Streptococci Flashcards
s. pyogenes M protein functions
- binds to keratinocytes
- prevents opsonization by complement (binds fibrinogen and binds complement control protein)
s. pyogenes hyaluronic acid capsule purpose
antiphagocytic structure that serves as camoflage to the immune system
hyaluronidase secreted by bacteria can ____ the capsule, and also allows s. pyogenes _____
digest; to spread through tissue
streptokinase binds _____- enzymatic conversion to ____
plasminogen; plasmin
plasmin coated GAS can degrade and spread through _____ resulting in invasive disease
fibrin (blood clots)
_____ has therapeutic use in treating _____
streptokinase; blood clots
_____ cause rash associated with scarlet fever (toxin spreads through blood)
erythrogenic toxins or streptococcal pyrogenic exotoxins (SpeA, SpeB, and SpeC)
____ is the most abundant extracellular protein
SpeB
SpeA and SpeC are bacterial _____ that non-specifically activate a large subset of ____
superantigens; T-cells
SpeA and SpeC cause ____
streptococcal toxic shock sundrome (STSS)
most common manifestations of GAS
- acute pharyngitis (strep throat)
- pyoderma- GAS infection of the skin- impetigo
suppurative (pus) infections of s. pyogenes GAS
upper respiratory tract: acute pharyngitis (strep throat) scarlet fever (toxigenic strains)
tx for suppurative infections
10 days penicillin
skin infections caused by GAS (also suppurative)
- cellulitis
- erysipelas
- impetigo
tx for skin infections:
topical antibiotics: mupirocin ointment, oral antibiotics if widespread infection
non-suppurative infections (autoimmune diseases) caused by GAS
- acute rheumatic fever (ARF)
- acute poststreptococcal glomerulonephritis (APSGN)
ARF only follows _____
pharyngeal infections by rheumatogenic strains
APSGN only follows ____
pharyngeal or skin infections by nephritogenic strains
Symptoms of ARF
- fever
- painful joints (arthritis)
- chorea (fidgity or abnormal movements)
- heart murmur
- non itchy erythema marginatum rash
symptoms of APSGN
- edema
- gross hematuria (tea colored urine)
- hypertension
tx for APSGN:
sodium reduction
diuretics
95% recover
group B streptococci, particularly s. agalactiae (aerobic) is the leading cause of _____
neonatal sepsis and meningitis
Group B streptococci have _____ that prevents opsonization and phagocytosis
polysaccharide capsule
____ streptococci also have hyaluronic acid capsule, similar to group A
Group C
groups C and D streptococci are implicated in ____ but not _____
APSGN; ARF
enterococci cause:
nosocomial infections, urinary tract infections, and endocarditis
non-enterococcal group D streptococci
s. bovis- most common for human disease (from cows, sheep, other ruminants)
s. suis- pigs to humans
viridans (greening) streptococci is ____ strep
alpha-hemolytic
viridans most common cause of _____
subacute bacterial endocarditis
