Blastomyces dermatitidis

Blastomyces dermatitidis is the causative agent of North American blastomycosis, which can affect humans and animals (Ditmyer H et al. 2011). Blastomyces dermatitidis is a dimorphic fungus that occurs in mycelium form in the environment and as thick-walled budding yeast in tissues (at 37 ° C). Blastomyces dermatitidis grows in soil and in moist, rotting wood, often in an area near a waterway such as a lake, river or stream. Indoor growth can also occur in accumulated deposits in damp sheds or huts, for example.

The fungus is endemic in parts of eastern North America, particularly northern Ontario, southeastern Manitoba, Quebec south of the St. Lawrence River, parts of the U.S. Appalachian Mountains and interconnected eastern mountain ranges, the western shore of Lake Michigan, the state of Wisconsin and the entire Mississippi Valley, including the valleys of some major tributaries such as the Ohio River. In addition, Blastomyces dermatitidis is rare in Africa both north and south of the Sahara desert, as well as on the Arabian Peninsula and the Indian subcontinent. Human-to-human transmission has only been reported in very few cases (Morris SK et al. 2006, Litvinov IV et al.2013).

After aerogenic intake, Blastomyces dermatitidis first attacks the lungs where the fungus can multiply as a yeast. However, an infection can also occur transcutaneously when the skin is injured (Court H 2019).

Clinic (see below Blastomycosis, North American)

Blastomyces dermatitidis can be detected microscopically from the pus of the skin lesions, from bioptic material and sputum or bronchial lavage in direct preparation as thick-walled, round yeast cells (see figure) and cultivated on suitable culture media. The culture then develops after approx. 3-4 weeks incubation time. Faster results are obtained by PCR directly from the test samples.

1. Ditmyer H et al (2011) Mycotic mastitis in three dogs due to Blastomyces dermatitidis. J Am Anim Hosp Assoc 47:356 - 358.
2. Guinn DJ et al (2016) Fungal osteomyelitis with vertebral reossification. Int J Surg Case Rep 19:1-3.
3. Court H (2019). Blastomyces dermatitidis. In: Hof H, Schlüter D, Dörries R, ed. dual series Medical Microbiology. 7th, completely revised and extended edition. Stuttgart: Thieme S 508
4. Morris SK et al (2006) Blastomycosis in Ontario, 1994-2003external icon. Emerg Infect Dis12:274-279.
5. Litvinov IV et al (2013) Endemic human blastomycosis in Quebec, Canada, 1988-2011external icon. Epidemiol Infect 141:1143-1147.
6. Sanghvi Y et al. (2017) Blastomyces dermatitidis peritonitis complicating peritoneal dialysis. Semin Dial 30: 453-455.