The variability of unstandardized plaques obtained from single or multiple subjects

Direct microscopic and anaerobic viable counts on a non-selective medium were made of unstandardized plaques sampled once from a number of subjects and repetitively from single subjects. The direct counts of 40 plaques had a mean of 24.7 × 10⁷ and a range of 16.1–33.0 × 10⁷ organisms/mg wet weight of plaque. Viable counts of 33 plaques had a mean of 12.3 × 10⁷ and a range of 3.2–27.0 × 10⁷ organisms/mg wet weight of plaque. The means and variances of plaques obtained repetitively from single subjects were generally not significantly different from those of plaques obtained from multiple subjects.