Helminthosporium
Characteristics: No cases of infection caused by a true Helminthosporium have been reported in humans or animals. No information is available regarding toxicity.
Allergenicity has not been studied, although cross reactivity may exist.Description: Helminthosporium spores superficially resemble Drechslera, Bipolaris, and Exserohilum spores but the mechanism of sporulation is quite different. The taxonomy of this entire group has been widely debated. Helminthosporium is rare, and has never been isolated by our laboratory. The culture examined by us as a study culture came from the southern U.S. from Dr. Luttrell, one of the key players in the taxonomic saga. The antigen labeled “Helminthosporium” in use by allergists for skin testing has been found to be either Drechslera, or Bipolaris. No cases of infection caused by a true Helminthosporium have been reported in humans or animals. No information is available regarding toxicity. Allergenicity has not been studied, although cross reactivity may exist between all the above mentioned genera. Natural habitat includes dead stems of herbaceous plants, and twigs and branches of many different kinds of trees. Helminthosporium solani is the cause of “silver scurf” disease in potatoes.
Hyalodendron
Characteristics: No information is available regarding health effects or toxicity. Allergenicity has not been studied.
Description: Hyalodendron species appear to be common during certain periods of the year. They are morphologically related to Cladosporium but do not have the olive and brown pigments of Cladosporium. No information is available regarding health effects or toxicity. Allergenicity has not been studied. May be identified on surfaces by tape lifts, tease mounts from bulk samples, and in air by culturable (Andersen) samples. Spores look very close to Cladosporium and would most probably be thought of as “young” unpigmented Cladosporium spores on spore trap samples. Reported to be rarely isolated from soil by Barron; reported to be isolated from utility poles by Wang. Our laboratory sees this organism in moderate numbers on Andersen air sampling during certain periods of the year, most frequently from northern California and from the southern areas of the United States. Natural habitat is most probably woody plant materials.
Hyphal Fragments
These are organisms that have not sporulated under the culture conditions provided. Most never sporulate in culture (sterile mycelia). Some represent non-sporulating colonies of common fungi (e.g., Cladosporium, Alternaria, even Aspergillus).
