Influence of keratinized mucosa width on the resolution of peri-implant mucositis: A prospective cohort study.

BACKGROUND: The prevalence of peri-implant diseases, driven by biofilm accumulation and influenced by factors such as the width of keratinized mucosa (KM), underscores the need for understanding their etiology and management. PURPOSE: To evaluate the association between the KM width and the clinical resolution of peri-implant mucositis after mechanical therapy. MATERIALS AND METHODS: Patients with an implant diagnosed with peri-implant mucositis were allocated to two groups: wide band of KM (WKM ≥ 2 mm) and narrow/no band of KM (NKM < 2 mm). Data and submucosa biofilm were collected at baseline and at 8, 12, and 24 weeks after nonsurgical therapy. A Brunner-Langer model was estimated for longitudinal data to evaluate and compare changes in any clinical parameter throughout follow-up between both groups. Furthermore, the microbial profiles were evaluated by 16S rRNA gene sequencing. RESULTS: A total of 38 implants were analyzed. At 24 weeks, bleeding on probing was substantially reduced in both groups, reaching statistical significance (p < 0.001). Treatment resulted in 23.9% less effective in achieving success for NKM. As such, NKM reduced the odds of disease resolution by 80% compared to WKM. The rest of the explored clinical parameters yielded more favorable outcomes for WKM versus NKM. Neither the alpha nor the beta diversity of the microbial profiles were significantly modulated by KM. CONCLUSIONS: KM width influences the clinical resolution of peri-implant mucositis after mechanical therapy (https://clinicaltrials.gov/study/NCT04874467?cond=keratinized%20mucosa&rank=8, NCT04874467, 04/30/2021).

Oral microbiota of adolescents with dental caries: A systematic review.

OBJECTIVE: This systematic review summarizes the current knowledge on the association between the oral microbiota and dental caries in adolescents. DESIGN: An electronic search was carried out across five databases. Studies were included if they conducted research on generally healthy adolescents, applied molecular-based microbiological analyses and assessed caries status. Data extraction was performed by two reviewers and the Newcastle-Ottawa Scale was applied for quality assessment. RESULTS: In total, 3935 records were reviewed which resulted in a selection of 20 cross-sectional studies (published 2005-2022) with a sample size ranging from 11 to 614 participants including adolescents between 11 and 19 years. The studies analyzed saliva, dental biofilm or tongue swabs with Checkerboard DNA-DNA hybridization, (q)PCR or Next-Generation Sequencing methods. Prevotella denticola, Scardoviae Wiggsiae, Streptococcus sobrinus and Streptococcus mutans were the most frequently reported species presenting higher abundance in adolescents with caries. The majority of the studies reported that the microbial diversity was similar between participants with and without dental caries. CONCLUSION: This systematic review is the first that shows how the oral microbiota composition in adolescents appears to differ between those with and without dental caries, suggesting certain taxa may be associated with increased caries risk. However, there is a need to replicate and expand these findings in larger, longitudinal studies that also focus on caries severity and take adolescent-specific factors into account.

Cetylpyridinium Chloride-Containing Mouthwashes Show Virucidal Activity against Herpes Simplex Virus Type 1.

The oral cavity is particularly susceptible to viral infections that are self-recovering in most cases. However, complications may appear in severe cases and/or immunocompromised subjects. Cetylpyridinium chloride (CPC)-containing mouthwashes are able to decrease the infectivity of the SARS-CoV-2 virus by disrupting the integrity of the viral envelope. Here, we show that CPC, as the active ingredient contained in commercialized, exerts significant antiviral activity against enveloped viruses, such as HSV-1, but not against non-enveloped viruses, such as HPV. CPC-containing mouthwashes have been used as antiseptics for decades, and thus, they can represent a cost-effective measure to limit infection and spread of enveloped viruses infecting the oral cavity, aiding in reducing viral transmission.

Bacterial Adhesion of TESPSA and Citric Acid on Different Titanium Surfaces Substrate Roughness: An In Vitro Study with a Multispecies Oral Biofilm Model.

This in vitro study analyzed the influence of substrate roughness on biofilm adhesion and cellular viability over triethoxysilylpropyl succinic anhydride silane (TESPSA)- and citric acid (CA)-coated surfaces at 12 and 24 h, respectively. A multispecies biofilm composed of S. oralis, A. naslundii, V. parvula, F. nucleatum, P. intermedia, P. gingivalis, P. endodontalis and F. alocis was developed over titanium discs grouped depending on their roughness (low, medium, high) and antibacterial coating (low-TESPSA, medium-TESPSA, high-TESPSA, and CA). The biofilm was quantified by means of quantitative polymerase chain reaction (PCR) and viability PCR and assessed through confocal laser scanning microscope (CLSM). Quantitative PCR revealed no significant differences in bacterial adhesion and biofilm mortality. CA was the surface with the lowest bacterial counts and highest mortality at 12 and 24 h, respectively, while high harbored the highest amount of biofilm at 24 h. By CLSM, CA presented significant amounts of dead cells compared to medium-TESPSA and high-TESPSA. A significantly greater volume of dead cells was found at 12 h in low-TESPSA compared to medium-TESPSA, while CA also presented significant amounts of dead cells compared to medium-TESPSA and high-TESPSA. With regard to the live/dead ratio, low-TESPSA presented a significantly higher ratio at 12 h compared to medium-TESPSA and high-TESPSA. Similarly, CA exhibited a significantly higher live/dead ratio compared to medium-TESPSA and high-TESPSA at 12 h. This multispecies in vitro biofilm did not evidence clear antiadhesive and bactericidal differences between surfaces, although a tendency to reduce adhesion and increase antibacterial effect was observed in the low-TESPSA and CA.

Reducing opioid use for chronic non-cancer pain in primary care using an evidence-based, theory-informed, multistrategic, multistakeholder approach: a single-arm time series with segmented regression.

BACKGROUND: Many countries have high opioid use among people with chronic non-cancer pain. Knowledge about effective interventions that could be implemented at scale is limited. We designed a national intervention that included audit and feedback, deprescribing guidance, information on catastrophising assessment, pain neuroscience education and a cognitive tool for use by patients with their healthcare providers. METHOD: We used a single-arm time series with segmented regression to assess rates of people using opioids before (January 2015 to September 2017), at the time of (October 2017) and after the intervention (November 2017 to August 2019). We used a cohort with historical comparison group and log binomial regression to examine the rate of psychologist claims in opioid users not using psychologist services prior to the intervention. RESULTS: 13 968 patients using opioids, 8568 general practitioners, 8370 pharmacies and accredited pharmacists and 689 psychologists were targeted. The estimated difference in opioid use was -0.51 persons per 1000 persons per month (95% CI -0.69, -0.34; p<0.001) as a result of the intervention, equating to 25 387 (95% CI 24 676, 26 131) patient-months of opioid use avoided during the 22-month follow-up. The targeted group had a significantly higher rate of incident patient psychologist claims compared with the historical comparison group (rate ratio: 1.37, 95% CI 1.16, 1.63; p<0.001), equating to an additional 690 (95% CI 289, 1167) patient-months of psychologist treatment during the 22-month follow-up. CONCLUSIONS: Our intervention addressed the cognitive, affective and sensory factors that contribute to pain and consequent opioid use, demonstrating it could be implemented at scale and was associated with a reduction in opioid use and increasing utilisation of psychologist services.

Association of nine pathobionts with periodontitis in four South American and European countries.

Aim: Our aim was to compare the prevalence and load of nine pathobionts in subgingival samples of healthy individuals and periodontitis patients from four different countries. Methods: Five hundred and seven subgingival biofilm samples were collected from healthy subjects and periodontitis patients in Belgium, Chile, Peru and Spain. The prevalence and load of Eubacterium brachy, Filifactor alocis, Fretibacterium fastidiosum, Porphyromonas endodontalis, Porphyromonas gingivalis, Selenomonas sputigena, Treponema denticola, Tannerella forsythia and Treponema socranskii were measured by quantitative PCR. Results: The association with periodontitis of all species, except for T. socranskii, was confirmed in all countries but Peru, where only P. endodontalis, P. gingivalis and T. denticola were found to be significantly associated. Moreover, most species showed higher loads at greater CAL and PPD, but not where there was BOP. Through Principal Component Analysis, samples showed clearly different distributions by diagnosis, despite observing a smaller separation in Peruvian samples. Conclusions: Unlike prevalence, relative load was found to be a reliable variable to discriminate the association of the species with periodontitis. Based on this, F. alocis, P. endodontalis, P. gingivalis, T. denticola and T. forsythia may be biomarkers of disease in Belgium, Chile and Spain, due to their significantly higher abundance in periodontitis patients.

The quorum quenching enzyme Aii20J modifies in vitro periodontal biofilm formation.

Introduction: Recent studies have revealed the presence of N-acyl-homoserine lactones (AHLs) quorum sensing (QS) signals in the oral environment. Yet, their role in oral biofilm development remains scarcely investigated. The use of quorum quenching (QQ) strategies targeting AHLs has been described as efficient for the control of pathogenic biofilms. Here, we evaluate the use of a highly active AHL-targeting QQ enzyme, Aii20J, to modulate oral biofilm formation in vitro. Methods: The effect of the QQ enzyme was studied in in vitro multispecies biofilms generated from oral samples taken from healthy donors and patients with periodontal disease. Subgingival samples were used as inocula, aiming to select members of the microbiota of the periodontal pocket niche in the in vitro biofilms. Biofilm formation abilities and microbial composition were studied upon treating the biofilms with the QQ enzyme Aii20J. Results and Discussion: The addition of the enzyme resulted in significant biofilm mass reductions in 30 - 60% of the subgingival-derived biofilms, although standard AHLs could not be found in the supernatants of the cultured biofilms. Changes in biofilm mass were not accompanied by significant alterations of bacterial relative abundance at the genus level. The investigation of 125 oral supragingival metagenomes and a synthetic subgingival metagenome revealed a surprisingly high abundance and broad distribution of homologous of the AHL synthase HdtS and several protein families of AHL receptors, as well as an enormous presence of QQ enzymes, pointing to the existence of an intricate signaling network in oral biofilms that has been so far unreported, and should be further investigated. Together, our findings support the use of Aii20J to modulate polymicrobial biofilm formation without changing the microbiome structure of the biofilm. Results in this study suggest that AHLs or AHL-like molecules affect oral biofilm formation, encouraging the application of QQ strategies for oral health improvement, and reinforcing the importance of personalized approaches to oral biofilm control.

Precision public-health intervention for care coordination: a real-world study.

BACKGROUND: Health emergencies disproportionally affect vulnerable populations. Digital tools can help primary care providers find, and reach, the right patients. AIM: To evaluate whether digital interventions delivered directly to GPs' clinical software were more effective at promoting primary care appointments during the COVID-19 pandemic than interventions delivered by post. DESIGN AND SETTING: Real-world, non-randomised, interventional study involving GP practices in all Australian states. METHOD: Intervention material was developed to promote care coordination for vulnerable older veterans during the COVID-19 pandemic, and sent to GPs either digitally to the clinical practice software system or in the post. The intervention material included patient-specific information sent to GPs to support care coordination, and education material sent via post to veterans identified in the administrative claims database. To evaluate the impact of intervention delivery modalities on outcomes, the time to first appointment with the primary GP was measured; a Cox proportional hazards model was used, adjusting for differences and accounting for pre-intervention appointment numbers. RESULTS: The intervention took place in April 2020, during the first weeks of COVID-19 social distancing restrictions in Australia. GPs received digital messaging for 51 052 veterans and postal messaging for 26 859 veterans. The digital group was associated with earlier appointments (adjusted hazard ratio 1.38 [1.34 to 1.41]). CONCLUSION: Data-driven digital solutions can promote care coordination at scale during national emergencies, opening up new perspectives for precision public-health initiatives.

Bacterial decontamination of toothbrushes by immersion in a mouthwash containing 0.05% chlorhexidine and 0.05% cetylpyridinium chloride: A randomized controlled trial.

OBJECTIVE: Toothbrushes are colonized by microorganisms, implying a risk of infection. That risk can be reduced by decreasing the microbial contamination of the filaments. Therefore, this study aimed to determine the antiseptic efficacy of a 0.05% chlorhexidine + 0.05% cetylpyridinium chloride mouthwash on toothbrushes. METHODS: A total of twelve toothbrushes used three times/day for 14 days by orally and systemically healthy people were randomly split into two groups, and their heads were immersed for 2 h in PBS (control) or Perio·Aid Active Control (treatment). The microorganisms were recovered, and their number was calculated by culture, quantitative PCR, and viability PCR. Statistical differences were first assessed with a two-way mixed ANOVA and subsequently with Student's t-test. RESULTS: The results showed no statistical differences in the total number of cells for the treatment (mean ± CI95% of 7.27 ± 1.09 log10 bacteria/ml) and the control (7.62 ± 0.64 log10 bacteria/ml) groups, but a significantly lower number of live cells in the treatment group (4.58 ± 0.61 log10 viable bacteria/ml and 2.15 ± 1.42 log10 cfu/ml) than in the control group (6.49 ± 1.39 log10 viable bacteria/ml and 5.04 ± 0.93 log10 cfu/ml). CONCLUSIONS: Based on our findings, sanitization of toothbrushes with this mouthwash reduces the number of live microorganisms adhered to the filaments. Such decrease of the bacterial load could include bacteria from the oral cavity, from the environment, and from nearby toothbrushes since the quantification was not limited to any bacterial taxon.

Microbial profile of placentas from Tanzanian mothers with adverse pregnancy outcomes and periodontitis.

AIM: To investigate microbial profiles in placentas from a population of East African mothers with and without adverse pregnancy outcomes and with regard to their periodontal status. MATERIAL AND METHODS: Thirty-six placentas from pregnant women from Tanzania were classified into three groups according to both pregnancy outcome and the mother's periodontal health. The microbial composition in each group was then compared using 16S rRNA metagenomics. Additionally, placenta specimens were analyzed histologically for chorioamnionitis by a single pathologist blinded to the clinical data. RESULTS: The greatest differences were observed in the group of mothers with periodontitis. The microbial load was low in all three groups of mothers. Periodontitis had a notable influence on the structure of the placental microbiota. Three phyla and 44 genera were associated with periodontitis, whereas only the Tenericutes phylum was associated with the adverse pregnancy variable. Streptococcaceae and Mycoplasmataceae families were associated with both periodontitis and adverse pregnancy outcomes. Finally, although the differences for chorioamnionitis were not significant, this intra-amniotic infection was more frequent in the placentas from mothers with periodontitis. CONCLUSIONS: Our findings suggest that bacteria from the oral cavity may involve the feto-placental unit, and that periodontitis may be a modulating factor of the microbial community present in this niche.

A review of the sustainability of vaccine funding across Europe and implications for post-COVID policymaking.

BACKGROUND: Approaches to routine vaccine funding and the underlying budget-setting process vary greatly across European countries. The ongoing COVID-19 pandemic has put enormous pressure on healthcare systems, affecting resilience of the overall vaccine ecosystem. METHODS: This article reviews how vaccine budgets are structured across 8 European countries (England, Finland, France, Germany, Italy, Norway, Romania, and Spain). First a literature review of the landscape was undertaken, followed by expert interviews to review the findings and consider policy principles to secure prioritisation and sustainability of routine vaccination budgets post-COVID. RESULTS: The organisation of budgets and vaccine spending varies greatly across Europe. In 2/8 countries (France and Germany) vaccine spending is subsumed into a wider healthcare budget. In 2/8 countries (Italy and Romania) the budget differentiates public health and prevention spending from other areas of healthcare, though there is no standalone vaccine budget. In 4/8 countries (England, Finland, Norway and Spain) there is a standalone vaccine budget, however this may not cover all elements needed for immunisation delivery and is not always transparent. CONCLUSION: Ensuring adequate and dynamic country vaccine budgets, with horizon scanning approaches like in England and Finland, or flexible vaccines expenditures like Germany, would greatly help the timely availability of public funding for new vaccines and strengthen vaccines supply security in Europe through a more virtuous European vaccine ecosystem.

Impact of smoking on peri-implant bleeding on probing.

BACKGROUND: Studies around natural dentition demonstrated that smoking can reduce the tendency of inflamed tissue to bleed upon probing after controlling for possible confounders. In addition, previous research suggested that smokers may present alterations of the peri-implant microbiome. AIM: This study aimed at investigating the impact of smoking on: (1) peri-implant bleeding on probing (BOP; primary objective); (2) the association between BOP/bone loss and BOP/visible gingival inflammation; (3) peri-implant microbiome. METHODS: Partially edentulous patients with implants restored with a single crowns were included in this study. Subjects were either smokers (≥1 cigarettes per day) or nonsmokers (never smokers). The primary outcome of this cross-sectional study was BOP and secondary outcomes included: Probing pocket depth (PPD), Modified gingival Index (mGI) and Progressive Marginal Bone Loss. In addition, microbial profiles of the subjects were assessed through sequencing of the 16S rRNA gene. Univariate and multilevel multivariate analyses by means of Generalized Estimating Equations were conducted to analyze the association between smoking and peri-implant BOP. RESULTS: Overall, 27 nonsmokers and 27 smokers were included and 96.3% and 77.78% of patients presented peri-implant BOP in the nonsmoker and smoker group, respectively (p = 0.046). Smoking was inversely associated with BOP in the multivariate multilevel analysis (OR = 0.356; 95% CI: 0.193-0.660; p = 0.001) whereas a positive correlation was demonstrated for mGI > 0 (OR = 3.289; 95% CI: 2.014-5.371; p < 0.001); PPD (OR = 1.692; 95% CI: 0.263-0.883; p = 0.039) and gender (OR = 2.323; 95% CI: 1.310-4.120 p = 0.004). A decrease of BOP sensitivity in detecting visible gingival inflammation (mGI > 0) was observed in smokers. Besides, taxonomic and changes in diversity regarding the peri-implant microbiota were detected comparing the two groups. Significantly higher richness of the microbiota was demonstrated in the smoker group when implants affected by peri-implantitis were compared to either healthy implants or implants presenting mucositis. CONCLUSIONS: Smoking is a potential modifier of BOP and peri-implant microbiota.

Erythritol-enriched powder and oral biofilm regrowth on dental implants: an in vitro study / Polvo enriquecido con eritritol y crecimiento de biopelículas orales sobre implantes dentales: un estudio in vitro

Backgroud: Peri-implant mucositis and peri-implantitis are the main biological complications associated withdental implants. Since most authors agree that bacteria play a major etiological role, the main aims of this studywere to determine if a formulation of erythritol and chlorhexidine applied with an air polishing system inhibitsbiofilm re-growth over dental implants and to compare the decontamination capacity of this therapy with that ofmechanical removal by saline and gauze.Material and Methods: A multispecies biofilm (P. gingivalis, A. actinomycetemcomitans, F. nucleatum, A. naes-lundii, V. parvula and S. oralis) was grown for 14 days on 52 dental implants in an artificial mouth. These implantswere divided into three groups according to the applied treatment: 14 negative control (CON), 19 erythritol-chlorhexidine (ERY) and 19 gauze with saline (GAU) samples. Twelve dental implants from the ERY and GAUgroups and 8 implants from the CON group were re-incubated for 7 additional days after treatment. The bacterialcount was performed by quantitative polymerase chain reaction (qPCR) using propidium monoazide (PMA). Adescriptive and bivariate analysis of the data was performed.Results: The erythritol and chlorhexidine formulation significantly inhibited biofilm regrowth in comparison withthe mechanical treatment (GAU), since a significant decrease in all the species was observed in the ERY group(except for Aggregatibacter actinomycetemcomitans). The antibiofilm and antibacterial capacity of the two activetreatment groups (ERY and GAU) was similar for a 14 days multispecies in vitro biofilm, except for the lowercount of A. naeslundii in the GAU group. Conclusions: The use of erythritol powder with chlorhexidine applied with an air polishing system reduces biofilmregrowth over dental implants when compared with mechanical removal by saline and gauze. This effect might bebeneficial for patients included in peri-implant maintenance programs.(AU)

Responding to the Under-Utilisation of Necessary Health Care in the Time of COVID-19: A Precision Public Health intervention.

The Veterans' Medicines Advice and Therapeutics Education Services (MATES) program is a national data driven, behaviorally informed, health intervention to improve the use of medicines among Australian veterans. The program, which has been operating since 2004, has led the way in the use of government held data assets to generate evidenced-based health information, which, when provided to clinicians alongside educational materials, can make demonstrable improvements in health and promote practice change.

Impact of a patient-specific national programme aimed at increasing the use of emollient moisturisers to reduce the risk of skin tears: a longitudinal cohort study.

OBJECTIVES: To evaluate the impact of a patient-specific national programme targeting older Australians and health professionals that aimed to increase use of emollient moisturisers to reduce to the risk of skin tears. DESIGN: A prospective cohort intervention. PARTICIPANTS: The intervention targeted 52 778 Australian Government's Department of Veterans' Affairs patients aged over 64 years who had risk factors for wound development, and their general practitioners (GPs) (n=14 178). OUTCOME MEASURES: An interrupted time series model compared the rate of dispensing of emollients in the targeted cohort before and up to 23 months after the intervention. Commitment questions were included in self-report forms. RESULTS: In the first month after the intervention, the rate of claims increased 6.3-fold (95% CI: 5.2 to 7.6, p<0.001) to 10 emollient dispensings per 1000 patients in the first month after the intervention. Overall, the intervention resulted in 10 905 additional patient-months of treatment. The increased rate of dispensing among patients who committed to talking to their GP about using an emollient was six times higher (rate ratio: 6.2, 95% CI: 4.4 to 8.7) than comparison groups. CONCLUSIONS: The intervention had a sustained effect over 23 months. Veterans who responded positively to commitment questions had higher uptake of emollients than those who did not.

Acyl homoserine lactone-mediated quorum sensing in the oral cavity: a paradigm revisited.

Acyl homoserine lactones (AHLs), the quorum sensing (QS) signals produced by Gram-negative bacteria, are currently considered to play a minor role in the development of oral biofilm since their production by oral pathogens has not been ascertained thus far. However, we report the presence of AHLs in different oral samples and their production by the oral pathogen Porphyromonas gingivalis. The importance of AHLs is further supported by a very high prevalence of AHL-degradation capability, up to 60%, among bacteria isolated from dental plaque and saliva samples. Furthermore, the wide-spectrum AHL-lactonase Aii20J significantly inhibited oral biofilm formation in different in vitro biofilm models and caused important changes in bacterial composition. Besides, the inhibitory effect of Aii20J on a mixed biofilm of 6 oral pathogens was verified using confocal microscopy. Much more research is needed in order to be able to associate specific AHLs with oral pathologies and to individuate the key actors in AHL-mediated QS processes in dental plaque formation. However, these results indicate a higher relevance of the AHLs in the oral cavity than generally accepted thus far and suggest the potential use of inhibitory strategies against these signals for the prevention and treatment of oral diseases.

Resistance to ß-lactams and distribution of ß-lactam resistance genes in subgingival microbiota from Spanish patients with periodontitis.

OBJECTIVES: The aim of this study was to analyze the distribution of ß-lactamase genes and the multidrug resistance profiles in ß-lactam-resistant subgingival bacteria from patients with periodontitis. MATERIALS AND METHODS: Subgingival samples were obtained from 130 Spanish patients with generalized periodontitis stage III or IV. Samples were grown on agar plates with amoxicillin or cefotaxime and incubated in anaerobic and microaerophilic conditions. Isolates were identified to the species level by the sequencing of their 16S rRNA gene. A screening for the following ß-lactamase genes was performed by the polymerase chain reaction (PCR) technique: blaTEM, blaSHV, blaCTX-M, blaCfxA, blaCepA, blaCblA, and blaampC. Additionally, multidrug resistance to tetracycline, chloramphenicol, streptomycin, erythromycin, and kanamycin was assessed, growing the isolates on agar plates with breakpoint concentrations of each antimicrobial. RESULTS: ß-lactam-resistant isolates were found in 83% of the patients. Seven hundred and thirty-seven isolates from 35 different genera were obtained, with Prevotella and Streptococcus being the most identified genera. blaCfxA was the gene most detected, being observed in 24.8% of the isolates, followed by blaTEM (12.9%). Most of the isolates (81.3%) were multidrug-resistant. CONCLUSIONS: This study shows that ß-lactam resistance is widespread among Spanish patients with periodontitis. Furthermore, it suggests that the subgingival commensal microbiota might be a reservoir of multidrug resistance and ß-lactamase genes. CLINICAL RELEVANCE: Most of the samples yielded ß-lactam-resistant isolates, and 4 different groups of bla genes were detected among the isolates. Most of the isolates were also multidrug-resistant. The results show that, although ß-lactams may still be effective, their future might be hindered by the presence of ß-lactam-resistant bacteria and the presence of transferable bla genes.

Tetracycline and multidrug resistance in the oral microbiota: differences between healthy subjects and patients with periodontitis in Spain.

Introduction: Antibiotic resistance is widely found even among bacterial populations not having been exposed to selective pressure by antibiotics, such as tetracycline. In this study we analyzed the tetracycline-resistant subgingival microbiota of healthy subjects and of patients with periodontitis, comparing the prevalence of tet genes and their multidrug resistance profiles. Methods: Samples from 259 volunteers were analyzed, obtaining 813 tetracycline-resistant isolates. The prevalence of 12 antibiotic resistance genes was assessed, and multidrug profiles were built. Each isolate was identified by 16S rRNA sequencing. Differences in qualitative data and quantitative data were evaluated using the chi-square test and the Mann-Whitney-U test, respectively. Results: tet(M) was the most frequently detected tet gene (52.03%). We observed significant differences between the prevalence of tet(M), tet(W), tet(O), tet(32) and tet(L) in both populations studied. Multidrug resistance was largely observed, with resistance to kanamycin being the most detected (83.64%). There were significant differences between the populations in the prevalence of kanamycin, chloramphenicol, and cefotaxime resistance. Resistant isolates showed significantly different prevalence between the two studied groups. Conclusion: The high prevalence of multidrug resistance and tetracycline resistance genes found in the subgingival microbiota, highlights the importance of performing wider and more in-depth analysis of antibiotic resistance in the oral microbiota.

Detection and expression analysis of tet(B) in Streptococcus oralis.

Tetracycline resistance can be achieved through tet genes, which code for efflux pumps, ribosomal protection proteins and inactivation enzymes. Some of these genes have only been described in either Gram-positive or Gram-negative bacteria. This is the case of tet(B), which codes for an efflux pump and, so far, had only been found in Gram-negative bacteria. In this study, tet(B) was detected in two clinical Streptococcus oralis strains isolated from the gingival sulci of two subjects. In both cases, the gene was completely sequenced, yielding 100% shared identity and coverage with other previously published sequences of tet(B). Moreover, we studied the expression of tet(B) using RT-qPCR in the isolates grown with and without tetracycline, detecting constitutive expression in only one of the isolates, with no signs of expression in the other one. This is the first time that the presence and expression of the tet(B) gene has been confirmed in Gram-positive bacteria, which highlights the potential of the genus Streptococcus to become a reservoir and a disseminator of antibiotic resistance genes in an environment so prone to horizontal gene transfer as is the oral biofilm.

Development and viability of biofilms grown on experimental abutments mimicking dental implants: An in vivo model

Background: To determine whether an experimental abutment mimicking the macro- and microstructure of a dental implant is a suitable method for recovering biofilm, and to describe the features of biofilms formed around such abutments on healthy implants. Material and Methods: Experimental abutments were used in 15 patients without peri-implant diseases. After 14 days' absence of dental hygiene in this area, the abutments were retrieved and analyzed through confocal laser scanning microscopy and scanning electron microscopy. The biofilm formation on the surface of the first 5 abut-ments was determined by a fluorescence-staining method using SYTO9 nucleic acid stain. In order to study the biofilm's coverage and vitality, 10 additional abutments were assessed using live & dead bacterial viability. Descriptive and bivariate analyses of the data were performed. Results: A global plaque coverage of the abutments was observed in all cases. The submucosal area of the abutment was mostly covered with biofilm (over 21%). Moreover, significant differences between supra- and subgingival locations were detected. Conclusions: This in vivo experimental model allows detailed observation of the extensive plaque growth found on exposed experimental abutments mimicking dental implants when hygiene measures are absent. The biofilm cover-age is significantly higher in the supragingival zone than in the subgingival portion

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