Evaluation of disinfection effects of dental unit waterlines based on combinations of different culture media and microbial detection methods

OBJECTIVE To explore the differences in disinfection effects of dental unit waterlines (DUWLs) among the combinations of different culture media and microbial detection methods so as to provide scientific bases for the water sample test of the DUWLs. METHODS The water samples were collected from 35 dental units of 15 grass-roots medial institutions in a district of Chengdu by random sampling method. The microbial detections were carried out for each water sample with 6 types of combinations including 2 types of culture media (R2A culture media, NA culture media) and 3 types of microbial detection methods (pour plate method, smear method, membrane filtration method). The qualified rates of disinfection of DUWLs were observed and compared among the combinations of culture media and microbial detection methods by chi-square test. RESULTS A total of 122 DUWLs samples were finally collected, and totally 732 culture media plates were prepared. Chromatographic analysis was performed for the different culture media and microbial detection methods, and the result showed that there were significant differences in the qualified rates of disinfection of DUWLs of the two culture media between the pour plate method and the smear method(P＜0.001); the qualified rate of the two types of culture media were respectively 97.54%(119/122) and 72.13%(88/122) by pour plate method; the qualified rates of the two types of culture media were respectively 94.26%(115/122) and 77.87%(95/122) by the smear method. The qualified rates of disinfection of the three types of microbial detection methods with R2A culture media were respectively 72.13%(88/122), 77.87%(95/122) and 90.98(111/122) for the DUWLs, and there was significant difference (P＜0.001). CONCLUSIONS The combination of R2A culture media with the pour plate method or the smear method can evaluate the disinfection effect of DUWLs more accurately. It is suggested that this combination should be adopted for the microbial test for DUWLs water sample.