Abstract: Objective: To investigate the distribution of oral lactobacillus and its relationship with caries among 3-5 years old children of Uygur and Han nationalities in Bo Zhou area. Methods: Totally 722 healthy children aged 3 to 5 years were selected with a stratified cluster random sampling method. Dental plaque samples were collected, and lactobacillus was cultured selectively through Rogosa and MRS agar medium. The isolates were further identified by methods of gram staining, hydrogen peroxide test, and polymerase chain reaction molecular biology methods. Pearson χ² test was used for statistical analysis of classification data. Results: The prevalence of lactobacillus were 69.5% in Han children and 58.2% in Uygur children, respectively (P=0.001). The tested rate of lactobacillus in severe early childhood caries children group (75.4%) was significantly higher than that of early childhood caries children group (66.8%) and caries-free group (40.4%) (P=0.000). Lactobacillus could be isolated from 62.6% boys and girls of Uygur children and 63.8% of Han children (P=0.794) in the overall samples. The prevalence of lactobacillus was 57.5% in 3 years old children, 65.2% in 4 years old children, and 65.9% in 5 years old children, respectively (P=0.119). Conclusion: There was difference in the distribution of oral lactobacillus between Uygur and Han ethnic groups. There were significant differences in prevalence of lactobacillus between groups of severe early childhood caries, early childhood caries, and caries-free children. Lactobacillus may be a risk factor in the development of caries.

Key words: Dental caries, Lactobacillus, Minority ethnicity, Polymerase chain reaction