Occurrence of thermophilic actinomycetes in natural substrates in Nigeria.

Thermophilic actinomycetes were isolated from 163 (48.95%) of 333 samples of vegetable substrates and soil from different sites in Anambra and Enugu States in Nigeria. Thermoactinomyces (Tha.) vulgaris was the most common, occurring in 32.4% of samples while Tha. thalpophilus was isolated from 20.1%. Tha. sacchari, Saccharomonospora (Sam.) viridis and Saccharopolyspora (Sap.) rectivirgula were isolated from 3-10.5% of the samples examined. Streptomyces (Stm.) thermovulgaris occurred in 2.7% and Thermomonospora spp. in 0.6% of samples. Except for Stm. thermovulgaris and, perhaps, Thermomonospora spp., all the species isolated are known to be allergenic in man. The five known allergenic species were abundant in hay and maize silage. T. vulgaris and T. thalpophilus were also frequently isolated from rice straw. Tha. vulgaris, Tha. thalpophilus and Sap. rectivirgula were all most numerous in hay while Tha. sacchari was most numerous in maize silage. The widespread occurrence of thermophilic actinomycetes in Nigeria emphasizes the need for investigation of their role in allergic respiratory disorders.