Subcutaneous mycoses (2) Chromoblastomycosis& Sporotrichosis

Mrs. Dalia Kamal Eldien

Msc in MicrobiologyLecture NO(7)

Objectives

Identify the main causes of subcutaneous fungal infections

Chromoblastomycosis: Etiological agents, Epidemiology, Clinical presentation, Laboratory diagnosis& Treatment

Sporotrichosis: Etiological agents, Epidemiology, Clinical presentation, Laboratory diagnosis& Treatment

Subcutaneous mycoses

Subcutaneous mycoses include a heterogeneous group of fungal infections that develop at the site of transcutaneous trauma.

Infection slowly evolves as the etiologic agent survives and adapts to the host tissue environment.

The main subcutaneous fungal infections include: Mycetoma Chromoblastomycosis Sporotrichosis Lobomycosis Rhinosporidiosis Subcutaneous zygomycosis Subcutaneous phaeohyphomycosis.

Chromoblastomycosis

Also known as chromomycosis or Fonseca's disease Caused by darkly pigmented (dematiaceous) molds,

which form thick-walled, dark-colored, multicelled structures called muriform cells or sclerotic bodies or Medlar bodies in tissue.

The infection occurs most commonly in tropical or subtropical climates, often in rural areas.

It can be caused by traumatic inoculation of a specific group of dematiaceous fungi through the skin, often by thorns or splinters.

Etiology

The most common of the etiologic agents are Cladophialophora carrionii Fonsecaea pedrosoi. Less common pathogens include Fonsecaea compactum Phialophora verrucosa Exophiala jeanselmei

Epidemiology

It is distributed worldwide. However the incidence is greater in tropical and subtropical regions located between 30° N and 30° S.

Clinical presentation

Patients are usually asymptomatic. Patients visit hospital only in cases of secondary infection or elephantiasis.

A previous unnoticed or unremembered trauma to the skin is often the site of infection.

After several years a small, raised, erythematous, asymptomatic papule develops, known as verrucous Lesions

The verrucous Lesions spread laterally to contiguous healthy tissue.

The verrucous lesions are frequently ulcerated and may be raised about 1 to 3 cm above the skin surface with rough irregular surfaces, giving a cauliflower like appearance and hence it is also called as verrucosa dermatitis.

verrucous lesions

Diagnosis

Depend on clinical presentation, histopathology, and culture of the etiologic agents.

Laboratory diagnosisThe most useful test is the direct examination of 10%

KOH cleared lesion scrapings. Results: Muriform cells or also name as sclerotic bodies or

Medlar bodies are seen. They are thick-walled and multi cellular-colored cells, these cells are pathognomonic of chromoblastomycosis, but they do not give any specific information about the agent.

Also the Dematiaceous hyphae can also be observed.

Sclerotic bodies: round, thick-walled fungal elements

Culture: Slow-growing, dark, velvety colony with a black obverse is seen on culture of the infectious agents. It is isolated on SDA with actidione and antibiotics.

For identification of individual species various characteristics, including conidia production have to be observed.

Plate culture of Cladophialophora carrionii, at four weeks growth

The biopsy specimen is stained with H&E, Giemsa stain and Fontana- Masson stain.

Biopsy specimens show hyperkeratosis, with central neutrophilic abscesses and granulomas.

Tissue infiltrates may present with variable pigmented fungal structures, such as muriform cells (Medlar bodies)

Biopsy specimens show Medlar bodies

Treatment

Chromoblastomycosis spreads very slowly; it is rarely fatal and usually has a good prognosis, but it can be very difficult to cure.

The several treatment options include medication and surgery.

Treatment options include oral &locally applied itraconazole, heat therapy, cryosurgery, laser therapy& surgery

Surgical excision of an early solitary lesion is preferred.

Sporotrichosis

Sporotrichosis is an infection caused by dimorphic fungus called Sporothrix schenckii.

Dimorphic fungi that exhibits a hyphal morphology in its low temperature saprophytic phase, but is found primarily as a budding yeast in host tissues.

The fungus lives throughout the world in soil, plants, and decaying vegetation.

Cutaneous (skin) infection is the most common form of infection and usually occurs after handling contaminated plant material, when the fungus enters the skin through a small cut or scrape.

although pulmonary infection can occur if a person inhales the microscopic airborne fungal spores

Most Sporothrix infections only involve the skin.

Symptoms of Sporotrichosis

The first symptom is usually a small painless nodule resembling an insect bite, may appear any time from 1 to 12 weeks after exposure to the fungus.

The nodule can be red, pink, or purple in color, and it usually appears on the finger, hand, or arm where the fungus has entered through a break in the skin.

The nodule will eventually become larger in size and may look like an open sore or ulcer that is very slow to heal.

Additional nodules may appear later near the original lesion.

However, the infection can spread to other parts of the body, including the bones, joints, and the central nervous system.

Usually, these types of disseminated infections only occur in people with weakened immune systems.

In rare cases, a pneumonia-like illness can occur after inhaling Sporothrix spores, which can cause symptoms such as shortness of breath, cough, and fever.

Nodule resembling an insect bite

Sources of Sporotrichosis infectionThe fungus lives in sphagnum moss, hay, other plant

materials, and soil. The fungus can enter the skin through small cuts or

punctures from thorns, pine needles, or wires. In rare cases, inhalation of the fungus can cause

pulmonary infection. Sporotrichosis is not spread from person to person;

however, a small number of human cases have been caused by scratches or bites from infected animals such as cats.

Risk & PreventionPeople who handle thorny plants, sphagnum moss, or

bales of hay are at increased risk of getting sporotrichosis

The infection is more common among people with weakened immune systems, but it can also occur in otherwise healthy people.

Diagnosis

Specimen; swab or a biopsy of the infected site for microscopy and a fungal culture.

Culture: specimen inoculate on Sabouraud agar or brain heart infusion agar, two media one incubate at 22°C, other at 37°C

In the filamentous form:  Colonial morphology: colonies are moist, leathery to velvety,

and have a finely wrinkled surface. The color is white initially and may change color over time to become cream to dark brown (“dirty candle-wax” color)

Microscopically: filamentous hyphae are septate approximately 1 to 2μm in diameter. Conidia are oval shaped and glass like (hyaline) in appearance. They may be colorless or darkly colored. Conidia are sometimes referred to as resembling a flower.

In the yeast form: At 37°C either in the laboratory or in host tissue, S.

schenckii assumes its yeast form.  Macroscopically, the yeast form grows as smooth white or

off-white colonies. Microscopically, yeast cells are 2 to 6μm long and show an

elongated cigar-shaped morphology Serological tests are not always useful in the diagnosis of

sporotrichosis due to limitations in sensitivity and specificity.  PCR methods that specifically amplify the ribosomal

RNA gene have been shown to detect S. schenckii in clinical samples 

`Filamentous form colonies

Sporothrix schenckii, yeast form colonies

yeast form of Sporothrix schenckii when grown on brain heart infusion agar 

prevention

There is no vaccine to prevent sporotrichosis. can reduce your risk of sporotrichosis by wearing

protective clothing such as gloves and long sleeves when handling wires, rose bushes, bales of hay, pine seedlings, or other materials that may cause minor cuts or punctures in the skin.

It is also advisable to avoid skin contact with sphagnum moss.

Treatment

Most cases of sporotrichosis only involve the skin and/or subcutaneous tissues and are non-life-threatening, but the infection requires treatment with prescription antifungal medication for several months.

The most common treatment is oral itraconazole for 3 to 6 months, but treatment should continue for at least 12 months.