A new method for the estimation of mutans streptococci in human saliva.

A new method for quantitating the numbers of mutans streptococci in saliva--the "Strip mutans" test--was developed. It includes the following steps: A prepared plastic spatula is contaminated with saliva, transferred to a selective broth, incubated for two days, and dried. A predetermined area is counted or evaluated for CFUs of mutans streptococci. The medium contains sucrose to promote adhesion of mutans streptococci to the strip. Bacitracin, added just before use, is the basis for the selectivity. Results with the new medium were compared with those from the "spatula technique" and with those from conventional saliva sampling with dilution. The studies involved 302 and 60 schoolchildren, respectively. There was a highly significant correlation between the results from the new method and those from conventional methods. The strip mutans test is easy to used and has long shelf-life, and the spatulas with adherent colonies can be saved for future comparisons.