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