180 BACTERIOLOGICAL CHEMISTRY 



Streptomycin. — Streptomyces griseus, one of the soil 

 organisms, the Actinomycetes, forms the substance 

 streptomycin which resembles streptothricin in inhibiting 

 the growth of Gram -negative as well as Gram -positive 

 organisms, but is more active against Pr. vulgaris and 

 Ps. ceruginosa among the former and against B. mycoides 

 and M. tuberculosis among the latter. It is also bacterio- 

 static to E. typhosa, Sal. schottmillleri, Br. abortus, H. 

 influenzce, H. pertussis, Serratia ')narcescens , B. subtilis, 

 Staph, aureus and CI. butylicum. Streptomycin is poorly 

 absorbed from the intestine but is not destroyed and so 

 may be useful for controlling intestinal infections. In 

 man it is rapidly absorbed and excreted in the urine 

 after parenteral administration, but therapeutic levels 

 can be maintained in the blood and urine more easily 

 than with penicillin. It has low toxicity for animals. 

 Preliminary trials indicate that it may be of therepeutic 

 use against typhoid fever and human tuberculosis. If 

 these claims are substantiated streptomycin is likely to 

 be as valuable as penicillin. 



Streptomycin can be adsorbed on charcoal from the 

 culture fluid resulting from the growth of S. griseus on 

 a corn steep liquor medium. After elution from the 

 charcoal with acid ethanol it can be purified and re- 

 crystallised as the hydrochloride, [a]D-84°, the sulphate, 

 the helianthate or reineckate, m.p. 162-1 64 °C. It is 

 an organic base soluble in water but not in most organic 

 solvents. It is fairly stable to heat, losing about half 

 its activity in ten minutes at 100°C. It is inactivated by 

 cysteine, 2-aminoethanethiol and, to a less extent, by 

 thioglycollic acid. The inactivation is reversed by 

 iodine. Its activity increases with the alkalinity of the 

 medium up to ^H 9. 



Streptomycin hydrochloride is completely inactivated 

 by standing for 24 hours with anhydrous methanol 

 containing N HCl. Addition of ether to the solutioji 

 precipitates a diguanidine base, streptidine, leaving an 



