M-protein
Important potential virulence factor of S. pyogenes; causes AGN
*can also be DNAse (+), hyaluronidase (+), or have Streptolysin O or S
Impetigo
Contagious superficial infection seen in children; purulent w/ crusting
- Can also be bullous or pustular w/ crusted lesions; presents in warm, humid times
- Caused by S. aureus or S. pyogenes
Bullous impetigo
Assoc. w/ Scalded Skin Syndrome; caused by exfoliative toxin A from S. aureus
- Destruction of intracellular connections in the epidermis
- Highly contagious
Erysipelas
A sharply demarcated, salmon red lesion that is a superficial erythematous lesion (does not go to dermis)
-Presents in the face or leg
**ALWAYS CAUSED BY S. PYOGENES
Cellulitis
Elevated and inflamed lesion accompanied by lymphadenitis of the draining node
- MOST COMMON CAUSE IS S. AUREUS
- Also caused by S. pyogenes, H. influenzae (unvaccinated), and P. multocida (after dog/cat bite)
Necrotizing Fasciitis
Type I: Occurs after surgery and in pts. w/ diabetes; mixed Gram pos and neg infxn
Type II: Caused specifically by S. pyogenes
- C. perfringens can cause myonecrosis and produce gas in the skin
- Extensive tissue destruction, thrombosis, destruction of fascia and fat (subcutaneous layer)
V. vulnificus
Causes severe necrotizing fasciitis characterized by initial swelling, erythema, and eventual necrosis
- Occurs after exposure to contaminated sea water
- Very fatal (~50%)
Ecthyma gangrenosum
Causes tissue necrosis in neutropenic pts. w/ P. aeuruginosa bactermia
-Can also cause “bath tub folliculitis” or infect burn pts.
Leprosy
Tuberculoid: Red-blotchy lesions that are non-infective
=»Treat w/ rifampin, dapsone
Lepromatous: Diffuse lesions that are highly infective
=»Treat w/ rifampin, dapson, and clofazimine (possibly for life)
Bacillus anthracis characteristics
“King Anthra’s Axe”
Spore-forming GPR; encapsulated w/ D-glutamic acid
Contains exotoxin w/ 3 parts:
Edema factor (cya)- AC that increases intracellular cAMP inhibiting the flow of ions and water
Lethal factor (Lef)- protease that induces macrophages to release cytokines and initiate shock
Protective antigen (Pag)- promotes the entry into phagocytic cells only
Diagnosis: Examination of material from lesions; grows non-hemolytic, sticky colonies on culture
Treatment: Penicillin, Cipro, and Doxy for 60 days
-Short-term vaccine also available
Inhalation anthrax
Inhalation of aerosolized spores =» fever, SOB, malaise, chest/abdominal pain
-Death 3 days later
-Will also see mediastinal widening on x-ray
Cutaneous anthrax
Painless papule forms at site of inoculation that =» necrotic, black eschar
-Localized tissue necrosis caused by toxin release