Mastitis: effect of pH, temperature, and emollients on disinfecting action of N,N-dimethyldodecanamine

Growth inhibition of bacteria over time by N,N-dimethyldodecanamine, a tertiary alkyl amine, was studied to evaluate disinfecting action with changes in pH and temperature and with addition of emollients. Because alkyl amines have limited solubility in aqueous solutions, the effect of pH on solubility of the tertiary amine was determined. Non-growing cultures of Streptococcus agalactiae or Escherichia coli were added to sterile buffer or buffer containing the amine, and at specific intervals aliquots were removed, neutralized in a lecithin/Tween 80 quencher, and then plated to determine the number of surviving bacteria per plate. Survival curves were used to determine the effect of changing environmental conditions on antimicrobial activity. Antimicrobial activity was greater at pH 7 than at pH 8 and was least at pH 6. Increases in temperature from 20 to 40 degrees C caused a corresponding increase in antimicrobial activity. Addition of up to 10% glycerin or propylene glycol caused no significant decrease in antimicrobial activity of the tertiary amine.