Skin and Soft Tissue Infections

Published on 07/03/2015 by admin

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Last modified 07/03/2015

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Chapter 38 Skin and Soft Tissue Infections

Erica S. Shenoy, MD, PhD , David C. Hooper, MD

General Principles

1 If patients with skin or soft tissue infection are seen with signs of systemic toxicity, what laboratory studies should be undertaken?

Blood cultures, cultures of drainage from skin infection site, complete blood cell count with differential, and serum creatinine, bicarbonate, creatine phosphokinase, glucose, albumin, and calcium levels should be obtained. (See Table 38-1.)

Table 38-1 Evaluation of Cellulitis and Soft Tissue Infections

image

2 What are clinical signs of potential severe deep tissue infection?

image Pain disproportionate to physical findings

image Skin findings: violaceous bullae, ecchymoses, cutaneous hemorrhage, sloughing, anesthesia

image Rapid progression

image Gas in tissue

image Edema beyond the margin of erythema

image Signs and symptoms of systemic involvement

3 Which common causative organisms have shown emerging antibiotic resistance?

image Staphylococcus aureus (methicillin resistance with resistance to all β-lactams except ceftaroline): Assume resistance because of high prevalence of methicillin-resistant S. aureus (MRSA), both community and hospital acquired.

image Streptococcus pyogenes (erythromycin resistance): Resistance is increasing to macrolides (approximately 7% in the United States, 2% to 32% reported in Europe), although the majority remain susceptible to clindamycin, and all are susceptible to penicillin.

Cellulitis

4 What are the common presentation patterns of cellulitis caused by S. aureus or S. pyogenes?

image S. aureus: cellulitis with associated furuncles, carbuncles, or subcutaneous abscesses

image S. pyogenes: cellulitis that is more diffuse and can spread rapidly

5 What distinguishes impetigo from cellulitis?

Impetigo is characterized by discrete purulent lesions, usually on the face, arms, and legs. Bullous and nonbullous forms exist. Whereas impetigo is superficial, cellulitis involves the deep dermis and subcutaneous fat.

6 Lack of response to initial therapy could signify what?

image If a patient does not respond to initial therapy, consider the possibility of resistant strains, atypical organisms, deeper processes such as necrotizing fasciitis or abscess (which may require surgical intervention), as well as underlying conditions such as diabetes, chronic venous insufficiency, or lymphedema (which may slow the clinical response to antimicrobial therapy).

image Timely administration of appropriate antibiotic therapy is essential. One study found that each hour of delay between documented hypotension and administration of antibiotics was associated with an average decrease in survival of 7.6% across all sources of infection; subgroup analysis for patients with skin and soft tissue infections demonstrated a significant increase in the adjusted odds ratio of death. This same study found that time to initiation of effective antimicrobial therapy was the strongest predictor of hospital survival. Despite the impact of delayed therapy, the study found that the median time to effective therapy was 6 hours.

7 What risk factors predispose individuals to development of cellulitis?

image Obesity

image Previous episodes of cellulitis in the same location (may result in damage to lymphatics)

image Toe-web abnormalities (i.e., maceration, tinea pedis)

image Breach in skin barrier, such as ulcers, trauma, fungal infection, eczema

image Surgical procedures that affect lymphatic drainage such as radical mastectomy with lymph node dissection or coronary artery bypass graft for which the saphenous vein has been harvested

image Chronic medical conditions such as diabetes, arterial insufficiency, chronic venous insufficiency, chronic renal disease, neutropenia, cirrhosis, hypogammaglobulinemia

8 What organisms are associated with cellulitis in:

image Cat or dog bites? Pasteurella multocida, Capnocytophaga canimorsus

image Fresh water exposure? Aeromonas hydrophila

image Saltwater exposure? Vibrio vulnificus and other vibrios

image Exposure to fish farming and aquaculture? Streptococcus iniae

image Exposure to meatpacking or shellfish? Erysipelothrix rhusiopathiae

image Preorbital cellulitis in children? Haemophilus influenzae

image Hosts with deficiencies in cell-mediated immunity? Cryptococcus neoformans

image Combat trauma patient? Acinetobacter baumannii

See Table 38-2.

Table 38-2 Antimicrobial Therapy for MSSA and MRSA Skin and Soft Tissue Infections

image

Cutaneous abscesses

9 How are abscesses managed?

image Large abscesses should be incised and drained, with careful attention to the potential for loculated cavities (and the disruption of these cavities through probing of the pus pocket).

image Once drained, the lesion can be left packed or unpacked depending on its extent.

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