Non-Necrotizing Infections of the Dermis and Subcutaneous Tissue at a Glance
- Approximately 7%–10% of hospitalizations in North America are due to skin and soft-tissue infections (SSTI), including cellulitis and erysipelas.
- The incidence of SSTI is increasing, paralleling the rise of methicillin-resistant Staphylococcus aureus.
- A high index of suspicion for resistant organisms shoamaintained for cases that do not improve rapidly with empiric therapy, or in areas where resistant strains have been reported.
- Newer antibiotics are currently available or undergoing testing to treat resistant infections caused by methicillin-resistant or vancomycin-resistant strains.
- Microbiologic data from various culture techniques is helpful, but swabs, aspirations, and tissue cultures generally have a low yield for uncomplicated cellulitis and erysipelas.
- Non-necrotizing soft-tissue infections are treated with antibiotics and supportive measures, with drainage of collections as needed.
Skin and soft tissue infections (SSTI) are characterized by clinical findings that include an acute, tender, spreading, edematous, suppurative inflammation of the skin, subcutaneous fat, or muscle, often associated with systemic symptoms of malaise, fever, chills, and local pain. Cellulitis is an infection of the dermis and subcutaneous fat, while erysipelas is a more superficial variant affecting the superficial dermal lymphatics and adjacent tissues. Along with the pyodermas (see Chapter 176), cellulitis and erysipelas, are the predominant forms of non-necrotizing SSTI, which account for 7%–10% of hospitalizations in North America.1 Over the past two decades, the incidence of SSTI has increased faster than the incidence of other acute infections, paralleling the rise of methicillin-resistant Staphylococcus aureus (MRSA) rates.2
Cellulitis and erysipelas are usually caused by S. aureus or β-hemolytic Streptococci [primarily group A Streptococcus (GAS)] (see Table 178-1). Factors that increase the likelihood of SSTI include exposure to pathogenic organisms, local breach of the skin barrier function (including atopic dermatitis, and less often, allergic contact dermatitis, psoriasis, trauma, intravenous drug use, surgical and cosmetic procedures, toe-web intertrigo, arthropod bites, and chronic ulcers), immunocompromise (including acquired immunodeficiency syndrome [AIDS], diabetes, end-stage renal disease/dialysis, neutropenia, cancer, and immunosuppressive medications), obesity, and circulatory compromise (see Chapter 175).
Table 178-1 Etiology of Non-Necrotizing Soft-Tissue Infections |Favorite Table|Download (.pdf)
Table 178-1 Etiology of Non-Necrotizing Soft-Tissue Infections
Type of Infection
Most Common Cause (s)
|Erysipelas||Group A Streptococcus||Group B, C, and G Streptococci, Staphylococcus aureus|
|Cellulitis||S. aureus, group A Streptococcus||Group B, C, and G Streptococci; Streptococcus iniae; Pneumococcus; Haemophilus influenzae (children); Escherichia coli; Proteus, other Enterobacteriaceae; Campylobacter jejuni; Moraxella; Cryptococcus neoformans; Legionella pneumophila, Legionella micdadei; Bacillus anthracis (anthrax); Aeromonas hydrophila; Erysipelothrix rhusiopathiae; Vibrio vulnificus, Vibrio alginolyticus, Vibrio cholera non-01|
|Cellulitis in children||S. aureus, group A Streptococcus||Group B Streptococcus (neonates)|
|Facial/periorbital cellulitis||S. aureus, group A Streptococcus||Neisseria meningitides, H. influenzae (young children)|
|Perianal cellulitis||Group A Streptococcus||S. aureus|
|Cellulitis secondary to bacteremia||Pseudomonas aeruginosa||V. vulnificus; Streptococcus pneumoniae; group A, B, C and G ...|