14G BACTERIOLOGICAL CHEMISTRY 



Following the lead given l)y the discovery of the 

 ^-aminobenzoic acid-sulphonamide inhibition mechanism 

 of drug action a number of other systems have been 

 investigated with analagous results. In some cases it 

 has been possible to devise a substance which should 

 have antibacterial properties in virtue of its close chemical 

 relationship with a compound participating in the 

 metabolism of bacteria. As examples may be quoted 



the effect of pyridine-3-sulphonic acid, I ^ ' ^^^ 



/\ 



N 



its amide, L J , on the growth of Staph, aureus 



N 



and Proteus vulgaris which require nicotinic acid for 

 their metabolism. Pyridine- 3 -sulphonamide inhibits the 

 growth of these organisms in presence of ordinarily 

 adequate amounts of nicotinamide, and the effect is lost 

 on increasing the amount of nicotinamide present. 

 E. coli does not require nicotinamide as a growth factor 

 and is only little affected by pyridine-3-sulphonamide 

 at a concentration of 10~^ molar, but the inhibition is 

 completely reversed by nicotinic acid or the amide. 

 Pyridine- 3 -sulphonic acid, however, at a concentration 

 10~2 molar completely inhibits the growth of E. coli 

 and the effect is not reversed by addition of nicotinic 

 acid, nicotinamide or co -enzyme. 



It is possible that the greater potency of sulphapyridine 

 compared with that of sulphanilamide is due to its 

 effect on nicotinic acid metabolism in addition to that 

 on p-aminobenzoic acid. A similar inhibition by sulpha- 

 pyridine is observed on the respiration of the dysentery 

 bacillus stimulated by co -enzyme I (diphosphopyridine 



