4. Family Streptococcaceae Flashcards
Catalase reaction of the family Streptococcaceae
Catalase negative
Type of hemolysis; conversion of hemoglobin to methemoglobin resulting in a green zone in the blood agar around a colony
Alpha (α)
Type of hemolysis; lysis of sheep RBCs in the blood agar plates
Beta (β)
Lancefield grouping; nonhemolytic
Gamma (γ)
Lancefield group of Streptococcus pyogenes
Group A
Causative agent of pharyngitis: “strep throat”
S. pyogenes
2 complications of S. pyogenes infections
Rheumatic fever
Acute glomerulonephritis
S. pyogenes sequelae; can cause chronic, progressive damage to the heart
Rheumatic fever
S. pyogenes sequelae; circulating immune complexes deposit in glomeruli; inflammatory response causes damage
Acute glomerulonephritis
Virulence factor of S. pyogenes; for attachment
M protein
Lipoteichoic acid
Virulence factor of S. pyogenes; inhibits phagocytosis
Hyaluronic acid capsule
S. pyogenes toxin that causes the rash in scarlet fever
Pyrogenic (erythrogenic) toxin
Enzyme by S. pyogenes; lyses fibrin clot
Streptokinase
Enzyme by S. pyogenes; dissolves purulent/fibrinous secretions
Streptodornase (DNase B)
Streptolysins by S. pyogenes
Streptolysin O and S
Microscopic appearance of S. pyogenes
Gram-positive cocci in chains
Colony morphology of S. pyogenes
Small
Transparent
Smooth
β-hemolytic colonies
Bacitracin susceptibility of S. pyogenes
Bacitracin susceptible
L-pyrrolidonyl arylamidase (PYR) reaction of S. pyogenes
PYR positive
Penicillin susceptibility of S. pyogenes
Penicillin susceptible
Lancefield group of S. agalactiae
Group B
Body parts/organs where S. agalactiae is normal flora
Female genital tract
Gastrointestinal tract
Diseases caused by S. agalactiae
- Pneumonia in elderly
- UTI
- Neonatal sepsis and meningitis
PUN
When is S. agalactiae transmitted vertically from the mother?
In early-onset neonatal disease (0-6 days)
When is S. agalactiae transmitted horizontally?
In late-onset meningitis (7 days - 3 months age)
Virulence factors for S. agalactiae
Capsule
Hemolysin
Hyaluronidase
Protease
CHHP
Colony morphology of S. agalactiae
Grayish-white
Slightly mucoid
Larger colony than group A
Small-zone of β-hemolysis
Hippurate reaction of S. agalactiae
Hippurate positive
CAMP test reaction of S. agalactiae
CAMP test positive
Penicillin susceptibility of S. agalactiae
Penicillin susceptible
Group D Streptococcus is normal flora in the
GI tract
Urogenital tract
Clinical significance of Group D Streptococcus
Bacteremia
Endocarditis
Examples of Group D Strep
S. gallolyticus (bovis)
S. equinus
Colony morphology of Group D Strep
Small
White colonies with hemolysis on blood agar
Bile esculin reaction of Group D Strep
Bile esculin positive
Bile esculin reaction of Enterococcus
Bile esculin positive
PYR reaction of Enterococcus
PYR positive
True/False. Enterococcus grows in lower NaCl concentration
False. Enterococcus thrives in higher NaCl concentration
Enumerate the α-hemolytic streptococci
- S. pneumoniae
- Viridans group streptococci
- Nutritionally variant streptococci
- Sometimes enterococcal species
Lancefield group of S. pneumoniae
No Lancefield group
True/False. S. pneumoniae infects humans and animals
False. S. pneumoniae infects humans EXCLUSIVELY, it has no reservoir in nature
Most significant disease caused by S. pneumoniae
Pneumococcal pneumonia
Microscopic appearance of S. pneumoniae
Gram-positive cocci in pairs
Lancet-shaped
Colony morphology of S. pneumoniae
Round
Usually wet, glistening, mucoid
Type of hemolysis exhibited by S. pneumoniae
α-hemolysis
Optochin susceptibility of S. pneumoniae
Optochin susceptible
Bile solubility of S. pneumoniae
Bile soluble
Viridans strep is normal flora in the
Upper respiratory tract
Urogenital tract
Clinical significance of Viridans strep
Subacute bacterial endocarditis
Type of hemolysis of Viridans strep
α-hemolysis
Optochin susceptibility of Viridans strep
Optochin resistant
Enumerate the Viridans strep
S. mutans
S. anginosus
S. gallolyticus (bovis)
S. salivarius
Microscopic characteristics of the family Streptococcaceae
Gram-positive cocci in chains or pairs