Module 13.3 - Cellulitis

Question 1

What is and what causes cellulitis?

Answer 1

• A skin or soft tissue infection with manifested as an area of erythema, warmth and edema.
• Resulting from a bacterial infection which occurs due to a break in the skin.
• Commonly caused by Gram positive cocci (group A Beta-hemolytic streptococci and Staphylococcus aureus), but can involve other organisms.
• Commonly involves the lower extremities
• Often complicated by deep vein thrombosis, especially in the elderly
• Predisposes individuals to recurrent infections

Question 2

What are some predisposing factors for cellulitis?

Answer 2

• Preexisting skin infection
• Diabetes
• Trauma to area, including pressure ulcer, venous stasis ulcer, insect bites, etc.
• Obesity
• Immunosuppressive states
• Edema secondary to venous insufficiency
• Edema secondary to altered lymphatic drainage
• Inflammatory conditions- post radiation therapy, eczema
• Injection drug use

Question 3

What are the subjective/physical exam findings associated with cellulitis?

Answer 3

Subjective:

• Pain at site, tenderness, swelling, erythema and warmth
• Usually unilateral in presentation
• Symptoms intensify over days
• Fever, chills and fatigue/malaise
• Hypotension/shock should sepsis develop

Physical Exam:

• Erythema with indistinct margins, warmth and tenderness to palpation
• Lymphadenopathy of regional nodes
• Linear streaks of erythema- lymphangitis

Question 4

What lab/diagnostic tests are used to diagnose cellulitis?

Answer 4

• Diagnosis is usually based on clinical exam
• Laboratory testing is usually not required for individuals with uncomplicated infections and a lack of co-morbidities
• Blood cultures should be obtained if patients have:
  
  • Failed to respond to standard therapy- persistent cellulitis
  • Serious co-morbidities (DM, lymphedema, malignancy, splenectomy)
  • Extensive soft tissue involvement
  • Abscess development
  • Lymphedema
  • Periorbital cellulitis
  • Any infection associated with salt or freshwater
  • High-grade fevers/chills
  • Immunodeficiency

Question 5

What conditions should be on your differential when diagnosing cellulitis?

Answer 5

Cellulitis must be distinguished from the following infectious disorders:

• Erythema migrans- an early manifestation of Lyme disease
• Herpes Zoster
• Septic arthritis
• Septic bursitis
• Osteomyelitis
• Necrotizing fasciitis

Cellulitis must be distinguished from the following non-infectious disorders:

• Contact dermatitis
• Acute gout
• Drug reaction
• Vasculitis
• Deep Vein Thrombosis
• Stasis dermatitis from chronic venous insufficiency
• Lymphedema- peripheral

Question 6

How do you treat a patient with cellulitis?

Answer 6

Medications:

• PCN VK 500mg qid x 5 days
• Cephalexin 500mg po qid x 5 days
• Dicloxacillin 250mg or 500mg qid x 5 days

For PCN allergy:

• Erythromycin 250mg po qid
• Clindamycin 300mg po qid x 5 days

Other:

• Patients who appear toxic or have underlying co-morbidities that causes an impaired immune response should be hospitalized.
• Immobilization and elevation of affected limb may be helpful
• Moist heat may help to localize infection
• Follow-ups are necessary to ensure treatment is sufficient

Question 7

What drugs are given to treat community acquired MRSA cellulitis?

Answer 7

For community acquired MRSA:

• Doxycycline 100mg po bid
• TMP-SMX DS 1 tab po bid
• Clindamycin 300mg po qid x 5 days
• Linezolid 600mg po bid