Counts from samples that contained low numbers of bacteria were determined by mixing the samples with double-strength agar media in 42-oz (1.2-L) Whirl-Pak bags. The bag-plate method was compared with other direct-plating methods and the most-probable-number and membrane-filtration procedures. Results obtained by using the bag method were as reliable as methods commonly used for analysis of samples that contain low numbers of viable bacteria.

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1Journal Paper No. J-12402 of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa. Project 2678.