SSTI's Flashcards
What layer(s) of skin do the following diseases effect? Impetigo Erysipelas Cellulitis Necrotizing fasciitis
Impetigo - epidermis
Erysipelas - dermis
Cellulitis - dermis and subQ
Necrotizing fasciitis - subQ and fascia
Erysipelas
Characteristics
Cause
Tx
Bright red w/ sharp borders, typically affecting face. Raised, indurated, and painful.
Caused by GAS.
Tx w/ penicillin.
Cellulitis
Characteristics
Cause of purulent
Cause of nonpurulent
No sharp borders. Deeper. Red, hot, swollen.
Purulent caused by S aureus (>50% MRSA)
Nonpurulent caused by beta-hemolytic strep, especially GAS. More common.
What is most important and overlooked aspect of cellulitis?
What is tx?
What increases risk?
Lymphadenopathy / lymphedema
Tx w/ support stockings or ACE wraps (not diuretics)
Prior cellulitis increases risk of lymphedema.
Portals of entry for cellulitis (5 things)
Tinea pedis (most common), ulcer (diabetics), trauma, eczema, psoriasis
Diagnosing cellulitis (4 things)
- Blood cultures if hospitalized (low yield)
- Needle aspiration – good for fluctuant (fluid-filled) areas such as bullae, and immunocompromised pxs
- ASO (antistreptolysin O) titer good for GAS
- MRSA swabs in nose, groin, and axilla
When is AB prophylaxis used?
Which AB’s?
AB prophylaxis may be used for recurrent cellulitis (2+ episodes / year) or in pxs where lymphedema is difficult to tx (post-mastectomy). Daily low dose of penicillin, dicloxacillin, clindamycin, or erythromycin for 1 year or longer.
Causes of cellulitis in the following settings: Fresh water trauma Salt water trauma Butcher Periorbital Inmates / MSM / Athletes / Children Fish tank Dog / cat bite
Fresh water trauma - Aeromonas hydrophila
Salt water trauma - Vibrio species
Butcher - Erysipelothrix
Periorbital - S aureus or GAS > 5 y/o
Inmates / MSM / Athletes / Children - CA-MRSA
Fish tank - Mycobacterium marinum
Dog / cat bite - Pasteurella multocida
Risk factors for necrotizing SSTI’s (7 things)
Trauma, surgery, peripheral vascular disease, diabetes, obesity, alcohol / IV drug abuse, immunocompromised.
Clues to suggest severe SSTI’s (5 things)
- Pain out of proportion to visible presentation
- Systemic toxicity – anion gap, creatinine, CK, shock, organ failure
- Rapid progression
- Necrosis, gangrene, bullae, cutaneous hemorrhage, crepitus (gas-forming)
- Anesthesia – due to nerve destruction
GAS Necrotizing Fasciitis
Characteristics
Affected sites (5 places)
Tx
Often background of skin lesion such as boil, abrasion, injection site, insect bite, or minor trauma.
SEVERE pain.
Swelling → bullae (clear → red/purple) → gangrene.
Systemic toxicity may cause shock and organ failure.
•Most commonly found in extremities, anterior abdominal wall, perineum, perianal area, and surgery sites.
•Tx w/ penicillin + clindamycin
Polymicrobial Necrotizing Fasciitis
Characteristic
Example of disease w/ characteristics, population, and organism.
Synergistic infection w/ aerobic and anaerobic bacteria.
Fornier’s Gangrene - polymicrobial infection of perineum / scrotum. Most common in diabetics. Often involves Pseudomonas.
What type of necrotizing fasciitis is caused by salt water, shellfish, or plankton?
Sxs
Population
Vibrio vulnificus necrotizing fasciitis.
Causes large blisters / ulcers
Pxs: cirrhosis and CMI impairment
Gas gangrene Caused by? Mediated by? Sxs Tx
Clostridium perfringes
Toxin-mediated
Sxs - severe pain, edema, bullae, purple hue, “dirty dishwater” drainage, gas, and systemic toxicity.
Tx w/ debridement, penicillin, and clindamycin.
Diabetic foot infection
Acute caused by?
Chronic caused by?
Tx
Acute due to S aureus or Strep
Chronic ulcers often polymicrobial.
Tx w/ debridement, abscess drainage, amputation (if needed), and broad spectrum AB’s.
