Association between commensal bacteria and opportunistic pathogens in the dental plaque of elderly individuals

ABSTRACTOpportunistic infections in the oral cavity of the elderly may increase the incidence of systemic disease. The objective of this study was to investigate the differences in the oral bacterial flora between dependent elderly (in-patients) and independent elderly (community-dwelling residents). After multiplevariables were taken into account, in-patients had significantly lower detection rates than community-dwelling residents for α-streptococci (p < 0.001) and Neisseria (p 0.004), and higher detection rates for Pseudomonas aeruginosa (p 0.024), methicillin-resistant Staphylococcus aureus (MRSA) (p 0.011) and Actinomyces spp. (p 0.005). Among in-patients, the requirement for a high degree of care was related negatively to detection of α-streptococci, but was related significantly to detection of P. aeruginosa (p 0.018) or MRSA (p 0.004). Tube-fed in-patients had a significantly lower detection rate for αstreptococci (p 0.041) and a higher detection rate for P. aeruginosa (p 0.004) than those who did not require tube feeding. Inpatients with a history of antibiotic use had a significantly lower detection rate for α-streptococci (p 0.049) and a higher detection rate for MRSA (p 0.007) than those without a history of antibiotic use. The detection rates for P. aeruginosa or MRSA in patients without α-streptococci were higher than in in-patients with α-streptococci after controlling for age and gender (P. aeruginosa, p 0.006; MRSA, p 0.001). Overall, detection of α-streptococci had an inverse correlation with the detection of P. aeruginosa and MRSA in the oral cavity and is likely to be an indicator of pathogenic bacterial infection

Roles of Salivary Components in Streptococcus mutans Colonization in a New Animal Model Using NOD/SCID.e2f1−/− Mice

Streptococcus mutans plays an important role in biofilm formation on the tooth surface and is the primary causative agent of dental caries. The binding of S. mutans to the salivary pellicle is of considerable etiologic significance and is important in biofilm development. Recently, we produced NOD/SCID.e2f1−/− mice that show hyposalivation, lower salivary antibody, and an extended life span compared to the parent strain: NOD.e2f1−/−. In this study we used NOD/SCID.e2f1−/− 4 or 6 mice to determine the roles of several salivary components in S. mutans colonization in vivo. S. mutans colonization in NOD/SCID.e2f1−/− mice was significantly increased when mice were pre-treated with human saliva or commercial salivary components. Interestingly, pre-treatment with secretory IgA (sIgA) at physiological concentrations promoted significant colonization of S. mutans compared with sIgA at higher concentrations, or with human saliva or other components. Our data suggest the principal effects of specific sIgA on S. mutans occur during S. mutans colonization, where the appropriate concentration of specific sIgA may serve as an anti-microbial agent, agglutinin, or an adherence receptor to surface antigens. Further, specific sIgA supported biofilm formation when the mice were supplied 1% sucrose water and a non-sucrose diet. The data suggests that there are multiple effects exerted by sIgA in S. mutans colonization, with synergistic effects evident under the condition of sIgA and limited nutrients on colonization in NOD/SCID.e2f1−/− mice. This is a new animal model that can be used to assess prevention methods for dental biofilm-dependent diseases such as dental caries

Outer Membrane Vesicles of Porphyromonas gingivalis Elicit a Mucosal Immune Response

We previously reported that mutation of galE in Porphyromonas gingivalis has pleiotropic effects, including a truncated lipopolysaccharide (LPS) O-antigen and deglycosylation of the outer membrane protein OMP85 homolog. In the present study, further analysis of the galE mutant revealed that it produced little or no outer membrane vesicles (OMVs). Using three mouse antisera raised against whole cells of the P. gingivalis wild type strain, we performed ELISAs to examine the reactivity of these antisera with whole cells of the wild type or the galE mutant. All three antisera had significantly lower reactivity against the galE mutant compared to wild type. OMVs, but not LPS, retained the immunodominant determinant of P. gingivalis, as determined by ELISAs (with wild type LPS or OMVs as antigen) and absorption assays. In addition, we assessed the capacity of OMVs as a vaccine antigen by intranasal immunization to BALB/c mice. Synthetic double-stranded RNA polyriboinosinic polyribocytidylic acid [Poly (I∶C)], an agonist of Toll-like receptor 3 (TLR3), was used as the mucosal adjuvant. Vaccination with OMV elicited dramatically high levels of P. gingivalis-specific IgA in nasal washes and saliva, as well as serum IgG and IgA. In conclusion, the OMVs of P. gingivalis have an important role in mucosal immunogenicity as well as in antigenicity. We propose that P. gingivalis OMV is an intriguing immunogen for development of a periodontal disease vaccine

Role of oral streptococci in the pH-dependent carious dentin

The aim of the present study was to investigate the extent to which oral streptococci or lactic acid producing bacteria are able to regulate pH value, especially at low pH values associated with dentinal carious activity using a PCR method. One millimeter-thick sections were sliced from 24 extracted carious human molars. The pH values on the tooth sections were evaluated using a pH-imaging microscope. A dentin sample (1X1X1mm) was prepared from the areas with the lowest or highest pH and homogenized to extract bacterial genomic DNA. Specific primers were used for nested PCR to mutans streptococci (MS: Streptococcus mutans and Streptococcus sobrinus). Conserved primers were also used for PCR to lactobacilli and gram positive bacteria. The PCR products were separated by electrophoresis, and then oral bacteria were identified. There was no significant difference between carious and intact dentin in MS identification. However, the frequency of the product ampli-fied by the conserved primers in carious dentin (16/24, 66.7%) was significantly higher than that in intact dentin (2/24, 8.3%), and PCR products demonstrated, by sequence analysis, various bacteria, including oral streptococci. It was concluded that oral streptococci may be associated with the development of "low pH-carious dentin".link_to_subscribed_fulltex