Basics
Description
- Cellulitis is an acute, spreading pyogenic inflammation of the dermis and subcutaneous tissue, often complicating a wound or other skin condition.
- Cellulitis may be further classified by the unique area of the body it affects (e.g., periorbital or orbital cellulitis, peritonsillar cellulitis, etc.).
Epidemiology
- The most common cause of cellulitis in children is Staphylococcus aureus or Streptococcus pyogenes infection, which develop secondary to local trauma of the integument.
- Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) infections continue to increase in incidence, but much more commonly cause purulent abscesses rather than cellulitis.
- The prevalence of CA-MRSA among purulent skin and soft tissue infections is >60% in some communities.
- Clinical failures caused by penicillin-resistant Streptococcus pneumoniae have not yet become a significant problem in cases of uncomplicated cellulitis.
- Bacteremic disease is uncommon, owing to the tremendous efficacy of vaccines against both Haemophilus influenzae type b (Hib) and S. pneumoniae.
General Prevention
- Good wound care is paramount.
- All wounds should be cleaned with soap and water, then covered with a clean, dry cloth.
- Topical antibiotic ointment is optional with minor wounds.
Pathophysiology
- Cellulitis usually occurs after local trauma that breaches in the integument (abrasions, lacerations, bite wounds, excoriated dermatitis, varicella, etc.).
- Secondary to local invasion or infection (e.g., sinusitis leading to orbital cellulitis)
- Hematogenous dissemination (rarely)
Etiology
- S. aureus: methicillin-susceptible Staphylococcus aureus (MSSA) and MRSA
- Group A β-hemolytic streptococci (GABHS, or S. pyogenes)
- S. pneumoniae (uncommon)
- Group B streptococci (GBS) and gram-negative rods (GNRs): neonates
- Hib (rare)
- Pseudomonas aeruginosa and anaerobic bacteria: immunocompromised children
- Pasteurella species: from cat and dog bites
- Eikenella corrodens: from human bites
Commonly Associated Conditions
- Periorbital
- Usually from local trauma (scratch, impetigo, eczema, excoriated varicella)
- Hematogenous spread is very uncommon.
- Rarely associated with infectious conjunctivitis
- Orbital
- Commonly associated with severe sinusitis
- Less commonly: dental abscess, trauma, hematogenous spread
- Buccal: usually from local trauma; hematogenous seeding also very rare.
- Peritonsillar
- Commonly due to GABHS pharyngitis
- Cellulitis may progress to a peritonsillar abscess.
- Extremity: usually secondary to local trauma
- Breast: usually with mastitis (neonates)
- Perianal
- Seen in infants and young children
- Etiology: GABHS
- Perianal pain, pruritus, and erythema; sometimes associated with bloody stools
- Cellulitis-adenitis syndrome
- Neonates and infants
- Etiology: GBS, S. aureus, GNRs
- Bacteremia/meningitis commonly associated.
Diagnosis
History
- An expanding, red, painful area of swelling is the most common presentation.
- Mild constitutional symptoms (with or without fever) are commonly associated with cellulitis.
- A history of local trauma to the integument is the clue to the portal of bacterial entry.
- Visual changes, proptosis, and painful or limited eye movements are classic findings in orbital cellulitis.
- Painful swallowing, pain with opening the mouth (trismus), and muffled ("hot potato") voice are classic presenting symptoms of peritonsillar cellulitis/abscess.
Physical Exam
- Erythema, edema, tenderness, and warmth: usual clinical findings of cellulitis
- Distinct demarcation of raised erythema: classic description of erysipelas, a superficial cellulitis usually associated with S. pyogenes
- A red streak extending proximally from the extremity: lymphangitis, which usually implies more serious involvement
- Regional adenopathy: commonly associated with minor cellulitis; occasionally complicated by lymphadenitis
Diagnostic Tests & Interpretation
Lab
- WBC: normal or elevated
- Blood culture: rarely positive. Ill-appearing children and children with extensive areas of cellulitis may warrant a blood culture.
- Wound culture: As resistance continues to rise (especially MRSA), wound cultures are useful.
Imaging
- Radiographs: sometimes helpful to rule out complications such as osteomyelitis. Also useful in cases of suspected foreign bodies
- Ultrasound: often useful to distinguish cellulitis from abscess, which might need incision and drainage (I&D).
- Head CT scan: important in cases when clinical distinction between periorbital and orbital cellulitis is difficult. Useful in orbital cellulitis to delineate extent of disease
Diagnostic Procedures/Other
In some cases, a cutaneous biopsy, examined by an experienced pathologist, may be needed to identify the correct diagnosis.
Differential Diagnosis
- Allergic angioedema can be excluded by its lack of tenderness and the absence of fever.
- Allergic reactions to insect stings are usually pruritic and may present with mild to severe local erythema, a bite history confirmatory.
- Red giant urticarial lesions, similarly, may masquerade as cellulitis.
- Contact dermatitis is distinguished by its painlessness, pruritus, and the Koebner phenomenon (appearance of isomorphic lesions in the lines of scratching).
- Nummular eczema is a pruritic dermatitis consisting of one or more circular lesions with papules, scales, and/or crusting, typically distributed on the trunk or extremities.
- The erythema migrans rash of Lyme disease starts as a red macule at the tick bite site, then expands to a large, annular, erythematous lesion; the classic "bulls eye" lesion with central clearing is not always seen.
- A traumatic contusion may be mistaken for cellulitis; the history confirms the diagnosis.
- Severe conjunctivitis presents with conjunctival injection, chemosis, and discharge.
- "Popsicle panniculitis," a cold-induced fat injury to the cheeks of infants; mimics buccal cellulitis; a history of cold weather exposure, eating ice, or popsicle sucking, are classic.
- Erythema nodosum, a panniculitis with raised, tender lesions that are frequently over the shins; may present as a single erythematous lesion. Associated with systemic disorders, including inflammatory bowel disease
- Superficial thrombophlebitis is distinguished by a tender cord palpable along the course of the affected superficial vein.
- An eye malignancy (retinoblastoma), invasive tumor (rhabdomyosarcoma), or metastatic disease (neuroblastoma, leukemia, lymphoma) may simulate periorbital or orbital cellulitis.
Treatment
Medication
- Most cases of uncomplicated, superficial "nonpurulent" cellulitis (cellulitis with no purulent drainage or exudate, and no associated abscess) may be treated with β-lactam oral antibiotics active against β-hemolytic streptococci and MSSA (e.g., cephalexin or amoxicillin-clavulanate).
- Coverage for MRSA is indicated in patients who do not respond to initial therapy, patients with signs of systemic illness, patients with recurrent infection in the setting of underlying predisposing conditions, and patients with a previous episode of MRSA infection.
- Additionally, MRSA coverage should be considered in patients with MRSA risk factors, and in areas where the prevalence of MRSA is greater than 30%.
- Patients with purulent cellulitis (cellulitis associated with purulent drainage or exudate, in the absence of a drainable abscess) should be treated with antibiotics active against MRSA.
- Clindamycin is an excellent initial choice due to its activity against β-hemolytic streptococci and both MSSA and MRSA.
- Trimethoprim-sulfamethoxazole covers both MSSA and MRSA, but not β-hemolytic streptococci; consequently, some combine it with amoxicillin.
- Some experts feel that initial coverage against β-hemolytic streptococci is not always mandatory in patients with purulent cellulitis; thus, monotherapy with trimethoprim-sulfamethoxazole is also sometimes used.
- Doxycycline and minocycline are additional alternatives with good MRSA coverage, especially for penicillin-allergic patients.
- Erythromycin is also sometimes used in patients allergic to penicillin; isolates resistant to erythromycin exist, however, and may be cross-resistant to clindamycin as well.
- Ill-appearing children or those with extensive cellulitic lesions require IV antibiotics.
- As MRSA infections continue to rise, most experts now recommend clindamycin as initial parenteral therapy.
- Oxacillin, nafcillin, cefazolin, and ampicillin-sulbactam are reasonable alternatives when MRSA is not strongly suspected.
- Vancomycin is used as empiric therapy in ill-appearing children or with severe or rapidly progressive infections.
- Linezolid, a newer antibiotic that can be given IV or PO, is very effective against MRSA, but it is expensive and should mostly be reserved for multiresistant organisms.
- If hematogenous dissemination is a strong possibility, an agent active against Hib also should be added (e.g., ceftriaxone, cefotaxime).
- The duration of antibiotics (IV and PO) should generally be 7-10 days.
- Bite wounds should have tetanus and rabies prophylaxis issues addressed.
Alert
- Remember to consider the possibility of MRSA in all deep, invasive, or persistent infections (i.e., consider clindamycin).
- Penicillin and amoxicillin are never good empiric choices for cellulitis because they have poor S. aureus coverage.
Additional Treatment
General Measures
Local care of cellulitis involves elevation and immobilization of the limb to reduce swelling, and cool sterile saline dressings to remove purulence from open lesions.
Surgery/Other Procedures
Abscesses should always be drained.
Ongoing Care
Follow-up Recommendations
- Steady improvement should be expected.
- If daily improvement is not noted, consider the following:
- Inappropriate antimicrobial coverage
- A deeper infection or abscess that needs drainage
- Foreign body
Prognosis
The prognosis for complete recovery is good as long as appropriate antimicrobials are administered in a timely fashion.
Complications
- Local or distant spread of infection is possible.
- Suppuration and abscess formation may occur (e.g., peritonsillar abscess).
- Extremity cellulitis may extend into the deep tissues to produce an arthritis or osteomyelitis, or it may extend proximally as a lymphangitis.
- Orbital cellulitis may be complicated by visual loss and/or cavernous sinus thrombosis.
- Prior to widespread immunization against Hib, the bacteremia associated with facial cellulitis was associated with pneumonia, meningitis, pericarditis, epiglottitis, arthritis, and osteomyelitis.
Additional Reading
- Elliott DJ, Zaoutis TE, Troxel AB, et al. Empiric antimicrobial therapy for pediatric skin and soft-tissue infections in the era of methicillin-resistant Staphylococcus aureus. Pediatrics. 2009;123(6):e959-e966. [View Abstract]
- Hyun DY, Mason EO, Forbes A, et al. Trimethoprim-sulfamethoxazole or clindamycin for treatment of community-acquired methicillin-resistant Staphylococcus aureus skin and soft tissue infections. Pediatr Infect Dis J. 2009;28(1):57-59. [View Abstract]
- Khawcharoenporn T, Tice A. Empiric outpatient therapy with trimethoprim-sulfamethoxazole, cephalexin, or clindamycin for cellulitis. Am J Med. 2010;123(10):942-950. [View Abstract]
- 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(3):e18-e55. [View Abstract]
- Moran GJ, Krishnadasan A, Gorwitz RJ, et al. Methicillin-resistant S. aureus infections among patients in the emergency department. N Engl J Med. 2006;355(7):666. [View Abstract]
- Odell CA. Community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA) skin infections. Curr Opin Pediatr. 2010;22(3):273-277. [View Abstract]
- Pallin DJ, Binder WD, Allen MB, et al. Comparative effectiveness of cephalexin plus trimethoprim-sulfamethoxazole versus cephalexin alone for treatment of uncomplicated cellulitis: a randomized controlled trial. Clin Infect Dis. 2013;56(12):1754-1762. [View Abstract]
- Stevens DL, Eron LL. Cellulitis and soft-tissue infections. Ann Intern Med. 2009;150(1):ITC11. [View Abstract]
- Swartz MN. Clinical practice. Cellulitis. N Engl J Med. 2004;350(9):904-912. [View Abstract]
Codes
ICD09
- 682.9 Cellulitis and abscess of unspecified sites
- 376.01 Orbital cellulitis
- 475 Peritonsillar abscess
ICD10
- L03.90 Cellulitis, unspecified
- H05.019 Cellulitis of unspecified orbit
- J36 Peritonsillar abscess
SNOMED
- 128045006 cellulitis (disorder)
- 194005002 orbital cellulitis (disorder)
- 102453009 Peritonsillar cellulitis (disorder)
- 239162003 Wound cellulitis (disorder)
FAQ
- Q: Is IV ampicillin-sulbactam adequate initial parenteral therapy for cellulitis with abscess?
- A: No. MRSA should be covered in these patients. IV clindamycin is a better choice.
- Q: When should IV vancomycin be used?
- A: IV vancomycin should be reserved for ill-appearing children or those with severe or rapidly progressive infections. These are cases where any treatment delay waiting for definitive culture and sensitivity results is prohibitive.