Senior Demonstrator MicrobiologyKEMU Lahore Streptococci Characters of Streptococci Gram positive cocci 1µm in diameter Chains or pairs Usually capsulated Non motile CapnophiliC Non spore forming ID: 933794
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Slide1
Slide2STREPTOCOCCI
Dr.Qurat-Ul-Ain
Senior Demonstrator,
Microbiology,KEMU
, Lahore
Slide3Slide4Streptococci
Characters of Streptococci
Gram positive
cocci
1µm in diameter
Chains or pairsUsually capsulatedNon motileCapnophiliCNon spore formingFacultative anaerobesFastidiousCatalase negative (Staphylococci are catalase positive)
Slide5Streptococci can be classified according to:
Oxygen requirements
Anaerobic (
Peptostreptococcus
)
Aerobic or facultative anaerobic (Streptococcus)Serology (Lanciefield Classification)Hemolysis on Blood Agar (BA)Classification Of Streptococci
Slide6Slide7Hemolysis
on Blood agar
-hemolysis
-hemolysis
-hemolysis
Slide8Slide9Serology: Lancefield classification
Slide10Streptococci classified into many groups from A-K & H-V
One or more species per group
Classification based on C- carbohydrate antigen of cell wall
Groupable
streptococci
A, B and D (more frequent)C, G and F (Less frequent)
Non-
groupable
streptococci
S.
pneumoniae
(pneumonia)
viridans
streptococci
e.g.
S.
mutans
Causing dental carries
Slide11Slide12Slide13Slide14Include only
S.
pyogenes
Group A streptococcal infections affect all ages peak incidence at 5-15 years of age
90% of cases of
pharyngitisGroup A Streptococci
Slide15GAS: Strep
pyogenes
Slide16Strep. Virulence Factors
Slide17Determinants of
Pathogenicity
Cellular Virulence Factors
1.Capsule
Antiphagocytic; Nonspecific adherenceHyaluronic acid (polysaccharide) mimics animal tissue2. Lipoteichoic AcidCytotoxic
for wide variety of cells
Adherence:
Complexes with M protein (LTA-M) and binds to
fibronectin
on epithelial
cells
3. M-Protein
LTA-M protein is
adhesin
Antiphagocytic
Inhibits
alternate C’ pathway and
opsonization
4. M-like
Proteins:
bind
IgM
and
IgG
5. F
Protein:
mediates adherence
Slide18Extracellular Virulence
Factors
Exotoxins
:
1.Streptolysin
O (SLO): Hemolytic and Cytolytic Prototype of oxygen-labile and thiol-activated cytolytic exotoxins
(e.g.,
Streptococcus, Bacillus, Clostridium,
Listeria
)
Lytic
for variety of cells:
bind to cholesterol-containing membranes and form arc- or ring- shaped
oligomers
that make cell leaky (RBC's, WBC’s, PMN's, platelets, etc.)
Causes
sub-surface
hemolysis
on BAP
Stimulate release
of
lysosomal
enzymes
SLO
titer
indicates recent infection (300-500 in pediatric populations)
Slide19Extracellellular
Virulence Factors
(cont.)
Exotoxins
(cont.):
2. Streptolysin S (SLS): Hemolytic and Cytolytic Oxygen
stable
, non-antigenic
Lytic
for red and white blood cells and wall-less forms (protoplast, L- forms
)
Causes
surface
hemolysis
on BAP
Slide20Extracellular Virulence Factors
(cont.)
Exotoxins
(cont
): 3. Pyrogenic (Erythrogenic) Exotoxins (Types A, B &C)Produced
by more than 90% of
Grp
A strep
Mediate
pyrogenicity
(fever)
Causes
scarlet fever
(
scarletiniform
)
rash
Increase
susceptibility to
endotoxic
shock
Type
C toxin increases permeability of blood-brain
barrier
Mitogenic
for T lymphocytes (cause cell division), myocardial and hepatic necrosis, decrease in antibody synthesis
Immunomodulators
(
superantigens
): stimulate T cells to release cytokines
Cardiohepatic
toxin
Slide21Extracellular Virulence Factors
(cont.)
Enzymes
:
1. Nucleases
: Four antigenic types (A,B,C,D) Facilitate liquefication of pus generating growth substratesNucleases A, C have DNase activity
Nucleases B, D also have
RNase
activity
2.
Streptokinases
:
Lyse
blood clots:
catalyze conversion of
plasminogen
to
plasmin
, leading to digestion of fibrin
3. C5a
Peptidase:
destroys C’
chemotactic
signals (C5a
)
4.
Hyaluronidase
:
hydrolyzes
hyaluronic
acid
5. Others
:
Proteinase
,
NADase
,
ATPase
,
phosphatase
, etc.
Slide22Slide23Strep
pyogenes
diseases
Pharyngitis
Scarlet Fever (rash)SkinPyodermaImpetigoErysipelasCellulitisStrep TSSNecrotizing fasciitisMyositisImmune Mediated Rheumatic feverGlomerulonephritis
Slide241.
Suppurative
Non-Invasive:
Pharyngitis
(“strep throat”)-inflammation of the pharynx
Skin infection, ImpetigoInvasiveScarlet fever-rash that begins on the chest and spreads across the bodyPyoderma-confined, pus-producing lesion that usually occurs on the face, arms, or legsNecrotizing fasciitis-toxin production destroys tissues and eventually muscle and fat tissueDiseases Caused By
S.Pyogenese
Slide25Non
Suppurative
:
Rheumatic fever:
Life threatening inflammatory disease that leads to damage of heart valves muscle
Glomerulonephritits:Immune complex disease of kidney
inflammation of the
glomeruli
and
nephrons
which obstruct blood flow through the kidneys
Slide26Strep
pyogenes infections
Slide27Slide28Slide29Slide30Slide31Slide32Necrotizing Fasciitis and Meningitis
Slide33Nonsuppurative
Sequelae
of Acute Group A Streptococcal Infection
Acute Rheumatic Fever
(ARF)Inflammatory reaction characterized by arthritis, carditis, chorea (disorder of CNS with involuntary spastic movements), erythema marginatum (skin redness with defined margin), or subcutaneous nodulesWithin 2-3 weeks following pharyngitis
Morbidity
& mortality linked to subsequent disease of
heart valve (Rheumatic Heart Disease)
Poorly understood pathogenesis with several proposed theories including
cross-reactivity of heart tissues & strep AGNs
?? (
Type ??
II
hypersensitivity,
exotoxins
, direct invasion)
Slide34Slide35Nonsuppurative
Sequelae
of Acute Group A Streptococcal Infection
(cont
.)Acute Glomerulonephritis :Follows either respiratory (pharyngitis) or cutaneous (pyoderma) streptococcal infectionAssociated with well-defined group of M-types
Most
often seen in children
manifesting as dark, smoky urine with RBC's, RBC casts, white blood cells, depressed serum complement, decreased
glomerular
filtration
rate
Latent
period:
1-2 weeks after skin infection and 2-3 weeks after
pharyngitis
Granular
accumulations of immunoglobulin due to
deposition of immune complexes within the kidney
(Type
??III
Hypersensitivity)
Slide36Differentiation between
-hemolytic streptococci
The following tests can be used to differentiate between
-hemolytic streptococci
Lanciefield
ClassificationBacitracin susceptibility TestSpecific for S. pyogenes (Group A)CAMP testSpecific for S. agalactiae (Group B)
Slide37Bacitracin
sensitivity
Principle:
Bacitracin
test is used for presumptive identification of group A
To distinguish between S. pyogenes (susceptible to B) & non group A such as S. agalactiae (Resistant to B)Bacitracin will inhibit the growth of gp A Strep. pyogenes giving zone of inhibition around the disk
Procedure:
Inoculate BAP with heavy suspension of tested organism
Bacitracin
disk (0.04 U) is applied to inoculated BAP
After incubation, any zone of inhibition around the disk is considered as susceptible
Slide38CAMP test
Principle:
Group B streptococci produce extracellular protein (CAMP factor)
CAMP act synergistically with staph.
-
lysin to cause lysis of RBCsProcedure:Single streak of Streptococcus to be tested and a Staph. aureus are made perpendicular to each other
3-5 mm distance was left between two streaks
After incubation, a positive result appear as an arrowhead shaped zone of complete
hemolysis
S.
agalactiae
is CAMP test positive while non
gp
B streptococci are negative
Slide39CAMP test
Slide40Differentiation between
-hemolytic streptococci
The following definitive tests used to differentiate between
S.
pneumoniae
& viridans streptococciOptochin TestBile Solubility TestInulin Fermentation
Slide41Optochin
Susceptibility Test
Optochin
susceptible
S.
pneumoniaeOptochin resistantS. viridans
Slide42Slide43Slide44Slide45Slide46Slide47GBS
: Strep
agalactiae
Epidemiology
GI
UritogenitalPathogenicityCapsuleEnzymesProteasesHemolysinsBeta hemolysisHyaluronidase
Disease
Puerperal fever
Vaginitis
UTI
Endocarditis
Osteomyelitis
Newborn
Meningitis, sepsis, pneumonia
Slide48Slide49Slide50Slide51Outline of differentiation between Gram-Positive
cocci
Slide52Slide53Slide54Slide55Slide56Slide57Slide58Slide59Strep. pneumoniae
Slide60Strep pneumonia capsule
Slide61Strep pneumoniae
Epidemiology
Mouth
Upper respiratory
Dz = lungs
PathogenicityCapsuleProtein APhosphorylcholineAdhesinsProteasesProtects from IgApneumolysins
Slide62Slide63Slide64Strep pneumonia
diseases
Slide65Slide66Slide67Slide68Slide69Slide70Slide71Slide72Slide73Slide74Slide75Slide76Group D Strep
Examples
E. faecalis
E. faecium
S. bovis
S. equinesLocation: GITestsGamma hemolysisSalt tolerantBile tolerantPathogenicityBacterocinsNosocomial
Slide77Enterococcus
Sequella
Slide78Slide79Slide80Slide81Slide82Slide83Slide84Slide85Slide86Slide87Slide88Slide89Slide90Slide91Slide92Slide93Slide94