Identification and phylogenetic analysis of oral Veillonella species isolated from the saliva of Japanese children

Abstract

Background:As the most frequent infectious disease among children worldwide, dental caries have a strong relationship with oral hygiene status, specifically in the development of infection. OralVeillonellaspecies have a main role as early colonizers in the oral biofilm formation. Previously, oralVeillonellastrains were detected at the species level in the saliva of Thai children with different oral hygiene statuses. Here, we studied the oral hygiene status by examining the composition and proportion of oralVeillonellaspecies in saliva of Japanese children to compare with the previous results found in Thai children.Methods:Microbial samples collected from 15 Japanese children divided into three oral hygiene groups were cultured under anaerobic conditions after homogenization and dilution, and inoculated onto brain heart infusion and selective mediumVeillonellaagar. Genomic DNA was extracted from each isolate.Veillonellaspecies were detected by one-step PCR usingrpoBspecies-specific primers. To analyse the phylogenetic properties of the unknownVeillonellastrains, PCR amplification and sequence analysis ofrpoBwere conducted for 10 representative strains.Results:AlthoughV. rogosaewas found as the predominant species among all groups, its prevalence was significantly lower in the children with poor oral hygiene than in those with good oral hygiene.V. parvulawas the prevalent species in the poor oral hygiene group. Approximately 10% of the isolatedVeillonellastrains were not classified to any established species; the phylogenetic analysis showed that they were most closely related toV.infantiumConclusions:This study demonstrates that the composition and proportion of oralVeillonellaspecies in the saliva of Japanese children is correlated with different oral hygiene status. Changes in detection ratios ofV. parvulaandV. rogosaecan be useful indicators of oral hygiene status. Furthermore, new strains closely related toV.infantiumwere isolated from the saliva of Japanese children.