SUMMARY : Effects of phenol, 2-phenoxyethanol and cetyltrimethylammonium bromide on the oxygen uptake of suspensions of Escherichia coli supplied with various single oxidizable substrates were examined. Phenol and 2-phenoxyethanol at low concentrations caused a stimulation of oxygen uptake in the presence of mannitol, glucose or lactose which was not associated with an increase in viable count, no stimulation with glycerol, and a retarded oxygen uptake with lactate, succinate or pyruvate. At higher concentrations phenol and 2-phenoxyethanol caused a retardation of oxygen uptake with all substrates, the degree varying with the substrate. Cetyltrimethylammonium bromide was toxic a t very low concentrations and no stimulation of oxygen uptake by low concentrations or differential response in presence of different substrates was found.Phenol, 2-phenoxyethanol (phenoxetol) and cetyltrimethylammonium bromide (cetrimide) chosen as representative of anionic, non-ionizing and cationic antiseptics respectively, were examined for their effect on respiratory mechanisms of Esch. coli as shown by the effect on oxygen uptake in presence of various substrates.
EXPERIMENTALOrganism. The organism used was Esch. coli NCTC 5934. It was subcultured in nutrient broth, and freeze-dried (Proom & Hemmons, 1949). Culture medium. Nutrient broth was prepared by the tryptic digestion of lean meat; after autoclaving it had a pH of 7.2-7-4. It was solidified when required by the addition of 2 yo agar.Chemicals. The 2-phenoxyethanol (phenoxetol) was supplied by Nipa Laboratories Ltd., Cardiff. The cetyltrimethylammonium bromide (cetrimide) was a commercial sample which, assayed by the method of The British Pharmaceutical Codex (1949), contained 84.4 % (w/w) of CI9H3,( CH,),NBr.The sugars and mannitol used were of bacteriological quality as supplied by Messrs T. Kerfoot Ltd.; sodium pyruvate was prepared by the method of Robertson (1942); all other chemicals were of A.R. quality.Phosphate buffirs. 0.1 M or 0.05 M-KH,PO, and Na2HP04. 12H20 were mixed immediately before use, to give a pH value of 7.0 (electrometric). Ringer's solution was prepared according to Wilson (1922) and sterilized by autoclaving; final pH c. 7.5.Bacterial suspensions. The contents of a tube of freeze-dried material were reconstituted with nutrient broth, grown at 37" for 18 hr., then subcultured * Present address :