256 NATURE OF ANTIBIOTIC ACTION 



tated from the medium with acetone, alcohol, dioxane, sodium tung- 

 state, and saturated ammonium sulfate solution. Highly purified prepa- 

 rations have been prepared from B. cereus, i mg. of the product de- 

 stroying completely 165,000 units of crystalline penicillin in 3 hours at 

 fH 7.0 and 30° C. (44). In a dry state, penicillinase is thermostable 3 in 

 solution, it is more readily inactivated by heat. In a purified state, it is 

 labile 3 at 45° C, 66 per cent of it is destroyed in 20 minutes and 95 per 

 cent in an hour (611). The inactivation of penicillin by penicillinase is 

 accompanied by the evolution of COo from the bicarbonate in solution, 

 thus pointing to acid formation (279). The optimum fVL for the action 

 of the enzyme is between 8.0 and 9.0. 



Penicillinase can be utilized for the purpose of testing the sterility of 

 penicillin preparations (550). The penicillin, which would otherwise 

 cause inhibition of growth of the contaminating organism in the test 

 medium, is destroyed by the enzyme previous to the test. There is no 

 apparent relation between the resistance of an organism to penicillin 

 and its ability to produce penicillinase (1027). 



Certain bacteria, as E. coli, produce a thermostable fungistatic factor 

 which must be differentiated from penicillinase j the effect of this factor 

 consists in reducing the rate of growth of the fungus, rather than in de- 

 stroying the penicillin (1009). 



Bacterial extracts, pus fluids, peptone, and ^-amino-benzoic acid, 

 which interfere with the action of sulfonamides, do not affect penicillin. 



Cephalin and extracts of gram-negative bacteria, of milk, and of 

 blood serum were found to inhibit the action of gramicidin. Because of 

 this, cephalin is capable of reviving bacterial cells killed with grami- 

 cidin. This phenomenon is similar to the inhibition by phospholipins of 

 the action of synthetic detergents upon bacterial metabolism. Mucin 

 inhibits the action of tyrothricin, especially on meningococci and pneu- 

 mococci (192). 



Tannic acid is able to neutralize the antibiotic action of actinomycin. 

 Humus compounds of the soil have a similar capacity. This effect was 

 believed to be responsible for rendering harmless, to living plant and 

 animal forms, the actinomycin produced in the soil (976). Ascorbic 

 acid also has an effect in reducing the activity of this substance. Since 

 vitamin C is a strong reducing agent and actinomycin is a reversible 



