Detection of mutans streptococci in plaque samples from Mongolian preschool and school children

Mutans streptococci, in particular Streptococcus mutans and Streptococcus sobrinus, are generally considered to be the principal microbial pathogen of dental caries. The objective of the study was to isolate S. mutans and S. sobrinus, identify them by PCR, and to compare their presence with the caries status and caries risk in Mongolian preschool and school children. Forty one preschool children aged 3–5 years and 40 school children aged 12–15 years were enrolled in this study. As assessed using Cariostat test, 75.6% of preschool children had high caries risk and 37.5% of school children had high caries risk. In preschool children, the prevalence of S. mutans and S. sobrinus were 100% and 36.6%, respectively; 63.4% were positive for S. mutans alone and 36.6% were positive for both S. mutans and S. sobrinus. In school children, the prevalence of S. mutans and S. sobrinus were 100% and 25.0%, respectively; 75.0% carried S. mutans alone and 25.0% had both S. mutans and S. sobrinus. The percentage of children positive for both S. mutans and S. sobrinus in the high caries risk group were significantly higher than those in the low risk group of either preschool (42.0% vs. 10.0%, P< 0.001) or school children (46.6% vs. 12.0%, P<0.001). Moreover, the caries status of children positive for both S. mutans and S. sobrinus were significantly higher than those positive for S. mutans alone (P< 0.01 for preschool children, and P< 0.05 for school children).     

Mucosal immune features to phosphorylcholine by nasal Flt3 ligand cDNA-based vaccination

Phosphorylcholine (PC) is an immunodominant epitope in some pathogens including Streptococcus pneumoniae and it is well-known that PC-specific antibodies (Abs) play a key role in the induction of protective immunity against pneumococcal infection. In this study, we examined whether nasal administration of DNA plasmid encoding Flt3 ligand gene (pFL) as a mucosal adjuvant plus PC-conjugated keyhole limpet hemocyanin (PC-KLH), would elicit PC-specific immune responses, and characterized mucosal immune responses to PC induced by this nasal vaccination. Nasal immunization with pFL plus PC-KLH enhanced induction of PC-specific IgA and IgM Abs in airway secretions when compared with mice given PC-KLH with or without empty plasmid gene (pORF) as controls; in addition to the mucosal immune responses, PC-specific immune responses in serum were also induced. Furthermore, the mucosal and serum IgA and IgM Abs in mice given pFL plus PC-KLH nasally, exhibited high-specificity for the PC molecule. Of interest, the PC-specific Abs bound dose-dependently to anti-T15 idiotype (AB1-2). Thus, the inhibition of S. pneumoniae colonization on the nasal cavity and lungs after nasal challenge with the live organism was significantly elicited in mice immunized with pFL plus PC-KLH compared to that of mice immunized with antigen with pORF. Taken together, these findings show that nasal administration of pFL with PC-KLH elicited T15-like anti-PC IgA and IgM Abs in the respiratory tracts, and further attenuated S. pneumoniae colonization on the respiratory tracts. Nasal administration of Flt3 ligand cDNA with PC may contribute to the development of nasal vaccination for prevention of S. pneumoniae infection.