Porphyromonas Gingivalis Strains Research Articles

The Antimicrobial Susceptibility of Porphyromonas gingivalis: Genetic Repertoire, Global Phenotype, and Review of the Literature.

The in vitro antimicrobial susceptibility of 29 strains of the major periodontal pathogen Porphyromonas gingivalis and three P. gulae (as an ancestor) to nine antibiotics (amoxicillin, amoxicillin/clavulanate, clindamycin, metronidazole, moxifloxacin, doxycycline, azithromycin, imipenem, and cefoxitin) was evaluated by E-testing of minimal inhibitory concentration (MIC) according to international standards. The results were compared with 16 international studies reporting MICs from 1993 until recently. In addition, 77 currently available P. gingivalis genomes were screened for antimicrobial resistance genes. E-testing revealed a 100% sensitivity of P. gingivalis and P. gulae to all antibiotics. This was independent of the isolation year (1970 until 2021) or region, including rural areas in Indonesia and Africa. Regarding studies worldwide (675 strains), several method varieties regarding medium, McFarland inoculation standards (0.5–2) and incubation time (48–168 h) were used for MIC-testing. Overall, no resistances have been reported for amoxicillin + clavulanate, cefoxitin, and imipenem. Few strains showed intermediate susceptibility or resistance to amoxicillin and metronidazole, with the latter needing both confirmation and attention. The only antibiotics which might fail in the treatment of P. gingivalis-associated mixed anaerobic infections are clindamycin, macrolides, and tetracyclines, corresponding to the resistance genes erm(B), erm(F), and tet(Q) detected in our study here, as well as fluoroquinolones. Periodical antibiotic susceptibility testing is necessary to determine the efficacy of antimicrobial agents and to optimize antibiotic stewardship.

A Novel Regulation of K-antigen Capsule Synthesis in Porphyromonas gingivalis Is Driven by the Response Regulator PG0720-Directed Antisense RNA.

The periodontal pathogen Porphyromonas gingivalis strain W83 displays at least three different surface glycans, specifically two types of lipopolysaccharides (O-LPS and A-LPS) and K-antigen capsule. Despite the importance of K-antigen capsule to the virulence of P. gingivalis, little is known as to how expression of genes involved in the synthesis of this surface glycan is regulated. The genes required for K-antigen capsule synthesis are located in a locus that encodes a number of transcripts, including an operon (PG0104 to PG0121, generating ~19.4-kb transcript) which contains a non-coding 77-bp inverted repeat (77 bpIR) region near the 5'-end. Previously, we identified a 550-nucleotide antisense RNA molecule (designated asSuGR for antisense Surface Glycan Regulator) encoded within the 77-bpIR element that influences the synthesis of surface glycans. In this study, we demonstrate that the DNA-binding response regulator PG0720 can bind the promoter region of asSuGR and activate expression of asSuGR, indicating that PG0720 may indirectly influence transcript levels of the K-antigen capsule operon expressed from the sense strand. The data show that deletion of the PG0720 gene confers a defect in the presentation of surface polysaccharides compared with the parent strain and quantitative RT-PCR (qPCR) analysis determined that the overall expression of genes involved in K-antigen capsule synthesis were down-regulated in the PG0720 mutant. Furthermore, the defects of the PG0720 deletion mutant were restored by complementation. Importantly, the PG0720 deletion mutant showed reduced virulence. Altogether, our data show that the response regulator PG0720 regulates expression of asSuGR, a trans-acting antisense RNA molecule involved in modulating the production of surface polysaccharides in P. gingivalis strain W83. The data provide further evidence that surface glycans are key virulence determinants and significantly advances our understanding of the molecular mechanisms controlling the synthesis of P. gingivalis K-antigen capsule, a key virulence determinant.

Evaluation of biofilm colonization on multi-part dental implants in a rat model

BackgroundPeri-implant mucositis and peri-implantitis are highly prevalent biofilm-associated diseases affecting the tissues surrounding dental implants. As antibiotic treatment is ineffective to fully cure biofilm mediated infections, antimicrobial modifications of implants to reduce or prevent bacterial colonization are called for. Preclinical in vivo evaluation of the functionality of new or modified implant materials concerning bacterial colonization and peri-implant health is needed to allow progress in this research field. For this purpose reliable animal models are needed.MethodsCustom made endosseous dental implants were installed in female Sprague Dawley rats following a newly established three-step implantation procedure. After healing of the bone and soft tissue, the animals were assigned to two groups. Group A received a continuous antibiotic treatment for 7 weeks, while group B was repeatedly orally inoculated with human-derived strains of Streptococcus oralis, Fusobacterium nucleatum and Porphyromonas gingivalis for six weeks, followed by 1 week without inoculation. At the end of the experiment, implantation sites were clinically assessed and biofilm colonization was quantified via confocal laser scanning microscopy. Biofilm samples were tested for presence of the administered bacteria via PCR analysis.ResultsThe inner part of the custom made implant screw could be identified as a site of reliable biofilm formation in vivo. S. oralis and F. nucleatum were detectable only in the biofilm samples from group B animals. P. gingivalis was not detectable in samples from either group. Quantification of the biofilm volume on the implant material revealed no statistically significant differences between the treatment groups. Clinical inspection of implants in group B animals showed signs of mild to moderate peri-implant mucositis (4 out of 6) whereas the mucosa of group A animals appeared healthy (8/8). The difference in the mucosa health status between the treatment groups was statistically significant (p = 0.015).ConclusionsWe developed a new rodent model for the preclinical evaluation of dental implant materials with a special focus on the early biofilm colonization including human-derived oral bacteria. Reliable biofilm quantification on the implant surface and the symptoms of peri-implant mucositis of the bacterially inoculated animals will serve as a readout for experimental evaluation of biofilm-reducing modifications of implant materials.

Antibiofilm effects of titanium surfaces modified by laser texturing and hot-pressing sintering with silver.

Peri-implant diseases are one of the main causes of dental implant failure. New strategies for dental implants manufacturing have been developed to prevent the accumulation of bacteria and related inflammatory reactions. The main aim of this work was to develop laser-treated titanium surfaces covered with silver that generate a electrical dipole to inhibit the oral bacteria accumulation. Two approaches were developed for that purpose. In one approach a pattern of different titanium dioxide thickness was produced on the titanium surface, using a Q-Switched Nd:YAG laser system operating at 1064 nm. The second approach was to incorporate silver particles on a laser textured titanium surface. The incorporation of the silver was performed by laser sintering and hot-pressing approaches. The anti-biofilm effect of the discs were tested against biofilms involving 14 different bacterial strains growth for 24 and 72 hr. The morphological aspects of the surfaces were evaluated by optical and field emission guns scanning electronical microscopy (FEGSEM) and therefore the wettability and roughness were also assessed. Physicochemical analyses revealed that the test surfaces were hydrophilic and moderately rough. The oxidized titanium surfaces showed no signs of antibacterial effects when compared to polished discs. However, the discs with silver revealed a decrease of accumulation of Porphyromonas gingivalis and Prevotella intermedia strains. Thus, the combination of Nd:YAG laser irradiation and hot-pressing was effective to produce silver-based patterns on titanium surfaces to inhibit the growth of pathogenic bacterial species. The laser parameters can be optimized to achieve different patterns, roughness, and thickness of the modified titanium layer regarding the type and region of the implant.

Antibacterial activity of melatonin against prime periodontal pathogens: An in vitro study

Aim: Accumulated data make it clear that by introducing large amount of antibiotics into the ecosystem, we have provided an environment conducive to antibiotic resistance and periodontal microbes are no different. Therefore, in the quest of finding a suitable drug as an alternate to antibiotic, we investigated the antibacterial activity of melatonin against predominantly Gram-negative periodontal pathogens in vitro. Melatonin with varied functions has driven its usage enormously; therefore, identifying its action against periodontal pathogens has driven this laboratory investigation. Materials and Methods: American type culture collection (ATCC) strains of Porphyromonas gingivalis, Fusobacterium nucleatum, and Aggregatibacter actinomycetemcomitans were used to determine minimum inhibitory and bactericidal concentrations (MIC and MBC) of melatonin using macro broth dilution method. MIC values were determined at 24, 48, and 72 h and sensitive MIC values were sub-cultured to determine MBC value at 24 h. Qualitative data were obtained and it was recorded as “sensitive” or “resistant” at respective concentrations. Results: When tested over a dilution range of 0.2–100 µg/mL, melatonin significantly inhibited microbial growth. At 48 h, the MIC value against A. actinomycetemcomitans, P. gingivalis, and F. nucleatum was 6.25, 0.8, and ≤0.2 µg/mL, respectively. The MBC value determined at 24 h demonstrated significant bactericidal activity against the pathogens. Conclusion: Melatonin exhibited bactericidal activity against prime periodontal pathogens even at low concentrations in comparison to previously documented evidences suggesting greater potency of the drug. Hence, renewed effort to find and develop new class of drug which can inhibit periodontal pathogens, rather than just improvements on already-existing drugs can potentially prevent the development of resistant strains in periodontal microenvironment.

High-salt and glucose diet attenuates alveolar bone recovery in a ligature-induced rat model of experimental periodontitis

Excessive intake of sodium caused by high salt diet promotes the expression of inflammatory cytokines and differentiation of helper T cells resulting in inflammatory responses. High-glucose diet also contributes to the pathogenesis of periodontitis by inducing changes in the oral microbiome and reducing salivation. However, the effect of a high-salt and glucose diet (HSGD) on the prognosis of periodontitis remains unclear. In this study, a rat model of experimental periodontitis was established by periodic insertion of absorbable sutures containing Porphyromonas gingivalis and Fusobacterium nucleatum strains into the right gingival sulcus to analyze the effect of HSGD on the incidence and progression of periodontitis. The alveolar bone heights (ABH) was measured with microcomputed tomography imaging of the HSGD- and general diet (GD)-treated groups. The right ABH was significantly decreased compared to the left in both groups at 4 weeks after induction of inflammation; however, no significant difference was noted between the groups. Notably, the ABH in the HSGD-treated group was significantly decreased at 8 weeks after induction of inflammation, whereas in the GD-treated group, an increase in the ABH was observed; a significant difference of the ABH was noted between the two groups (p < 0.05). At 12 weeks, recovery of the alveolar bone was observed in both groups, with no significant differences in ABH between the two groups. These findings indicate that the intake of excessive sodium attenuates the recovery rate of the alveolar bone even after the local infectant is removed. In addition, this study demonstrates the use of HSGD in establishing a new animal model of periodontitis.

Antibacterial efficacy of commercially available activated carbon tooth powder: An in vitro study

There has been an indiscriminate use of commercial antimicrobials in the previous decades, leading to emergence of multidrug resistant bacteria. This has become a frequent occurrence, so natural antimicrobial agents have grabbed attention of researchers as potential alternatives. Of particular interest is cow dung which has been shown to have antibacterial and antiseptic properties. It is known to be used predominantly in rural areas. This paper aims to evaluate the antibacterial activity of Goshala Activated Carbon toothpowder against three strains of periodontopathogennic and cariogenic bacteria. Standardized strains of Streptococcus mutans, Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis were cultured in BHI (Brain Heart Infusion Broth) media and Minimum Inhibitory Concentration (MIC) of Activated Carbon tooth powder was assessed by serial dilution method. Likewise, Amoxicillin, Metronidazole and Chlorhexidine were tested against the same pathogens. Porphyromonas gingivalis, Streptococcus mutans and Aggregatibacter actinomycetemcomitans were shown to be sensitive at an MIC of 50mg/ml, 25mg/ml and 0.8mg/ml for activated carbon toothpowder respectively. Given some limitations of this study, we can conclude that activated carbon powder presents a ray of hope in developing a targeted agent for aggressive periodontitis patients.

Comparison of Minimum Inhibitory Concentrations of Hypericum Perforatum L. Essential Oils, 0.2 % Chlorhexidine and 10 % Povidone-iodine Over Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis

Hypericum perforatum is a useful plant because of its biological features, such as bactericidal, virucidal, and fungicidal effects. Elimination of periodontal pathogens, including Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis, from the oral environment, is important for the stability of periodontal health. Therefore, we aimed to determine the antimicrobial activity of the Hypericum perforatum L. essential oils over these pathogens using cell cultures. The standard and clinical bacterial strains were used in this study. The essential oils extracted from Hypericum perforatum L. flowers were analyzed with gaschromatography/mass spectrometry. The antimicrobial activities of the essential oils along with 0.2 % chlorhexidine, 10 % povidone-iodine, and combinations of essential oils and 0.2 % chlorhexidine, and essential oils and 10 % povidone-iodine were evaluated by measuring the minimum inhibitory concentrations. Essential oils’ minimum inhibitory concentration value for clinical A. actinomycetemcomitans strains was significantly lower than that of the povidone-iodine solution (P<0.05). However, despite the low minimum inhibitory concentration value of essential oils, when compared to 0.2 % chlorhexidine, there was no statistically significant difference between the agents (P=0.113). For clinical strains of Porphyromonas gingivalis, the essential oils showed a lower minimum inhibitory concentration value compared to chlorhexidine and povidone-iodine. The essential oils combined with chlorhexidine or povidone-iodine showed significantly lower minimum inhibitory concentration value for both strains of Aggregatibacter actinomycetemcomitans (P<0.05). With the lower minimum inhibitory concentration values, the essential oils showed strong antimicrobial activity. Moreover, when combined with chlorhexidine or the povidone-iodine, the antimicrobial effect of essential oils on Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis strains increased synergistically.

Actividad antibacteriana del extracto etanólico de Caesalpina spinosa (Molina) Kuntze “tara” Fabaceae sobre bacterias de la biopelícula bucal

Objetivo: Determinar la actividad antibacteriana, in vitro, del extracto etanólico de Caesalpinia spinosa “tara”, sobre cultivos de bacterias de la biopelícula bucal. Material y métodos: Se realizó un estudio experimental in vitro, en el cual se comparó la actividad antibacteriana de un extracto etanólico de C. spinosa y controles (clorhexidina al 0,12% (CHX 0,12%), antiséptico bucal (AB), etanol y agua destilada), frente a cultivos de cepas de Streptococcus mutans (ATCC® 25175), Streptococcus sanguinis (ATCC® 10556), Enterococcus faecalis (ATCC® 29212), Staphylococcus aureus (ATCC® 6538) y Porphyromonas gingivalis (ATCC® 30277). Se utilizó el método de difusión de agar con pocillos de 6 mm de diámetro, en el grupo experimental y controles. Resultados: Se evidenció que el promedio del halo de inhibición formado por la aplicación del extracto etanólico de C. spinosa sobre el S. aureus, fue mucho mayor que el obtenido con la CHX 0,12% o el AB (p&lt;0,000). También se observó, que el promedio de halo de inhibición del extracto de C. spinosa fue mayor que los controles, frente a las cepas de S. sanguinis (p&lt;0,000). Conclusión: La C. spinosa demostró tener actividad antibacteriana in vitro frente a la presencia de S. aureus, S. sanguinis, S. mutans y E. faecalis. No mostró actividad sobre la P. gingivalis.

Fetal growth restriction is a host specific response to infection with an impaired spiral artery remodeling-inducing strain of Porphyromonas gingivalis

Porphyromonas gingivalis is a periodontal pathogen implicated in a range of pregnancy disorders that involve impaired spiral artery remodeling (ISAR) with or without fetal growth restriction (FGR). Using a rodent periodontitis model, we assessed the ability of P. gingivalis to produce ISAR and FGR in Sprague Dawley (SD) and Wistar (WIS) rats. Both infected SD and WIS rats developed ISAR, but only WIS rats developed FGR despite both rat strains having equivalent microbial loads within the placenta. Neither maternal systemic inflammation nor placental (fetal) inflammation was a feature of FGR in WIS rats. Unique to infected WIS rats, was loss of trophoblast cell density within the junctional zone of the placenta that was not present in SD tissues. In addition, infected WIS rats had a higher proportion of junctional zone trophoblast cells positive for cytoplasmic high temperature requirement A1 (Htra1), a marker of cellular oxidative stress. Our results show a novel phenomenon present in P. gingivalis-induced FGR, with relevance to human disease since dysregulation of placental Htra1 and placental oxidative stress are features of preeclamptic placentas and preeclampsia with FGR.

Novel Coatings to Minimize Bacterial Adhesion and Promote Osteoblast Activity for Titanium Implants.

Titanium nitride (TiN) and silicon carbide (SiC) adhesion properties to biofilm and the proliferation of human osteoblasts were studied. Quaternized titanium nitride (QTiN) was produced by converting the surface nitrogen on TiN to a positive charge through a quaternization process to further improve the antibacterial efficiency. The SiC required a nitridation within the plasma chamber of the surface layer before quaternization could be carried out to produce quaternized SiC (QSiC). The antimicrobial activity was evaluated on the reference strains of Porphyromonas gingivalis for 4 h by fluorescence microscopy using a live/dead viability kit. All the coatings exhibited a lower biofilm coverage compared to the uncoated samples (Ti—85.2%; TiN—24.22%; QTiN—11.4%; SiC—9.1%; QSiC—9.74%). Scanning Electron Microscope (SEM) images confirmed the reduction in P. gingivalis bacteria on the SiC and TiN-coated groups. After 24 h of osteoblast cultivation on the samples, the cell adhesion was observed on all the coated and uncoated groups. Fluorescence images demonstrated that the osteoblast cells adhered and proliferated on the surfaces. TiN and SiC coatings can inhibit the attachment of Porphyromonas gingivalis and promote osteoblast adhesion on the titanium used for implants. These coatings may possess the ability to prevent the development of peri-implantitis and stimulate osteointegration.

Assessment of the antibacterial activity of Catharanthus roseus leaf extract on periodontal pathogens, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, and Prevotella intermedia: An In vitro study

Aim: The aim of this study was to evaluate the in vitro antimicrobial efficacy of Catharanthus roseus leaf extract against standard strains of periodontal pathogens, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, and Prevotella intermedia. Methodology: The C. roseus leaves were identified, shade dried, and ground, and ethanol extract was obtained. The antimicrobial efficacy of this extract was done using disc diffusion assay, minimum inhibitory concentration, and minimum bactericidal concentration. Results: C. roseus leaf extract showed antimicrobial activity against all the three test organisms. However, P. gingivalis was found to be more susceptible to C. roseus leaf extracts, since their growth was inhibited at relatively lower concentration as compared to A. actinomycetemcomitans and P. intermedia. Conclusion: Within the limitations of the study, the present results have provided preliminary scientific evidence for the development of antimicrobial products, and further studies and clinical trials need to be performed.

Oral dysbiosis induced by Porphyromonas gingivalis is strain-dependent in mice

ABSTRACT Background: Porphyromonas gingivalis strain W83, one of the most widely investigated, is considered virulent in the context of periodontitis. The recently isolated P. gingivalis TDC60 has been reported to be highly pathogenic, although it has not yet been investigated in a mouse periodontitis model by oral gavage. Aim: Our aim was to compare the virulence of both strains by evaluating their impact on alveolar bone loss and the composition of oral microbiota. Methods: We inoculated by oral gavage C57BL/6 mice with either one of the two P. gingivalis strains and compared to a sham-treated group, without antibiotics pre-treatment. The mandibular alveolar bone of treated mice and controls were assessed, one month after the final inoculation, by microCT measurements. Moreover, at this time, we characterized their oral microbiota by 16S rRNA gene sequencing. Results: While P. gingivalis W83 successfully initiated periodontitis, TDC60-treated mice only experienced moderate lesions. Furthermore, only W83-treated mice exhibited a specific distinct microbiota, with significantly lower richness and evenness than other samples, and decreased proportions of taxa usually found in healthy individuals. Conclusion: This association between alveolar bone loss and a major persistent shift of the oral microbiota gives insights into virulence discrepancies among these bacterial strains.

Antimicrobial efficacy of 0.8% Hyaluronic Acid and 0.2% Chlorhexidine against Porphyromonas gingivalis strains: An in-vitro study.

Objective:The aim of the present in-vitro study was to assess antimicrobial efficacy of 0.8% hyaluronic acid (HA) and 0.2% Chlorhexidine gluconate (CHX) against Porphyromonas gingivalis (P. gingivalis).Methods:The study was performed between December 2018 and March 2019 at the College of Dentistry at the Princess Nourah Bint Abdulrahman University, Riyadh, Saudi Arabia. The P. gingivalis biofilms were formed and grown for 72 hours at 37°C under anaerobic conditions on glass slides coated with human saliva. The slides were individually positioned and exposed to 0.8% HA or 0.2% CHX. Therapeutically, the biofilms were divided into 3 groups as follows: (a) negative group; (b) 0.8% HA group and (c) 0.2% CHX group. P-values less than 0.05 were considered statistically significant.Results:In the 0.8% HA group, P. gingivalis CFUs/ml were significantly higher at baseline than at 24- (P<0.05), 48 (P<0.05) and 72 hours (P<0.05) intervals. In the 0.2% CHX group, P. gingivalis CFUs/ml were significantly higher at baseline than at 72 hours interval (P<0.05). In the CHX group, there was no difference in P. gingivalis CFUs/ml between baseline, 24- and 48-hours intervals. At 48- and 72-hours intervals, the P. gingivalis CFUs/ml were significantly higher in the 0.2% CHX group compared with the 0.8% HA group.Conclusion:In-vitro, 0.8% HA is more effective in reducing the P. gingivalis CFUs/ml compared with 0.2% CHX.

Antibiotic Susceptibility Patterns of Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis Strains from Different Decades.

The aim of this study was to determine the antibiotic susceptibility patterns of 57 Aggregatibacter actinomycetemcomitans and 56 Porphyromonas gingivalis strains isolated from subgingival biofilm samples of periodontitis patients in Switzerland from 1980 to 2017. The minimal inhibitory concentrations (MIC) of the most commonly used antibiotics in periodontal therapy (amoxicillin, metronidazole, azithromycin, and doxycycline) or in severe body infections (amoxicillin/clavulanic acid, clindamycin, ertapenem, and moxifloxacin) were determined. Furthermore, all the strains were screened for beta-lactamase activity and the presence of selected resistance genes (cfxA, ermF, and tetQ). Overall, there was no significant increase in MIC values over the 37‑year period. Two of the most recent P. gingivalis isolates yielded the highest MIC values. The first isolate was ermF-positive with MIC values >8 µg/mL, 2 µg/mL, and 0.25 µg/mL for clindamycin, azithromycin, and moxifloxacin, respectively. The second isolate showed a high MIC value of 4 µg/mL for moxifloxacin, which was associated with a confirmed single-point mutation in the quinolone resistance-determining region (QRDR) of the gyrA gene. Although there was no significant increase in the antibiotic resistance among the oral bacterial isolates tested, the detection of resistant P. gingivalis isolates underlines the need to optimize the antibiotic therapeutic protocols in dentistry.

The Distinct Immune-Stimulatory Capacities of Porphyromonas gingivalis Strains 381 and ATCC 33277 Are Determined by the fimB Allele and Gingipain Activity.

The Porphyromonas gingivalis strain ATCC 33277 (33277) and 381 genomes are nearly identical. However, strain 33277 displays a significantly diminished capacity to stimulate host cell Toll-like receptor 2 (TLR2)-dependent signaling and interleukin-1β (IL-1β) production relative to 381, suggesting that there are strain-specific differences in one or more bacterial immune-modulatory factors. Genomic sequencing identified a single nucleotide polymorphism in the 33277 fimB allele (A→T), creating a premature stop codon in the 33277 fimB open reading frame relative to the 381 fimB allele. Gene exchange experiments established that the 33277 fimB allele reduces the immune-stimulatory capacity of this strain. Transcriptome comparisons revealed that multiple genes related to carboxy-terminal domain (CTD) family proteins, including the gingipains, were upregulated in 33277 relative to 381. A gingipain substrate degradation assay demonstrated that cell surface gingipain activity is higher in 33277, and an isogenic mutant strain deficient for the gingipains exhibited an increased ability to induce TLR2 signaling and IL-1β production. Furthermore, 33277 and 381 mutant strains lacking CTD cell surface proteins were more immune-stimulatory than the parental wild-type strains, consistent with an immune-suppressive role for the gingipains. Our data show that the combination of an intact fimB allele and limited cell surface gingipain activity in P. gingivalis 381 renders this strain more immune-stimulatory. Conversely, a defective fimB allele and high-level cell surface gingipain activity reduce the capacity of P. gingivalis 33277 to stimulate host cell innate immune responses. In summary, genomic and transcriptomic comparisons identified key virulence characteristics that confer divergent host cell innate immune responses to these highly related P. gingivalis strains.

“Lemon grass oil mouth wash- A natural alternative”

Aim and Objective: The objective of the study was to evaluate the anti-plaque efficacy of lemongrass oil mouthwash. It also assessed the antibacterial properties of lemon grass oil against Prevotella intermedia (Pi), Porphyromonas gingivalis (Pg), and Aggregatibacter actinomycetemcomitans (Aa) in vitro. Materials and Methods: Forty-five periodontally healthy subjects between the age group of 18 and22 years were enrolled in a 4-day plaque re-growth study. Subjects were divided into three groups, i.e., 15 in each group. Mouthwashes were labelled as A (0.25% lemongrass oil mouthwash), B (0.2% Chlorhexidine mouthwash) and C (placebo). Subjects were advised to refrain from any kind of mechanical oral hygiene procedure for four days. Plaque index (PI) was evaluated at baseline and on the fifth day. In vitro testing of lemon grass oil mouthwash was done against strains of Prevotella intermedia, Porphyromonas gingivalis, and Aggregatibactor actinomycetemcomitans, to evaluate the antimicrobial concentration of lemon grass oil mouthwash. Results: PI significantly increased from day 1 to day 5 (P &lt; 0.05) in Groups A, B, and C. In inter-group comparison, there was a statistically significant difference between the three groups. However, chlorhexidine showed superior antiplaque activity. Lemon grass also demonstrated antiplaque activity, however, not as superior as chlorhexidine. In vitro test, lemon grass showed effective inhibition against all three bacterial strains Pi, Pg, and Aa at 0.01% concentration. Conclusion: Lemongrass oil mouthwash potently inhibits plaque formation and hence can be used as a natural herbal alternative. Key Words: lemongrass oil, antiplaque, antibacterial, chlorhexidine.

PgFur participates differentially in expression of virulence factors in more virulent A7436 and less virulent ATCC 33277 Porphyromonas gingivalis strains

BackgroundPorphyromonas gingivalis is considered a keystone pathogen responsible for chronic periodontitis. Although several virulence factors produced by this bacterium are quite well characterized, very little is known about regulatory mechanisms that allow different strains of P. gingivalis to efficiently survive in the hostile environment of the oral cavity, a typical habitat characterized by low iron and heme concentrations. The aim of this study was to characterize P. gingivalis Fur homolog (PgFur) in terms of its role in production of virulence factors in more (A7436) and less (ATCC 33277) virulent strains.ResultsExpression of a pgfur depends on the growth phase and iron/heme concentration. To better understand the role played by the PgFur protein in P. gingivalis virulence under low- and high-iron/heme conditions, a pgfur-deficient ATCC 33277 strain (TO16) was constructed and its phenotype compared with that of a pgfur A7436-derived mutant strain (TO6). In contrast to the TO6 strain, the TO16 strain did not differ in the growth rate and hemolytic activity compared with the ATCC 33277 strain. However, both mutant strains were more sensitive to oxidative stress and they demonstrated changes in the production of lysine- (Kgp) and arginine-specific (Rgp) gingipains. In contrast to the wild-type strains, TO6 and TO16 mutant strains produced larger amounts of HmuY protein under high iron/heme conditions. We also demonstrated differences in production of glycoconjugates between the A7436 and ATCC 33277 strains and we found evidence that PgFur protein might regulate glycosylation process. Moreover, we revealed that PgFur protein plays a role in interactions with other periodontopathogens and is important for P. gingivalis infection of THP-1-derived macrophages and survival inside the cells. Deletion of the pgfur gene influences expression of many transcription factors, including two not yet characterized transcription factors from the Crp/Fnr family. We also observed lower expression of the CRISPR/Cas genes.ConclusionsWe show here for the first time that inactivation of the pgfur gene exerts a different influence on the phenotype of the A7436 and ATCC 33277 strains. Our findings further support the hypothesis that PgFur regulates expression of genes encoding surface virulence factors and/or genes involved in their maturation.

PHOTOTOXIC EFFECT OF VISIBLE BLUE LIGHT ON AGGREGATIBACTER ACTINOMYCETEMCOMITANS AND PORPHYROMONAS GINGIVALIS ISOLATED FROM PATIENTS WITH CHRONIC PERIODENTITIS: AN IN-VITRO EXPERIMENTAL STUDY

Chronic periodentitis is a quite common disease in adult patients characterized by pocket formation and/or recession while progressive loss of periodontal attachment occurs slowly to moderately local risk factors, e.g. bacterial plaque. Wide array of microorganisms have been associated with periodontal disease, out of which Aggregatibacter actinomycetemcomitans (Aa) and Porphyromonas gingivalis (Pg) have been predominantly associated with periodontal diseases. The objectives of this study were to determine phototoxic effect of visible blue light on Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis clinical isolates from chronic periodentitis patients, and to study their antibiotic sensitivity against selected antibiotics. The test was carried out on 15 strains of Aggregatibacter actinomycetemcomitans and 15 strains of Porphyromonas gingivalis isolated from pockets of chronic periodentitis patients aged between 30-50 years old with pocket depths of 5-6 mm. The bacteria cultured, isolated, and identified by standard bacteriological methods, then subjected to visible blue light at different periods of time exposures. After light exposure, the bacterial killing rates were calculated from colony forming unit (CFU) counts after 48hours of anaerobic incubation. There was a decrease in CFU for both microorganisms as we proceeded from zero, 20, 40 and 60 seconds of blue light exposure. In conclusions, there was a phototoxic effect for the visible blue light emitted from the light curing device against the anaerobic periodontal pathogens and blue light exposure is effective in reducing periodontal pathogens. It is recommended that an adjunctive exogenous photosensitizer be used and that pathogens be exposed to visible light for clinical antimicrobial periodontal therapy.

In vitro biofilm formation on different ceramic biomaterial surfaces: Coating with two bactericidal glasses

ObjectivesTo compare biofilm formation on the surface of different ceramic biomaterials to be used in implant dentistry. MethodsIn vitro biofilm formation was investigated from mixtures of standard reference strains of Streptococcus oralis, Veillonella parvula, Actinomyces naeslundii, Fusobacterium nucleatum, Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis. Sterile ceramic calcium hydroxyapatite discs (HA) as control, sterile Al2O3/Ce-TZP nanocomposite sandblasted discs (material A1) and sterile Al2O3/Ce-TZP nanocomposite sandblasted discs and coated with two types of antimicrobial glasses (materials A2 and A3) were used. Biofilms were grown on the four surfaces and evaluated after 12, 24, 48 and 72 h of incubation. Biofilms were examined by confocal laser scanning microscopy (CLSM). In addition, counts of live bacterial cells of the target species A. actinomycetemcomitans, F. nucleatum and P. gingivalis were calculated by quantitative polymerase chain reaction (qPCR) combined with propidium monoazide (PMA). For data analysis, bacterial counts were compared with a multivariate general lineal model. ResultsUsing CLSM, cell vitality decreased in A2 and A3. With qPCR-PMA, significant differences in vitality were observed forA. actinomycetemcomitans in A3 after 48 and 72 h of incubation. With respect to the development of the biofilms, a significant increase in counts on HA and materials A1 and A2 was observed for A. actinomycetemcomitans and F. nucleatum. Conversely, for P. gingivalis, no differences were found for HA and materials A1 and A2. SignificanceDifferences in biofilm formation were detected among the different tested materials. The ceramic material A3 has an effect on the vitality of A. actinomycetemcomitans growing in an in vitro biofilm model.