Cellulitis and erysipelas

Management Strategy

The management of SSTIs should initially assess illness severity and determine the appropriate treatment setting (i.e., outpatient vs. hospital), identifying the organism responsible when indicated, and then directing antimicrobial therapy. Underlying and predisposing conditions should be treated to prevent recurrence.

In the United States, the Infectious Diseases Society of America (IDSA) has published treatment guidelines for non-purulent and purulent SSTIs; however, there is little agreement on regimen. As published by Raff and Kroshinsky (2016), the following is derived in combination from the IDSA 2014 guidelines, Johns Hopkins antibiotic guidelines, and results from the literature for non-purulent cellulitis ( Box 39.1 ) and purulent cellulitis ( Box 39.2 ). Systemic inflammatory response syndrome (SIRS) is identified by two or more symptoms including fever or hypothermia, tachycardia, tachypnea, and change in blood leucocyte count.

For both non-purulent and purulent cellulitis, the following definitions apply:

• Mild cellulitis – cellulitis without systemic signs of infection

• Moderate cellulitis – cellulitis in a patient who meets 1 point of the following criteria: heart rate greater than 90/min; temperature greater than 38°C or lower than 36°C; respiratory rate greater than 20/min; or white blood cell count greater than 12,000 cells/mm ³ or fewer than 4000 cells/mm ³

• Severe cellulitis – cellulitis in a patient with any of the moderate cellulitis criteria and hypotension, rapid progression, or immunocompromise

Mild non-purulent cellulitis should be treated with amoxicillin/clavulanate, cephalexin, dicloxacillin, penicillin VK, or, in cases of true penicillin allergy, clindamycin to provide antistreptococcal coverage.

The same agents used for mild cellulitis may be used in cases of moderate cellulitis. Intravenous antibiotics such as cefazolin, ceftriaxone, and penicillin G should be considered in patients who fail oral therapy or meet two or more SIRS criteria. Clindamycin may be used in penicillin allergy.

Patients with severe non-purulent cellulitis should receive broad coverage therapy. Intravenous vancomycin with piperacillin/tazobactam, imipenem, or meropenem may be used. If necrotizing infection is suspected, urgent surgical evaluation with cultures and sensitivities should be sought. If streptococcal toxic shock syndrome is suspected, penicillin G and clindamycin should be used.

Other risk factors that should prompt broad-spectrum coverage with vancomycin or linezolid include cases secondary to penetrating trauma, active injection drug use, or evidence of MRSA infection or colonization. Patients who cannot receive vancomycin may be treated with oral linezolid. Severely immunocompromised patients should receive broad-spectrum coverage.

Purulent cellulitis should be accompanied by culture and sensitivity testing. Cases of purulent cellulitis are more likely to be S. aureus , and patient risk factors for MRSA may guide empiric antibiotic choice. Risk factors for MRSA include athletes, children, men who have sex with men, prisoners, military recruits, residents of long-term care facilities, individuals with previous MRSA exposure, and intravenous drug use.

Mild purulent cellulitis therapy is based on suspicion for methicillin-sensitive S. aureus (MSSA) versus MRSA. If MSSA is suspected, consider cephalexin, dicloxacillin, amoxicillin/clavulanate, or clindamycin if there is a penicillin allergy. If MRSA is suspected, trimethoprim-sulfamethoxazole, doxycycline, or minocycline should be used. If both streptococcal and staphylococcal organisms are suspected, cephalexin or penicillin should be added to therapy, with clindamycin or linezolid for penicillin-allergic patients.

Moderate purulent cellulitis in patients meeting only one SIRS criterion may be treated with the same initial therapy as mild non-purulent disease, with empiric therapy selected based on suspicion for MSSA versus MRSA. Intravenous antibiotics should be considered if patients meet two or more SIRS criteria. For suspected MSSA, agents of choice include cefazolin, oxacillin, or nafcillin. For suspected MRSA, vancomycin, clindamycin, or linezolid should be used.

Empiric MRSA coverage with intravenous vancomycin, clindamycin, linezolid, daptomycin, or ceftaroline should be used in patients with severe cellulitis. If necrotizing cellulitis is suspected, surgical evaluation with culture and sensitivity should be obtained.

Newer antibiotic agents include telavancin, tedizolid, dalbavancin, and oritavancin. These agents may be considered; however, they currently have limited clinical applications. Second-line therapies for cellulitis discussed below are limited in clinical practice due to cost and concern for adverse effects.

Sites of entry for infection should be sought and should be treated, such as tinea pedis and chronic skin ulcers. Lymphedema can be associated with recurrence of cellulitis and so should be managed with long-term compression and elevation, when possible.

The use of long-term antibiotics for the prevention of recurrent cellulitis has produced conflicting evidence but may be considered for at least 3–4 recurrent cases/year once underlying risk factors have been mitigated. There are no supporting data for antibiotic prophylaxis for MRSA cellulitis.

The IDSA recommends against performing routine blood or tissue cultures, except in cases of malignancy on chemotherapy, severe cell-mediated immunodeficiency, neutropenia, animal bites, or immersion injuries. Routine use of procalcitonin to diagnose or evaluate cellulitis is not recommended.

Ultrasound may be helpful in identifying abscesses.

In the case of SSTIs of the lower leg, skin scrapings from toe web spaces, sides of feet, or toenail subungual debris may be taken for mycologic examination. Facial erysipelas should warrant sinus radiographs to exclude underlying sinusitis. Crepitus should prompt the clinician to the presence of either Clostridia or non-spore–forming anaerobes, either alone or mixed with other organisms, and warrants surgical consultation and/or imaging.