Abstract
The bacteriostatic action of various soaps has undergone a considerable amount of study by many investigators. Recently, a somewhat related class of substances, the sodium alkyl sulfates, has been synthesized. These substances have also been made use of as detergents in such preparations as “Dreft,” “Drene” and other commercial products.
The alkyl sulfates are half-esters of sulfuric acid. In this respect they differ from soaps which are combinations of fatty acids and alkalis. In both cases, however, the alkyl chain probably determines its bactericidal effectiveness. Sodium lauryl sulfate is a sodium alkyl sulfate containing 12 carbon atoms.
The similarity of these substances to soaps suggested the possibility that similar bacteriostatic action might be exhibited by them. Accordingly, sodium lauryl sulfate as such, and “Dreft” which contains a large amount of sodium lauryl sulfate were tested for their bacteriostatic action. Twenty-one strains of Gram positive bacteria, 20 strains of Gram negative bacteria and 6 strains of common molds were used in these studies. In general, all tests were made on Difco standard nutrient agar to which the test substances had been added in varying amounts so as to make concentrations of 1.0% sodium lauryl sulfate and of 1.0, 0.5, 0.25, and 0.1% “Dreft”. The plates were streaked with heavy suspensions of the organisms and then incubated at appropriate temperatures for 48 hours.
The effects of sodium lauryl sulfate and of “Dreft” on the growth of the 41 strains of bacteria and 6 strains of molds studied in this investigation are shown in Table I. It is evident that the Gram positive organisms were prevented from growing, whereas the Gram negative bacteria grew as freely as, on the nutrient agar controls. There were 3 exceptions to the latter statement: Vibrio comma, Alcaligenes fecalis, and Neisseria catarrhalis were definitely inhibited in their growth.
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