Cutaneous Infections & Infestations

IMPetigo — What is impetigo?

Contagious infection of the epidermis caused by staphylococci or streptococci

Impetigo — What are the classic skin findings?

Macules, vesicles, bullae, pustules, and honey-colored crusts

Impetigo — What areas are most commonly involved?

Face and other exposed parts

Impetigo — How is impetigo diagnosed?

Gram stain and culture confirm the diagnosis

Impetigo — Which organism is associated with temperate climates?

Staphylococcus aureus

Impetigo — Which organism is associated with tropical climates?

Streptococcus

Impetigo — What is first-line treatment?

Mupirocin, ozenoxacin, or retapamulin

Impetigo — What can be used to unroof pus?

Soaks and scrubs

Impetigo — What is used for widespread cases?

Oral cephalexin

Impetigo — What can be used for community-acquired MRSA?

Doxycycline or trimethoprim-sulfamethoxazole

Impetigo — What is associated with recurrent cases?

Nasal carriage of S. aureus

Impetigo — How can recurrent S. aureus carriage be treated?

Rifampin or intranasal mupirocin

Bullous impetigo — What organism causes it?

Staphylococcus aureus

Bullous impetigo — Who commonly develops it?

Children

Bullous impetigo — What areas are commonly affected?

Diaper region and other intertriginous areas

Bullous impetigo — What are the characteristic lesions?

Bullae with erythematous, moist erosions

Bullous impetigo — How is it diagnosed?

Clinical diagnosis ± bacterial culture

Bullous impetigo — How is it treated?

Mupirocin ointment; cephalexin for widespread disease

Ecthyma — What is ecthyma?

An ulcerative bacterial infection and deeper form of impetigo involving the dermis

Ecthyma — What organism is associated with it?

Beta-hemolytic streptococci

Ecthyma — What are risk factors?

Immunosuppression, poor hygiene, trauma, and overcrowding

Ecthyma — Where does it commonly occur?

Shins, legs, and buttocks

Ecthyma — What are the characteristic findings?

Vesicles, thick gray/yellow crusts, and superficial ulcers with raised edges

Ecthyma — How is it diagnosed?

Clinically

Ecthyma — What is the treatment?

Cephalexin or dicloxacillin

Cellulitis — What is cellulitis?

Diffuse spreading infection of the dermis and subcutaneous tissue

Cellulitis — What are the most common causative organisms?

Group A beta-hemolytic streptococci and S. aureus

Cellulitis — What is the most common predisposing condition?

Interdigital tinea pedis fissuring

Cellulitis — What other conditions predispose to cellulitis?

Prior episode, chronic edema, venous insufficiency, lymphatic obstruction, saphenectomy, and other disruption of the skin barrier

Cellulitis — Is bacterial cellulitis usually bilateral?

No; bacterial cellulitis is almost never bilateral

Cellulitis — How does cellulitis initially present?

Tender small patch followed by swelling, erythema, and pain

Cellulitis — How quickly does cellulitis expand?

Over hours

Cellulitis — How long after onset do patients typically present?

Approximately 6–36 hours

Cellulitis — What systemic symptoms can develop?

Chills, fever, and malaise

Cellulitis — What complications can occur?

Lymphangitis, lymphadenopathy, septicemia, hypotension, and shock

Cellulitis — What CBC findings may be present?

Leukocytosis or neutrophilia

Cellulitis — Are blood cultures always positive?

No; they are variably positive

Cellulitis — When can wound culture be helpful?

When a pustule, abscess, or central ulceration is present

Cellulitis — When may IV/parenteral antibiotics be required?

For 2–5 days in appropriate cases

Cellulitis — What medications are listed for MSSA?

Nafcillin, cefazolin, clindamycin, cephalexin, doxycycline, TMP-SMZ, or dicloxacillin

Cellulitis — What medications are listed for MRSA?

Vancomycin, linezolid, clindamycin, doxycycline, or TMP-SMZ

Cellulitis — How is recurrent lower-leg cellulitis treated?

Oral penicillin or erythromycin

Cellulitis — When should a patient be admitted?

Severe local symptoms/signs, signs of sepsis, elevated WBC with left shift, or failure to respond to oral antibiotics

Erysipelas — What is erysipelas?

A superficial form of cellulitis

Erysipelas — What organism causes it?

Beta-hemolytic streptococci

Erysipelas — Where can it begin?

Near a fissure at the angle of the nose or an interdigital fissure from tinea pedis

Erysipelas — What systemic symptoms occur?

Pain, malaise, chills, and moderate fever

Erysipelas — What is the characteristic skin lesion?

Bright-red patch that spreads into a tense, sharply demarcated, glistening, smooth, hot plaque

Erysipelas — What happens to the edge of the plaque?

It has a raised edge that may pit with finger pressure

Erysipelas — What additional lesions may develop?

Vesicles or bullae

Erysipelas — What is outpatient treatment?

Penicillin VK, dicloxacillin, or a first-generation cephalosporin

Erysipelas — What is used for penicillin-allergic patients?

Clindamycin

Erysipelas — What is the greatest risk factor for recurrence?

Lymphedema

Abscess — What is an abscess?

Localized inflammatory response where WBCs accumulate at the site of infection

Abscess — What are the characteristic findings?

Painful/tender, erythematous, warm, fluctuant lesion

Abscess — What is the main treatment?

Incision and drainage (I&D)

Abscess — What supportive measures can be used?

Warm compresses and proper wound care

Lymphangitis — What is lymphangitis?

Inflammation of the lymphatic system caused by spread of a primary infection

Lymphangitis — What infections can lead to lymphangitis?

Cellulitis, erysipelas, abscess, or an infected wound

Lymphangitis — What are the symptoms?

Throbbing pain, malaise, sweating, chills, fever, red streaking, and lymphadenopathy

Lymphangitis — What supportive treatment is recommended?

Heat, elevation, and immobilization

Lymphangitis — What organisms should empiric antibiotics target?

Streptococci and S. aureus

Lymphangitis — What antibiotics are listed?

Cephalosporins or extended-spectrum penicillins

Necrotizing fasciitis — What is necrotizing fasciitis?

Rapidly spreading infection involving the fascia of deep muscle

Necrotizing fasciitis — What are common locations?

Extremities, head/neck, and perianal or genital region

Necrotizing fasciitis — What is Fournier gangrene?

Necrotizing fasciitis involving the perianal/genital region

Necrotizing fasciitis — What may precede infection?

Skin or blunt trauma

Necrotizing fasciitis — What is the most common organism in monomicrobial disease?

S. pyogenes (group A beta-hemolytic streptococci)

Necrotizing fasciitis — What other organisms can cause monomicrobial disease?

Other streptococcal species and S. aureus

Necrotizing fasciitis — What organisms can cause polymicrobial disease?

Mixed aerobic and anaerobic organisms

Necrotizing fasciitis — What organisms are associated with brackish water exposure?

Vibrio vulnificus, Aeromonas species, and Erysipelothrix rhusiopathiae

Necrotizing fasciitis — What organism is associated with burn injuries?

Pseudomonas species

Necrotizing fasciitis — What are the major clinical findings?

Severe cellulitis, systemic toxicity, severe pain, anesthesia of the involved area, and possibly crepitus

Necrotizing fasciitis — Why can anesthesia occur?

Destruction of nerves

Necrotizing fasciitis — What lab abnormalities may be present?

Elevated WBC, ESR, CRP, and creatine kinase

Necrotizing fasciitis — What does elevated creatine kinase suggest?

Muscle involvement

Necrotizing fasciitis — What scoring system can be used?

Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC)

Necrotizing fasciitis — What cultures can be obtained?

Blood and wound cultures

Necrotizing fasciitis — What imaging can be used?

CT or MRI

Necrotizing fasciitis — What might CT/MRI demonstrate?

Gas in tissues or fascial-plane infection

Necrotizing fasciitis — What is the key treatment?

Early, extensive, and often repeated surgical debridement

Necrotizing fasciitis — What broad-spectrum antibiotics are listed?

Meropenem or imipenem, or piperacillin-tazobactam

Necrotizing fasciitis — What additional antibiotics may be added?

Vancomycin, linezolid, or daptomycin plus clindamycin

Necrotizing fasciitis — What determines targeted therapy?

Exposure history

Necrotizing fasciitis — What adjunctive therapy has shown reduced mortality in streptococcal necrotizing infections?

IV immunoglobulin

Furuncle — What is a furuncle?

Deep-seated S. aureus infection involving a hair follicle and adjacent subcutaneous tissue

Furuncle — Where do furuncles commonly occur?

Areas of friction, pressure, or moisture

Furuncle — What conditions increase the risk?

Diabetes mellitus, injection drug use, allergy injections, and HIV

Carbuncle — What is a carbuncle?

Several furuncles developing in adjoining hair follicles and forming a deeply situated mass with multiple drainage points

Furunculosis/Carbunculosis — What are the typical symptoms?

Pain and tenderness

Furunculosis/Carbunculosis — What does the abscess look like?

Round or conical; gradually enlarges and becomes fluctuant before softening

Furunculosis/Carbunculosis — What happens when the lesion opens?

It may discharge a core of necrotic tissue and pus

Furunculosis/Carbunculosis — What can be cultured?

Pus to rule out MRSA

Furunculosis/Carbunculosis — What is the mainstay of treatment?

Incision and drainage

Furunculosis/Carbunculosis — When are systemic antibiotics indicated?

Multiple lesions, surrounding cellulitis, or immunosuppression

Furunculosis/Carbunculosis — What antibiotics are listed?

TMP-SMZ, clindamycin, dicloxacillin, or cephalexin

Furunculosis/Carbunculosis — What antibiotics are listed for MRSA?

Doxycycline, TMP-SMZ, clindamycin, or linezolid

Furunculosis/Carbunculosis — How are recurrent cases treated?

Cephalexin/doxycycline plus rifampin or long-term clindamycin

Furunculosis/Carbunculosis — What can promote spontaneous drainage?

Moist heat

Furunculosis/Carbunculosis — What prevention measures are recommended?

Eliminate the source of infection, avoid sharing towels/clothing/personal hygiene products, and use 4% chlorhexidine washes