Characterising healthy Australian oral microbiomes for 'super donor' selection.

OBJECTIVES: Among healthy people, we understand very little about the sociodemographic, lifestyle, and dental hygiene behaviours that shape their oral microbiota. This study investigates how sociodemographic, lifestyle and dental hygiene behaviours shape oral microbiota diversity and composition in an Australian population to better inform healthy oral microbiota donors for Oral Microbiota Transplantation (OMT). METHODS: The study comprised 93 healthy adults who underwent comprehensive oral examinations and questionnaires to assess their health status. Participants were excluded if they had any active systemic or oral disease. All completed a questionnaire containing information on socio-economic, lifestyle, behavioural, and oral health factors. Supragingival plaque was collected, and 16S ribosomal RNA (rRNA) amplicon sequencing was used to analyse microbial composition. Associations between the core microbiome, alpha- (within-sample), beta-diversity (between-sample) and an individual's co-variates were tested for statistical significance. A redundancy analysis (RDA), multivariate adonis, differential abundance and correlation analysis were performed to characterise which factors drive the variation in the healthy oral microbiome. RESULTS: Streptococcus and Corynebacterium were the most prevalent and abundant genera among healthy Australians. The alpha and beta diversity were higher among unemployed non-Australian-born students who consumed low carbohydrates, fat, and sugar and had not visited the dentist for over 12 months. Additionally, beta diversity was significantly higher among daily flossers who abstained from fluoride treatment and had high salivary pH, although no single factor explained >4 % of the total variation (R2= 0.042). Alloprevotella, Lachnosporacea, and Parvimonas were significantly abundant among non-Australians who did not visit the dentist within a year. The RDA analysis revealed associations between microbiome composition and factors such as high carbohydrate, sugar, and fat consumption, low fibre intake, and regular dental checks among Australian-born individuals. CONCLUSION: These findings indicate that alpha and beta diversity of the oral microbiome varied significantly with sociodemographic, lifestyle, and dietary factors, including non-Australian birthplaces, unemployment, diet, and infrequent dental visits. CLINICAL SIGNIFICANCE: These findings underscore the importance of considering diverse sociodemographic, lifestyle, and dietary factors in oral health management. Before microbiome transplantations, clinicians should account for individual characteristics that may be beneficial for shaping and maintaining optimal oral microbiome diversity and health.

Characterising the role of enolase in a stable Small Colony Variant of Staphylococcus aureus isolated from a diabetic foot infection patient with osteomyelitis.

The switch to alternate cell types by Staphylococcus aureus creates sub-populations even within an active population, that are highly resilient, tolerant to antibiotics and lack clinical symptoms of infection. These cells present a challenge for clinical treatment where even after initial intervention has seemingly cleared the infection, these alternate cell types persist within tissue to revert and cause disease. Small colony variants (SCV) are a cell type which facilitate persistent infection but clinically isolated SCVs are often unstable in laboratory conditions. We have isolated a pair of S. aureus isolates from an individual patient with osteomyelitis presenting with heterogenous phenotypes; a stable SCV (sSCV) and a SCV that reverts upon laboratory culturing to the usual, active and non-SCV cell type. Thus we are able use this pair to investigate and compare the genetic mechanisms that underlie the clinical variatons of SCV phenotype. The switch to the sSCV phenotype was associated with frameshift mutations in the enolase eno and the histidine kinase arlS. The phenoptye of the sSCV was an impeded growth dependent on amino acid catabolism and modulated biofilm. These mutations present potentially a new molecular mechanism which confer persistence within osteomyelitis.

Development of "Intelligent particles" for the treatment of dental caries.

Dental caries is one of the most prevalent non-communicable diseases worldwide, mediated by a multispecies biofilm that consists of high levels of acidogenic bacteria which ferment sugar to acid and cause teeth demineralization. Current treatment practice remains insufficient in addressing 1) rapid clearance of therapeutic agents from the oral environment 2) destroying bacteria that contribute to the healthy oral microbiome. In addition, increasing concerns over antibiotic resistance calls for innovative alternatives. In this study, we developed a pH responsive nano-carrier for delivery of polycationic silver nanoparticles. Branched-PEI capped silver nanoparticles (BPEI-AgNPs) were encapsulated in a tannic acid - Fe (III) complex-modified poly(D,L-lactic-co-glycolic acid) (PLGA) particle (Fe(III)-TA/PLGA@BPEI-AgNPs) to enhance binding to the plaque biofilm and demonstrate "intelligence" by releasing BPEI-AgNPs under acidic conditions that promote dental caries The constructed Fe(III)-TA/PLGA@BPEI-AgNPs (intelligent particles - IPs) exhibited significant binding to an axenic S. mutans biofilm grown on hydroxyapatite. Ag+ ions were released faster from the IPs at pH 4.0 (cariogenic pH) compared to pH 7.4. The antibiofilm results indicated that IPs can significantly reduce S. mutans biofilm volume and viability under acidic conditions. Cytotoxicity on differentiated Caco-2 cells and human gingival fibroblasts indicated that IPs were not cytotoxic. These findings demonstrate great potential of IPs in the treatment of dental caries.

Development of an in vitro biofilm model of the human supra-gingival microbiome for Oral microbiome transplantation.

The high prevalence of dental caries and periodontal disease place a significant burden on society, both socially and economically. Recent advances in genomic technologies have linked both diseases to shifts in the oral microbiota - a community of >700 bacterial species that live within the mouth. The development of oral microbiome transplantation draws on the success of fecal microbiome transplantation for the treatment of gut pathologies associated with disease. Many current in vitro oral biofilm models have been developed but do not fully capture the complexity of the oral microbiome which is required for successful OMT. To address this, we developed an in vitro biofilm system that maintained an oral microbiome with 252 species on average over 14 days. Six human plaque samples were grown in 3D printed flow cells on hydroxyapatite discs using artificial saliva medium (ASM). Biofilm composition and growth were monitored by high throughput sequencing and confocal microscopy/SEM, respectively. While a significant drop in bacterial diversity occurred, up to 291 species were maintained in some flow cells over 14 days with 70% viability grown with ASM. This novel in vitro biofilm model represents a marked improvement on existing oral biofilm systems and provides new opportunities to develop oral microbiome transplant therapies.

pH-Responsive Biomaterials for the Treatment of Dental Caries-A Focussed and Critical Review.

Dental caries is a common and costly multifactorial biofilm disease caused by cariogenic bacteria that ferment carbohydrates to lactic acid, demineralizing the inorganic component of teeth. Therefore, low pH (pH 4.5) is a characteristic signal of the localised carious environment, compared to a healthy oral pH range (6.8 to 7.4). The development of pH-responsive delivery systems that release antibacterial agents in response to low pH has gained attention as a targeted therapy for dental caries. Release is triggered by high levels of acidogenic species and their reduction may select for the establishment of health-associated biofilm communities. Moreover, drug efficacy can be amplified by the modification of the delivery system to target adhesion to the plaque biofilm to extend the retention time of antimicrobial agents in the oral cavity. In this review, recent developments of different pH-responsive nanocarriers and their biofilm targeting mechanisms are discussed. This review critically discusses the current state of the art and innovations in the development and use of smart delivery materials for dental caries treatment. The authors' views for the future of the field are also presented.

The bacteriology of diabetic foot ulcers and infections and incidence of Staphylococcus aureus Small Colony Variants.

Introduction. Uninfected diabetes-related foot ulcer (DFU) progression to diabetes-related foot infection (DFI) is a prevalent complication for patients with diabetes. DFI often progresses to osteomyelitis (DFI-OM). Active (growing) Staphylococcus aureus is the most common pathogen in these infections. There is relapse in 40-60 % of cases even when the initial treatment at the DFI stage apparently clears infection.Hypothesis. S. aureus adopts the quasi-dormant Small Colony Variant (SCV) state during DFU and consequently infection, and when present in DFI cases also permits survival in non-diseased tissues as a reservoir to cause relapse.Aim. The aim of this study was to investigate the bacterial factors that facilitate persistent infections.Methodology. People with diabetes were recruited from two tertiary hospitals. Clinical and bacterial data was taken from 153 patients with diabetes (51 from a control group with no ulcer or infection) and samples taken from 102 patients with foot complications to identify bacterial species and their variant colony types, and then compare the bacterial composition in those with uninfected DFU, DFI and those with DFI-OM, of whom samples were taken both from wounds (DFI-OM/W) and bone (DFI-OM/B). Intracellular, extracellular and proximal 'healthy' bone were examined.Results. S. aureus was identified as the most prevalent pathogen in diabetes-related foot pathologies (25 % of all samples). For patients where disease progressed from DFU to DFI-OM, S. aureus was isolated as a diversity of colony types, with increasing numbers of SCVs present. Intracellular (bone) SCVs were found, and even within uninfected bone SCVs were present. Wounds of 24 % of patients with uninfected DFU contained active S. aureus. All patients with a DFI with a wound but not bone infection had previously had S. aureus isolated from an infection (including amputation), representing a relapse.Conclusion. The presence of S. aureus SCVs in recalcitrant pathologies highlights their importance in persistent infections through the colonization of reservoirs, such as bone. The survival of these cells in intracellular bone is an important clinical finding supporting in vitro data. Also, there seems to be a link between the genetics of S. aureus found in deeper infections compared to those only found in DFU.

Subpopulations in Strains of Staphylococcus aureus Provide Antibiotic Tolerance.

The ability of Staphylococcus aureus to colonise different niches across the human body is linked to an adaptable metabolic capability, as well as its ability to persist within specific tissues despite adverse conditions. In many cases, as S. aureus proliferates within an anatomical niche, there is an associated pathology. The immune response, together with medical interventions such as antibiotics, often removes the S. aureus cells that are causing this disease. However, a common issue in S. aureus infections is a relapse of disease. Within infected tissue, S. aureus exists as a population of cells, and it adopts a diversity of cell types. In evolutionary biology, the concept of "bet-hedging" has established that even in positive conditions, there are members that arise within a population that would be present as non-beneficial, but if those conditions change, these traits could allow survival. For S. aureus, some of these cells within an infection have a reduced fitness, are not rapidly proliferating or are the cause of an active host response and disease, but these do remain even after the disease seems to have been cleared. This is true for persistence against immune responses but also as a continual presence in spite of antibiotic treatment. We propose that the constant arousal of suboptimal populations at any timepoint is a key strategy for S. aureus long-term infection and survival. Thus, understanding the molecular basis for this feature could be instrumental to combat persistent infections.

Preventing Peri-implantitis: The Quest for a Next Generation of Titanium Dental Implants.

Titanium and its alloys are frequently the biomaterial of choice for dental implant applications. Although titanium dental implants have been utilized for decades, there are yet unresolved issues pertaining to implant failure. Dental implant failure can arise either through wear and fatigue of the implant itself or peri-implant disease and subsequent host inflammation. In the present report, we provide a comprehensive review of titanium and its alloys in the context of dental implant material, and how surface properties influence the rate of bacterial colonization and peri-implant disease. Details are provided on the various periodontal pathogens implicated in peri-implantitis, their adhesive behavior, and how this relationship is governed by the implant surface properties. Issues of osteointegration and immunomodulation are also discussed in relation to titanium dental implants. Some impediments in the commercial translation for a novel titanium-based dental implant from "bench to bedside" are discussed. Numerous in vitro studies on novel materials, processing techniques, and methodologies performed on dental implants have been highlighted. The present report review that comprehensively compares the in vitro, in vivo, and clinical studies of titanium and its alloys for dental implants.

Functional mgrA Influences Genetic Changes within a Staphylococcus aureus Cell Population over Time.

Prolonged survival in the host-bacteria microenvironment drives the selection of alternative cell types in Staphylococcus aureus, permitting quasi-dormant sub-populations to develop. These facilitate antibiotic tolerance, long-term growth, and relapse of infection. Small Colony Variants (SCV) are an important cell type associated with persistent infection but are difficult to study in vitro due to the instability of the phenotype and reversion to the normal cell type. We have previously reported that under conditions of growth in continuous culture over a prolonged culture time, SCVs dominated a heterogenous population of cell types and these SCVs harbored a mutation in the DNA binding domain of the gene for the transcription factor, mgrA. To investigate this specific cell type further, S. aureus WCH-SK2-ΔmgrA itself was assessed with continuous culture. Compared to the wild type, the mgrA mutant strain required fewer generations to select for SCVs. There was an increased rate of mutagenesis within the ΔmgrA strain compared to the wild type, which we postulate is the mechanism explaining the increased emergence of SCV selection. The mgrA derived SCVs had impeded metabolism, altered MIC to specific antibiotics and an increased biofilm formation compared to non-SCV strain. Whole genomic sequencing detected single nucleotide polymorphisms (SNP) in phosphoglucosamine mutase glmM and tyrosine recombinase xerC. In addition, several genomic rearrangements were detected which affected genes involved in important functions such as antibiotic and toxic metal resistance and pathogenicity. Thus, we propose a direct link between mgrA and the SCV phenotype. IMPORTANCE Within a bacterial population, a stochastically generated heterogeneity of phenotypes allows continual survival against current and future stressors. The generation of a sub-population of quasi-dormant Small Colony Variants (SCV) in Staphylococcus aureus is such a mechanism, allowing for persistent or relapse of infection despite initial intervention seemingly clearing the infection. The use of continuous culture under clinically relevant conditions has allowed us to introduce time to the growth system and selects SCV within the population. This study provides valuable insights into the generation of SCV which are not addressed in standard laboratory generated models and reveals new pathways for understanding persistent S. aureus infection which can potentially be targeted in future treatments of persistent S. aureus infection.

Enterococcus faecalis V583 cell membrane protein expression to alkaline stress.

Enterococcus faecalis is able to adapt to alkaline conditions and is commonly recovered from teeth in which endodontic treatment has failed. The role that E. faecalis membrane proteins play in survival strategies to extreme alkaline conditions is unclear. We grew E. faecalis V583 in a chemostat at pH 8 and 11 at one-tenth the organism's relative maximum growth rate. Following membrane shaving, isotope-coding protein labels were added at the peptide level to samples and then combined. The relative proportion of membrane proteins were identified using LC-ESI mass spectrometry and MaxQuant analysis. Ratios of membrane proteins were log2 transformed, with proteins deviating by more than 1 SD of the mean considered to be up- or down-regulated. A total of six proteins were up-regulated in pH 11 including: EF0669 (polysaccharide biosynthesis family); EF1927 (glycerol uptake facilitator), and EF0114 (glycosyl hydrolase). A total of five proteins were down-regulated including: EF0108 (C4-dicarboxylate transporter); EF1838 (PTS system IIC component); EF0456 (PTS system IID component); and EF0022 (PTS mannose-specific IID component). In extreme alkaline conditions, the membrane proteins of E. faecalis seem to be involved in a shift of carbohydrate metabolism from the PTS system to glycerol, which supports the formation of a protective capsule protecting the cell.

Effect of Periodontal Interventions on Characteristics of the Periodontal Microbial Profile: A Systematic Review and Meta-Analysis.

Our systematic review aimed to evaluate the effect of periodontal interventions on the diversity and composition of periodontal microbiota assessed by high throughput sequencing (HTS) metagenomics analysis. An electronic search was conducted from database inception to November 2021. All clinical trials that evaluated the effect of periodontal interventions on the gingival microbiota through HTS were selected. The measures of alpha diversity, richness, Shannon diversity index, and the Chao1 index, were used as the primary outcome, whereas relative abundances of bacterial genera were considered as the secondary outcome. Overall, 24 studies were eligible for the systematic review, of which 13 studies were included in the meta-analysis. Periodontal intervention for the test group decreased Shannon diversity, richness, and Chao1 index (alpha diversity), as observed from baseline to post-treatment. The most common genera that increased after periodontal therapy were Rothia, Actinomyces, Streptococcus, Veillonella, and Hemophilus, whilst Porphyromonas, Tannerella, Fusobacterium, and Treponema decreased after periodontal therapy. Periodontal interventions may decrease the bacterial diversity and richness and alter the composition of oral microbiota in the short term. Periodontal microbiota signatures could potentially be used for the assessment of periodontal disease development, progression, and success of the intervention.

The central role of arginine in Haemophilus influenzae survival in a polymicrobial environment with Streptococcus pneumoniae and Moraxella catarrhalis.

Haemophilus influenzae, Streptococcus pneumoniae and Moraxella catarrhalis are bacterial species which frequently co-colonise the nasopharynx, but can also transit to the middle ear to cause otitis media. Chronic otitis media is often associated with a polymicrobial infection by these bacteria. However, despite being present in polymicrobial infections, the molecular interactions between these bacterial species remain poorly understood. We have previously reported competitive interactions driven by pH and growth phase between H. influenzae and S. pneumoniae. In this study, we have revealed competitive interactions between the three otopathogens, which resulted in reduction of H. influenzae viability in co-culture with S. pneumoniae and in triple-species culture. Transcriptomic analysis by mRNA sequencing identified a central role of arginine in mediating these interactions. Arginine supplementation was able to increase H. influenzae survival in a dual-species environment with S. pneumoniae, and in a triple-species environment. Arginine was used by H. influenzae for ATP production, and levels of ATP generated in dual- and triple-species co-culture at early stages of growth were significantly higher than the combined ATP levels of single-species cultures. These results indicate a central role for arginine-mediated ATP production by H. influenzae in the polymicrobial community.

Polycationic Silver Nanoclusters Comprising Nanoreservoirs of Ag+ Ions with High Antimicrobial and Antibiofilm Activity.

Silver-based nano-antibiotics are rapidly developing as promising alternatives to conventional antibiotics. Ideally, to remain potent against a wide range of drug-resistant and anaerobic bacteria, silver-based nano-antibiotics should easily penetrate through the bacterial cell walls and actively release silver ions. In this study, highly monodispersed, ultrasmall (<3 nm), polycationic silver nanoclusters (pAgNCs) are designed and synthesized for the elimination of a range of common Gram-negative and Gram-positive pathogens and their corresponding established and matured biofilms, including those composed of multiple species. The pAgNCs also show greatly enhanced antibacterial efficacy against anaerobic bacteria such as Fusobacterium nucleatum and Streptococcus sanguinis. These results demonstrate that the cationic nature facilitates better penetration to the bacterial cell membrane while the presence of a high percentage (>50%) of silver ions (i.e., Ag+ nanoreservoirs) on the cluster surface maintains their efficiency in both aerobic and anaerobic conditions. Significantly, the pAgNCs showed a strong capacity to significantly delay the development of bacterial resistance when compared to similar-sized negatively charged silver nanoparticles or conventional antibiotics. This study demonstrates a novel design strategy that can lay the foundation for the development of future highly potent nano-antibiotics effective against a broad spectrum of pathogens and biofilms needed in many everyday life applications and industries.

Development and characterization of an oral microbiome transplant among Australians for the treatment of dental caries and periodontal disease: A study protocol.

BACKGROUND: Oral microbiome transplantation (OMT) is a novel concept of introducing health-associated oral microbiota into the oral cavity of a diseased patient. The premise is to reverse the state of oral dysbiosis, and restore the ecological balance to maintain a stable homeostasis with the host immune system. This study will assess the effectiveness, feasibility, and safety of OMT using an interdisciplinary approach. METHODS/DESIGN: To find donors suitable for microbial transplantation, supragingival plaque samples will be collected from 600 healthy participants. Each sample (200µL) will subsequently be examined in two ways: 1) 100µL of the sample will undergo high-throughput 16S rRNA gene amplicon sequencing and shotgun sequencing to identify the composition and characterisation of a healthy supragingival microbiome, 2) the remaining 100µL of the plaque sample will be mixed with 25% artificial saliva medium and inoculated into a specialised in-vitro flow cell model containing a hydroxyapatite disk. To obtain sufficient donor plaque, the samples would be grown for 14 days and further analysed microscopically and sequenced to examine and confirm the growth and survival of the microbiota. Samples with the healthiest microbiota would then be incorporated in a hydrogel delivery vehicle to enable transplantation of the donor oral microbiota. The third step would be to test the effectiveness of OMT in caries and periodontitis animal models for efficacy and safety for the treatment of oral diseases. DISCUSSION: If OMTs are found to be successful, it can form a new treatment method for common oral diseases such as dental caries and periodontitis. OMTs may have the potential to modulate the oral microbiota and shift the ecological imbalances to a healthier state.

Disruption of Enterococcus Faecalis biofilms using individual and plasma polymer encapsulated D-amino acids.

OBJECTIVE: Our aim was to assess the anti-biofilm ability of previously unverified individual D-amino acids (DAAs), to produce plasma polymer encapsulated DAAs (PPEDAAs), to measure the shell thickness and subsequent release of DAAs, and to assess the effects of PPEDAAs on Enterococcus faecalis biofilms. MATERIALS AND METHODS: Microtitre tray assays were used to evaluate the effect of individual DAAs (D-leucine, D-methionine, D-tryptophan, and D-tyrosine) on E. faecalis biofilms of different maturity. A mixture and individual DAAs were encapsulated with a plasma polymer for 10, 20, 40, and 60 min. The shell thickness of PPEDAAs was analyzed by ultra-high-resolution scanning electron microscopy. The release of DAAs from the PPEDAAs encapsulated for 60 min was measured over 7 days using high-performance liquid chromatography. Static biofilms were used to assess the effect of PPEDAAs on E. faecalis biofilms. RESULTS: Individual DAAs reduced biofilm formation to various degrees, according to the DAA and the experimental times. The shell thicknesses of the PPEDAAs ranged between 31 and 76 nm and increased with encapsulation time. Diffusion of DAAs from the PPEDAAs occurred over 60 min for encapsulated D-leucine, D-methionine, and D-tyrosine and up to 7 days for D-tryptophan. PPEDAAs disrupted biofilms at every experimental time. CONCLUSIONS: PPEDAAs of various shell thickness can be produced with the proposed methodology, DAAs are subsequently released, and the anti-biofilm activity remains unaltered. CLINICAL RELEVANCE: Individual DAAs and PPEDAAs have anti-biofilm ability and can be considered as part of a biological strategy in endodontics.

Effects of Osmotic Stress and Sodium Hypochlorite on Endodontic Microbiota: An In-Vitro Study.

OBJECTIVE: To assess the effect of osmotic stress on various bacteria in a planktonic milieu and the effect of exposure to sodium hypochlorite (NaOCl) on the microbial cells previously subjected to osmotic stress. METHODS: Enterococcus faecalis, Streptococcus sanguinis, Fusobacterium nucleatum, Porphyromonas gingivalis and Prevotella intermedia were suspended as follows: Iso-osmotic group 0.9% NaCl; Hypo-osmotic group "ultrapure water"; Hyper-osmotic group 9% NaCl solution for 120 hours before exposure to 0.0001% NaOCl for 10 minutes. Quantitative analyses of viable cells were performed at 0 and 120 hours and after exposure to NaOCl to obtain colony forming units (CFU/mL). A linear mixed-effects model was used to find the association between mean CFU/mL (logarithmic transformation) and the interaction of solution Group and Time (P<0.001). RESULTS: F. nucleatum, P. gingivalis and P. intermedia did not survive after 24 hours in any of the solutions and were excluded from further testing. For S. sanguinis there were significant differences at each time interval, when holding solution group constant. After 120 hours, the Hyper-osmotic group presented with the highest CFU/mL and was significantly different to the Iso-osmotic group (P<0.001). For E. Faecalis, there was a significant difference for each pairwise comparison of time (P<0.001) in mean CFU/mL between 0 hours and 120 hours for the Iso-osmotic and Hyper-osmotic groups. At 120 hours, no significant differences were found between the three groups. Significant differences were also found between 0 hours and Post-NaOCl administration, and between 120 hours and Post-NaOCl administration for all three groups (P<0.001). Exposure to NaOCl after hypo-osmotic stress was associated with significantly less CFU/mL for S. sanguinis compared to hyperosmosis and iso-osmosis (P<0.001) and for E. Faecalis only compared to hyperosmosis (P<0.001). CONCLUSION: S. sanguinis and E. faecalis were able to withstand osmotic stress for 120 hours. Hypo-osmotic stress before contact with NaOCl was associated with lower viable bacterial numbers, when compared to the other media for the above species. Hyper-osmotic stress was associated with higher viable bacterial numbers after NaOCl exposure for E. faecalis.

Comparison of the Biocidal Efficacy of Sodium Dichloroisocyanurate and Calcium Hydroxide as Intracanal Medicaments over a 7-Day Contact Time: An Ex Vivo Study.

INTRODUCTION: The use of medicaments has been recommended for the treatment of root canal infection. This study evaluated the antimicrobial effect of a well-known biocidal agent, sodium dichloroisocyanurate (NaDCC), by comparing it with calcium hydroxide [Ca(OH)2] using an engineered 3-species biofilm root canal model. METHODS: Thirty-eight human single-rooted teeth were decoronated and chemomechanically prepared before inoculation using Enterococcus faecalis, Actinomyces viscosus, and Streptococcus mutans using a flow cell model for 4 weeks for biofilm formation. The samples were randomly divided into 3 groups: NaDCC (n = 12), Ca(OH)2 (n = 12), and positive control (no medicament, n = 14). The medicaments were placed using a Lentulo spiral. After a contact time of 7 days, the roots were crushed and plated on selective media. Bacterial identities were confirmed with the use of selective media. Colony-forming units were calculated (CFU/ml). Descriptive statistics (mean and standard deviations) were calculated. RESULTS: Seven-day dressing with NaDCC or Ca(OH)2 presented with no growth. For the positive control, the mean colony-forming units were 2.97E4 ± 3.42E4 (CFU/ml). All previously inoculated strains were recovered in the control group. CONCLUSIONS: NaDCC and Ca(OH)2 when used as intracanal medicaments were able to eradicate an engineered 3-species biofilm in single-rooted teeth in an ex vivo model. NaDCC deserves further investigation as an intracanal medicament.

Probiotic Lactobacillus Rhamnosus GG Protects Against P. Gingivalis And F. Nucleatum Gut Dysbiosis.

OBJECTIVES: This study investigated changes induced by Porphyromonas gingivalis and on gastrointestinal histology and gut microbiome in a mouse model of experimental periodontitis. The effect of probiotic Lactobacillus rhamnosus GG (LGG) in altering these changes was also investigated. METHODS: IThirty-six mice were allocated into six groups. Experimental alveolar bone loss was induced by oral inoculation with P. gingivalis and F. nucleatum. LGG was orally inoculated or orally gavaged. Gastrointestinal tissue changes were assessed using histological analysis and immunohistochemistry. Caecal microbiome was analysed by sequencing 16S rRNA genes of caecal content. RESULTS: Inoculation with P. gingivalis and F. nucleatum induced inflammation throughout gastrointestinal tract (p less than 0.05), increased expression of IL-6 in ileum (p = 0.052) and altered composition of caecal microbiome (p less than 0.05) in experimental mice compared to controls. Mice treated with LGG had reduced tissue inflammation in duodenum (p = 0.044) and lowered levels of IL-6 in ileum (p = 0.048) when compared with disease. LGG therapy influenced gut microbiome changes. CONCLUSION: P. gingivalis and F. nucleatum inoculation induced significant changes in intestinal inflammation and caecal microbiome. Oral gavage with LGG exerted a protective effect against intestinal inflammation and limited gut microbiome changes associated with P. gingivalis and F. nucleatum.

Novel Research Models for Staphylococcus aureus Small Colony Variants (SCV) Development: Co-pathogenesis and Growth Rate.

Staphylococcus aureus remains a great burden on the healthcare system. Despite prescribed treatments often seemingly to be successful, S. aureus can survive and cause a relapsing infection which cannot be cleared. These infections are in part due to quasi-dormant sub-population which is tolerant to antibiotics and able to evade the host immune response. These include Small Colony Variants (SCVs). Because SCVs readily revert to non-SCV cell types under laboratory conditions, the characterization of SCVs has been problematic. This mini-review covers the phenotypic and genetic changes in stable SCVs including the selection of SCVs by and interactions with other bacterial species.

Efficacy of laser and ultrasonic-activated irrigation on eradicating a mixed-species biofilm in human mesial roots.

This study investigated the efficacy of Er,Cr:YSGG laser and ultrasonic activated irrigation on eradicating a mixed-species biofilm grown in root canals with complex anatomy. The biofilm was grown over 4-weeks in the root canals of decoronated human mandibular molar teeth. Control roots received no further treatment. The remaining roots were chemomechanically prepared using different irrigating protocols: 4% NaOCl and 15% EDTAC with ultrasonic activated irrigation and laser activated irrigation using power settings of 0.5 W and 0.75 W. Cellular viability was determined using serial plating. One tooth from each group was subjected to qualitative SEM analysis. Quantification by culturing revealed significant differences between control group and all other treatment groups. This study demonstrated that chemomechanical irrigation with laser and ultrasonic activated irrigation significantly reduced the bacterial load from complex root canal systems; however, there were no significant differences found between the experimental groups.