Chapter 14: Streptococci, Enterococci and Related Genera Flashcards
How does Streptococci being classified?
- Colony morphology and hemolytic reactions on blood agar
- Serologic specificity of the cell wall group-specific substance
- Biochemical reactions and resistance to physical and chemical factors
- Ecologic features
Complete disruption of erythrocytes with clearing of the blood around the bacterial growth
B-hemolysis
Incomplete lysis of erythrocytes with reduction pf hemoglobin and the formation of green pigment
a-hemolysis
Group A pyogenic Streptococci
B hemolysis
Streptococcus pyogenes
Group B pyogenic Streptococci
B hemolysis
Streptococcus agalactiae
Group C, G pyogenic Streptococci
B hemolysis (human infections)
A hemolysis
Streptococcus dysgalactiae
Subspecies: Equisimilis
Group D Viridans Streptococci with no hemolysis
Streptococci bovis group
Group F Viridans Streptococci
a hemolysis
Streptococcus anginosus group
Group A Viridans Streptococci
Streptococcus anginosus
Group C Viridans Streptococci
Streptococcus intermedius
Group G Viridans Streptococci
Streptococcus constellatus
No group specific substance but they are a hemolytic
Mutans group
Streptococcus mutans
Mitis-Sanguinis group with a hemolysis
Streptococcus pneumoniae
Streptococcus mitis
Salivarius group
Pyogenic Streptococci that has inhibited by bacitracin
Streptococcus pyogenes
Pyogenic Streptococci that positive in hippurate hydrolysis and CAMP-factor positive
Streptococcus agalactiae
Grow in the presence of bile, hydrolyze esculin, no growth in 6.5% NaCl, degrades starch
Streptococcus bovis
Group A Viridans Streptococci that is bacitracin resistant and PYR negative
Streptococcus anginosus
All Viridans Streptococci are Voges Proskauer (VP) positive except?
Mitis group
Mitis-sanguinis group that is susceptible to optochin
Streptococcus pneumoniae
Mitis-Sanguinis group that has high-level resistance to penicillin
Streptococcus mitis
The serologic specificity of the group-specific carbohydrate is determined by?
An amino sugar
Serologic specificity sugar for group A Streptococci.
Rhamnose-N-acetylglucosamine
Serologic specificity sugar for group B Streptococci.
Rhamnose-glucosamine polysaccharide
Serologic specificity sugar for group C Streptococci.
Rhamnose-N-acetylgalactosamine
Serologic specificity sugar for group D Streptococci
Glycerol teichoic acid containing D-alanine and glucose
Serologic specificity sugar for group F Streptococci.
Glucopyranosyl-N-acetylgalactosamine
For grouping Streptococci, what are the extraction methods prepared to determine their group-specific antigen
- Centrifuged culture treated with
Hot hydrochloric acid
Nitrous acid
Formamide
- Enzymatic lysis with streptococcal cells with
pepsin and trypsin - Autoclaving of cell suspensions
Antigenic specificity of the capsular polysaccharide is used to classify
Streptococcus pneumoniae
Main human pathogen associated with local or systemic invasion and poststreptococcal immunologic disorders
Streptococcus pyogenes
Gram stain of Streptococci
Positive
Capsules of group A Streptococci are composed of?
Hyaluronic Acid
How does the capsule of S.pyogenes causes virulence?
By binding to hyaluronic-acid-binding protein, CD44 that are present on human epithelial cells that induce disruption of intercellular junctions
present in the cell wall of Streptococcus pyogenes
Proteins (M,T,R antigens)
Carbohydrates (group specific)
Peptidoglycans
Composition of pili of Streptococcus pyogenes
M proteins covered with lipoteichoic acid
Responsible for the attachment of Streptococci to the epithelial cells
Lipoteichoic acid
Most Streptococci grow in solid media as?
1-2 mm discoid colonies
Growth of Streptococci are poor on solid media or broth unless enriched with?
Blood or Tissue fluids
Growth and hemolysis of Streptococci are aided by
incubation in 10% CO
Pathogenic hemolytic streptococci grow best at temperature
37 degrees Celcius
Most Streptococci are __________ anaerobes
Facultative
Colonies of Streptococci pyogenes that has many M proteins and are virulent
Matte colonies
Colonies of Streptococci pyogenes that produce little M protein and not virulent.
Glossy colonies
Major virulence factor of S. pyogenes
M protein
How does M protein contributes to the virulence of S. pyogenes?
Resist phagocytosis
Inhibits activation of alternate C pathway
Class of M protein of S.pyogenes that react with human cardiac muscle and the virulence determinant for rheumatic fever
Class 1 M protein
Toxins and enzymes exhibited by S.pyogenes
Streptokinase Deoxyribonucleases Hyaluronidase Hemolysins Erythrogenic Toxin
Enzyme of S.pyogenes that transforms plasminogen to plasmin allowing them to escape from blood clots
Streptokinase (Fibrolysin)
Enzymes that facilitate the spread of Streptococci in tissue by liquefying pus
Deoxyribonucleases (A,B,C,D) degrade DNAses
How does the enzymatic activity of DNAses can be measured in DNA solutions?
Decrease in viscosity
Enzymes used in enzymatic debridement that liquefies exudates and facilitates removal of pus and necrotic tissue
Streptokinase & DNAses
Enzyme that aid in spreading infecting microorganism (spreading factor)
Hyaluronidase
Pyrogenic exotoxin of S.pyogenes that carry lysogenic phage
Spe A (most widely studied)
Pyrogenic exotoxin of S.pyogenes that contributes to the streptococcal toxic shock syndrome and encoded in phage
Spe C
Pyrogenic exotoxin of S.pyogenes that is a potent protease that interferes with phagocytosis
Spe B
The group A Streptococci associated with toxic shock syndrome are primarily of M protien types?
Types 1 & 3
How does pyrogenic exotoxins causes toxic shock syndrome?
They act as superantigens that binds to MHC II in the Vb region of T-cell and activates them and release of cytokines mediates the shock
Hemolysins that is hemolytically active in reduced state and inactivated in the presence of oxygen
Streptolysin O
Antibody that appears in human after infection of any Streptococci that produce streptolysin O
Anti-streptolysin O (ASO)
Units in ASO titer that indicates recent infection of S.pyogenes
160-200 units
Hemolysin of S.pyogenes that is responsible for the hemolytic zones around streptococcal colonies growing on blood agar plates
Streptolysin S
Diseases attributable to invasion by S.pyogenes
Erysipelas Cellulitis Necrotizing fasciitis (streptococcal gangrene) Puerperal fever Bacteremia or Sepsis
S.pyogenes portal of entry is the skin, that leads to raised,red lesion with edema and sharply demarcated margin of infection
Erysipelas
rapidly spreading infection of the skin and subcutaneous tissue caused by S.pyogenes with mild trauma, burns, wounds or surgical incisions. Not raised lesion and line between the involved and uninvolved tissue is indistinct
Cellulitis
Extensive and very rapidly spreading necrosis of the skin, tissues and fascia.
Necrotizing fasciitis (streptococcal gangrene)
S.pyogenes enter the uterus after delivery that leads to septicemia originating in the infected wound (endometritis)
Puerperal fever
Most common infection caused by B-hemolytic S.pyogenes
Streptococcal sore throat or pharyngitis
In streptococcal pharyngitis, this glycoprotein serves as lipoteichoic acid ligand.
Fibronectin
Local infection of superficial layers of skin in children, consists if superficial vesicles and crusty lesion
Streptococcal pyoderma
Invasive S. pyogenes infections characterized by shock, bacteremia, respiratory failure and multiorgan failure.
Streptococcal toxic shock syndrome
Group A streptococcal skin infection are often attributable to M types?
49, 57, 59, 60, 61