124- 



ACTINOMYCETES AS ANTAGONISTS 



been established (969). Other members of the genus are capable of 

 forming different antibiotics (498). 



S. grlseus produces an antibiotic substance, designated as streptomy- 

 cin, that is also active against both gram-positive and gram-negative 

 bacteria. It is similar in its solubility and certain chemical properties to 

 streptothricinj however, it acts readily against B. mycoides and is more 

 active than streptothricin against certain gram-negative bacteria, such 

 as M. tuberculosis, S. marcescens, and Ps. aeruginosa. The bacteriostatic 

 spectrum of streptomycin is given in Table 22. Streptomycin is also 

 active in vivo against a variety of other bacteria, as shown later. It is 

 also active against spirochetes, but it is not active against fungi, ana- 

 erobic bacteria or viruses (791). 



TABLE 22. BACTERIOSTATIC SPECTRUM OF STREPTOMYCIN 



From Waksman and Schatz (970). 



Note. Unit of activity is the number of micrograms of streptomycin per 



required to inhibit growth. 



iter of suitable medium 



