BACTERIOSTATIC AND BACTERICIDAL AGENTS 207 



sessed both properties. Some strains of rhizobia were stimulated by lim- 

 ited concentrations of actinomycin. 



Streptothricin is far less toxic than these four substances. It acts 

 largely upon gram-negative bacteria, and thus is quite distinct from the 

 other four antibiotic agents. In this respect, it is similar to clavacin, 

 which, however, is far more toxic. 



Clavacin not only is bacteriostatic on gram-negative bacteria but pos- 

 sesses marked bactericidal properties, as is brought out in Table 37 

 (page 192) and in Figure 23. Fumigacin, on the other hand, is active 

 only upon gram-positive bacteria and has far more limited bactericidal 

 action. 



Gliotoxin is active against both gram-positive and gram-negative bac- 

 teria (Table 38). The substance is rather toxic to animals, the minimum 

 lethal dose being 45 to 6$ mg. per kilogram body weight j hematusia 

 is caused by even lower concentrations (459). 



TABLE 38. BACTERIOSTATIC ACTION OF GLIOTOXIN 

 TEST ORGANISM ACTIVITY 



S. aureus 4,000,000 



5. -pyogenes 1,000,000 



Pneumococcl 4,000,000 



5. enteritidis 250,000 



A. aerogenes 200,000 



K. fneumoniae 250,000 



E. coli 80,000 



From Johnson, Bruce, and Dutcher (459)- 

 Note. Units of activity by dilution method. 



On comparing the action of citrinin with penicillic acid, the first was 

 found (661) to act largely upon gram-positive bacteria j the second, 

 like quinones, had a more widespread action, especially against the 

 colon-typhoid group, 



BACTERIOSTATIC AND BACTERICIDAL AGENTS 



Fleming (268) divided all selective bacteriostatic agents, exclusive 

 of the action of oxygen on anaerobic bacteria, into three groups: (a) 



