The surface behaviour of antibacterial substances

Abstract

The electrokinetic mobility of suspensions of Escherichia coli in dilute aqueous solns. of sulfanilamide, p-aminobenzoic acid and chemically related substances was detd. using an improved all-glass form of the Smith and Lisse cataphoresis cell, giving results reproducible to [plus or minus]3%. The effect of sulfanilamide and related antibacterials on the mobility of the organism is quite different from that of inactive substances such as aniline, benzenesulfonamide and metanilamide, but closely resembles that of p-aminobenzoic acid. Sulfanilamide and related drugs apparently behave like p-aminobenzoic acid at the bacterial surface. The effects of sulfanilamide, benzenesulfonamide and aniline hydrochloride on the mobility were compared, leading to the conclusion that the association of the drug with the organism is a function of the[long dash]NH2 group, and that the polarity produced by resonance of active molecules is one of the factors determining antibacterial activity.