Fig. 1

Multiple inocula preparations from fresh overnight cultures display greater variability than inocula preparations from frozen stocks. The ratio of “Actual” bacterial numbers (as measured by CFU counts one day following preparation) to “Aimed-for” concentration was used as a measure of the cumulative accuracy of each method. For fresh preparations, the “Aimed-for” concentration values of washed subcultures were estimated by determining OD₆₀₀ readings. For frozen vials, the “Aimed-for” concentration values were calculated by using the known, predetermined concentrations of the batch. We typically aim for < +/−15 % variance from the targeted inoculum (as denoted by the shaded region). Numbers within the shaded region denote the percentages of the 20 measurements per group that fell within the 15 % range