The survival of bacteria in dust. I. The distribution of bacteria in floor dust

Abstract

The viable bacteria in 10 mg. portions of dust were estimated by shaking with 5 ml. of Ringer's solution in 1 oz. bottles containing glass beads. The extract was allowed to stand for a few minutes, and 0·1 ml. amounts were then plated out at suitable dilutions. Successive portions from the same sample of dust showed very great variation in the bacterial counts, and this variation has been examined in series of twenty such portions. The distribution of the counts for three groups of organisms appears to approximate to a log-normal form, and the graphical estimate of the log-median is taken as a suitable parameter for the study of the influence of environmental factors on the survival of dust flora.