To the Editor.—
Recently, we have isolated Thermoactinomyces organisms (a cause of hypersensitivity pneumonitis) from 28 of 123 samples of weathered sawdust received from 32 states, Nova Scotia, and the Philippines. The samples were obtained either personally or mailed in by cooperating forest products companies. The samples were incubated at 55 °C in a sealed plastic bag from one to five days.
Previously, Thermoactinomyces organisms were found in overheated hay, grain, and bagasse as well as in home no-frost refrigerators, heating systems, air conditioners, and humidifiers (236:344, 1976). All of these sources fulfill the three criteria for growth of Thermoactinomyces: the presence of moisture, nutrients, and an elevated temperature.
We recommend drying of the sawdust as a means of preventing growth of mesophilic microorganisms. Otherwise, metabolic heat accumulates during growth and provides the proper temperature conditions for the subsequent germination and growth of Thermoactinomyces spores.
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