Streptococci Flashcards
Gamma hemolysis is ______________.
no hemolysis
Incomplete hemolysis is also called ______________.
alpha hemolysis
Complete hemolysis is also referred to as _____________.
beta hemolysis
____________ are an offshoot of Streptococci and were formerly called group D Streptococci.
Enterococcus
What virulence factor determines the strain of Streptococcus pyogenes?
The M factor (like the M on the baker’s hat)
It is anti-phagocytic.
Like Neisseria, group A Streptococci have ________.
pili
Why would bacteria need a DNAse?
Because DNA inhibits the mobility of bacteria –it is what makes pus gooey –so digesting it allows bacteria to spread.
What are current AAP guidelines regarding testing for Strep.?
If the rapid antigen test comes back negative, then place one sample on a blood agar.
Rheumatic heart disease is a _____________ Streptococcal infection.
non-suppurative (meaning S. pyogenes will not be cultured on blood agar)
Erysipelas is more ____________ than cellulitis.
superficial
Given what this lecturer told you about the kinds of infections caused by Streptococcus, why does it make sense that S. pyogenes is the bacterium that produces streptolysin?
Because S. pyogenes spreads, and streptolysin helps spread.
PSGN and RHF are both caused by ____________ strains of GAS.
non-invasive
Why is clindamycin recommended for severe Streptococcal infections?
Because clindamycin inhibits protein synthesis, which is important in severe infections because bactericidal antibiotics can cause the sudden release of toxins.
True or false: M protein prevents phagocytosis of Streptococcus agalactiae.
False. GBS lacks M protein, but it still has the anti-phagocytic polysaccharide capsule.
Streptococcus milleri has a distinct smell: ______________.
butterscotch
Which Streptococcus strain is Camp-test positive?
Group B Strep (agalactiae)
Which Streptococcus strain grows in 6.5% NaCl?
Enterococcus (all types)
What does Lancefield testing test for?
Group-specific carbohydrates
What Lancefield group does S. pyogenes fall in?
C-carbohydrate (group A)
What kind of protein is M protein?
Fine fimbriae that help lipoteichoic acid bind to epithelium (strains lacking this are avirulent)
Antibodies to _______________ provide immunity to Streptococcus pyogenes.
M protein
Note: this confers lifelong immunity, but there are so many subtypes that you can always get infected with more strains of S. pyogenes.
In addition to serving adhesive properties, M protein also _________________.
is antiphagocytic
What is the capsule around Streptococcus pyogenes composed of?
Hyaluronic acid (remember the Hot Apple Pie from Sketchy)
Why does Streptococcus produce better hemolysis when inserted deep into the blood agar?
Because streptolysin O –the toxin that hemolyzes RBCs –is destroyed by oxygen