ANTIBACTERIAL ACTION 



205 



blood, or serum exerted no inhibiting effect, A marked difference was 

 found in the action of penicillin and sulfonamides, the latter merely de- 

 creasing the rate of multiplication and the former actually bringing 

 about a decrease in the number of organisms present. This is brought 

 out in Figure 21. The rates of activity of penicillin, gramicidin, and 

 tyrocidine are compared in Table 36 (page 192). The bactericidal ac- 

 tion of penicillin is not accompanied by lysis. No penicillin is absorbed 

 or destroyed by the bacteria. 



Penicillin is not very stable j it is sensitive to reaction and temperature 

 changes. The effect of reaction upon the stability of penicillin is shown 

 in Figure 22. 



Para-amino-benzoic acid and sulfapyridine were found to have a 

 synergistic effect on penicillin. A solution of sodium penicillin with 

 1,200 units per milliliter gave 100 B. suhtilu units in a synthetic casein 



57 HOURS 



2 4 6^ 



REACTION (pHJ 



2 4 6 8 10 



REACTION (pH) 



Figure 22. Inactivating effect of reaction upon penicillin. From Foster and 

 Wilker (283). 



