Development of Porphyromonas gingivalis-specific quantitative real-time PCR primers based on the nucleotide sequence of rpoB

Host insulin resistance caused by Porphyromonas gingivalis-review of recent progresses

Porphyromonas gingivalis (P. gingivalis) is a Gram-negative oral anaerobic bacterium that plays a key role in the pathogenesis of periodontitis. P. gingivalis expresses a variety of virulence factors that disrupt innate and adaptive immunity, allowing P. gingivalis to survive and multiply in the host and destroy periodontal tissue. In addition to periodontal disease, P.gingivalis is also associated with systemic diseases, of which insulin resistance is an important pathological basis. P. gingivalis causes a systemic inflammatory response, disrupts insulin signaling pathways, induces pancreatic β-cell hypofunction and reduced numbers, and causes decreased insulin sensitivity leading to insulin resistance (IR). In this paper, we systematically review the studies on the mechanism of insulin resistance induced by P. gingivalis, discuss the association between P. gingivalis and systemic diseases based on insulin resistance, and finally propose relevant therapeutic approaches. Overall, through a systematic review of the mechanisms related to systemic diseases caused by P. gingivalis through insulin resistance, we hope to provide new insights for future basic research and clinical interventions for related systemic diseases.

Characteristics of the Salivary Microbiota in Periodontal Diseases and Potential Roles of Individual Bacterial Species To Predict the Severity of Periodontal Disease

The purposes of this study were to examine the compositional changes in the salivary microbiota according to the severity of periodontal disease and to verify whether the distribution of specific bacterial species in saliva can distinguish the severity of disease. Saliva samples were collected from 8 periodontally healthy controls, 16 patients with gingivitis, 19 patients with moderate periodontitis, and 29 patients with severe periodontitis. The V3 and V4 regions of the 16S rRNA gene in the samples were sequenced, and the levels of 9 bacterial species showing significant differences among the groups by sequencing analysis were identified using quantitative real-time PCR (qPCR). The predictive performance of each bacterial species in distinguishing the severity of disease was evaluated using a receiver operating characteristic curve. Twenty-nine species, including Porphyromonas gingivalis, increased as the severity of disease increased, whereas 6 species, including Rothia denticola, decreased. The relative abundances of P. gingivalis, Tannerella forsythia, Filifactor alocis, and Prevotella intermedia determined by qPCR were significantly different among the groups. The three bacterial species P. gingivalis, T. forsythia, and F. alocis were positively correlated with the sum of the full-mouth probing depth and were moderately accurate at distinguishing the severity of periodontal disease. In conclusion, the salivary microbiota showed gradual compositional changes according to the severity of periodontitis, and the levels of P. gingivalis, T. forsythia, and F. alocis in mouth rinse saliva had the ability to distinguish the severity of periodontal disease. IMPORTANCE Periodontal disease is one of the most widespread medical conditions and the leading cause of tooth loss, imposing high economic costs and an increasing burden worldwide as life expectancy increases. Changes in the subgingival bacterial community during the progression of periodontal disease can affect the entire oral ecosystem, and bacteria in saliva can reflect the degree of bacterial imbalance in the oral cavity. This study explored whether the specific bacterial species in saliva can distinguish the severity of periodontal disease by analyzing the salivary microbiota and suggested P. gingivalis, T. forsythia, and F. alocis as biomarkers for distinguishing the severity of periodontal disease in saliva.

Oral Microbiota Identifies Patients in Early Onset Rheumatoid Arthritis

Rheumatoid arthritis (RA) is the most common autoimmune inflammatory disease, and single periodontitis-associated bacteria have been suggested in disease manifestation. Here, the oral microbiota was characterized in relation to the early onset of RA (eRA) taking periodontal status into consideration. 16S rRNA gene amplicon sequencing of saliva bacterial DNA from 61 eRA patients without disease-modifying anti-rheumatic drugs and 59 matched controls was performed. Taxonomic classification at 98.5% was conducted against the Human Oral Microbiome Database, microbiota functions were predicted using PICRUSt, and periodontal status linked from the Swedish quality register for clinically assessed caries and periodontitis. The participants were classified into three distinct microbiota-based cluster groups with cluster allocation differences by eRA status. Independently of periodontal status, eRA patients had enriched levels of Prevotella pleuritidis, Treponema denticola, Porphyromonas endodontalis and Filifactor alocis species and in the Porphyromonas and Fusobacterium genera and functions linked to ornithine metabolism, glucosylceramidase, beta-lactamase resistance, biphenyl degradation, fatty acid metabolism and 17-beta-estradiol-17-dehydrogenase metabolism. The results support a deviating oral microbiota composition already in eRA patients compared with healthy controls and highlight a panel of oral bacteria that may be useful in eRA risk assessment in both periodontally healthy and diseased persons.

Candida albicans as an Essential "Keystone" Component within Polymicrobial Oral Biofilm Models?

Background: Existing standardized biofilm assays focus on simple mono-species or bacterial-only models. Incorporating Candida albicans into complex biofilm models can offer a more appropriate and relevant polymicrobial biofilm for the development of oral health products. Aims: This study aimed to assess the importance of interkingdom interactions in polymicrobial oral biofilm systems with or without C. albicans, and test how these models respond to oral therapeutic challenges in vitro. Materials and Methods: Polymicrobial biofilms (two models containing 5 and 10 bacterial species, respectively) were created in parallel in the presence and absence of C. albicans and challenged using clinically relevant antimicrobials. The metabolic profiles and biomasses of these complex biofilms were estimated using resazurin dye and crystal violet stain, respectively. Quantitative PCR was utilized to assess compositional changes in microbial load. Additional assays, for measurements of pH and lactate, were included to monitor fluctuations in virulence "biomarkers." Results: An increased level of metabolic activity and biomass in the presence of C. albicans was observed. Bacterial load was increased by more than a factor of 10 in the presence of C. albicans. Assays showed inclusion of C. albicans impacted the biofilm virulence profiles. C. albicans did not affect the biofilms' responses to the short-term incubations with different treatments. Conclusions: The interkingdom biofilms described herein are structurally robust and exhibit all the hallmarks of a reproducible model. To our knowledge, these data are the first to test the hypothesis that yeasts may act as potential "keystone" components of oral biofilms.

Periodontal inflamed surface area as a novel numerical variable describing periodontal conditions

Purpose

A novel index, the periodontal inflamed surface area (PISA), represents the sum of the periodontal pocket depth of bleeding on probing (BOP)-positive sites. In the present study, we evaluated correlations between PISA and periodontal classifications, and examined PISA as an index integrating the discrete conventional periodontal indexes.

Methods

This study was a cross-sectional subgroup analysis of data from a prospective cohort study investigating the association between chronic periodontitis and the clinical features of ankylosing spondylitis. Data from 84 patients without systemic diseases (the control group in the previous study) were analyzed in the present study.

Results

PISA values were positively correlated with conventional periodontal classifications (Spearman correlation coefficient=0.52; P<0.01) and with periodontal indexes, such as BOP and the plaque index (PI) (r=0.94; P<0.01 and r=0.60; P<0.01, respectively; Pearson correlation test). Porphyromonas gingivalis (P. gingivalis) expression and the presence of serum P. gingivalis antibodies were significant factors affecting PISA values in a simple linear regression analysis, together with periodontal classification, PI, bleeding index, and smoking, but not in the multivariate analysis. In the multivariate linear regression analysis, PISA values were positively correlated with the quantity of current smoking, PI, and severity of periodontal disease.

Conclusions

PISA integrates multiple periodontal indexes, such as probing pocket depth, BOP, and PI into a numerical variable. PISA is advantageous for quantifying periodontal inflammation and plaque accumulation.

In Vitro Effect of Porphyromonas gingivalis Methionine Gamma Lyase on Biofilm Composition and Oral Inflammatory Response

Methanethiol (methyl mercaptan) is an important contributor to oral malodour and periodontal tissue destruction. Porphyromonas gingivalis, Prevotella intermedia and Fusobacterium nucleatum are key oral microbial species that produce methanethiol via methionine gamma lyase (mgl) activity. The aim of this study was to compare an mgl knockout strain of P. gingivalis with its wild type using a 10-species biofilm co-culture model with oral keratinocytes and its effect on biofilm composition and inflammatory cytokine production. A P. gingivalis mgl knockout strain was constructed using insertion mutagenesis from wild type W50 with gas chromatographic head space analysis confirming lack of methanethiol production. 10-species biofilms consisting of Streptococcus mitis, Streptococcus oralis, Streptococcus intermedius, Fusobacterium nucleatum ssp polymorphum, Fusobacterium nucleatum ssp vincentii, Veillonella dispar, Actinomyces naeslundii, Prevotella intermedia and Aggregatibacter actinomycetemcomitans with either the wild type or mutant P. gingivalis were grown on Thermanox cover slips and used to stimulate oral keratinocytes (OKF6-TERT2), under anaerobic conditions for 4 and 24 hours. Biofilms were analysed by quantitative PCR with SYBR Green for changes in microbial ecology. Keratinocyte culture supernatants were analysed using a multiplex bead immunoassay for cytokines. Significant population differences were observed between mutant and wild type biofilms; V. dispar proportions increased (p<0.001), whilst A. naeslundii (p<0.01) and Streptococcus spp. (p<0.05) decreased in mutant biofilms. Keratinocytes produced less IL-8, IL-6 and IL-1α when stimulated with the mutant biofilms compared to wild type. Lack of mgl in P. gingivalis has been shown to affect microbial ecology in vitro, giving rise to a markedly different biofilm composition, with a more pro-inflammatory cytokine response from the keratinocytes observed. A possible role for methanethiol in biofilm formation and cytokine response with subsequent effects on oral malodor and periodontitis is suggested.

Viable Compositional Analysis of an Eleven Species Oral Polymicrobial Biofilm

Purpose: Polymicrobial biofilms are abundant in clinical disease, particularly within the oral cavity. Creating complex biofilm models that recapitulate the polymicrobiality of oral disease are important in the development of new chemotherapeutic agents. In order to do this accurately we require the ability to undertake compositional analysis, in addition to determine individual cell viability, which is difficult using conventional microbiology. The aim of this study was to develop a defined multispecies denture biofilm model in vitro, and to assess viable compositional analysis following defined oral hygiene regimens.

Methods: An in vitro multispecies denture biofilm containing various oral commensal and pathogenic bacteria and yeast was created on poly (methyl methacrylate) (PMMA). Denture hygiene regimens tested against the biofilm model included brushing only, denture cleansing only and combinational brushing and denture cleansing. Biofilm composition and viability were assessed by culture (CFU) and molecular (qPCR) methodologies. Scanning electron microscopy and confocal laser scanning microscopy were also employed to visualize changes in denture biofilms following treatment.

Results: Combinational treatment of brushing and denture cleansing had the greatest impact on multispecies denture biofilms, reducing the number of live cells by more than 2 logs, and altering the overall composition in favor of streptococci. This was even more evident during the sequential testing, whereby daily sequential treatment reduced the total and live number of bacteria and yeast more than those treated intermittently. Bacteria and yeast remaining following treatment tended to aggregate in the pores of the PMMA, proving more difficult to fully eradicate the biofilm.

Conclusions: Overall, we are the first to develop a method to enable viable compositional analysis of an 11 species denture biofilm following chemotherapeutic challenge. We were able to demonstrate viable cell reduction and changes in population dynamics following evaluation of various denture cleansing regimens. Specifically, it was demonstrated that daily combinational treatment of brushing and cleansing proved to be the most advantageous denture hygiene regimen, however, residual organisms still remained within the pores of PMMA surface, which could act as a reservoir for further biofilm regrowth. We have identified an industry need for denture cleansing agents with the capacity to penetrate these pores and disaggregate these complex biofilm consortia.

Chronic Periodontitis Is Associated With Spinal Dysmobility in Patients With Ankylosing Spondylitis

BACKGROUND

Although microbes have been suggested to play a role in the pathogenesis of ankylosing spondylitis (AS), several studies present contradictory results regarding the association between AS and chronic periodontitis (CP).

METHODS

Clinical, laboratory, and medication data were collected from 84 patients with AS and 84 age- and sex-matched controls. Periodontal measurements, including probing depths (PDs), clinical attachment loss (AL), serum anti-Porphyromonas gingivalis titers, and the detection of P. gingivalis DNA in gingival crevicular fluid, were recorded. All participants with periodontitis with PD ≥4 to <7 mm received scaling and root planing and were re-evaluated at 12 weeks; those still exhibiting periodontitis with PD of ≥4 to <7 mm at 12 weeks were followed at 24 weeks.

RESULTS

The prevalence of moderate-to-severe CP was not different between patients with AS and controls (70.2% versus 66.6%). The P. gingivalis detection rate was not different between patients with AS and controls or between patients with AS receiving and not receiving anti-tumor necrosis factor (TNF)-α agents. However, CP was positively associated with impaired spinal mobility of patients with AS in multivariate analyses. After periodontal treatment, PD and AL levels were improved in both groups, but the change was significantly greater in patients with AS than in controls. Patients with AS receiving anti-TNF-α agents exhibited a greater improvement in PD and AL than those who did not.

CONCLUSIONS

Although AS was not associated with the presence of CP, CP was associated positively with the severity of spinal dysmobility in Korean patients with AS. These results suggest that periodontitis can have a negative effect on axial movement in AS.

Development of species-specific quantitative real-time PCR primers for detecting anginosus group streptococci based on the rpoB

In this study, we introduced species-specific quantitative real-time PCR (qPCR) primers designed based on a DNA-dependent RNA polymerase beta-subunit gene for detecting anginosus group streptococci (AGS), Streptococcus anginosus, S. constellatus, and S. intermedius. The specificity of the qPCR primers was confirmed by conventional PCR with the genomic DNAs of 76 strains regarding 44 bacterial species including the type strain for the target species. The standard curves revealed the lower detection limits of these species-specific qPCR primers was 40 fg at below a cycle threshold (CT) value of 35. These results suggest that AGS species-specific qPCR primers are suitable for applications in epidemiological studies associated with infectious diseases related to AGS.

Development of Streptococcus gordonii-specific quantitative real-time polymerase chain reaction primers based on the nucleotide sequence of rpoB

In this study, Streptococcus gordonii-specific quantitative real-time polymerase chain reaction (qPCR) primers, RTSgo-F2/RTSgo-R2, were developed based on the nucleotide sequences of RNA polymerase β-subunit gene (rpoB). The specificity of the RTSgo-F2/RTSgo-R2 primers was assessed by conventional PCR on 99 strains comprising 63 oral bacterial species, including the type strain and eight clinical isolates of S. gordonii. PCR products were amplified from the genomic DNAs of only S. gordonii strains. The qPCR primers were able to detect as little as 40 fg of S. gordonii genomic DNA at a cycle threshold value of 33. These findings suggest that these qPCR primers detect S. gordonii with high specificity and sensitivity.

The unique hmuY gene sequence as a specific marker of Porphyromonas gingivalis

Porphyromonas gingivalis, a major etiological agent of chronic periodontitis, acquires heme from host hemoproteins using the HmuY hemophore. The aim of this study was to develop a specific P. gingivalis marker based on a hmuY gene sequence. Subgingival samples were collected from 66 patients with chronic periodontitis and 40 healthy subjects and the entire hmuY gene was analyzed in positive samples. Phylogenetic analyses demonstrated that both the amino acid sequence of the HmuY protein and the nucleotide sequence of the hmuY gene are unique among P. gingivalis strains/isolates and show low identity to sequences found in other species (below 50 and 56%, respectively). In agreement with these findings, a set of hmuY gene-based primers and standard/real-time PCR with SYBR Green chemistry allowed us to specifically detect P. gingivalis in patients with chronic periodontitis (77.3%) and healthy subjects (20%), the latter possessing lower number of P. gingivalis cells and total bacterial cells. Isolates from healthy subjects possess the hmuY gene-based nucleotide sequence pattern occurring in W83/W50/A7436 (n = 4), 381/ATCC 33277 (n = 3) or TDC60 (n = 1) strains, whereas those from patients typically have TDC60 (n = 21), W83/W50/A7436 (n = 17) and 381/ATCC 33277 (n = 13) strains. We observed a significant correlation between periodontal index of risk of infectiousness (PIRI) and the presence/absence of P. gingivalis (regardless of the hmuY gene-based sequence pattern of the isolate identified [r = 0.43; P = 0.0002] and considering particular isolate pattern [r = 0.38; P = 0.0012]). In conclusion, we demonstrated that the hmuY gene sequence or its fragments may be used as one of the molecular markers of P. gingivalis.

Development of quantitative real-time PCR primers for detecting 42 oral bacterial species

In this study, we introduced species-specific quantitative real-time PCR (qPCR) primers designed based on a DNA-dependent RNA polymerase beta-subunit gene (rpoB) for detecting 42 oral bacterial species. The specificity of the qPCR primers was confirmed by conventional PCR with the genomic DNAs of 73-79 strains regarding 73-75 bacterial species including the type strain for the target species. The standard curves revealed the lower detection limits of 42 bacterial species-specific qPCR primers ranged from 4 to 40 fg below a cycle threshold (C T) value of 35, except Atopobium rimae, Fusobacterium nucleatum, Neisseria meningitidis, and Porphyromonas asaccharolytica which were 400 fg. These results suggest that 42 bacterial species-specific qPCR primers are suitable for applications in epidemiological studies related to oral infectious diseases such as periodontal diseases, endodontic infection, and dental caries.

Analysis of viable vs. dead Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis using selective quantitative real-time PCR with propidium monoazide

BACKGROUND AND OBJECTIVES

One of the major disadvantages of DNA-based microbial diagnostics is their inability to differentiate DNA between viable and dead microorganisms, which could be important when studying etiologically relevant pathogens. The aim of this investigation was to optimize a method for the selective detection and quantification of only viable Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis cells by combining quantitative real-time polymerase chain reaction (qPCR) and propidium monoazide (PMA).

MATERIAL AND METHODS

Three different concentrations of PMA (10, 50 or 100 μm) were added to suspensions of 10(6) (CFU)/mL of viable/dead A. actinomycetemcomitans and P. gingivalis cells. After DNA isolation, qPCR was carried out using specific primers and probes for the tested bacteria. PMA was further tested with different mixtures containing varying ratios of viable and dead cells. The efficacy of PMA to detect viable/dead cells was tested by analysis of variance.

RESULTS

For these specific bacterial pathogens, 100 μm PMA resulted in a significant reduction of qPCR amplification with dead cells (10(6) CFU/mL), while with viable cells no significant inhibition was detected. PMA was also effective in detecting selectively viable cells by qPCR detection, when mixtures of varying ratios of viable and dead bacteria were used.

CONCLUSIONS

This study demonstrated the efficiency of PMA for differentiating viable and dead A. actinomycetemcomitans and P. gingivalis cells. This method of PMA-qPCR may be useful for monitoring new antimicrobial strategies and for assessing the pathogenic potential of A. actinomycetemcomitans and P. gingivalis in different oral conditions when using molecular diagnostic methods.