A Statistical Comparison of Analyst Accuracy and Speed in Counting Standard Methods Agar Plates Within Selected Colony Count Ranges.

摘要

Agar plates, prepared from serially diluted food homogenate and containing from 30-300 colonies per plate, are used by food microbiology testing laboratories to estimate the microbial population of food samples. Six analysts counted plates with 0-<400 colonies per plate. Analyst accuracy in the 20-200 colonies per plate range was comparable to the 30-300 range and resulted in a 27% reduction in counting time. A method using agar plates and photographs of the same plates was used to establish the number of colonies per plate. The resulting number was compared to the counts obtained by the individual analysts. In the 30-300 colonies per plate range analysts counted within 5% of the photo count on 60% of the plates and within 5% of the mean count on 68% of the plates. Similarly, in the 20-200 colonies per plate range analysts counted within 5% of the photo and mean count on 60 and 67% of the plates, respectively.