Symptoms and Diagnosis
- Diagnosis of skin and soft tissue infections (SSTIs) is based primarily on clinical examination.1
- Microbiological investigation recommended where possible in purulent infections. Etiology is confirmed in over 60% of these cases.2
- Radiological examination and laboratory tests can also aid diagnosis of the severity of acute bacterial skin and skin structure infections (ABSSSI) including the need for hospitalization.1,3
Patients with ABSSSIs present with erythema, warmth, edema, and pain over the affected site.1 Systemic features of infection may follow, their intensity reflecting the severity of infection. Common pathogens include Staphylococcus aureus and other Gram-positive bacteria.1,2,4
Characteristics of ABSSSIs
Image available at: https://ercare24.com/cellulitisemergency/
Cellulitis/erysipelas are diffuse, non-purulent skin infections characterized by spreading areas of redness, edema, and/or induration. The red area of the skin tends to expand and the conditions are associated with swelling, tenderness, warmth and fever, and common pathogens are Streptococcus pyogenes and other β-hemolytic streptococci.
- Red area of skin that tends to expand
- Streptococcus pyogenes
- Other β-hemolytic streptococci
- Skin conditions
Image courtesy of Gregory Moran, M.D, via the Centers for Disease Control and Prevention
Major cutaneous abscesses are characterized by a collection of pus with surrounding granulation within the dermis or deeper tissues that is accompanied by redness, edema, and/or induration. They present as painful swelling with induration and central fluctuance.
- Clear collection of pus in the skin with possible drainage
- Staphylococcus aureus
- Other Gram-positive pathogens
- IV drug use
- Impaired circulation
Image courtesy of https://www.clinimed.co.uk/woundcare/symptom-management/management-of-exudateand-infection
Wound infections are characterized by purulent drainage from a wound with surrounding redness, edema, and/or induration. Wound infections are associated with pain, tenderness and ulceration and may be caused by Staphylococcus aureus and are occasionally polymicrobial.
- Staphylococcus aureus
- Occasionally polymicrobial
- Poor circulation
Comprehensive diagnosis of SSTIs often starts with a clinical history and findings from physical examination that help assess the severity of an infection. Although diagnosis of SSTIs is based on clinical presentation, microbiologic investigation is recommended in certain situations; for example, routine Gram-stain and culture of purulent material from carbuncles and abscesses are recommended by the Infectious Disease Society of America (IDSA).11 A precise diagnosis guides the decision on prompt and appropriate treatment.3,11
Radiological examination and imaging aid investigations of deep tissue infections to assess site and size of infection and any vascular involvement which can guide surgical drainage procedures.1,3 For patients with severe infection or comorbid conditions, common laboratory investigations can include complete blood count, C-reactive protein level, and liver and kidney function tests.1,3
Diagnosis of SSTIs relies primarily on clinical examination and findings, although microbiological investigation confirms the cause in over 60% of cases, suggesting a predominance of Gram-positive bacteria.2 The approach to diagnosis should follow the principles set out in guidelines from the Infectious Diseases Society of America (IDSA) on SSTIs, which involves assessment of severity, and recommends management approaches based on whether infections are purulent or non-purulent.
Considerations for Diagnosis of SSTIs1,3
- Assess physical characteristics of infection site, e.g., bullae, hemorrhagic lesion, pain, redness, warmth, tenderness
- Assess systemic manifestations, e.g., body temperature, hypotension, and signs of sepsis
- Tissue specimen for open wounds
- Needle aspiration for non-open wounds
- Blood culture for severe infection
- Incision and drainage (I&D)
- To aid investigation of deep tissue infections including x-ray, ultrasound, computed tomography (CT), magnetic resonance imaging (MRI)
- To assess for signs of infection and inflammation, including complete blood count and C- reactive protein
- Ramakrishnan K, Salinas RC, Agudelo Higuita NI. Skin and Soft Tissue Infections. Am Fam Physician. 2015;92(6):474-483.
- Pulido-Cejudo A, Guzmán-Gutierrez M, Jalife-Montaño A, et al. Management of acute bacterial skin and skin structure infections with a focus on patients at high risk of treatment failure. Ther Adv Infect Dis. 2017;4(5):143-161.
- Leong HN, Kurup A, Tan MY, et al. Management of complicated skin and soft tissue infections with a special focus on the role of newer antibiotics. Infect Drug Resist. 2018;11:1959-1974.
- Dryden MS. Complicated skin and soft tissue infection. J Antimicrob Chemother. 2010;65 (Suppl 3):iii35-44.
- Esposito S, Bassetti M, Concia E, et al. Diagnosis and management of skin and soft-tissue infections (SSTI). A literature review and consensus statement: an update. J Chemother. 2017;29(4):197-214.
- Tognetti L, Martinelli C, Berti S, et al. Bacterial skin and soft tissue infections: review of the epidemiology, microbiology, aetiopathogenesis and treatment: a collaboration between dermatologists and infectivologists. J Eur Acad Dermatol Venereol. 2012;26(8):931-941.
- FDA. Guidance for Industry Acute Bacterial Skin and Skin Structure Infections: Developing Drugs for Treatment. Available from: https://www.fda.gov/ media/71052/download (accessed October 15 2020).
- Dalal A, Eskin-Schwartz M, Mimouni D, et al. Interventions for the prevention of recurrent erysipelas and cellulitis. Cochrane Database Syst Rev. 2017;6(6):Cd009758.
- Sibbald RG, Orsted H, Schultz GS, et al. Preparing the wound bed 2003: focus on infection and inflammation. Ostomy Wound Manage. 2003;49(11):24-51.
- Esposito S, Noviello S, Leone S. Epidemiology and microbiology of skin and soft tissue infections. Curr Opin Infect Dis. 2016;29(2):109-115.
- Stevens DL, Bisno AL, Chambers HF, et al. Practice guidelines for the diagnosis and management of skin and soft tissue infections: 2014 update by the Infectious Diseases Society of America. Clin Infect Dis. 2014;59(2):147-159