Microorganisms in spent steamed mushroom compost and its dust were enumerated, and identified. Some phase II (indoor composting) compost samples were also examined. Steaming of spent compost resulted in a 70-76% reduction in microbial numbers. Total counts made with compost fusion agar were approximately two logs greater than those for nutrient agar. The most common bacterial isolate was Bacillus licheniformis. The most common actinomycete isolates were Streptomyces diastaticus and Thermoactinomyces vulgaris. Other actinomycete isolates included Streptomyces albus, Streptomyces griseus, Thermoactinomyces thalpophilis, Thermomonospora chromogena, and Thermomonospora fusca. The most common fungal isolates were Aspergillus fumigatus and Humicola grisea var. thermoidea. Other fungal isolates included Aspergillus flavus, Aspergillus nidulans, Aspergillus terreus, Aspergillus versicolor group. Chrysosporium luteum, Mucor spp., Nigrospora spp., Oidiodendron spp., Paecilomyces spp., Penicillium chrysogenum, Penicillum expansum, Trichoderma viride, and Trichurus spp.
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' 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 ormushroom 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.
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