Microbial aerosols and actinomycetes in etiological considerations of mushroom workers' lungs

Spent steamed compost, phase II compost, and dust emanating from spent compost during dumping of stationary-bed mushroom houses were examined bacteriologically. The total count for spent compost was 16 X 10(8) microorganisms per g. The total count for dust was 333 microorganisms per liter of air. Actinomycetes belonging to the genus Streptomyces often constituted 90% or more of isolates from dust, whereas mold spores constituted approximately 5%. Dust weight averaged 3.4 mg/liter of air and contained approximately 33% inanimate and 67% animate (microbial) particles. Spent compost and casing contained approximately 60% moisture; the average pH of compost was 6.93, and that of casing was 7.70. Ouchterlony precipitin results with antisera from workers afflicted with either farmer's or mushroom worker's lung were positive for Bacillus licheniformis, Micropolyspora faeni, Thermoactinomyces vulgaris, Aspergillus fumigatus, Humicola grisea var. thermoidea, spent compost, and phase II compost. Their usefulness in determining the etiology of this and related forms of allergic alveolitis is questioned and discussed. The relationship of dust particle size; microbial species, prevalence and antigenicity; and compost antigenicity to the etiology of mushroom worker's lung is discussed. The microbial ecology of mushroom compost and moldy hay associated with farmer's lung is compared.