Cellulitis is a skin infection that involves the deeper dermis and subcutaneous fat. Erysipelas are more superficial infections that affect the dermis and upper subcutaneous tissues. Most common pathogens are beta-hemolytic streptococci and S. aureus.
Anything that creates a port of entry due to disruption of the skin barrier, such as eczema, radiation therapy, ulcers, tinea pedis, animal bites, obesity and edema.
SIGNS AND SYMPTOMS:
Common manifestations include areas of skin erythema, edema, and warmth. Systemic symptoms may be present (malaise, fever, chills). Lymphadenopathy is also possible.
Cellulitis usually is less well defined (no skin elevation) with a dull red color. The systemic symptoms are insidious. It may present with or without pus.
Erysipelas, on the other hand, have a bright-red color with elevated areas that provide a clear demarcation of the infection. The systemic symptoms in erysipelas are usually more acute, with abrupt onset of fever. Blisters may be present.
History and physical exam are usually sufficient to diagnose the conditions. Additional testing (blood cultures, CBC, CMP, inflammatory markers) may be necessary in cases of patients with prominent systemic symptoms, multiple comorbidities, large lesions, and persistent cellulitis. Patients with trauma, diabetes, lymphedema or ulcers may need radiographic examination to rule out underlying osteomyelitis.
A myriad of skin conditions, infectious and noninfectious, can present in a way that may mimic cellulitis and erysipelas. Details about the history and physical examination may help to distinguish these entities. Among the differential diagnosis, three pathologies are particularly dangerous and require quick intervention: toxic shock syndrome, myonecrosis due to clostridium (gas gangrene) and necrotizing fasciitis.
Patients should be assessed regarding the severity of disease before the provider decide between oral vs parenteral and inpatient vs outpatient therapy. They should also be assessed regarding their risk for MRSA infection in order to choose the proper antibiotics.
Criteria for parenteral therapy (inpatient if necessary) includes: rapid progression, systemic signs of sepsis, infection near prosthetic device, inability to tolerate oral therapy and lack of response to oral therapy after 48 hours.
Criteria for MRSA suspicion and empiric antibiotic coverage includes: abscess, prior MRSA infection or colonization, recent hospitalization, residence in a long-term care facility, recent surgery, hemodialysis, HIV infection, lack of response to antibiotics without MRSA coverage, infection near prosthetic device and signs of sepsis.
If the patient has one abscess, it should be drained and cultures of the material should be performed. A small, single abscess may be treated with incision and drainage only. Larger, multiple abscesses need antibiotic therapy.
Lesions in the mouth or lesions associated with ulcers or skin necrosis may need anaerobic and gram-negative coverage.
Oral antibiotic options:
For regular pathogens (beta-hemolytic Streptococcus) and MSSA: Cephalexin, Dicloxacilin, Cefadrexil, Clindamycin, Flucloxacilin.
For beta-hemolytic streptococcus only: Penicillin or Amoxacilin.
For beta-hemolytic Streptococcus and MRSA: Clindamycin, Amoxicillin PLUS doxycycline OR minocycline OR trimethoprim-sulfamethoxazole.
For MRSA: clindamycin, trimethoprim-sulfamethoxazole, doxycycline, minocycline, linezolid or tedizolid.
Parenteral antibiotic options:
For beta-hemolytic Streptococcus: Cefazolin, Ceftriaxone, Flucloxacilin.
For beta-hemolytic Streptococcus and MSSA: Cefazolin, Clindamycin, Nafcilin, Oxacilin, Flucloxacilin.
For beta-hemolytic Streptococcus and MRSA: Vancomycin, Daptomycin.
For MRSA, gram-negative bacilli and anaerobes: Vancomycin OR Daptomycin PLUS Ampicillin-sulbactam OR Piperacillin-tazobactam OR Ticarcilin-clavulonate OR Ceftriaxone, Ciprofloxacine or Levofloxacine PLUS Metronidazole.
Treatment duration is 7 to 14 days, with first results being visible after 24 to 48 hours.
Examples of Treatment:
Patient with erysipela, no systemic symptoms and no comorbidities: Amoxicillin 500mg PO q8hrs.
Patient with cellulitis, no systemic symptoms, no comorbidities and no MRSA risk: Cephalexin 500mg PO q6hr.
Patient with cellulitis, no systemic symptoms, no comorbidities and MRSA risk: Clindamycin 300-450mg PO q6-8hr
Patient with cellulitis, systemic symptoms, no comorbidities and no MRSA risk: Cefazolin 1-2g IV q8hr.
Patient with cellulitis, systemic symptoms, no comorbidities and MRSA risk: Vancomycin 500mg IV q6hr.
Patient with cellulitis associated with an ulcer: Vancomycin 500mg IV q6hr PLUS Piperacillin-tazobactam 3.375-4.5 g IV q6hr.
REFERENCES & FURTHER READING:
- Stevens DL. et al. Executive Summary: Practice Guidelines for the Diagnosis and Management of Skin and Soft Tissue Infections: 2014 Update by the Infectious Diseases Society of America. Clin Infect Dis (2014) 59 (2): 147-159.
- Swartz MN. Cellulitis. N Engl J Med 2004; 350:904-912
- Björnsdóttir S. et al. Risk Factors for Acute Cellulitis of the Lower Limb: A Prospective Case-Control Study. Clin Infect Dis (2005) 41 (10): 1416-1422.