The growth of Escherichia coli in buffer substrate and distilled water.

Heinmets, Taylor, and Lehman (1954) treated a suspension of cells of Escherichia coli strain B/r with disifectant and found that after treatment none or only a few viable organisms were present. However, when the liquid (containing the cells which had been exposed to the disinfectant) was mixed with a solution of a metabolite in phosphate buffer and incubated overnight at 37 C, a large number of viable cells was found. (Similar results were obtained with several disinfectants, including sodium hypochlorite.) Heinmets et al. suggest that the increase in numbers was due to reactivation of the damaged, but not dead, cells and was not due to multiplication of a few viable cells remaining in the buffer substrate. This would necesitate a radical alteration in the present method of assay of disinfectants. If surfaces after treatment with a disinfectant were likely to come in contact with a fluid, such as milk, containing a selection of metabolites, the action of the disinfectant might be nullified. Garvie and Clarke (1955, in press) used a strain (28.D.10) of E. colt for estimating the bactericidal properties of disinfectants, and, in order to examine the validity of the results they obtained, the work of Heinmets et al. was repeated as nearly as possible using, however, E. coli strain 28.D.10. It became evident that this strain could grow in the buffer substrate, and the work was continued to study some of the conditions for bacterial growth.