Sporothrix schenckii Case File

Sporothrix schenckii Case File

Eugene C.Toy, MD, Cynthia Debord, PHD, Audrey Wanger, PHD, Gilbert Castro, PHD, James D. Kettering, PHD, Donald Briscoe, MD

CASE 44

A 44-year-old woman presents to the physician’s office for evaluation of skin growths on her right arm. She reports that a few weeks ago she developed some small, red bumps on her right palm, which seemed to come together into a larger nodule. This then ulcerated, but it never was painful. She has been putting topical antibiotic on this area, and it seemed to be improving. However, in the past week she has noticed new growths extending up her forearm that appear just like the original lesion. She denies having skin lesions anywhere else, denies systemic symptoms such as fever, and has no history of anything like this before. She has no significant medical history and takes no medications. She is employed as a florist and floral arranger. On examination, she is comfortable appearing and has normal vital signs. On her right palm you see a circular, 1-cm-diameter, ulcerated area with a surrounding red, raised border. There are two identical appearing, but smaller, lesions on the forearm. Microscopic examination of a biopsy taken from one of the lesions reveals numerous white blood cells and cigar-shaped yeast forms.

◆ What is the most likely infectious cause of these lesions?

◆ What is the most likely route by which this infection was transmitted?

ANSWERS TO CASE 44: Sporothrix schenckii

Summary: A 44-year-old florist has painless, ulcerated lesions on her right hand and arm.

◆ Most likely infectious etiology: Sporothrix schenckii.

◆ Most likely route by which this infection was transmitted: Most likely mechanism of infection is inoculation into the skin via a puncture of the hand with an infected plant (most likely a rose thorn).

CLINICAL CORRELATION

Cutaneous sporotrichosis results from the inoculation of the organism into the skin via a puncture or other minor trauma. Most cases occur in persons with occupational or avocational exposure to infected material, such as in gardening or farming. The most common exposures are to rose thorns and sphagnum moss. The initial lesions are usually in areas that are prone to trauma, such as the extremities. They are often erythematous papules or nodules, which then ulcerate. Secondary lesions develop along the lines of lymphatic drainage. The lesions are usually painless, can wax and wane, and systemic symptoms are rare. Extracutaneous infections with S. schenckii have occurred, most commonly involving the joints, particularly hand, elbow, ankle, or knees. Cases of pulmonary sporotrichosis as well as meningitis have been described. Invasive and disseminated disease may occur in the severely immunosuppressed, particularly patients with advanced HIV disease.

APPROACH TO THE SUSPECTED SPOROTRICHOSIS PATIENT

Objectives

1. Know the morphologic characteristics of the yeast and mycelial forms of S. schenckii.

2. Know the common sources, routes of transmission, and clinical syndromes associated with S. schenckii infections.

Definitions

Dematiaceous fungi: Fungi with dark colored (brown or black) conidia and/or hyphae.

Lymphadenitis: Inflammation of the lymph node(s).

DISCUSSION

Characteristics of Sporothrix schenckii

Sporothrix schenckii is a dimorphic fungus that is most often isolated from soil, plants, or plant products. When cultured at 37°C (98.6°F) or in vivo, it exists as cigar-shaped yeast. At lower temperatures, it exists as a white, fuzzy mold that on further incubation develops a brown pigment. The hyphal form has numerous conidia, which develop in a rosette pattern at the ends of conidiophores. The fungus is found in the soil and on vegetation in all parts of the world, but most commonly in the tropical regions of North and South America. Transmission from animals to man has also been rarely described.

Diagnosis

Skin lesions associated with sporotrichosis can resemble those of other infectious and noninfectious entities, such as other fungal infections, Mycobacterium infections, or collagen vascular diseases. Diagnosis can be made by culture of biopsy material or demonstration of the characteristic cigar-shaped yeast forms on microscopic examination of a biopsy specimen. Multiple attempts at biopsy and culture may be required to recover the organism.

Sporothrix schenckii grows well within several days to several weeks on routine fungal media such as Sabouraud dextrose agar. Colonies initially are small and white to cream color that eventually turn brown to black. Laboratory confirmation of S. schenckii can be established by demonstration of characteristic mold structures after culture at room temperature. The rosette formation of the conidia on the conidiophore is characteristic, but not diagnostic. Conversion from the hyphal form to the yeast form on subculture of a specimen at 37°C (98.6°F) can aid in the specific identification of the fungus.

Treatment and Prevention

Cutaneous sporotrichosis is usually treated orally with either a saturated solution of potassium iodide or an antifungal agent such as itraconazole. Extracutaneous or disseminated disease is difficult to treat, but usually treated with itraconazole. Patients with concomitant HIV and sporotrichosis are usually treated prophylactically for the rest of their life with oral itraconazole.

COMPREHENSION QUESTIONS

[44.1] Which of the following fungi is most likely to cause cutaneous disease?

A. Aspergillus fumigatus

B. Candida albicans

C. Cryptococcus neoformans

D. Histoplasma capsulatum

E. Sporothrix schenckii

[44.2] A woman who pricked her finger while pruning some rose bushes develops a local pustule that progressed to an ulcer. Several nodules then developed along the local lymphatic drainage. The most reliable method to identify the etiologic agent is which of the following?

A. Culture of the organism in the laboratory

B. Gram stain of smear prepared from the lesion

C. India ink preparation

D. Skin test for delayed hypersensitivity

E. Stain the culture with potassium iodide

Answers

[44.1] E. Aspergillus, Cryptococcus, and Histoplasma infections routinely involve the respiratory system and form cellular components recognizable in the diagnostic laboratory. Candida species are usually endogenous flora that may be opportunistic under the right circumstances (e.g., immunocompromised patient). Cutaneous and systemic infections are possible under these conditions. S. schenckii is typically introduced into the skin by trauma, often related to outdoor activities and/or plants. About three-fourths of the cases are lymphocutaneous, with multiple subcutaneous nodules and abscesses along the lymphatics.

[44.2] A. The most reliable method of diagnosing S. schenckii is by culture. Specimens are usually biopsy materials or exudate from granulose or ulcerative lesions and are usually streaked on a selective medium such as Sabouraud agar containing antibacterial antibiotics. Initial incubation is usually 25ºC–30ºC (77ºF–86ºF), followed by growth at 35ºC (95ºF) and confirmation by conversion to the yeast form. Staining procedures are usually nonspecific unless fluorescent antibody.

MICROBIOLOGY PEARLS ❖ Sporothrix schenckii is a dimorphic fungus found in the soil of many areas of the world and associated with skin lesions following traumatic implantation most commonly from rose thorns. ❖ Cutaneous sporotrichosis is commonly treated with oral potassium iodide. ❖ Extracutaneous sporotrichosis, although rare, occurs in severely immunocompromised patients such as those with HIV.

REFERENCES

Fitzpatrick TB, Johnson RA, Polano MK, et al. Color Atlas and Synopsis of Clinical Dermatology, 2nd ed. New York: McGraw-Hill, 1992. 

Gorbach SL, Bartlett JG, Blacklow NR. Infectious Diseases, 2nd ed. Philadelphia,PA: W.B. Saunders, 1998. 

Harmon EM, Szwed T. Aspergillosis. eMedicine, 2002. http://www.emedicine.com/ med/topic174.html 

Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases, 5th ed. Philadelphia, PA: Churchill Livingstone, 2000. 

Murray PR, Rosenthal KS, Pfaller MA. Medical Microbiology, 5th ed. St. Louis, MO: Mosby, 2005:738,799. 

Rex JH, Okhuysen PC. Sporothrix schenckii. In: Mandell GL, Bennett JE, Dolin R, eds. Principles and Practice of Infectious Diseases, 6th ed. Philadelphia, PA: Churchill Livingstone, 2005:2695–702. 

Shafazand S, Doyle R, Ruoss S, et al. Inhalational anthrax: epidemiology, diagnosis and management. Chest 1999;116(5):1369–76. 

Todar K. University of Wisconsin-Madison Dept. of Bacteriology, 2002; http:www. bact.wisc.edu/bact330/lymelecture

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