of the organism to be

    tested to one part (tested to one part (11 ml) ofml) of 22% Na deoxycholate (bile) into the% Na deoxycholate (bile) into thetest tubetest tube

    Negative control is made by adding saline instead of bile to theNegative control is made by adding saline instead of bile to thecultureculture Incubate at 37oC for 15 min

    Record the result afterRecord the result after 1515 minmin

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    Bile Solubility testBile Solubility test

    Results:Results: Positive test appears as clearing inPositive test appears as clearing in

    the presence of bile while negativethe presence of bile while negativetest appears as turbidtest appears as turbid

    S. pneumoniaeS. pneumoniaesoluble in bilesoluble in bilewhereaswhereas S. viridansS. viridansinsolubleinsoluble

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    Differentiation betweenDifferentiation between FF--hemolytic streptococcihemolytic streptococci

    CAMP testCAMP testBacitracinBacitracin

    sensitivitysensitivity

    HemolysisHemolysis

    NegativeNegativeSusceptibleSusceptibleFFS. pyogenesS. pyogenes

    PositivePositiveResistantResistantFFS. agalactiaeS. agalactiae

    InulinInulin

    FermentationFermentation

    BileBile

    solubilitysolubility

    OptochinOptochin

    sensitivitysensitivity

    HemolysisHemolysis

    Not fermentNot fermentSolubleSolubleSensitiveSensitive( 14 mm)( 14 mm)

    EES. pneumoniaeS. pneumoniae

    FermentFermentInsolubleInsolubleResistantResistant

    (13 mm)(13 mm)

    EEViridans strepViridans strep

    Differentiation betweenDifferentiation between EE--hemolytic streptococcihemolytic streptococci

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    Outline of differentiation betweenOutline of differentiation between

    GramGram--Positive cocciPositive cocci

    e.g. S. epidermidis