Cellulitis and erysipelas – collectively referred to as skin and soft tissue infections (SSTIs) – are a seemingly simple entity to manage. Yet the burden of SSTIs and the complexity of this disease process may surprise you!
From 1997 to 2005, the number of Americans seeking medical care for SSTIs increased by 50%, totalling 14.2 million visits in 2005 alone.1 Although Canadian data is lacking, a single Vancouver ED diagnosed 2234 patients with a SSTI between January 2003 and September 2004.2 Hospitalization for complicated SSTIs result in an average cost of $8023 with a mean hospital length of stay of 4.9 days.3 Despite this increasing burden, current evidence is lacking regarding optimal management. A recent Cochrane review concluded that the optimal antimicrobial therapy for SSTIs remains unclear, as no two RCTs (of the 25 studies identified) compared the same two antibiotic regimens. Furthermore, outpatient management of SSTIs initially seen in the ED varies widely.4 Lack of evidence regarding the best management is highlighted by the fact that the most current guidelines for managing cellulitis are based on expert opinion.5-7 

Diagnosing Necrotizing Fasciitis: Is the LRINEC Score Useful?

It is critical that you do not miss the diagnosis of necrotizing fasciitis (NF) given the associated mortality rate of 25 – 35%. The original derivation study of the LRINEC (Laboratory Risk Indicator for NECrotizing fasciitis) score, a retrospective cohort study, reported a PPV = 92% and a NPV = 96%.8.The authors proposed that the LRINEC score is a useful tool to diagnose NF:


CRP (mg/L)
WBC (/mm3)
15 – 25
Hb (g/L)
110 – 135
Na (mmol/L)
< 135
Serum Cr (mmol/L)
Glucose (mmol/L)
Low Risk
Intermediate Risk
High Risk
< 5
6 – 7
>³ 8
Table 1. LRINEC Score
However, the only external validation study of the LRINEC score in the ED setting (Note: pending publication) reported a sensitivity of only 52% (38 – 66%).Ultimately, necrotizing fasciitis remains a clinical diagnosis.

MRSA: Risk Factors and Novel Therapies

The prevalence of MRSA in Canada is unknown (it is not a reportable disease). At The Ottawa Hospital, 18% of SSTIs that can be cultured are MRSA positive. A study in the ED of The Ottawa Hospital identified community acquired MRSA risk factors that you should consider in your patients.10

Risk Factors
Odds Ratio
95% Confidence Interval
Hepatitis C
3.5 – 55
Substance Abuse
4.4 – 25.1
Previous MRSA / known colonization
1.6 – 97.5
Antibiotics in past 1 year
1.5 – 6.6
Homelessness in past 1 year
3.5 – 68.8
Communal living
2.6 – 51.1
2.8 – 45.8
Table 2. CA-MRSA: Risk Factors
There are novel once-weekly antibiotics (dalbavancin, oritavancin) that are active against typical pathogens plus MRSA. 
Semisynthetic analogs of teicoplanin and vancomycin
Inhibit cell wall synthesis (bactericidal)
MSSA, MRSA, Streptococci, Enterococci
2 weeks
1 g IV (day 1)
500 mg IV (day 8)
1.2 g IV (single dose)
Cost (USD)
$1100 – 1300
(500 mg vial)
(1.2 g vial)
Table 3. Characteristics of Once-Weekly Antibiotics
Two large non-inferiority RCTs found that dalbavancin is non-inferior to vancomycin linezolid11, and that oritavancin is non-inferior to vancomycin.12

Cellulitis: Who Should Get IV Therapy? Who should be admitted?

The treatment failure rate of SSTIs in Canadian EDs is approximately 20%.13,14 ED observation units are of limited value for determining whether a patient should be admitted or managed as an outpatient – one study found that 29.2% of patients are subsequently admitted anyway.15 

ED physicians most commonly cite a need for IV antibiotics as the primary reason for admitting patients to hospital, yet the rate of serious adverse events with out of hospital treatment is rare (0.5%).16 

A Canadian ED study13 found 5 risk factors associated with treatment failure for cellulitis (fever, chronic leg ulcers, lymphedema, prior cellulitis in the same area, and cellulitis at a wound site) – consider these factors when deciding on admission vs. outpatient therapy.

Take Home Points

Necrotizing Fasciitis is a clinical diagnosis:
The sensitivity of the LRINEC score is unacceptable for use in the ED. Consider adjuncts if you have a high clinical suspicion: CT, MRI or ultrasound.
There are MRSA Risk Factors you should consider for your patients:
Hepatitis C, substance abuse, previous MRSA infection/colonization, antibiotics in past year, homelessness in past year, communal living, incarceration.
Novel Once-Weekly Antibiotics are Non-Inferior to Conventional Therapy against MRSA:
Dalbavancin and Oritavancin are FDA approved (could be in Canada soon!). Once-weekly antibiotics have the potential to revolutionize the way SSTIs are managed.
Which patients require hospital admission? Who Should Get IV versus Oral Antibiotic Therapy for SSTIs? It is still UNCLEAR!
There is a significant evidence gap: we do not know who actually requires admission versus inpatient stay. 
There is even less guidance for optimal route of antibiotic therapy. 
This is a big deal: the treatment failure rate for SSTIs in Canadian EDs is 20%.
o   This suggests that there is LOTS of research still to be done!
Dr. Krishan Yadav is a 5th year Emergency Medicine resident at the University of Ottawa, with a special interest in Clinical Epidemiology.
Edited by Dr. Shahbaz Syed, 4th year Emergency Medicine resident, University of Ottawa


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