156 AXTISEPTICS 



stances. Methionine counteracts low concentrations of 

 sulfonamides, but not larger doses (Kolm and Harris, 

 1941, 1942). These authors designate as "secondary 

 antagonists" some other substances with similar effects, 

 such as xanthine, serine, glycine, which function only 

 in the presence of methionine. 



Several other amino acids have been claimed to be an- 

 tagonistic to sulfonamide retardation of growth, and 

 even mercuric chloride can produce this effect, accord- 

 ing to Lamanna and Shapiro (1943). 



Snell and Mitchell (1943) found jDurines to be antagon- 

 istic to sulfanilamide, but only in the presence of very 

 small amounts of ^j-amino benzoic acid. Quite generally, 

 substances which are excellent foods and increase the 

 growth rate materially, have a slight antagonistic effect 

 which, however, cannot be considered specific. 



The picture of the mode of action of sulfonamides is 

 still rather hazy and indefinite. But one of their char- 

 acteristic features seems well established, it is that, in 

 contrast to other antiseptics, they act more strongly on 

 growing than on resting cells. The status of the cells is 

 of great importance, and failure to realize this is prob- 

 ably the reason for some seemingly contradictory evi- 

 dence. The kind of medium used is also of importance 

 since it may contain appreciable amounts of one or sev- 

 eral antagonists. 



Concerning the influence of temperature. White (1939) 

 found that the efficiency of sulfanilamide is 10 times as 

 high at 37° as at 30°, and that above 37° it increases 

 about 10 times for a rise of one degree. This latter in- 

 crease may be partly due to the harmful effect of high 

 temperature alone. The minimal bactericidal concentra- 

 tions were determined with Streptococcus pyogenes incu- 

 bated in broth, the criteria being cloudiness and presence 

 of viable bacteria after 48 hours. 



