Abstract
Wetting agents in general possess the properties of penetrating and emulsifying surface films of fatty substances to a high degree, and are powerful surface tension reducers. For these reasons, it is of interest to observe their action on tubercle bacillli with their enveloping fatty capsule. The bactericidal action of several wetting agents on some organisms have been investigated, but little has been done in testing the effect of these compounds on the growth of tubercle bacilli.
The following compounds were tested for bacteriostatic action: Nacconol NR,† an alkyl aryl sulfonate; Aerosol OT-100, an ester of a sulfonated bi-carboxylic acid; Aerosol OS, a sodium salt of an alkyl naphthalene sulfonic acid; and Zephiran, a mixture of high molecular alkyl-dimethyl-benzyl-ammonium chlorides. All the agents were approximately neutral in solution.
A non-virulent Novy strain of tubercle bacilli was grown on liquid synthetic asparagin media containing 6% glycerin, with pH 7.4. This produces a heavy surface growth in 2 to 3 days. Dilutions of the wetting agents were made in normal saline and added in equal amounts to tubes containing 4.5 cc of media. A large loopful of surface growth of a 3-day culture of tubercle bacilli was inoculated on a cork float in each tube. The tubes were then slanted and incubated at 37°C. Readings of the amount of growth were made at 2-day intervals.
The results are shown in Table I. The most effective wetting agent is Zephiran, which produced complete inhibition of growth in dilution of 1:80,000, and retardation of growth in dilutions as high as 1.400,000. Nacconol NR and Aerosol OT-100 prevented growth in dilution of 1:5,000, and retarded growth in dilution of 1:40,000. Aerosol OS produced the lowest bacteriostatic action, permitting growth in dilution of 1:1,000, and retarding growth slightly in dilution of 1:10,000.
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