COMPARISON OF "DROP" AND "POUR" PLATE COUNTS OF BACTERIA IN RAW MILK

Abstract

In the preceding paper it was shown that a "drop plate" method of determining the number of viable bacteria in pure cultures gives slightly higher counts than the usual "pour plate" method. In this paper it is shown that, in parallel counts made by the two methods on a series of samples of raw milk, the "drop plate" counts are some 27% higher than the "pour plate" counts. It is suggested that this discrepancy results from the more efficient breaking up of clumps and chains of bacteria by the dilution procedure used in preparing the "drop plates."