ANTIBIOTICS 150 



concent latiuiis of 1 in 100,000 to I in 400,000. It is 

 bactericidal at dilutions of 1 in 25,000 to 1 in 50,000. 

 It is relatively highly toxic to animals. It will not 

 protect mice against infection with lisemolytic streptt)- 

 cocci or pneumococci but prevents the lethal action on 

 mice of gonococci suspended in mucin solution and 

 saves guinea-pigs from the action of gas gangrene 

 organisms. Its antibacterial activity can be measured 

 by its inhibition of the luminescence of Photobacterhmi 

 fischeri. A. flavus when groA\TL as a submerged culture 

 in agitated Czapek-Dox medium does not produce 

 aspergillic acid but a substance w^hich is very similar 

 to or identical with penicillin in chemical and biological 

 properties (see p. 171 et seq.). 



Citrinin. — PenicilUum citrinum when grown on Czapek- 

 Dox or Raulin medium produces citrinin, 



C C.OH luuf.. ,oD - - ' 



I I 



CH,.(! (J 



^9 ^C.CUOH 



I I 



CHg.CH 



which can be precipitated from the medium, in yields of 

 about 2 g. per litre, as a yellow microcrystalline substance 

 ])y the addition of hydrochloric acid. It is also formed 

 by Aspergillus candidus. It has m.p. 168° (decomp.). 

 Its sodiimi salt is soluble in w^ater. The culture filtrate 

 (containing about 2 g. /lit re of citrinin) is inhibitory to 

 Staph, aureus in dilutions of 1 in 160 to 1 in 320. Citrinin 

 itself is bacteriostatic to Gram -positive and Gram- 

 negative organisms in concentrations of 1 in 9000 to 1 in 

 30,000, the Gram-positive organisms, in general, being 

 the more sensitive. 



