Home humidifier thermophilic actinomycete isolates

Twenty-seven thermophilic actinomycete isolates obtained from humidification systems or living-bedroom areas of individuals with suspected but unproved home environment-related respiratory disease were characterized morphologically and biochemically. All isolates were demonstrated to be members of the Thermoactinomyces genus. Two previously misidentified isolates were reclassified as a Thermoacetinomyces sp. Thus, all of our thermophilic actinomycete humidifier isolates studied to date have been identified as either Thermoactinomyces vulgaris or Thermoactinomyces sp. Large numbers of unidentified thermotolerant bacteria have also been isolated from virtually all residual humidifier water samples and their possible role in production of "humidifier-associated" respiratory disease is unknown.