TABLE 2.

MICs of various quaternary ammonium compounds in E. coli strains expressing or not expressing sugE

CompoundMIC (μg/ml)a
TOP10F′ (pCR2.1)bTOP10F′ (pCR2.1-sugE)bDH5α (pBAD24)bDH5α (pBAD24-sugE)b
Cetylpyridinium chloride (C21H38NCl)2016020160
Cetylpyridinium bromide (C21H38NBr)4016040180
Cetyldimethylethyl ammonium bromide (C20H42NBr)6012060120
Hexadecyltrimethyl ammonium bromide (cetrimide) (C19H42NBr)8012060120
  • a Assayed on LB plates using the pBAD24 and pCR2.1 vectors without l-arabinose. Inclusion of l-arabinose, promoting high-level expression when using the pBAD24 vector, proved toxic.

  • b Cells did not show increased resistance to other quaternary ammonium compounds (benzyl-dimethyl tetradecylammonium chloride, benzalkonium chloride) or to cationic dyes (tetraphenyl-arsonium chloride, pyronine Y, crystal violet, ethidium bromide).