The differing effects of cetyltrimethylammonium bromide and cetrimide B.P. upon growing cultures of Escherichia coli NCIB 8277.

Growing cultures of Escherichia coli NCIB 8277, when treated with low concentrations of Cetrimide B.P., decrease in turbidity more markedly than when equivalent concentrations of cetyltrimethylammonium bromide (CTAB) are applied. Treatment with higher concentrations of CTAB but not of cetrimide evokes a prompt, extensive rise in turbidity. It is suggested that in growing cultures CTAB tends to cause cell aggregation whereas cetrimide tends to cause cell lysis, and that the lytic effect is related to the presence of impurities in cetrimide. The possibility that other antimicrobial surfactants promote lysis is considered.