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Image courtesy of Smuszkiewicz P, Trojanowska I, Tomczak H. Cases J. 2008; 1: 125. [Open access.] PMID: 18721475, PMCID: PMC2547098.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

Many species of bacteria, such as Staphylococcus, Acinetobacter, Brevibacterium, and Corynebacterium, are normal skin flora and are generally nonpathogenic. However, some bacteria can invade damaged or even healthy skin, resulting in skin and wound infections. The clinical picture can vary according to the tissue involved. Superficial skin and soft-tissue infection results in cellulitis, deeper infection results in abscess formation, and involvement of the follicular unit results in folliculitis. Although skin infections are common, even experienced clinicians may have difficulty recognizing their many presentations. Can you make the correct diagnosis for the following cases?

Shown is the left leg of a 43-year-old man who presented to the intensive care unit (ICU) with a delayed diagnosis of necrotizing fasciitis.

Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

A 60-year-old man presents with a lesion on his scalp (shown). It has a thick, oyster shell–like scale crust with underlying purulent material.

Which of the following is the most likely diagnosis?

  1. Ecthyma
  2. Erysipelas
  3. Furunculosis
  4. Impetigo
Image courtesy of Medscape.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

Answer: A. Ecthyma.

Ecthyma (shown) is an ulcerative pyoderma of the skin caused by streptococci or staphylococci. The infection begins with a pustule that later erodes and forms a punched-out ulcer with hemorrhagic crust. Ecthyma usually affects the lower extremities of children, persons with diabetes, and neglected elderly patients. The lesion in the preceding slide can be diagnosed clinically as staphylococcal ecthyma on the basis of the golden color of the purulent exudate. The presence of large clusters of gram-positive cocci confirms the diagnosis of staphylococcal ecthyma. Treatment of ecthyma includes administration of oral antibiotics and maintenance of good hygiene.[1,2]

Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

A 48-year-old man presents with draining sinus tracts on his elbow (arrows). The drainage resembles small grains of sand.

Which of the following is the most likely diagnosis?

  1. Yaws
  2. Necrotizing fasciitis
  3. Botryomycosis
  4. Cellulitis
Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

Answer: C. Botryomycosis.

Botryomycosis is a deep staphylococcal infection with formation of sinus tracts; histopathologic examination reveals very large colonies of cocci, referred to as grains (shown). Huge staphylococcal colonies are extruded from the sinus tracts and resemble grains of sand.

Image courtesy of Jessica Connett, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

An 18-month-old child presents with the rash shown in the slide. There is desquamation of skin at the granular layer, leaving a wet-appearing surface beneath.

Which of the following is the best diagnosis?

  1. Impetigo
  2. Candidiasis
  3. Staphylococcal scalded-skin syndrome (SSSS)
  4. Erysipelas
Image courtesy of Jessica Connett, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

Answer: C. Staphylococcal scalded-skin syndrome (SSSS).

SSSS (shown) is a toxin-mediated exfoliative dermatitis caused by systemic spread of the same exfoliative toxin that causes bullous impetigo. The major sites of involvement include the face, the retroauricular area, and the neck. The site of infection is usually distant from the site of skin damage. The diffuse erythematous rash often begins on the face and intertriginous sites and then generalizes and may be associated with systemic symptoms. Young children and neonates are slow to clear the toxin and are more prone to the syndrome because of lack of immunity and immature renal clearance capability. Adults with renal insufficiency and immunosuppression are particularly at risk: Their mortality risk is 60%, compared with 5% for children. Treatment of SSSS includes administration of intravenous (IV) antibiotics and fluid rehydration.[2,3]

Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

A 65-year-old man presents with an intensely painful eruption on his leg (shown).

Which of the following is the best diagnosis?

  1. Leishmaniasis
  2. Cellulitis
  3. Erysipelas
  4. Impetigo
Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

Answer: C. Erysipelas.

Both erysipelas (shown) and cellulitis are usually caused by group A streptococci. Erysipelas involves the superficial dermis and lymphatic vessels, leading to edema and a characteristic sharp, distinct outline. Cellulitis involves deeper tissue and fades gradually into the surrounding skin. Erysipelas can result in lymphatic scarring and chronic lymphedema. Involvement of the leg is more common than facial involvement. The lower extremities are involved in 70-80% of erysipelas cases; the face is affected in 5-20% of patients.[4] Complications of the infection usually are not life-threatening, and most cases resolve after antibiotic therapy.

Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

A 54-year-old man presents with fever and an acutely tender eruption on his leg (shown).

Which of the following is the best diagnosis?

  1. Necrotizing fasciitis
  2. Impetigo
  3. Botryomycosis
  4. Lymphangitis
Image courtesy of Medscape.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

Answer: D. Lymphangitis.

Lymphangitis results from inflammation of the lymphatic channels caused by a distal infection. The most common cause of lymphangitis is Streptococcus pyogenes. Patients with streptococcal lymphangitis can be quite toxic and febrile, and the infection can rapidly progress, leading to serious complications. Patients often present with a red streak traveling up the involved extremity, a raised border around the affected area, and lymphadenitis. A history of a recent cut or abrasion to an area of skin distal to the site of infection is common. Children with lymphangitis may have fever, chills, and malaise, and some children may report headache, loss of appetite, and muscle aches.[5]

Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

A 60-year-old woman found an 18-year-old bottle of eye drops in her medicine cabinet and decided to use them. She now presents with a purulent endophthalmitis (shown).

Which of the following is the most likely infecting organism?

  1. Pseudomonas aeruginosa
  2. Staphylococcus aureus
  3. S pyogenes
  4. Mycobacterium marinum
Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

Answer: A. Pseudomonas aeruginosa.

P aeruginosa is a gram-negative rod that grows well in aqueous environments. In healthy individuals, it can cause folliculitis after exposure to poorly chlorinated pools or hot tubs. P aeruginosa has low virulence; consequently, infections most commonly occur in patients with weakened immune systems and those who have been hospitalized longer than 1 week. Pseudomonal infections can involve any part of the body, but when the bacteria are introduced into the eye, they cause a rapidly progressive and destructive lesion. P aeruginosa is a common cause of bacterial keratitis, scleral abscess, and endophthalmitis in adults and of ophthalmia neonatorum in children. When this organism causes endophthalmitis, progression to pseudomonal sepsis can occur. Histologic examination in disseminated cases characteristically shows vascular necrosis with a distinct absence of inflammatory cells. The organisms are visible as a blue haze surrounding the vessel (blue arrow).[6]

Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

An 18-year-old male presents with presumed psoriasis (shown), which started within the past week.

Which of the following is the most likely diagnosis?

  1. Impetigo
  2. Ecthyma
  3. Pitted keratolysis
  4. Syphilis
Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

Answer: D. Syphilis.

Skin lesions associated with syphilis are notoriously polymorphous, but they most commonly present as papulosquamous lesions on the trunk and coppery papules on the palms and soles with peripheral adherent scale. Histopathologic examination reveals elongation of rete ridges, interface dermatitis, endothelial swelling, and a lymphoplasmacytic infiltrate (left). In syphilis, immunostaining may reveal treponemal organisms (right, arrows) within the lower third of the epidermis. Physicians must always have a degree of suspicion regarding a possible diagnosis of syphilis, in that it manifests as many other diseases and can mimic many other infections. The incidence of syphilis infection in the United States has been steadily increasing since 2000, with the highest incidence in men who have sex with men.[7]

Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

A 65-year-old man presents with a new cardiac murmur and a nontender skin lesion on the sole of his foot (shown).

Which of the following is the most correct description of this dermatologic finding?

  1. Janeway lesion
  2. Osler node
  3. Erythema multiforme
  4. Erythema marginatum
Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

Answer: A. Janeway lesion.

Janeway lesions present in the setting of acute bacterial endocarditis as hemorrhagic, stellate, nontender infarctions of skin on the palms or soles. Biopsy demonstrates staphylococcal embolization of arterioles (arrows). Osler nodes are associated with subacute bacterial endocarditis and are related to immune complex formation. Although similar to Janeway lesions, they present as tender, blanchable, pink papules on the digits.

Image courtesy of Medscape.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

A 50-year-old woman presents with a rash on her face (shown). Examination reveals pustules and honey-colored crusts on an erythematous base.

Which of the following is the best diagnosis?

  1. Ecthyma
  2. SSSS
  3. Botryomycosis
  4. Impetigo
Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

Answer: D. Impetigo.

Impetigo (shown) is an acute and highly contagious gram-positive bacterial infection of the superficial epidermis. Most cases begin as a streptococcal infection, though staphylococci may overgrow the streptococci in later phases of the infection. Impetigo is the most common bacterial infection in children. Risk factors include warm ambient temperatures and humidity, atopy, poor hygiene, trauma to the skin, and contact sports. Diagnosis of impetigo is often based solely on the patient’s history and clinical appearance. Bacterial culture and sensitivity can be used to confirm the diagnosis and are recommended when methicillin-resistant S aureus (MRSA) is suspected or in the presence of an impetigo outbreak or poststreptococcal glomerulonephritis.[8,9,10] Nasal decolonization and management of fomites can be helpful to prevent spread to other individuals and reinfection.

Image courtesy of D Scott Smith, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

A 43-year-old man presents with anesthetic, indurated, red lesions (shown).

Which of the following is the most likely diagnosis?

  1. Syphilis
  2. Leprosy
  3. Ecthyma
  4. Impetigo
Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

Answer: B. Leprosy.

Despite successful campaigns in the 1990s by the World Health Organization (WHO) to eliminate leprosy as a public health problem, the disease is still endemic in pockets of many countries, with the majority of new cases diagnosed in Brazil, India, Indonesia, and parts of Africa.[12] Leprosy is still rare in the United States, but with increasing travel and immigration, an average of 150-250 cases are diagnosed each year.[11,12] Skin lesions are indurated and anesthetic. Biopsy demonstrates granulomatous inflammation in a perivascular and perineural pattern (A) with Fite-positive acid-fast organisms (arrow) visible within histiocytes in multibacillary disease.

Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

A 35-year-old woman presents with acral hemorrhagic pustules (arrow) and arthralgia.

Which of the following is the most likely diagnosis?

  1. Syphilis
  2. Swimming-pool granuloma
  3. Gonococcemia
  4. Meningococcemia
Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

Answer: C. Gonococcemia.

Gonococcemia is defined as the presence of Neisseria gonorrhoeae in the bloodstream, which can lead to the development of disseminated gonococcal infection. Women commonly present with gonococcemia immediately following a menstrual period. The characteristic skin lesions are acral hemorrhagic pustules (arrow). Patients commonly have septic arthritis or arthralgia.[13]

Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

An infant from a daycare center develops a fluctuant nodule on the thigh (shown).

Which of the following should be the initial treatment measure?

  1. Drainage
  2. Oral sulfa drugs
  3. Oral doxycycline
  4. Oral clindamycin
  5. IV vancomycin
Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

Answer: A. Drainage.

The initial treatment for uncomplicated abscesses, including those caused by MRSA, is drainage. Abscesses up to 5 cm in diameter, when adequately drained, demonstrate similar outcomes with or without antibiotics. Antibiotic stewardship is increasingly important in the face of growing microbial resistance and the emergence of multidrug-resistant organisms. Additionally, antibiotics carry a risk of side effects, including severe adverse events such as Stevens-Johnson syndrome, and should be used only when medically necessary. Tetracyclines are contraindicated in children, except for the treatment of life-threatening infections such as rickettsioses.

Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

This patient has failed to respond to treatment with a cephalosporin. The culture shows MRSA.

Which of the following is the most appropriate next step?

  1. Drainage of individual lesions
  2. Oral sulfa drugs
  3. Oral doxycycline
  4. Oral clindamycin
  5. IV vancomycin
Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

Answer: A. Drainage of individual lesions.

Bacterial furuncles represent small follicular abscesses. Appropriate treatment requires drainage. Antibiotics have little effect until appropriate drainage has been completed. Surface carriage may result in spreading of the infection to adjacent follicles and can be addressed by topical agents such as chlorhexidine.

Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

After completing an ICU rotation, a pediatrics resident develops headache, fever, malaise, hypotension, and the rash shown in the slide.

For which of the following conditions is he most at risk?

  1. Acute renal failure
  2. Acute myocardial infarction
  3. Acute addisonian crisis
  4. Acute pneumonitis
Image courtesy of Dirk M Elston, MD.

Bacterial Skin Infections: Can You Make the Diagnosis?

Carly A Elston, MD; Dirk M Elston, MD | April 16, 2019 | Contributor Information

Answer: C. Acute addisonian crisis.

Meningococcemia, an acute infection of the bloodstream, presents with retiform purpura. The individual stellate lesions have an erythematous rim and a gun-metal gray hemorrhagic center. Bilateral adrenal necrosis with ensuing acute addisonian crisis is a potentially fatal complication, and patients should be treated with appropriate antibiotics as well as corticosteroids in the setting of acute hypotension.

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Identifying Lesions on Skin of Color

As US population demographics change, clinicians need to be familiar with variations in the prevalence and clinical presentation of dermatologic disease in people with skin of color. Learn how to recognize various lesions on skin of color.Slideshows, March 2019
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Impetigo

Impetigo is an acute, highly contagious gram-positive bacterial infection of the superficial layers of the epidermis. Skin lesions such as cuts, abrasions, and chickenpox can also become secondarily infected (impetiginized) with the same pathogens that produce classic impetigo.Diseases/Conditions, November 2018
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