Impetigo (see Impetigo): infection of superficial layers of the epidermis
Cellulitis (see Cellulitis): skin infection of deeper dermis and subcutaneous fat (resulting from bacterial breach of the skin) characterized by erythema, warmth, and edema without an underlying suppurative focus
Erysipelas (see Erysipelas): skin infection of upper dermis and superficial lymphatics (resulting from bacterial breach of the skin) characterized by erythema, warmth, and edema without an underlying suppurative focus
Furuncle (Boil) (see Skin Abscess): infection of hair follicle where purulent material extends through the dermis into the subcutaneous tissue, forming a small abscess
Carbuncle (see Skin Abscess): coalescence of several inflamed follicles into a single inflammatory mass with purulent drainage from multiple follicles
Skin Abscess (see Skin Abscess): collection of pus within dermis and deeper skin tissues
Necrotizing Soft Tissue Infection (see Necrotizing Soft Tissue Infection): deep tissue infection involving the hypodermis (and contained structures)
All of These are Characterized by Fulminant Tissue Destruction, Systemic Toxicity (Tachycardia >120 Beats/min, Hypotension, Elevated Creatine Kinase, CRP >15 mg/dL, LRINEC Score >6, etc), and High Mortality Rates
Sensitivity/Specificity: only positive in 20-30% of cases
Low Sensitivity Suggests that Relatively Small Numbers of Bacteria May Result in Significant Inflammation with Most of the Observed Findings Being Due to the Host Inflammatory Response
Usually not Performed
Needle Aspiration of Bullae
Sensitivity/Specificity: positive in <5-40% of cases
Low Sensitivity Suggests that Relatively Small Numbers of Bacteria May Result in Significant Inflammation with Most of the Observed Findings Being Due to the Host Inflammatory Response
May Be Useful in Some Cases to Exclude Skin Abscess or to Distinguish Cellulitis/Erysipelas from Osteomyelitis or Gas Gangrene
However, Radiologic Exams Cannot Reliably Differentiate Cellulitis from Necrotizing Fasciitis or Gas Gangrene and These Should Not Delay Surgical Intervention if Necrotizing Fasciitis or Gas Gangrene are Suspected
Clinical Manifestations
Radiologic Presence of Soft Tissue Gas May Allow Clinical Differentiation of Necrotizing Soft Tissue Infections (NEJM, 2017) [MEDLINE]
Dermatologic Manifestations
Skin Erythema, Warmth, and Edema without an Underlying Suppurative Focus
Most Common Site of Involvement: lower extremities
Clinical Guidelines for Short-Course Antibiotics in Common Infections (Annals of Internal Medicine, 2021) [MEDLINE]
In patients with nonpurulent cellulitis, clinicians should use a 5- to 6-day course of antibiotics active against streptococci, particularly for patients able to self-monitor and who have close follow-up with primary care)
References
General
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 Jul 15;59(2):e10-52. doi: 10.1093/cid/ciu444 [MEDLINE]
The Massachusetts abscess rule: a clinical decision rule using ultrasound to identify methicillin-resistant Staphylococcus aureus in skin abscesses. Acad Emerg Med. 2014 May;21(5):558-67. doi: 10.1111/acem.12379 [MEDLINE]
Cellulitis: A Review. JAMA. 2016;316(3):325 [MEDLINE]
Association of athlete’s foot with cellulitis of the lower extremities: diagnostic value of bacterial cultures of ipsilateral interdigital space samples. Clin Infect Dis. 1996;23(5):1162 [MEDLINE]
Streptococcal cause of erysipelas and cellulitis in adults. A microbiologic study using a direct immunofluorescence technique. Arch Dermatol. 1989;125(6):779 [MEDLINE]
The value of bacteriology and serology in the diagnosis of cellulitis and erysipelas. Br J Dermatol. 1985;112(5):559 [MEDLINE]
Risk factors for acute cellulitis of the lower limb: a prospective case-control study. Clin Infect Dis. 2005;41(10):1416 [MEDLINE]
Factors associated with complications and mortality in adult patients hospitalized for infectious cellulitis. Eur J Clin Microbiol Infect Dis. 2003;22(3):151 [MEDLINE]
The role of beta-hemolytic streptococci in causing diffuse, nonculturable cellulitis: a prospective investigation. Medicine (Baltimore). 2010;89(4):217 [MEDLINE]
Etiology of Cellulitis and Clinical Prediction of Streptococcal Disease: A Prospective Study. Open Forum Infect Dis. 2016;3(1):ofv181 [MEDLINE]
Treatment
Appropriate Use of Short-Course Antibiotics in Common Infections: Best Practice Advice From the American College of Physicians. Ann Intern Med. 2021 Apr 6. doi: 10.7326/M20-7355 [MEDLINE]