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

E2F1-deficient NOD/SCID mice are an experimental model for dry mouth

Saliva contains a wide variety of secretory proteins, including α-amylase, lysozyme, peroxidase, immunoglobulins, and mucins. Hyposecretion of saliva and consequent dry mouth will lead to severe dental caries, periodontal disease, and mucosal infections, resulting in degrade of quality of life. Polyposia development is one of sign usually seen in dry mouth patients. However, little is reported in dry mouth-model animal regarding the entire process of polyposia development. We investigated the behavior of polyposia in E2F1-deficient non-obese diabetic/severe combined immunodeficiency disease (NOD/SCID) mice, as a dry mouth-model. E2F1-deficient NOD/SCID mice secreted small amount of saliva under the stimulation with a cholinergic agonist, pilocarpine, compared with control mice. The frequency of water intake by E2F-1-deficient NOD/SCID mice was more than that by control mice. These results suggest that E2F-1-deficient NOD/SCID mice show a behavior similar to polyposia and are very useful experimental model of dry mouth patients

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

Relationship between oral status and prevalence of periodontopathic bacteria on tongues of elderly individuals.

Colonization of periodontopathic bacteria is associated with increased risk for systemic diseases. However, few studies have investigated the relationships between oral status factors as well as health related-quality of life (HR-QOL) and the prevalence of such bacteria in elderly individuals. This study investigated the prevalence of Porphyromonas gingivalis, Prevotella intermedia, Treponema denticola, and Tannerella forsythia in 165 community-dwelling functionally independent 85-year-old Japanese individuals (93 dentate, 72 edentulous) and the relationship to oral status, including oral malodor and HR-QOL. All 4 of the studied periodontopathic bacteria were found more frequently in tongue coating samples from dentate than edentulous subjects, and the prevalence of P. gingivalis, P. intermedia, and T. denticola was significantly related to the number of teeth with a periodontal pocket depth (>/= 4 mm). These results suggest the existence of a stable circulation of periodontopathic bacteria between the gingival sulcus and tongue coating over time with teeth. In addition, the presence of teeth with a deep pocket and colonization of T. denticola were positively related to the level of CH(3)SH, while the number of present teeth positively contributed to HR-QOL, especially in regard to mental health. In conclusion, since dentate state can retain colonization of periodontopathic pathogens in the oral cavity, both periodontal treatment and tongue care are important for maintaining a healthy oral status in the elderly, and possibly results in avoidance of a risk for tooth loss and decline in HL-QOL, as well as protects from systemic diseases

Effects of Complex DNA and MVs with GTF Extracted from Streptococcus mutans on the Oral Biofilm

Streptococcus mutans is one of the principal pathogens for the development of dental caries. Oral biofilms formed by S. mutans are constructed of insoluble glucan formation induced by the principal enzymes, GTF-I and GTF-SI, in sucrose-containing conditions. However, as another means of biofilm formation, extracellular DNA (eDNA) and membrane vesicles (MVs) are also contributors. To explore the roles of eDNA and MVs for biofilm formation, short and whole size pure DNAs, two types of sub-purified DNAs and MVs were extracted from S. mutans by beads destruction, treatment of proteinase K, and ultracentrifugation of culture supernatant, and applied into the biofilm formation assay using the S. mutans UA159 gtfBC mutant, which lost GTF-I and GTF-SI, on a human saliva-coated 96 well microtiter plate in sucrose-containing conditions. Sub-purified DNAs after cell lysis by beads destruction for total 90 and 180 s showed a complex form of short-size DNA with various proteins and MVs associated with GTF-I and GTF-SI, and induced significantly higher biofilm formation of the S. mutans UA159.gtfBC mutant than no sample (p &lt; 0.05). Short-size pure DNA without proteins induced biofilm formation but whole-size pure DNA did not. Moreover, the complex form of MV associated with GTFs and short-size DNA showed significantly higher biofilm formation of initial colonizers on the human tooth surface such as Streptococcus mitis than no sample (p &lt; 0.05). The short-size DNAs associated with MVs and GTFs are important contributors to the biofilm formation and may be one of additional targets for the prevention of oral biofilm-associated diseases

Role of peptide antigen for induction of inhibitory antibodies to Streptococcus mutans in the human oral cavity

The alanine-rich repeating region (A-region) in the surface protein antigen (PAc) of Streptococcus mutans has received much attention as an antigenic component for vaccines against dental caries. The PAc (residue 361–386) peptide in the A-region possesses a multiple binding motif (L- -V-K- -A) to various HLA-DR molecules and a B-cell core epitope (- Y- - -L- -Y- - - -) that recognizes the inhibiting antibody to S. mutans. In the present study, we investigated the immunogenicity of the PAc (361–386) peptide in humans and regulators of induction of the anti-PAc (361–386) peptide IgA antibody (aPPA) in saliva. The PAc (361–386) peptide was confirmed as an ideal peptide antigen for induction of the inhibiting antibody to S. mutans in 151 healthy human subjects (36·6 ± 12·6 years old) by quantitative analyses of oral bacteria and ELISA, as the aPPA titre in human saliva decreased significantly in an age-dependent manner. Homozygous DRB1*0405 and 1502, and heterozygous DRB1*0405/1502 showed a negative association with production of aPPA and tended to reduce the number of total streptococci in saliva. In contrast, the DRB1*1501 allele was significantly correlated with a high level of induction of the antibodies, and also tended to reduce lactobacilli and mutans streptococci. Further, peptide immunogenicity was confirmed in NOD-SCID mice grafted with human peripheral blood mononuclear cells. Our results indicate that the interplay between regulators such as age, DRB1 genotype, cytokines, and peptide immunogenicity may provide a potential means for developing a vaccine useful for the prevention of dental caries as well as their diagnosis

The Impact of Oral Health on Respiratory Viral Infection

Influenza virus and severe acute respiratory syndrome coronavirus (SARS-CoV-2) have caused respiratory diseases worldwide. Coronavirus disease 2019 (COVID-19) is now a global health concern requiring emergent measures. These viruses enter the human body through the oral cavity and infect respiratory cells. Since the oral cavity has a complex microbiota, influence of oral bacteria on respiratory virus infection is considered. Saliva has immune molecules which work as the front line in the biophylactic mechanism and has considerable influence on the incidence and progression of respiratory viral infection. Salivary scavenger molecules, such as gp340 and sialic acid, have been reported to exert anti-influenza virus activity. Salivary secretory immunoglobulin A (SIgA) has potential to acquire immunity against these viruses. Biological features of the oral cavity are thought to affect viral infection in respiratory organs in various ways. In this review, we reviewed the literature addressing the impact of oral conditions on respiratory infectious diseases caused by viruses