The position of actinomycetes in taxonomical systematization was not definite in its early studies. Actinomycetes resembles bacteria in some respects and fungi on the other hand. Harz (1877),¹⁾ Gedoelst (1902)²⁾ and Petruschky (1903)³⁾ had put actinomycetes in fungi. Lehman and Neuman (1896)⁴⁾ settled it in supplementary group of bacteria. Since the middle of 20th century, it was placed in bacteria “Schizomycetes”. Waksman (1950)⁵⁾ stated that the actinomycetes may tentatively be placed in taxonomical transition group between Schizomycetes and Hyphomycetes. But recent evidences seemed to point the fact that actinomycetes are not to be considered as higher fungi and they appeared to be more closely related to the bacteria. One of those evidences is that actinomycetes are usually sensitive to antibacterial antibiotics as well as bacteria but not to antifungal antibiotics. Waksman et al. (1953)⁶⁾ reported decreasing sensitivity to isoniazide in order of pathogenic Mycobacteria→saprophytic Mycobacteria→Micromonospora→Nocardia→Streptomyces.

In this paper, the authors made a survey of selective sensitivity of actinomycetes (especially streptomycetes) and related organisms to various antibiotics.