Severity of infection
Given the variety of clinical presentations of SSTIs, an evaluation of the severity of disease is essential to determining appropriate initial management, including the need for hospitalization and intravenous antibiotics. Several grading systems have been proposed to assist in determining severity. High-risk features that are common to these systems include:
• Evidence of systemic infection (fever, tachycardia, altered mental status, tachypnea, hypotension);
• Location of infection with increased risk of local complication (face, brain, hand, perineum);
• Indication of deep tissue infection (for example, crepitus, bullae, or hemorrhage);
• Comorbid conditions predisposing to more severe infection (liver or renal disease, immunocompromised state including neutropenia or active chemotherapy, vascular insufficiency).
Dr. Christopher Sankey
The presence of any of these risk factors indicates moderate severity disease, for which hospitalization and intravenous antibiotics are warranted.9,10 Evidence of systemic disease progressing to end-organ dysfunction (for example, sepsis spectrum disorders) or evidence of rapid progression of infection or deep tissue involvement suggests severe disease. In the absence of these clinical findings, mild disease can be diagnosed and a trial of outpatient management with oral antibiotics is appropriate.
In assessing for necrotic infection, the Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score can help to distinguish severe cellulitis from necrotizing infections that require immediate surgical evaluation. The LRINEC score uses readily available laboratory markers to stratify patients into tertiles of risk for necrotizing fasciitis. While this objective score can identify patients who may require immediate surgical intervention, any patient with a clinical history or exam concerning for necrotizing infection should be urgently evaluated for possible surgical debridement.11,12
Management
Nonpurulent disease
Nonpurulent SSTIs include cellulitis and necrotizing infections such as necrotizing fasciitis. In the absence of risk factors for particular infectious agents (see above), mild infections can be managed with a trial of oral antibiotics with coverage for streptococcal species such as cephalexin, clindamycin, or amoxicillin-clavulanate.
Empiric coverage for MRSA is not recommended and has been shown to have little benefit. In a trial of 146 patients with mild nonpurulent cellulitis, there was no significant difference in cure rate at 2 weeks between cephalexin monotherapy and dual therapy with cephalexin and trimethoprim-sulfamethoxazole.13
Moderate infections warrant admission for intravenous antibiotics, also with coverage for streptococcal species and MSSA such as penicillin or cefazolin. In most cases, coverage for MRSA is not required but may be considered in patients with risk factors for MRSA. Generally, blood or cutaneous cultures are not recommended given an expected yield of positive culture to be less than 5%,14 but may be considered in patients with immunosuppression or neutropenia or evidence of systemic inflammatory response.
Severe infections should be evaluated for the need for surgical debridement. Empiric antibiotic coverage for Streptococcus pyogenes, MRSA, and gram-negative and anaerobic species is warranted. If necrotizing infection is suspected or diagnosed, immediate surgical debridement is indicated. Culture data from surgical debridement should be obtained and can be useful for tailoring therapy. While blood cultures remain unlikely to yield useful data, it is reasonable to obtain them in severe disease. Empiric antibiotic coverage should be broad and narrowed based on surgical specimens. The general recommendation regarding duration of antibiotics is 5 days; however, longer courses of up to 10-14 days may be required if there is minimal improvement after initial therapy.9
Purulent disease
Purulent SSTIs by definition involve collections of pus and include abscesses, furuncles, and carbuncles. In all purulent SSTIs, incision and drainage is indicated.
For mild disease, incision and drainage is considered definitive management and deep wound cultures and antibiotics are not required. In moderate purulent SSTI, culture of the drained fluid should be obtained, and antibiotics administered with empiric therapy to include coverage for MRSA. Patients at risk for community-acquired MRSA can be given oral agents such as trimethoprim-sulfamethoxazole, clindamycin, or doxycycline (depending upon local antibiogram data) with antibiotics narrowed based on culture data.
In order to minimize treatment failure with oral agents, dosing should be weight based with a minimum of 5 mg/kg per day of bactrim or 10 mg/kg per day of clindamycin.15 Those with risk factors for nosocomial MRSA may warrant intravenous antibiotics, even in moderate disease. Patients with severe purulent disease require intravenous antibiotics with coverage for MRSA with vancomycin, daptomycin or linezolid and subsequently narrowed based on culture data.9
Back to the case
Our patient presented with a case of mild, nonpurulent cellulitis. While he does have a mildly elevated white blood cell count, he has no other signs of systemic infection or underlying conditions predisposing to more severe disease. Hospital admission is not required and de-escalation of antibiotics to an oral agent is appropriate.
If the patient exhibited other signs of systemic infection (that is, fever or tachycardia) hospital admission or admission to observation status for IV antibiotics would be appropriate; however, de-escalation would still be recommended as MRSA coverage is not warranted. We suggest discharge from the emergency department with oral cephalexin, provided no prohibitive allergy is known, with outpatient follow-up to ensure resolution of infection.
Bottom line
SSTIs encompass a wide variety of clinical presentations and severity, and can be mimicked by a number of noninfectious medical conditions. If an infectious process is considered most likely, the need for hospitalization and broad-spectrum antibiotics should be individually determined based on specific criteria, and not empirically initiated for all presentations.
Dr. Perry is an instructor in the Yale Academic Hospitalist Program at Yale University, New Haven, Conn. Dr. Fogerty is associate professor of medicine in the Yale Academic Hospitalist Program. Dr. Sankey is assistant professor of medicine and interim inpatient medicine clerkship director in the Yale Academic Hospitalist Program.
Key Points
• SSTIs encompass a wide variety of clinical presentations and severity, and can be mimicked by a number of noninfectious medical conditions
• The majority of SSTIs are caused by gram-positive organisms, most notably Staphylococcus aureus and B-hemolytic streptococci
• Evaluation of the severity of disease, using a grading system, is essential to determining appropriate initial management
• Hospitalization and broad-spectrum antibiotics should be individually determined based on specific criteria, not empirically initiated for all presentations
References
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