Slide-scoring method for estimation of Streptococcus mutans levels in saliva

A method was developed to facilitate the estimation of S. mutans levels in saliva. Paraffin-stimulated saliva was poured on a special slide coated with mitis-salivarius-sucrose agar. Two discs containing bacitracin (5 micrograms) were placed on the inoculated slide and the growth density of S. mutans around the bacitracin discs was scored after incubation in candle jars at 37 degrees C for 48 h. The obtained score values correlated well with the numbers of CFU of S. mutans per 1 ml of saliva estimated by a conventional method using mitis-salivarius-bacitracin agar. The experimental method was further tested by incubating the slides in an atmosphere created by CO2-generating tables that were placed into the cover tubes of the slides. These score values were similar to those after conventional incubation. The method is suggested for epidemiologic studies and in selecting persons at high risk for caries and in controlling the effectiveness of prophylactic measures of these patients.