Flashcards in Streptococci Deck (46):
The three most important human pathogens
Strep pyogenes (A), Strep agalactiae (B), Strep pnumonia
Are Strep facultative anaerobes?
What color is Alpha hemolysis on a blood agar plate?
What color is Beta Hemolysis
What about gamma hemolysis?
This is almost non-hemolytic.
What hemolysis pattern do AN and B follow?
Catalase negative or positive?
Negative...this differentiates them from staph
Oxidase negative or positive?
What is the largest Strep A burden in the world?
Acute Rheumatic Fever which follows pharyngitis. Can lead to Rheumatic heart disease.
Acute glomerulonephrits is a sequela of strep that follows what type of infections
Skin infections generally
ARF and AGN are immune mediated diseases?
Beta hemolysis due to what enzymes?
Streptolysin O and streptolysin S
Streptolysin S is oxygen stable
SLO is oxygen stable
False. SLO is oxygen unstable so you have to grow it below the surface of the agar to see its activity
Group A virulence factors
Hyaluronic acid capsule
What is significant about the hyaluronic acid capsule
It is antiphagocytic and the structure of the hyaluronic acid is identical to the structure of human hyaluronic acid meaning that there are no antibodies formed against it
M protein significance?
Binds to fibronectin and other host proteins which hides the bacteria from the immune system and makes it antiphagocytic. It is the serological marker for Group A strep.
adhesin, PAMP, and defense against antimicrobial peptides
What are streptococcal pyrogenic exotoxin A?
Superantigens...massively activate the immune system and create cytokine storms leading to sepsis
Treatment of Streptococcal pharyngitis with penicillin reduces the risk of
Can you get strep throat from strains with identical M proteins more than once?
Nope. You develop a type specific M- antibody to protect against the recurrence of infection with the infecting serotype.
streptococcal infection that frequently developed after giving birth.
Group A strep Impetigo
superficial purulent skin infection
Most common in children
Often follows insect bites
weeping vesicles that form honey colored crust
What can a GAS skin infection like Impetigo turn into?
What is Ecthyma
deep impetigo...pus filled center.
a form of streptococcal cellulitis, charactertized by red erythema, edema, pain, fever, lymphadenopathy
Acute inflammatory condition of the skin. Deeper than ecthyma or erysipelas. Pain edema, swelling, heat,
Streptococcal toxic shock and necrotizing fascitis
Infection begins inside. Just looks like a bruise, Rapid necrosis of up to an inch an hour. Flu-like, edema, extreme pain way out of proportion to the lesion appearance
Major virulence factors in necrotizing fascitis?
Streptococcal pyrogenic exotoxins.
Treatment of NF?
Rapid antibiotic treatment with penacillin or clindamycin if they have a penicillin allergy
Streptococcal toxic shock presentation
Shock, sepsis, rash that blanches when pressure is applied. Not as common as staph aureus tss
Clinical diagnosis of group A strep toxic shock syndrome
Isolation of GAS from a clinically significant specimen and two or more of the following:
Acute respiratory distress
soft tissue necrosis
skin rash that is a sign of ARF
Also a sign of ARF
edema, hypertension, hematuria, proteinuria, malaise, headache, back pain
Lab: Ig, C3
Group B strep
Bile esculin synthesis, Bacitracin resistant...the 3 Bs
What is CAMP factor
A factor produced by Group B strep that synergizes with staph aureus hemolysin to create increased lysis of red cells
Group B strep used to be the predominant cause of what in infants?
septicemia and meningitis in infants
What is a sensitive test for Group B strep>
Bile Esculin Hydrolysis
You cross streak a potential GBS sample with staph aureus and look to see if its Beta Hydrolysis ring expands. Will separate GBS from GAS.
GBS virulent factor
Capsule...antiphagocytic of course
Alpha protein and fibrinogen binding proteins
Early onset GBS infection in neonates falls during what time period?
7 days or younger.
Includes septicemia, resp distress, meningitis
Late onset GBS in infants when?
2 weeks to 2 months