Bullous impetigo

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Bullous impetigo
Bullous impetigo1.jpg
Bullous impetigo after rupture of the bullae
Specialty Infectious disease/dermatology

Bullous impetigo is a bacterial skin infection caused by Staphylococcus aureus that results in the formation of large blisters called bullae, usually in areas with skin folds like the armpit, groin, between the fingers or toes, beneath the breast, and between the buttocks. It accounts for 30% of cases of impetigo, the other 70% being non-bullous impetigo. [1]

Contents

The bullae are caused by exfoliative toxins produced by Staphylococcus aureus that cause the connections between cells in the uppermost layer of the skin to fall apart. [1] Bullous impetigo in newborns, children, or adults who are immunocompromised and/or are experiencing kidney failure, can develop into a more severe and generalized form called staphylococcal scalded skin syndrome (SSSS). The mortality rate is less than 3% for infected children, but up to 60% in adults. [2]

Signs and symptoms

Bullous impetigo on the arm Bullous impetigo2.jpg
Bullous impetigo on the arm
Bullous impetigo Impetigo.jpg
Bullous impetigo

Cause

Exposure is most commonly seen in hospital wards and nurseries, and can be passed from person to person in other settings, such as close contact sports. Therefore, the patient is advised to try to limit human contact as much as possible to minimize the risk of spreading the infection. [3]

Infectious period

After 48 hours the disease is considered no longer contagious assuming the proper antibiotic treatments have been administered.

Pathogenesis

Exfoliating toxins are serine proteases that specifically bind to and cleave desmoglein 1 (Dsg1). Previous studies suggested that exfoliating toxins bind to gangliosides, causing a release of protease by keratinocytes acting as superantigens in stimulating the skin's immune system. [2] A more recent proposal states there are three known exfoliating toxins; ETA, ETB, and ETD which act as a glutamic acid-specific serine protease with concentrated specificity. Which results in the cleavage of human Dsg1 at a unique site after glutamic acid residues causing deactivation. [2]

S. aureus

S. aureus expresses surface receptors for fibrinogen, fibronectin, and vitronectin. These surface receptors allow a bridge to be formed which binds to host endothelial cells. Lipases allow for the degradation of lipids on the skin surface and its expression can be directly correlated with its ability of the bacteria to produce abscesses. [4]

Diagnosis

Histology

The epidermis is composed of four layers, stratum basale, stratum spinosum, stratum granulosum, and stratum corneum. [5]

The cleavage plane can be found either subcorneally or within the upper stratum granulosum. The roof of the pustule is parakeratotic stratum corneum, and the floor is formed of keratinocytes, which may or may not be acantholytic. [6] Neutrophils begin to fill the pustule. Toxins are produced by S. aureus and target desmoglein, which is a desmosomal cell-cell adhesion molecule found in the upper levels of the epidermis. This correlates with the subcorneal localization of the bullae. [6]

Clinical Differential

Prevention

Management

Antibiotic creams are the preferred treatment for mild cases of impetigo, despite their limited systemic absorption. Such prescribed ointments include neosporin, fusidic acid, chloramphenicol and mupirocin. More severe cases of impetigo however (especially bullous impetigo) will likely require oral agents with better systemic bioavailability, such as cephalexin. Cases that do not resolve with initial antibiotic therapy or require hospitalization may also be indicative an MRSA infection, which would require consultation with a local microbiologist. [7]

Antibiotic treatment typically last 7–10 days, and although highly effective some cases of methicillin resistant S. aureus (MRSA) may require longer therapy depending on the severity of infection and how much it has spread.

See also

Related Research Articles

<span class="mw-page-title-main">Integumentary system</span> Skin and other protective organs

The integumentary system is the set of organs forming the outermost layer of an animal's body. It comprises the skin and its appendages, which act as a physical barrier between the external environment and the internal environment that it serves to protect and maintain the body of the animal. Mainly it is the body's outer skin.

<i>Staphylococcus aureus</i> Species of Gram-positive bacterium

Staphylococcus aureus is a gram-positive spherically shaped bacterium, a member of the Bacillota, and is a usual member of the microbiota of the body, frequently found in the upper respiratory tract and on the skin. It is often positive for catalase and nitrate reduction and is a facultative anaerobe that can grow without the need for oxygen. Although S. aureus usually acts as a commensal of the human microbiota, it can also become an opportunistic pathogen, being a common cause of skin infections including abscesses, respiratory infections such as sinusitis, and food poisoning. Pathogenic strains often promote infections by producing virulence factors such as potent protein toxins, and the expression of a cell-surface protein that binds and inactivates antibodies. S. aureus is one of the leading pathogens for deaths associated with antimicrobial resistance and the emergence of antibiotic-resistant strains, such as methicillin-resistant S. aureus (MRSA). The bacterium is a worldwide problem in clinical medicine. Despite much research and development, no vaccine for S. aureus has been approved.

Methicillin-resistant <i>Staphylococcus aureus</i> Bacterium responsible for difficult-to-treat infections in humans

Methicillin-resistant Staphylococcus aureus (MRSA) is a group of gram-positive bacteria that are genetically distinct from other strains of Staphylococcus aureus. MRSA is responsible for several difficult-to-treat infections in humans. It caused more than 100,000 deaths worldwide attributable to antimicrobial resistance in 2019.

<span class="mw-page-title-main">Epidermis</span> Outermost of the three layers that make up the skin

The epidermis is the outermost of the three layers that comprise the skin, the inner layers being the dermis and hypodermis. The epidermis layer provides a barrier to infection from environmental pathogens and regulates the amount of water released from the body into the atmosphere through transepidermal water loss.

<span class="mw-page-title-main">Desmosome</span> Cell junction involved in cell-to-cell adhesion

A desmosome, also known as a macula adherens, is a cell structure specialized for cell-to-cell adhesion. A type of junctional complex, they are localized spot-like adhesions randomly arranged on the lateral sides of plasma membranes. Desmosomes are one of the stronger cell-to-cell adhesion types and are found in tissue that experience intense mechanical stress, such as cardiac muscle tissue, bladder tissue, gastrointestinal mucosa, and epithelia.

<span class="mw-page-title-main">Stratum corneum</span> Outermost layer of the epidermis

The stratum corneum is the outermost layer of the epidermis. Consisting of dead tissue, it protects underlying tissue from infection, dehydration, chemicals and mechanical stress. It is composed of 15–20 layers of flattened cells with no nuclei and cell organelles.

<span class="mw-page-title-main">Desquamation</span> Skin peeling

Desquamation, or peeling skin, is the shedding of dead cells from the outermost layer of skin.

<span class="mw-page-title-main">Staphylococcal scalded skin syndrome</span> Medical condition

Staphylococcal scalded skin syndrome (SSSS) is a dermatological condition caused by Staphylococcus aureus.

<span class="mw-page-title-main">Stratum lucidum</span>

The stratum lucidum is a thin, clear layer of dead skin cells in the epidermis named for its translucent appearance under a microscope. It is readily visible by light microscopy only in areas of thick skin, which are found on the palms of the hands and the soles of the feet.

<span class="mw-page-title-main">Stratum granulosum</span> Cell layer in the epidermis

The stratum granulosum is a thin layer of cells in the epidermis lying above the stratum spinosum and below the stratum corneum. Keratinocytes migrating from the underlying stratum spinosum become known as granular cells in this layer. These cells contain keratohyalin granules, which are filled with histidine- and cysteine-rich proteins that appear to bind the keratin filaments together. Therefore, the main function of keratohyalin granules is to bind intermediate keratin filaments together.

<span class="mw-page-title-main">Dukes' disease</span> Medical condition

Dukes' disease, named after Clement Dukes (1845-1925), also known as fourth disease, Filatov-Dukes' disease, Staphylococcal Scalded Skin Syndrome (SSSS), or Ritter's disease is an exanthem (rash-causing) illness primarily affecting children and historically described as a distinct bacterial infection, though its existence as a separate disease entity is now debated.

A skin infection is an infection of the skin in humans and other animals, that can also affect the associated soft tissues such as loose connective tissue and mucous membranes. They comprise a category of infections termed skin and skin structure infections (SSSIs), or skin and soft tissue infections (SSTIs), and acute bacterial SSSIs (ABSSSIs). They are distinguished from dermatitis, although skin infections can result in skin inflammation.

<span class="mw-page-title-main">Pemphigus vulgaris</span> Medical condition

Pemphigus vulgaris is a rare chronic blistering skin disease and the most common form of pemphigus. Pemphigus was derived from the Greek word pemphix, meaning blister. It is classified as a type II hypersensitivity reaction in which antibodies are formed against desmosomes, components of the skin that function to keep certain layers of skin bound to each other. As desmosomes are attacked, the layers of skin separate and the clinical picture resembles a blister. These blisters are due to acantholysis, or breaking apart of intercellular connections through an autoantibody-mediated response. Over time the condition inevitably progresses without treatment: lesions increase in size and distribution throughout the body, behaving physiologically like a severe burn.

<span class="mw-page-title-main">Desmoglein-1</span> Protein found in humans

Desmoglein-1 is a protein that in humans is encoded by the DSG1 gene. Desmoglein-1 is expressed everywhere in the skin epidermis, but mainly it is expressed in the superficial upper layers of the skin epidermis.

<span class="mw-page-title-main">Lamellar bodies</span> Secretory organelles

In cell biology, lamellar bodies are secretory organelles found in type II alveolar cells in the lungs, and in keratinocytes in the skin. They are oblong structures, appearing about 300-400 nm in width and 100-150 nm in length in transmission electron microscopy images. Lamellar bodies in the alveoli of the lungs fuse with the cell membrane and release pulmonary surfactant into the extracellular space.

Corneocytes are terminally differentiated keratinocytes and compose most of the stratum corneum, the outermost layer of the epidermis. They are regularly replaced through desquamation and renewal from lower epidermal layers and are essential for its function as a skin barrier.

<span class="mw-page-title-main">Staphylococcal infection</span> Medical condition

A staphylococcal infection or staph infection is an infection caused by members of the Staphylococcus genus of bacteria.

Exfoliatin is a Staphylococcus aureus exotoxin that causes a blistering of the skin known as staphylococcal scalded skin syndrome, usually in infants.

mecA is a gene found in bacterial cells which allows them to be resistant to antibiotics such as methicillin, penicillin and other penicillin-like antibiotics.

<i>Staphylococcus hyicus</i> Species of bacterium

Staphylococcus hyicus is a Gram-positive, facultatively anaerobic bacterium in the genus Staphylococcus. It consists of clustered cocci and forms white circular colonies when grown on blood agar. S. hyicus is a known animal pathogen. It causes disease in poultry, cattle, horses, and pigs. Most notably, it is the agent that causes porcine exudative epidermitis, also known as greasy pig disease, in piglets. S. hyicus is generally considered to not be zoonotic, however it has been shown to be able to cause bacteremia and sepsis in humans.

References

  1. 1 2 Hartman-Adams H, Banvard C, Juckett G (August 2014). "Impetigo: diagnosis and treatment". American Family Physician. 90 (4): 229–235. PMID   25250996.
  2. 1 2 3 Hanakawa Y, Schechter NM, Lin C, Garza L, Li H, Yamaguchi T, et al. (July 2002). "Molecular mechanisms of blister formation in bullous impetigo and staphylococcal scalded skin syndrome". The Journal of Clinical Investigation. 110 (1). American Society for Clinical Investigation: 53–60. doi:10.1172/jci0215766. PMC   151035 . PMID   12093888.
  3. Lucky AW. "Blistering Disorders in Infancy". docstoc.com. Archived from the original on October 6, 2012.
  4. Kumar V, Abbas AK, Fausto N (2005). Robbins and Cotran Pathologic Basis of Disease. Philadelphia: W B Saunders Company. p. 620. ISBN   0-7216-0187-1.
  5. Roy S. "Normal Histology of the Skin". histopathology-india.net. Archived from the original on 2011-02-18.
  6. 1 2 Sternberg SS, Mills SE, Carter D (2004). Sternberg's Diagnostic Surgical Pathology. Philadelphia: Lippincott Williams & Wilkins. p. 17f. ISBN   0-7817-4051-7.
  7. "Impetigo: antimicrobial prescribing". NICE. 26 February 2020. Retrieved 8 July 2021.