export_ssti bacteria ii Flashcards
Alpha-hemolysis
Green coloration
Beta-hemolysis
Complete hemolysis
Gamma-hemolysis
No color change or lysis
Lancefield Ags
A, B, and D
Distinguish between Strep. species
A Lancefield Ag
Found in S. pyogenes
B Lancefield Ag
S. agalactiae
D Lancefield Ag
S. bovis
Enterococcus
Strep. without Lancefield Ag
S. pneumoniae
S. mutans
Group A strep disease
S. pyogenes
Strep throat
S. pyogenes features
Beta-hemolytic
Sensitive to Bacitracin
S. pyogenes virulence factors
Capsule
Adhesins (F and M protein, LTA)
Toxins (streptolysin O and S, superantigens)
LTA
Adhere to fibronectin
F and M protein
Invasion of epithelial cell
M protein
Anti-phagocytic
Inhibits complement
Facilitates cell invasion (fibrinogen, Ig, factor H)
Streptolysin O and S
Pore forming toxins
Allow invasion and destruction of cells/tissues
Strep. superantigens
SPEs
Proinflammatory cytokine response
C5a peptidase
Degrades C5a (chemoattractin that brings PMNs to site of infection)
SSTI by S. pyogenes
Impetigo
Erysipelas
Cellulitis
Necrotizing fasciitis
What is the most common cause of cellulitis?
S. pyogenes
Diagnostic symptom of necrotizing fasciitis
Pain and tenderness are usually severe
Difference between cellulitis and necrotizing fasciitis
Cellulitis generally looks worse early on, and is less painful
Treatment of necrotizing fasciitis
Debridement of area
Antibiotics are supplemental
Scarlet fever
Complication of GAS pharyngitis
Caused by SPE toxin
Diffuse erythematous rash
Acute rheumatic fever
Complication of GAS pharyngitis
Cross-reactive Abs attack joints, heart valves, etc.
Acute poststrep glomerulonephritis (APSGN) cause
Complication of either GAS pharyngitis OR SSTI
Type III hypersensitivity
Ag mimicry of M protein or streptokinase
APSGN symptoms
Hematuria, edema, HTN
Reduced serum complement
Difference between Strep. and Staph. TSS
Strep. often comes with bacteremia and necrotizing fasciitis, and is the result of SPEs
Diagnose and treat GAS infection
Anti-streptolysin O Abs in serum
Penicillin
Pseudomonas aeruginosa features
Oxidase positive
Antibiotic resistance
Minimalist
Production of pyocyanin pigment
Primarily nosocomial and opportunistic
P. aeruginosa virulence factors
Mucoid polysaccharide capsule (alginate)
Adhesins
Toxins (ETA, T3SS)
ETA
AB toxin
Inactivates EF2 - blocks protein synthesis
P. aeruginosa SSTIs
Infections in burn wounds
Folliculitis
Osteochondritis (following traumatic injury)
Ecthyma gangrenosum
Ecthyma gangrenosum
Infection of blood vessels resulting in characteristic necrotic skin lesions
“Green nails”
Biofilm of P. aeruginosa on the nails
Often associated with previous condition of candidal paronychia
Webspace intertrigo
Macerated and eroded skin between skin folds, most commonly associated with P. aeruginosa
Treatment of P. aeruginosa
Aminoglycosides and beta-lactam
Antibiotic resistance is a problem
