Skin and Soft Tissue Infections Flashcards
Erysipelas
o Acute spreading inflammation of dermis with prominent lymphatic involvement
o Bright red, tender, indurated (firm)
o Sharp borders, elevated
o Regional adenopathy common
o Almost always caused by Strep pyogenes
o Outpatient infection managed by oral antibiotics
• Penicillin, vancomycin
Cellulitis
o Acute spreading inflammation of dermis and subcutaneous tissues with prominent lymphatic involvement
o Red, warm, tender and swollen
o Borders are fuzzy, not elevated
o Regional adenopathy common
Majority caused by Group A Streptococci
• Staph aureus causes significant proportion
• Recent leading cause = Community associated MRSA (CA-MRSA)
• Also: important to assess history → unusual organisms may be present
Cellulitis: unusual organisms/settings
Fresh water trauma = aeromonas hydrophila
salt water trauma = vibrio species
fish handles/butcher = erysipelothrix
periorbital = S. aureus > GAS over age 5
Inmates, MSM, athletes, children, anybody? = CA-MRSA
immune compromised = aerobic Gram-negative rods, fungi, mycobacterial
fish tank = mycobacterium marinum
dog/cat bite = pasteurella multocida
Cellulits: pathophysiologic components
Portal of entry • Tinea pedis • Ulcer (diabetes) • Trauma • Eczema • Psoriasis • None evident
Lymphedema (localized collection of lymph in soft tissues)
• Priority in cellulitis treatment
• Chronic, non-resolving lymphedema has increased risk for cellulitis
• Etiologies: (variety of causes)
o Venous insufficiency
o Prior episodes of cellulitis
o Prior surgery (ex: leg vein harvest)
o Prior lymph node dissection (ex: breast cancer)
o Prior radiation therapy
o Prior deep vein thrombosis
o Congenital
Bacteria
Cellulitis management
- Identify clues for unusual bacteria
- Recognize and fix any portal of entry
- Manage lymphedema (raise affected limb above level of heart)
- Culture blister fluid, pus, abscess, blood
- Needle aspirate of advancing edge (in select patients)
- Only positive in <25% patients
- Due to relatively low number of organisms = can’t culture
- Useful when setting suggests unusual pathogen, immunocompromised host, or areas of fluctuance (fluid under skin) on exam
Antibiotics based on expected organism
- -Gp A Strep = penicllin
- -S. aureus (nonMRSA) = nafcilin, clindamycin, amoxicillin/clavulanate
- -S. aureus (MRSA) = vancomycin, clindamycin, linezolid, TMP-SMX, daptomycin, minocyclin
- -Aerobic GNR = fluoroquniolone
Necrotizing fasciitis
o Subcutaneous infection tracking along fascial planes
o Extends beyond superficial signs of infection
o Progressive destruction of fascia
o Can be polymicrobial or monomicrobial
Most causes: • Boil • Abrasion • Injection site • Insect bite • Other area of trauma • About 20% have not recognizable primary site of infection
Clinical signs:
• Brawny, hardened soft tissues
• Severe pain
• Swelling → bullae (clear → red/purple) → gangrene
• Systemic toxicity = shock and organ failure
Mono-microbial necrotizing fasciitis
Group A Streptococci
• High mortalitiy
• Often secondary to minor injuries
• Rapid progression, severe systemic toxicity, severe pain
• Prompt, aggressive surgical debridement needed
• Treat: penicillin and clindamycin
S. aureus (especially CA-MRSA)
• Risks: injection drug use, past MRSA infections, HIV/AIDS, diabetes, chronic hepatitis, cancer
• Result: need anti-MRSA antibiotics in initial treatment until microbiology results are known
Vibrio vulnificus
• Salt water, shellfish, plankton
• Rapidly progressive infection
• Often with large blisters and ulceration
• High risk: patients with cirrhosis or impaired cellular immunity
Gas gangrene
o Most common cause = C. perfringens
o Associated with trauma
o Toxin-mediated
Characterized: • Severe pain at injury site • Tense edema • Fluid-filled bullae • Purplish hue to skin • Thin “dirty dishwater” drainage • Gas in soft tissues
o Systemic toxicity develops rapidly
o Need aggressive surgical debridement
o Treatment: penicillin + clindamycin
List the polymicrobial infections
Fournier gangrene
diabetic foot ulcer
immunocompromised hosts
bite wound infections
Fournier gangrene
- Specific form of polymicrobial necrotizing fasciitis involving perineum
- Starts with at-risk host (especially diabetics) with mild infection or trauma in perianal/genital region
- Infection spreads to subcutaneous tissues, base of scrotum or anterior abdominal wall
- Mixed infection: aerobes and anaerobes
- Higher rate of Pseudomonas aeruginosa
Diabetic foot ulcer
- Often start with neuropathic ulcer = colonized by variety of bacteria
- Complex
- Associated osteomyelitis
- Ranges from mild to limb- and life-threatening
- Surgical debridement usually needed
- Broad spectrum antibiotics: cover strep, staph (including MRSA), Gram-negative aerobes, and anaerobes
Infections in Immunocompromised hosts
Neutropenia
Aerobic Gram-negative rods + staph/strep (fungi later)
Always include potent anti-pseudomonal coverage
Ecthyma gangrenosum:
o Cutaneous vasculitis
o Occurs in association with Pseudomonas aeruginosa
o Initial painless red macule → painful necrotic lesion
o Can be multiple lesions, often found in groin
CMI impairment
• Add mycobacteria, Nocardia, Cryptococcus, histoplasmosis, other fungi, Varicella-Zoster Virus, Herpes-Simples Virus, cytomegalovirus, scabies
• Critical to biopsy skin lesions
• Look for dissemination
Bite wound infections
Human bites Contain oral bacteria flora: o Strept and Staph o Hemophilus spp o Eikenella corrodens o Other anaerobes Carry risk of hepatitis B and C, syphilis, herpes simplex, HIV Treatment: o Wound irrigation and cleansing o Tetanus toxoid o Antibiotics regardless of wound appearance (use broad-spectrum antibiotics prophylactically) o Ex: amoxicillin/clavulanate or fluroquinolones + clindamycin
Cat and dog bites Contain oral flora: o Strep and Stah o Anaerobes o Pasteurella multocida o Capnocytophaga canimorsus: • Associated with dog bites • Gram-negative rod • Causes severe infection/sepsis in patients without spleens or with liver disease Cat bites = usually more severe → increased risk of joint and bone involvement Treatment: o Wound irrigation and cleansing o Antibiotics: amoxicillin/clavulanate or fluroquinolones or cerfuroxime + clindamycin
Describe the factors involved in recurrent cellulitis and the treatment strategies that are important in terms of decreasing the risk of future episodes
Cycle of cellulitis and lymphedema
• Need to interrupt cycle:
Treat predisposing factors
• Portal of entry management: tinea treatment
• Lymphedema management: support stockings, ACE wraps, others
o Long-term antibiotic prophylaxis if frequent (2 or more) episodes of cellulitis or erysipelas within 1 year
o Antibiotics include: low-dose penicillin VK, erythromycin, dicloxacillin, clindamycin
Describe the clinical features that suggest the presence of a life-threatening skin and soft tissue infection.
Necrotizing skin and soft tissue infections:
o Infections with massive tissue destruction, severe systemic illness, high mortality
o Require prompt and aggressive surgical debridement
Important:
• Recognition
• Emergent surgical evaluation at earliest stage of presentation
o Antibiotics alone cannot clear infection
Risk factors: • Trauma • Surgical wound • Peripheral vascular disease • Diabetes • Obesity • Alcohol abuse/injection drug abuse • Immunocompromised
Clinical clues:
• Pain out of proportion to what you see
• Systemic toxicity (early signs of sepsis)
• Rapid progression
• Necrosis (black) of the skin, gangrene, bullae, cutaneous hemorrhage, crepitus (popping sound under skin)
• Anesthesia (nerves have been infarcted)
