Scientists have long known that actinomycetes somehow kept soil bacteria populations in balance. This fact led scientists Selman Waksman and Albert Shatz to think that some of these actinobacteria might be useful as antibiotics against human disease. Shatz was particularly driven by his experience as a lab assistant at a Miami Hospital during the 2nd World War. Here he witnessed the death of many young soldiers at the hand of penicillin immune infections, especially Tuberculosis.
Shatz, when released from the Miami Hospital returned to Dr Selman's lab at Rutger's University. On October 19th, 1943, after three months of work, he managed to isolate two strands of actinobacteria that could effectively stop the growth of penicillin resistant bacteria. Streptomycin, the first antibiotic to cure tuberculosis, was the result of this work. Streptomycin is still used, but in combination with other drugs, in the battle against TB.
The Streptomyces produce over two-thirds of the clinically useful antibiotics that are natural in origin including Erythromycin, Neomycin, Tetracycline and Cefoxitin. Kind of puts mud baths and masks along with the age old childhood habit of eating dirt in a different light, doesn't it.