ABSTRACT
The distribution of thermophilic actinomycetes in the atmosphere of Cairo was studied. The concentrations of these organisms were higher in the crowded districts than in the quieter residential ones. Maximum counts were recorded during December, higher counts during January and November were also obtained. Seven genera of thermophilic actinomycetes were recorded in the atmosphere of Cairo: Streptomyces, thermomonospora [Saccharomonospora], thermoactinomyces, Micropolyspora, Microbispora, Pseudonocardia and Actinobifida. The first two genera were more frequent than other genera. The genus streptomyces included four series [of which the gray series was most frequent] and 30 different species, of these species S. thermovulgaris and S. sp. 15 [12] were the most common. All thermomonospora and thermoactinomyces isolates were identified as Th. viridis [saccharomonospora viridis] and T. vulgaris, respectively. Micropolyspora was represented by M. faeni, M. Caesia and M. thermoviridis. Species of the other genera were microbispora, bispora pseudonocardia thermophila and actinobifida alba. Results indicate that thermophilic actinomycetes known to cause farmer's lung disease and other respiratory troubles were commonly isolated from the atmosphere of the crowded district "Zeitoun" in Cairo