Novel Test Kit for S. mutans Proper to Chairside Use

Objectives: The assay of S. mutans level is important to evaluate susceptibility and activity of caries. The purpose of this study is to develop suitable test kit for chairside use, which requires no instruments, is completed within 20 minutes, and to examine the feasibility of this kit. Methods: The test kit which we developed (Oral Tester Mutans) contains an immunochromatography-device (chromato-device), a filtration-device, and reagents for pre-treatment of samples. The chromato-device employs affinity purified polyclonal antibody which is specific to S. mutans. Stimulated saliva was filtered using a filtration-device to capture S. mutans on the membrane of the device. A series of filtration of pre-treatment reagents was carried out to extract the specific antigens of S. mutans from the bacterial cells. The extracted solution was applied to the chromato-device, and the level of S. mutans was determined by comparing the intensity of the color of the test-line on the chromato-device with the model chart. The concentration of S. mutans (CFU/ml) was calculated by the number of colonies on MSB agar plate. The colonies of S. mutans were selected morphologically and counted (using this concentration as a standard). Saliva samples were also assayed by a commercial kit, Dentcult SM (Orion Diagnostica). Results: Using the developed kit, positive signals could be observed above 1x10⁵ CFU/ml of S. mutans within 15 minutes, and the intensity of the signals increased according to the concentration of S. mutans. Major bacteria in the oral cavity other than S. mutans could not make positive signals on the chromato-device. The developed kit and the MSB method showed good correlation (correlation efficiency was 0.52, N=186), almost the same as Dentcult (correlation efficiency was 0.53, N=186). Conclusion: Results indicate that this kit will be a good tool for caries risk assessment for clinical use.