Application of Statistics to Problems in Bacteriology

Abstract

To check previously published theoretical consideration of the dilution method for determining bacterial population, the authors determined bacterial populations by direct microscopic counts, and by plate counts, as well as by the dilution method, on pure cultures of E. coli, B. subtilis, Ps. pyocyanea, and S. aureus, and upon mixed cultures of E. coli and Ps. pyocyanea, and E. coli and S. aureus. A few determinations were also made upon mixed cultures as found in packing house curing pickle. After subjecting the data to statistical analysis, the authors conclude that the dilution method gives counts in general agreement with those obtained with the other methods of counting, except in a few cases of mixed culture where the dilution count may be higher than the plate count.