Streptococcus Flashcards
Characterized by greenish hemolysis around the colony
ALPHA (α)
Due to incomplete/ partial destruction of red blood cells
ALPHA (α)
Example of bacteria that has alpha hemolysis
Viridans streptococci and Streptococcus pneumoniae
Characterized by clear, colorless zone of hemolysis
BETA (β)
Due to complete destruction of red blood cells
BETA (β)
Example of bacteria that has beta hemolysis
Streptococcus pyogenes and
Streptococcus agalactiae
Non – hemolytic on blood agar
GAMMA (γ)
Example of bacteria that has gamma hemolysis
Enterococcus faecalis
LANCEFIELD CLASSIFICATION is Based on the ________ antigen found in the cell wall
C – carbohydrate
Bacteria’s that do not have carbohydrate cell wall antigen
Streptococcus pneumoniae & Viridans streptococci
LANCEFIELD CLASSIFICATION
A
Streptococcus pyogenes
LANCEFIELD CLASSIFICATION
B
Streptococcus agalactiae
LANCEFIELD CLASSIFICATION
C
Streptococcus equisimilis,
Streptococcus zooepidemicus,
Streptococcus equi
LANCEFIELD CLASSIFICATION
D (enterococci)
Enterococcus faecalis,
Enterococcus facium
LANCEFIELD CLASSIFICATION
D (non-enterococci)
Streptococcus bovis,
Streptococcus durans
LANCEFIELD CLASSIFICATION
G
Streptococcus arginosus
Lancefield Classification & Hemolytic Pattern (Smith & Brown)
Streptococcus pyogenes
A & beta
Lancefield Classification & Hemolytic Pattern (Smith & Brown)
Streptococcus agalactiae
B & beta
Lancefield Classification & Hemolytic Pattern (Smith & Brown)
Strep. agalactiae subsp. equisimilus
C & beta
Lancefield Classification & Hemolytic Pattern (Smith & Brown)
Enterococcus – Streptococcal faecalis
D
Alpha or Beta or None
Lancefield Classification & Hemolytic Pattern (Smith & Brown)
Non-enterococcus –Strep. bovis
D
Alpha or none
Lancefield Classification & Hemolytic Pattern (Smith & Brown)
Streptococcus pneumoniae
NA
Alpha
Lancefield Classification & Hemolytic Pattern (Smith & Brown)
Streptococcus viridans
NA
Alpha or none
produces large (1cm in diameter) zones of β hemolysis around
colonies greater that 0.5 mm in diameter
Group A β Hemolytic Streptococcus
main human pathogen associated with local or systemic invasion
and post – streptococcal immunologic disorders
Group A β Hemolytic Streptococcus
HABITAT:
Skin and Upper Respiratory tract of humans, carried on nasal, pharyngeal, sometimes anal mucosa
Group A β Hemolytic Streptococcus
Prone to progression with involvement of deeper tissues and organs, a characteristic that has earned the designation ‘’flesh – eating bacteria”
Group A β Hemolytic Streptococcus
Fastidious, requires enriched media for primary isolation incubated with 5% – 10% CO2
Streptococcus pyogenes
ferment wide variety of carbohydrate with production of lactic acid with or without gas
Streptococcus pyogenes
Blood agar:
Appears as circular, translucent, grayish to opalescent colonies, matte or glossy large zone beta hemolysis
Streptococcus pyogenes
Streptococcus pyogenes Morphological, Cultural and Biochemical Characteristics:
Catalase test
PYR
Bacitracin
Catalase negative
PYR positive
Bacitracin sensitive
test for Group A Streptococcus
PYR Hydrolysis Test (POSITIVE)
demonstrate presence of pyrrolidonyl arylamidase
PYR Hydrolysis Test (POSITIVE)
PYR Hydrolysis Test (POSITIVE): develops what color within a minute addition of reagent
Cherry red color
Bacitracin Susceptibility Test (+) =
any presence of ZOI
Presumptive test and Used to differentiate Streptococcus pyogenes and
Streptococcus agalactiae
Bacitracin Susceptibility Test (+)
Bacitracin Susceptibility Test (+)
S. pyogenes
S. agalactiae
S. pyogenes (sensitive)
S. agalactiae (resistant)
specialized polysaccharide or teichoic acid; found in the surface of the cell wall
C - carbohydrate
Group A specific cell wall antigen
C - carbohydrate
use as basis for serological classification using Lancefield method
C - carbohydrate
Protein antigens:
M - Protein
T - Protein
Protein antigens:
major virulence factor of group A S pyogenes.
M – Protein
appears as hair-like projections of the streptococcal cell wall
M – Protein
Immunity to infection with group A streptococci is related to the presence of type-specific antibodies to _______
M – Protein
Protein antigens:
acid-labile and heat-labile
T – Protein
PROTEIN ANTIGENS
obtained from streptococci by proteolytic digestion, which rapidly destroys M proteins.
T – Protein
PROTEIN ANTIGENS
permits differentiation of certain types of streptococci by agglutination with specific antisera
T – Protein
allows organism to cling to epithelial surfaces
Lipoteichoic Acid (LTA)
Cytotoxic; destroys rbc and wbc
Lipoteichoic Acid (LTA)
most important virulence factor
M protein antigen
aid in the attachment of the organism to portal of entry
M protein antigen
Antiphagocytic; promotes invasiveness of the organism
Capsule (Hyaluronic acid)
depolymerizes DNA; facilitate removal of purulent exudate/ discharges
Streptodornase (Streptococcal Deoxyribonuclease)
enzymatic activity can be measured by the decrease in viscosity of known DNA solutions.
Streptodornase (Streptococcal Deoxyribonuclease)
antibody to DNAse develops after streptococcal infections (normal limit = 100 units), especially after skin infections.
Streptodornase (Streptococcal Deoxyribonuclease)
produced by many strains of group A -hemolytic streptococci.
Streptokinase (Fibrinolysin)
transforms the plasminogen of human plasma into plasmin, an active proteolytic enzyme that digests fibrin and other proteins.
Streptokinase (Fibrinolysin)
are antigenic and specific for each bacterial or tissue source.
Hyaluronidase
splits hyaluronic acid, an important component of the ground substance of connective tissue.
Hyaluronidase
aids in spreading infecting microorganisms (spreading factor)
Hyaluronidase
An enzyme elaborated into the environment and is related to the organism’s ability to kill leukocytes, PMN’s and macrophages
Diphosphopyridine nucleotidase
EXTRACELLULAR ENZYMES
A. Streptodornase (Streptococcal Deoxyribonuclease)
B. Streptokinase (Fibrinolysin)
C. Hyaluronidase
D. Diphosphopyridine nucleotidase
Hemolysins
oxygen stable; non antigenic : surface BAP hemolysis during aerobic condition
Streptolysin S
Hemolysins
oxygen labile; antigenic
Streptolysin O
Immunogenic; responsible for some of the hemolysis seen when growth is in cuts deep into the medium in blood agar plates.
Streptolysin O
combines quantitatively with antistreptolysin O (ASO)
Streptolysin O
an antibody that appears in humans following infection with any streptococci that produce streptolysin O.
antistreptolysin O (ASO)
ASO serum titer in excess of___________ is considered abnormally high and suggests either recent infection with S. pyogenes
160–200 Todd units/mL