A rapid chair-side method for the estimation of oral bacterial colonization density

Caries and periodontal disease are associated with inadequate control of oral bacteria. Since conventional microbiological evaluations are impractical in dental clinics or public engagement activities, a rapid test for the quantification of oral bacteria represents a useful tool. We describe the development of a colour change test to rapidly estimate bacterial colonisation density in the mouth.

Volunteers rinsed with milk or milkshake. Viability indicators were added and colour changes quantified during incubation. Using milkshake and the resazurin-based solution PrestoBlue (9% v/v), the method distinguished between samples before and after brushing within 5 min. Colour changes were quantified and viable counts were obtained using oral rinses. Measured colour changes strongly correlated with total counts of both anaerobes and streptococci (Spearman's correlation coefficient of 0·782 and 0·769, respectively, P ≤ 0·001) and with perceived changes, as determined by volunteers (n = 10) visually ranking images.

The resazurin milkshake test can rapidly and visually quantify viable bacteria in oral samples.

The resazurin milkshake test could serve as a sensitive semi-quantitative method for measuring oral bacteria in human oral rinse samples.