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
What is the name of the family of exotoxins that cause scarlet fever, necrotizing fasciitis, and toxic shock?
Pyrogenic exotoxins A-C
Antibiotic therapy for Streptococcal pharyngitis is primarily aimed at preventing ______________.
acute rheumatic fever
What are the symptoms of scarlet fever?
Strawberry tongue
Fever
Red rash
Acute rheumatic fever occurs about __________ after an infection with Streptococcus pyogenes.
3-6 weeks
What are two big distinctions between the causes of PSGN and ARF?
ARF is only caused by pharyngitis and is preventable with antibiotics, while PSGN can be caused by impetigo or pharyngitis and is not preventable with antibiotics.
Group B Streptococci do not have ______________, found in S. pyogenes.
M, T, or R proteins
Which Streptococci can grow in bile?
Streptococcus viridans and the Enterococcus bacteria (which, until recently, were considered Group D Streptococci)
Which group A Streptococcal toxin is thought to play a role in acute rheumatic fever?
Streptolysin O
What clinical sign is suggestive of Streptococcal pharyngitis?
Red dots on the pharynx
What symptoms are more associated with viral infections?
Cough, runny nose, and age younger than 3 years
Which spots (to swab) are the most likely to produce positive rapid antigen tests in a person with Strep throat?
The tonsils and posterior wall of the pharynx
Positive rapid antigen tests will have ___________.
blue lines
Which autoimmune Streptococcal illness is more likely to present in the summer?
PSGN
“You get Coca-Cola-colored urine in the season when you drink Coca Cola.”
What are the symptoms of toxic shock?
DIC Liver failure Renal failure ARDS Scarlet fever rash
Which bacterium has been implicated in perianal and perineal skin infections?
Group A Strep (Group Anus Strep
True or false: Enterococci are susceptible to 3rd and 4th-generation cephalosporins.
False. Almost all Enterococci are resistant to penicillins, cephalosporins, Bactrim, clindamycin, and aminoglycosides. They can be treated with linezolid or tigecycline.
