Bipolaris and Drechslera
Growth & Distribution
Bipolaris, Drechslera, Exserohilum, & Helminthosporium are dematiaceous fungi, producing spores which are elongate, cylindrical, often with numerous septations or cells. These genera are grouped together due to spore similarity. These spores are common in both indoor and outdoor environments. They are found world wide with some species being exceptionally tolerant of dry environments (6).
Growth Rate: Rapid – Mature within 5 days (6)
Water Activity: 0.80 (this is a generalized number for common molds) (26)
Outdoors: These molds are most commonly found on grasses, grains and other plant materials. Bipolaris can be a plant pathogen causing spots, blights, rots, and other symptoms in staple crops like rice, wheat, and sorghum. In the past, plant disease caused by Bipolaris invasion has caused starvation of large human populations. In 1943-1944 the Bengal famine in India was caused by Bipolaris oryzae disease in rice. In the 1970s, Bipolaris maydis was responsible for a devastating leaf blight resulting in huge losses of corn crops in the USA & UK. (11)
Indoors: These mold may be found on water damaged materials, food stuffs, houseplants, and other organic materials.
Health Effects
Allergenic:
These molds are highly common in both indoor and outdoor environments; most people have some level of exposure on a daily basis.
In sensitive individuals can manifest Type I or Type III hypersensitivity reactions. These include allergic asthma, conjunctivitis (redness of the eye), rhinitis (hay fever), anaphylaxis, angioedema (dermal swelling), urticarial (hives) or hypersensitivity pneumonitis & allergic sinusitis (Type III). (5)
Pathogenic:
Bipolaris (rapid growth – mature within 5 days) can be pathogenic in rare instances, particularly in immunocompromised. May invade bone, cornea (keratomycosis), skin, aorta, lung, central nervous system or cause brain lesions (6).
Exserohilum (rapid growth – mature within 5 days) can cause phaeohyphomycosis (infection of mycelia/hyphae of dematiaceous fungi), most commonly in nasal sinuses, skin, subcutaneous tissue, and cornea. Rare reports of fatal disseminated infection (6).
Mycotoxins/Metabolites:
Cytochalasin, sporidesmin, sterigmatocystin (7)
