DESCRIPTION

• Acute, spreading erythematous superficial infection of skin and SC tissues:
  • Variety of pathogens
  • Extension into deeper tissues can result in necrotizing soft tissue infection
• Progressive spread of erythema, warmth, pain, and tenderness
• Predisposing factors:
  • Lymphedema
  • Tinea pedis
  • Open wounds
  • Pre-existing skin lesion (furuncle)
  • Prior trauma or surgery
  • Retained foreign body
  • Vascular or immune compromise
  • Injection drug use

ETIOLOGY

• Simple cellulitis:
  • Group A streptococci
  • Staphylococcus aureus—including resistant strains such as community-associated methicillin-resistant S. aureus (CA-MRSA; see below):
    • CA-MRSA risk factors include: Prior MRSA infection, household contact of CA-MRSA patient, daycare contact of MRSA patients, children, soldiers, incarcerated persons, athletes in contact sports, IV drug users, men who have sex with men
    • Different antibiotic susceptibility than nosocomial MRSA
    • CA-MRSA now sufficiently prevalent to warrant empiric treatment
    • Suspect CA-MRSA in unresponsive infections
• Nosocomial MRSA:
  • Risk factors: Recent hospital or long-term care admission, surgery, injection drug use, vascular catheter, dialysis, recent antibiotic use, unresponsive infection
  • Resistant to most antibiotics (see "Treatment")
• Extremity cellulitis after lymphatic disruption:
  • Nongroup A β-hemolytic streptococci (groups C, B, G)
• Cellulitis in diabetics:
  • Can be polymicrobial with S. aureus, streptococci, gram-negative bacteria, and anaerobes, especially when associated with skin ulcers
• Periorbital cellulitis:
  • S. aureus
  • Streptococcal species
• Buccal cellulitis:
  • Haemophilus influenzae type B
  • Anaerobic oral flora, associated with intraoral laceration or dental abscess
• Less common causes:
  • Clostridia
  • Anthrax
  • Pasteurella multocida—common after cat and dog bites
  • Eikenella corrodens—human bites
  • Pseudomonas aeruginosa:
    • Hot-tub folliculitis—self-limited
    • Foot puncture wound
    • Ecthyma gangrenosum in neutropenic patients
  • Erysipelothrix species—raw fish, poultry, meat, or hide handlers
  • Aeromonas hydrophila—freshwater swimming
  • Vibrio species—seawater or raw seafood

Pediatric Considerations

• Facial cellulitis in children:
  • Streptococcus pneumoniae
  • H. influenzae type B, although incidence declining since introduction of HIB vaccine
• Perianal cellulitis:
  • Group A streptococci
  • Associated or antecedent pharyngitis or impetigo
• Neonates:
  • Group B streptococci

[Outline]

• DESCRIPTION
• ETIOLOGY

SIGNS AND SYMPTOMS

• Common to all syndromes:
  • Pain, tenderness, warmth
  • Erythema
  • Edema or induration
  • Fever/chills
  • Tender regional lymphadenopathy
  • Lymphangitis
  • Accompanying SC abscess possible
  • Suspect deep abscess especially if treatment failure on initial antibiotic
  • Superficial vesicles
• Buccal cellulitis:
  • Odontogenic cases more serious:
    • Toothache, sore throat, or facial swelling
    • Progressive extension into soft tissues of neck with fever, erythema, neck swelling, and dysphagia

Pediatric Considerations

• Facial cellulitis in children:
  • Erythema and swelling of the cheek and eyelid
  • Rapidly progressive
  • Usually unilateral
  • Upper respiratory tract symptoms
  • Risk for cavernous sinus thrombosis and permanent optic nerve injury
• Perianal cellulitis:
  • Erythema and pruritus extending from the anus several centimeters onto adjacent skin
  • Pain on defecation
  • Blood-streaked stools

History

Patients often incorrectly attribute CA-MRSA infection with spontaneous abscess to a spider bite

Physical Exam

In simple cellulitis, physical findings can suggest the etiology and help narrow empiric antibiotic coverage:

• Staph etiology: Focal abscess or pustule with: Fluctuance, yellow or white center, central point or "head," or draining pus, indolent progression
• Strep etiology: Sharply demarcated borders, lymphangitis, pre-existing lymphedema, concomitant nausea from toxin

ESSENTIAL WORKUP

• Cellulitis is a clinical diagnosis.
• Physical exam to reveal infection source

DIAGNOSIS TESTS & INTERPRETATION

Lab

• WBC generally unnecessary
• Gram stain and culture to focus antimicrobial selection and reveal resistant pathogens (MRSA):
  • Aspirate point of maximal inflammation or punch biopsy if there is no wound to culture
  • Perform in treatment failures and consider in admitted patients
• Blood culture:
  • Usually negative in uncomplicated cellulitis
  • May identify organism in patients with:
    • Lymphedema
    • Buccal or periorbital cellulitis
    • Saltwater or freshwater source
    • Fever or chills

Imaging

• Plain radiographs may reveal abscess formation, SC gas, or foreign bodies:
  • Extension to bone (osteomyelitis) not visualized early on plain radiographs
• Extremity vascular imaging (Doppler US) can help rule out deep venous thrombosis (DVT).
• US useful for diagnosing abscess if physical exam is equivocal or if there is a broad area of cellulitis
  • In cellulitis may see characteristic "cobblestone" appearance and thickening of SC layer, both due to edema
• CT or MRI can help rule out necrotizing fasciitis

DIFFERENTIAL DIAGNOSIS

• Necrotizing fasciitis
• Lymphangitis or lymphadenitis
• Thrombophlebitis or DVT:
  • Differentiation from cellulitis:
    • Absence of initial traumatic or infectious focus
    • No regional lymphadenopathy
    • Presence of risk factors for DVT
• Insect bite
• Allergic reaction
• Acute gout or pseudogout
• Ruptured Baker cyst
• Herpetic whitlow
• Neoplasm
• Phytophotodermatitis
• Erythema chronicum migrans lesion of Lyme disease
• Differential diagnosis of facial cellulitis:
  • Allergic angioedema
  • Conjunctivitis
  • Contusion

Pediatric Considerations

Differential diagnosis of perianal cellulitis:

• Candida intertrigo
• Psoriasis
• Pinworm infection
• Child abuse
• Behavioral problem
• Inflammatory bowel disease

[Outline]

• SIGNS AND SYMPTOMS
• ESSENTIAL WORKUP
• DIAGNOSIS TESTS & INTERPRETATION
• DIFFERENTIAL DIAGNOSIS

INITIAL STABILIZATION/THERAPY

Airway compromise possible with deep extension of facial or neck cellulitis

ED TREATMENT/PROCEDURES

• General principles:
  • Consider local prevalence of resistant pathogens in addition to usual causes
  • In simple cellulitis, periorbital cellulitis, and diabetic patients, need to include CA-MRSA coverage in empiric therapy
  • Usual outpatient treatment: 7–10 days
  • Cool compresses for comfort
  • Analgesics
  • Extremity elevation
  • Treat predisposing tinea pedis with topical antifungal such as clotrimazole
• Simple cellulitis:
  • Outpatient:
    • Oral Cephalexin + TMP/SMX (to cover CA-MRSA)
    • Alternatives to cephalexin: Oral dicloxacillin, macrolide, or levofloxacin
    • Alternatives to TMP/SMX: Clindamycin or Doxycycline
  • Inpatient:
    • IV nafcillin or equivalent, + IV vancomycin (to cover CA-MRSA)
• Extremity cellulitis after lymphatic disruption:
  • Same as simple cellulitis
• Cellulitis in diabetics:
  • Outpatient:
    • Amoxicillin/clavulanate + TMP/SMX (to cover CA-MRSA), or clindamycin
  • Inpatient:
    • IV ampicillin/sulbactam or imipenem cilastatin or equivalent; + IV vancomycin (to cover CA-MRSA)
• Periorbital cellulitis in adults:
  • Outpatient: Oral dicloxacillin or azithromycin; + TMP/SMX (to cover CA-MRSA)
  • Inpatient: IV vancomycin
• Buccal cellulitis in adults:
  • Outpatient: Oral amoxicillin/clavulanate
  • Inpatient: IV ceftriaxone
  • Odontogenic source:
    • Drainage essential
    • Coverage for anaerobes: Clindamycin
• Facial cellulitis in children:
  • IV ceftriaxone
• Perianal cellulitis:
  • Outpatient: Oral penicillin VK
  • Inpatient: IV penicillin G (aqueous)
• Animal or human bite:
  • Oral amoxicillin/clavulanate
• Foot puncture wound:
  • Oral or IV ciprofloxacin or IV ceftazidime
• MRSA:
  • Nosocomial MRSA: IV vancomycin or oral or IV linezolid
  • CA-MRSA:
    • PO: TMP/SMX, clindamycin or doxycycline
    • IV: Vancomycin or clindamycin

MEDICATION

• Amoxicillin/clavulanate: 500–875 mg (peds: 45 mg/kg/24h) PO BID or 250–500 mg (peds: 40 mg/kg/24h) PO TID
• Ampicillin/sulbactam: 1.5–3 g (peds: 100–300 mg/kg/24h up to 40 kg; over 40 kg give adult dose) IV q6h
• Azithromycin: (Adults and peds) 10 mg/kg up to 500 mg PO on day 1, followed by 5 mg/kg up to 250 mg PO daily on days 2–5
• Ceftazidime: 500–1,000 mg (peds: 150 mg/kg/24h; max. 6 g/24h; use sodium formulation in peds) IV q8h
• Ceftriaxone: 1–2 g (peds: 50–75 mg/kg/24h) IV daily
• Cephalexin: 500 mg (peds: 50–100 mg/kg/24h) PO QID
• Ciprofloxacin: (Adult only) 500–750 mg PO BID or 400 mg IV q8–12h
• Clindamycin: 450–900 mg (peds: 20–40 mg/kg/24h) PO or IV q6h
• Dicloxacillin: 125–500 mg (peds: 12.5–25 mg/kg/24h) PO q6h
• Doxycycline: 100 mg PO BID for adults
• Erythromycin base: (Adult) 250–500 mg PO QID
• Imipenem cilastatin: 500–1,000 mg (peds: 15–25 mg/kg) IV q6h; max. 4 g/24h or 50 mg/kg/24h, whichever is less
• Levofloxacin: (Adult only) 500–750 mg PO or IV daily
• Linezolid: 600 mg PO or IV q12h (peds: 30 mg/kg/24h div. q8h)
• Nafcillin: 1–2 g IV q4h (peds: 50–100 mg/kg/24h divided q6h); max. 12 g/24h
• Penicillin VK: 250–500 mg (peds: 25–50 mg/kg/24h) PO q6h
• Penicillin G (aqueous): 4 mU (peds: 100,000–400,000 U/kg/24h) IV q4h
• Trimethoprim/sulfamethoxazole (TMP/SMX): 2 DS tabs PO q12h (peds: 6–10 mg/kg/24h TMP div. q12h)
• Vancomycin: 1 g IV q12h (peds: 10 mg/kg IV q6h; dosing adjustments required younger than age 5 yr); check serum levels

[Outline]

• INITIAL STABILIZATION/THERAPY
• ED TREATMENT/PROCEDURES
• MEDICATION

DISPOSITION

Admission Criteria

• Toxic appearing
• Tissue necrosis
• History of immune suppression
• Concurrent chronic medical illnesses
• Unable to take oral medications
• Unreliable patients

Discharge Criteria

• Mild infection in a nontoxic-appearing patient
• Able to take oral antibiotics
• No history of immune suppression or concurrent medical problems
• No hand or face involvement
• Has adequate follow-up within 24–48 hr

FOLLOW-UP RECOMMENDATIONS

• Follow-up within 24–48 hr
• Sooner if worsening symptoms, including new or worsening lymphangitis, increasing area of redness, worsening fever
• Outline the border of erythema before discharge to aid in assessing response to therapy

[Outline]

• DISPOSITION
• FOLLOW-UP RECOMMENDATIONS

• Strep and staph are most common causes
• CA-MRSA now significant cause of cellulitis, frequent enough to warrant including coverage in empiric treatment
• Clinicians not accurate at identifying MRSA at the bedside
• A deep abscess may be misclassified as cellulitis
• Use clinical suspicion and ultrasound to avoid missing an abscess

ICD9

• 682.3 Cellulitis and abscess of upper arm and forearm
• 682.6 Cellulitis and abscess of leg, except foot
• 682.9 Cellulitis and abscess of unspecified sites

ICD10

• H05.019 Cellulitis of unspecified orbit
• L03.90 Cellulitis, unspecified
• L03.119 Cellulitis of unspecified part of limb

[Outline]

• ICD9
• ICD10

• Abrahamian FM, Talan DA, Moran GJ. Management of skin and soft-tissue infections in the emergency department. Infect Dis Clin North Am. 2008;22:89–116.
• Gunderson CG. Cellulitis: Definition, etiology, and clinical features. Am J Med. 2011;124:1113–1122.
• Liu C, Bayer A, Cosgrove SE, et al. Clinical practice guidelines by the Infectious Diseases Society of America for the treatment of methicillin-resistant Staphylococcus aureus infections in adults and children. Clin Infect Dis. 2011;52:1–38.
• Pasternack MS, Swartz MN. Cellulitis, necrotizing fasciitis and subcutaneous tissue infections. In: Mandell GL, Bennett JE, Dolin R, eds. Mandell, Douglas and Bennett's Principles and Practice of Infectious Diseases. 7th ed. New York, NY: Elsevier/Churchill Livingstone; 2010:1289–1312.
• Phoenix G, Das S, Joshi M. Diagnosis and management of cellulitis. BMJ. 2012;345:e4955.
• Swartz MN. Cellulitis. New Engl J Med. 2004;350:904–912.

See Also (Topic, Algorithm, Electronic Media Element)

• Abscess, Skin/Soft Tissue
• Lymphadenitis
• Lymphangitis
• MRSA
• Necrotizing Fasciitis

John Mahoney

Dolores Gonthier