Microcycle conidiation and medusa head conidiophores of aspergilli on indoor construction materials and air filters from hospitals.

Microcycle conidiation and microniche colonization by aspergilli was observed in-situ on various indoor construction and finishing materials. Microcycle conidiation, direct conidiogenesis from a conidium or spore with minimal intervening hyphal development, for several decades has been considered a survival mechanism during stress for a variety of moulds. Adhesive transparent tape mounts and bulk materials from various indoor materials, including air filters from hospitals and healthcare institutions, were transported to the laboratory for light microscopic and scanning electron microscopic observations. Additional materials were held in moist chambers over nonsterile soils and examined periodically for fungal development. Microcycle conidiation was observed usually in areas of sparse fungal development, mostly in association with isolations of members of the Aspergillus flavus-, A. versicolor-, A. niger groups. Branched conidiophores and medusa heads, more often associated with colonization by Eurotium spp., were observed on some preserved woods. These conidiogenesis processes might be factors in the survival and blooms of indoor aspergilli.