Cellulitis
Kenneth Barnes
Shane Hudnall
BasicsAn inflammation of the skin and underlying subcutaneous tissues (specifically the dermal and subcutaneous fat layers) caused by a spreading infiltration of bacteria through the skin surface
Description
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Typically results from entry of bacteria through a break in the skin, from a contiguous foci (abscess), or from metastatic dissemination via bacteremia
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Most commonly involves the lower extremities where venous stasis predisposes to infection
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Can occur anywhere on the body, including periorbital area, upper extremities, and abdominal wall
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Gram positives (beta-hemolytic streptococcus, strep pyogenes especially, and Staphylococcus aureus) comprise >80% of the organisms responsible.
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Methicillin-resistant Staphylococcus aureus (MRSA) is a concern due to increasing prevalence in the community setting.
Epidemiology
Incidence
1 case per 500 patient years (1)
Risk Factors
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Disruption of skin from trauma or scratching
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Eczema or other inflammation
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Underlying skin infections (ie, tinea pedis)
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Elderly (thrombophlebitis)
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IV drug use
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Human or animal bites
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Edema (related to venous insufficiency)
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Surgeries
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MRSA risk factors:
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Recent antibiotics
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Recent hospitalization
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Homelessness
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Previous MRSA infection
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IV drug abuse
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Contact sports (2,3)
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Commonly Associated Conditions
Consider treating for the specific organisms identified in these populations (2):
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Diabetes: Anaerobes and gram negatives
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Neutropenia: Pseudomonas
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Human bite: Eikenella corrodens, Fusobacterium species
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Cat bite: Pasteurella multocida
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Dog bite: Pasteurella multocida, Capnocytophaga canimorsus
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Hot tub: Pseudomonas
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Fresh water: Aeromonas hydrophila
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Salt water: Vibrio species
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IV drug abuse: MRSA, Pseudomonas
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Immunocompromised: Cryptococcus neoformans
DiagnosisHistory
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Breakdown in normal skin barriers almost always precedes this infection.
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Preexisting venous stasis alone may predispose to cellulitis.
Physical Exam
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Area of involvement denoted by spreading erythema, warmth, and swelling with ill-defined margins
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Associated pain and tenderness
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Streaks of erythema and tenderness indicative of lymphatic spread
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Bullae may develop, but generally rash is not raised.
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Fever, sweats, shaking chills common, but bacteremia infrequent
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Regional lymphadenopathy
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Look for evidence of predisposing factors: Lower extremity venous stasis, tinea infection, IV drug abuse track marks, eczema, radiation (irritation and thinning of skin)
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Use of pen/marker to demarcate the leading edge of cellulitis is helpful in monitoring during follow-up.
Diagnostic Tests & Interpretation
Lab
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Current recommendations are to culture all wounds for bacterial identification and antimicrobial sensitivity testing.
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Blood cultures rarely helpful (<5%) (3,4)
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Needle aspiration of abscess or bullae most likely to be helpful if present
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Culture of overlying intact skin is not helpful and recommended against.
Imaging
Generally, imaging not recommended unless concerned about osteomyelitis, gas gangrene, underlying abscess, or other conditions in differential (ie, deep vein thrombosis)
Differential Diagnosis
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Erysipelas (infection of the superficial layers of the skin, usually caused by group A streptococci)
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Fasciitis/necrotizing fasciitis
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Myonecrosis/gas gangrene
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Toxic epidermal necrolysis
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Osteomyelitis
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Cutaneous candidal infection
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Septic arthritis
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Gout
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Zoster
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Erythema migrans
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Contact dermatitis
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Eczema
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Deep venous thrombosis
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Ruptured baker's cyst
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Drug rash
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Insect bite
TreatmentIf staph is isolated, consider treating for MRSA if patient has MRSA risk factors and/or if local prevalence of MRSA is high.
Medication
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Treat presumptively with close follow-up.
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Duration of therapy 10–14 days total
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Improvement anticipated in 1–2 days
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If no improvement or clinical deterioration, admit for parenteral antibiotics and broaden differential diagnosis to include possibility of potentially fatal infections such as necrotizing fasciitis.
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Treatment recommendations:
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Outpatient for non-MRSA infections: Dicloxacillin 500 mg PO q.i.d., cephalexin 500 mg PO q.i.d. May use clindamycin 300–450 mg PO q6–8h or fluoroquinolones if allergic to penicillins.
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Inpatient for non-MRSA infections: Nafcillin 1–2 g IV q4h
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Outpatient for MRSA infections: Bactrim DS 2 tabs PO b.i.d. or doxycycline 100 mg PO b.i.d. (not recommended for children <8 yrs old) or clindamycin 300–450 mg PO q6–8h (check local resistance patterns)
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Inpatient for MRSA infections: Vancomycin (15 mg/kg/dose IV q12h), linezolid 600 mg PO b.i.d. (expensive and need to monitor for thrombocytopenia) (3,5)
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P.67
Additional Treatment
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Human bites: Augmentin (outpatient), ampicillin/sulbactam (inpatient); penicillin allergy: Moxifloxacin + clindamycin or Bactrim + Flagyl
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Animal bites: Augmentin (outpatient), ampicillin/sulbactam (inpatient); penicillin allergy: (doxycycline or moxifloxacin or Bactrim) + (clindamycin or Flagyl) (3)
General Measures
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If abscess present, incision and drainage required
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If bullae noted, typically do not rupture as part of treatment
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If underlying venous stasis noted, elevation of affected limb and, if possible, compression stockings (not over area of skin involvement) recommended
Referral
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If patient not responding to antibiotic treatment in timely manner
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If development of crepitance suggesting a gas-forming organism
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If the cellulitis is on the face, there is a low threshold for referral.
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If a high-risk patient or immunocompromised for any reason, have a low threshold for involvement of an infectious disease specialist if not readily responding to treatment.
Additional Therapies
Recently recognized that use of cell-wall active antibiotics (ie, β-lactams) cause an initial worsening prior to improvement due to rapid release of a bolus of exotoxins (6)
Ongoing CarePatient Education
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Early identification is important.
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If infection considered contagious, must not participate in contact or collision sports
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MRSA becoming more prevalent in locker rooms as well as in the community.
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Do not share towels, razors, other products.
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Frequent skin inspections
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Cover all wounds.
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Disinfect all shared athletic equipment and whirlpools.
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Education and posters recommended in all training rooms and locker rooms
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Liberal use of antibacterial soap or alcohol-based hand sanitizer
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Return to play:
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Mild to moderate skin lesions: 72 hr after initiation of therapy, with clinical improvement and no new lesions for 48 hr
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Before and during sports participation: Cover completely with occlusive dressing.
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Multiple wound checks: If leakage, remove athlete, cleanse skin with soap and water, apply new dressing
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Removal of dressing once firm, adherent crust develops (7,8)
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References
1. McNamara DR, Tleyjeh IM, Berbari EF, et al. Incidence of lower-extremity cellulitis: a population-based study in Olmsted county, Minnesota. Mayo Clin Proc. 2007;82:817–821.
2. Eron LJ, Laine C, Goldmann DR, Sox HC. Cellulitis and soft-tissue infections. Ann Intern Med. 2009;150:ITC1–1.
3. Stevens DL, et al. Practice guidelines for the diagnosis and management of skin and soft-tissue infections. Clin Infect Dis. 2005;41:1373–1406.
4. Perl B, Gottehrer NP, Raveh D, et al. Cost-effectiveness of blood cultures for adult patients with cellulitis. Clin Infect Dis. 1999;29:1483–1488.
5. Gilbert DN, Moellering RC Jr, Sande MA, eds. The Sanford guide to antimicrobial therapy 2000, 30th ed. Hyde Park, VT: Antimicrobial Therapy, 2000.
6. Melzer M, Eykyn SJ, Gransden WR, et al. Is methicillin-resistant Staphylococcus aureus more virulent than methicillin-susceptible S. aureus? A comparative cohort study of British patients with nosocomial infection and bacteremia. Clin Infect Dis. 2003;37:1453–1460.
7. American Academy of Pediatrics, Committee on Sports Medicine and Fitness. Medical Conditions Affecting Sports Participation. Pediatrics. 2008;121:841–848.
8. Minooee A, Arezou, Rickmans LS, et al. Transmission of infectious diseases during sports. In: Schlossberg D, ed. Infections of leisure, 2nd ed. Washington, DC: American Society for Microbiology, 1999.
Additional Reading
Benjamin HJ, Nikore V, Takagishi J. Practical management: community-associated methicillin-resistant Staphylococcus aureus (CA-MRSA): the latest sports epidemic. Clin J Sport Med. 2007;17(5):393–397.
Reese RE, Betts RF, eds. A practical approach to infectious diseases, 4th ed. Boston: Little Brown, 1996.
Stevens DL. Cellulitis, pyoderma, and other skin and subcutaneous infections. In: Armstrong D, Cohen J, eds. Infectious diseases. Vol. 1. Mosby/Harcourt Publishers, 1999:2.2.6–2.2.8.
Swartz NN. Cellulitis and subcutaneous tissue. In: Mandell GL, Bennet JE, Dolin R, eds. Mandell, Douglas, and Bennetts principles and practice of infectious disease, 5th ed. Vol. 1. Philadelphia: Churchill Livingstone, 2000.
CodesICD9
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682.2 Cellulitis and abscess of trunk
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682.3 Cellulitis and abscess of upper arm and forearm
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682.9 Cellulitis and abscess of unspecified sites