EVALUATION OF ANTIMICROBIAL AGENTS. THE GERMICIDAL ACTIVITY OF A SYNTHETIC DETERGENT, DC-12

¹ Department of Bacteriology, Northwestern University Dental School, Chicago, Ill.

A quaternary ammonium salt, dimethyl benzyl lauryl ammonium chloride (DC-12), has been tested for its germicidal activity by the standard procedure for determination of phenol coefficients and by 2 of the newer procedures of testing disinfectants.

By the standard procedure, DC-12 was germicidal in a dilution of 1:30,000 with no organic matter present and in a dilution of 1:5,000 in the presence of 10% serum.

By the modified procedure in vitro, in which tests were made with several pyogenic cocci in the presence of both agar and serum, DC-12 was germicidal in a dilution of 1:1000.

Parallel experiments were made in vivo (mice) by the infection-prevention test of Nungester and Kempf, with the pneumococcus as test organism, of DC-12 in 1:1000 dilution as compared with 1:1000 concentrations of merthiolate and metaphen. The control solutions were 2% aqueous iodine and physiological saline. DC-12 in this concentration was more active than merthiolate and metaphen but less so than 2% iodine, which was nearly 100 per cent effective.

DC-12, even in 5% concentration, showed no fungicidal activity when tested against Trichophyton mentagrophytes, but a concentration of 0.1% killed spores of B. cereus and B. subtilis in 10 minutes.