Effects of Polyethylene Glycol 400 Monolaurate and Sodium Chloride Mixtures on the Antibacterial Activity of Solubilized Trichlorocarbanilide

S ummary . Polyethylene glycol 400 monolaurate (PGM), a nonionic surfactant, affected the solubility of trichlorocarbanilide (TCC), the amount solubilized being directly proportional to the concentration of PGM in the system. The bacteriostatic activity of TCC against Staphylococcus aureus was affected by high but not low concentrations of PGM; proportions of PGM to the germicide of up to 10: 1 did not interfere with the minimum inhibitory concentration (MIC) of TCC (0·08 μg/ml). The bactericidal activity against Staph. aureus of systems consisting of TCC and different proportions of PGM with and without 0·5% of NaCl was much higher than that of saturated aqueous solutions of TCC alone. However, TCC solutions containing NaCl and PGM were more bactericidal than corresponding systems without NaCl; the death rates in TCC-PGM-NaCl systems were 2–4 times that in TCC-PGM systems. The marked increase in the death rate was obtained with systems containing 2·5% of PGM.