Inhibition of Porphyromonas gingivalis biofilm by oxantel

Fumarate and nitrite reduction by Prevotella nigrescens and Prevotella buccae isolated from Chronic Periodontitis patients

OBJECTIVE

This study is an investigation of anaerobic nitrite and fumarate reduction/respiration abilities of two characterised Prevotella species namely Prevotella nigrescens (SS6B) and Prevotella buccae (GS6B) isolated from the periodontal pockets of chronic periodontitis (ChP) patients.

METHODS

Isolation and identification of the periodontal bacteria from 20 patients showing clinical symptoms of ChP. Characterisation of anaerobic nitrite and fumarate reduction was done in P. nigrescens (SS6B) and P. buccae (GS6B) using reduction assays, inhibition assays with use of specific inhibitors, growth assays and enzyme activity assays. Degenerate PCR was used to detect and amplify nitrite reductase (nrfA) and fumarate reductase (frdA) gene sequences in these Prevotella isolates. In addition, molecular and in silico analysis of the amplified anaerobic reductase gene sequences was performed using NCBI conserved domain analysis, Interpro database and MegaX.

RESULTS

We provided experimental evidence for presence of active nitrite and fumarate reductase activities through enzyme activity, reduction, inhibitor and growth assays. Moreover, we were able to detect presence of 505 bps nrfA gene fragment and 400 bps frdA gene fragment in these Prevotella spp. These fragments show similarity to multiheme ammonia forming cytochrome c nitrite reductases and fumarate reductases flavoprotein subunit, respectively.

CONCLUSION

Anaerobic nitrite and fumarate respiration abilities in P. nigrescens and P. buccae isolates appear to be important for detoxification process and growth, respectively.

In Vitro and In Vivo Anti-Inflammatory Effects of TEES-10®, a Mixture of Ethanol Extracts of Ligularia stenocephala Matsum. & Koidz. and Secale cereale L. Sprout, on Gingivitis and Periodontitis

Gingivitis and periodontitis are inflammatory disorders caused by dental plaque and calculus. These disorders often lead to tooth loss if not treated properly. Although antibiotics can be used, it is hard to treat them due to the difficulty in supplying effective doses of antibiotics to lesion areas and side effects associated with long-term use of antibiotics. In the present study, attempts were made to provide in vitro and in vivo evidence to support anti-inflammatory activities of TEES-10^®, a mixture of ethanol extracts of Ligularia stenocephala (LSE) and Secale cereale L. sprout (SCSE) toward gingivitis and periodontitis by performing the following experiments. TEES-10^® with a ratio of 6:4 (LSE:SCSE) showed the best effects in both stimulating the viability and inhibiting the cytotoxicity. In in vitro experiments, TEES-10^® showed an ability to scavenge 2,2-diphenyl-1-picrylhydrazyl and superoxide radicals and remove ROS generated in periodontal ligament cells treated with lipopolysaccharide. TEES-10^® also enhanced the viability of stem cells from human exfoliated deciduous teeth and stimulated the osteogenic differentiation of deciduous teeth cells. In in vivo experiments using rats with induced periodontitis, TEES-10^® significantly decreased inflammatory cell infiltration and the numbers of osteoclasts, increased alveolar process volume and the numbers of osteoblasts, decreased serum levels of IL-1β and TNF-α (pro-inflammatory cytokines), and increased serum levels of IL-10 and IL-13 (anti-inflammatory cytokines). These results strongly support the theory that TEES-10^® has the potential to be developed as a health functional food that can treat and prevent gingival and periodontal diseases and improve dental health.

New approaches to combat Porphyromonas gingivalis biofilms

In nature, bacteria predominantly reside in structured, surface-attached communities embedded in a self-produced, extracellular matrix. These so-called biofilms play an important role in the development and pathogenesis of many infections, as they are difficult to eradicate due to their resistance to antimicrobials and host defense mechanisms. This review focusses on the biofilm-forming periodontal bacterium Porphyromonas gingivalis. Current knowledge on the virulence mechanisms underlying P. gingivalis biofilm formation is presented. In addition, oral infectious diseases in which P. gingivalis plays a key role are described, and an overview of conventional and new therapies for combating P. gingivalis biofilms is given. More insight into this intriguing pathogen might direct the development of better strategies to combat oral infections.

Biofilm formation of periodontal pathogens on hydroxyapatite surfaces: Implications for periodontium damage

Biofilm formation of periodontal pathogens on teeth surfaces promotes the progression of periodontal disease. Hence, understanding the mechanisms of bacterial attachment to the dental surfaces may inform strategies for the maintenance of oral health. Although hydroxyapatite (HA) is a major calcium phosphate component of teeth, effect of biofilm formation on HA surfaces remains poorly characterized. In this study, biofilm-forming abilities by the periodontal pathogens Aggregatibacter actinomycetemcomitans Y4 and Porphyromonas gingivalis 381 were investigated on dense and porous HAs that represent enamel and dentin surfaces, respectively. These experiments showed greater biofilm formation on porous HA, but differing attachment profiles and effects of the two pathogens. Specifically, while the detachment of A. actinomycetemcomitans Y4 biofilm was observed, P. gingivalis 381 biofilm increased with time. Moreover, observations of HA morphology following formation of A. actinomycetemcomitans Y4 biofilm revealed gaps between particles, whereas no significant changes were observed in the presence of P. gingivalis 381. Finally, comparisons of calcium leakage showed only slight differences between bacterial species and HA types and may be masked by bacterial calcium uptake. © 2016 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 104A: 2873-2880, 2016.

The Cytochrome bd Oxidase of Porphyromonas gingivalis Contributes to Oxidative Stress Resistance and Dioxygen Tolerance

Porphyromonas gingivalis is an etiologic agent of periodontal disease in humans. The disease is associated with the formation of a mixed oral biofilm which is exposed to oxygen and environmental stress, such as oxidative stress. To investigate possible roles for cytochrome bd oxidase in the growth and persistence of this anaerobic bacterium inside the oral biofilm, mutant strains deficient in cytochrome bd oxidase activity were characterized. This study demonstrated that the cytochrome bd oxidase of Porphyromonas gingivalis, encoded by cydAB, was able to catalyse O2 consumption and was involved in peroxide and superoxide resistance, and dioxygen tolerance.

Oxantel disrupts polymicrobial biofilm development of periodontal pathogens

Bacterial pathogens commonly associated with chronic periodontitis are the spirochete Treponema denticola and the Gram-negative, proteolytic species Porphyromonas gingivalis and Tannerella forsythia. These species rely on complex anaerobic respiration of amino acids, and the anthelmintic drug oxantel has been shown to inhibit fumarate reductase (Frd) activity in some pathogenic bacteria and inhibit P. gingivalis homotypic biofilm formation. Here, we demonstrate that oxantel inhibited P. gingivalis Frd activity with a 50% inhibitory concentration (IC50) of 2.2 μM and planktonic growth of T. forsythia with a MIC of 295 μM, but it had no effect on the growth of T. denticola. Oxantel treatment caused the downregulation of six P. gingivalis gene products and the upregulation of 22 gene products. All of these genes are part of a regulon controlled by heme availability. There was no large-scale change in the expression of genes encoding metabolic enzymes, indicating that P. gingivalis may be unable to overcome Frd inhibition. Oxantel disrupted the development of polymicrobial biofilms composed of P. gingivalis, T. forsythia, and T. denticola in a concentration-dependent manner. In these biofilms, all three species were inhibited to a similar degree, demonstrating the synergistic nature of biofilm formation by these species and the dependence of T. denticola on the other two species. In a murine alveolar bone loss model of periodontitis oxantel addition to the drinking water of P. gingivalis-infected mice reduced bone loss to the same level as the uninfected control.

Antibiotic susceptibility of Aggregatibacter actinomycetemcomitans JP2 in a biofilm

BACKGROUND

Localized aggressive periodontitis (LAgP) is an inflammatory disease associated with specific bacteria, particularly Aggregatibacter actinomycetemcomitans, which can result in early tooth loss. The bacteria grow as a biofilm known as subgingival plaque. Treatment includes mechanical debridement of the biofilm, often associated with empirical antibiotic treatment.

OBJECTIVE

The aims of this study were to test in vitro the sensitivity of A. actinomycetemcomitans JP2 during planktonic and biofilm growth to doxycycline and to the combination of metronidazole and amoxicillin, which are two antibiotic protocols commonly used in clinical practice.

DESIGN

Two in vitro biofilm models were used to test the effects of the antibiotics: a static 96-well plate assay was used to investigate the effect of these antibiotics on biofilm formation whilst a flow chamber model was used to examine the effect on established biofilms.

RESULTS

Of the antibiotics tested in this model system, doxycycline was most efficacious with a minimal inhibitory concentration (MIC) against planktonic cells of 0.21 mg/L and minimal biofilm inhibitory concentration (MBIC) of 2.10 mg/L. The most commonly prescribed antibiotic regimen, amoxicillin + metronidazole, was much less effective against both planktonic and biofilm cells with an MIC and MBIC of 12.0 mg/L and 20.2 mg/L, respectively. A single treatment of the clinically achievable concentration of 10 mg/L doxycycline to sparse A. actinomycetemcomitans biofilms in the flow chamber model resulted in significant decreases in biofilm thickness, biovolume, and cell viability. Dense A. actinomycetemcomitans biofilms were significantly more resistant to doxycycline treatment. Low concentrations of antibiotics enhanced biofilm formation.

CONCLUSION

A. actinomycetemcomitans JP2 homotypic biofilms were more susceptible in vitro to doxycycline than amoxicillin + metronidazole.

Are we any closer to beating the biofilm: novel methods of biofilm control

PURPOSE OF REVIEW

A multidisciplinary approach to the treatment and management of biofilms has resulted from the growing appreciation of the role that biofilms play in modern medicine. Conventional antimicrobial agents are generally ineffective against biofilms, and as a result novel laboratory-based and clinical strategies have emerged. The purpose of this review is to analyse the recent literature relating to novel treatment strategies targeting the growing spectrum of clinically relevant biofilms.

RECENT FINDINGS

Microscopy and molecular techniques have provided greater insights into identifying the key bacterial and fungal biofilm pathogens. Knowledge of these microorganisms has provided a foundation for the development of specific molecules, often microbial derived, with antimicrobial and/or biofilm disruptive properties, augmenting conventional antibiotics treatments. The validity of some such rationally designed therapeutics has been explored in clinical trials.

SUMMARY

Biofilms are inherently difficult to treat, and mechanical disruption is the mainstay of clinical management. With scientific progress in molecular microbiology, there is an abundance of newly discovered molecules and pathways, providing novel therapeutic and prophylactic targets.