Microbial diagnostics in periodontal diseases

Microbial analytical methods have been instrumental in elucidating the complex microbial etiology of periodontal diseases, by shaping our understanding of subgingival community dynamics. Certain pathobionts can orchestrate the establishment of dysbiotic communities that can subvert the host immune system, triggering inflammation and tissue destruction. Yet, diagnosis and management of periodontal conditions still rely on clinical and radiographic examinations, overlooking the well-established microbial etiology. This review summarizes the chronological emergence of periodontal etiological models and the co-evolution with technological advances in microbial detection. We additionally review the microbial analytical approaches currently accessible to clinicians, highlighting their value in broadening the periodontal assessment. The epidemiological importance of obtaining culture-based antimicrobial susceptibility profiles of periodontal taxa for antibiotic resistance surveillance is also underscored, together with clinically relevant analytical approaches to guide antibiotherapy choices, when necessary. Furthermore, the importance of 16S-based community and shotgun metagenomic profiling is discussed in outlining dysbiotic microbial signatures. Because dysbiosis precedes periodontal damage, biomarker identification offers early diagnostic possibilities to forestall disease relapses during maintenance. Altogether, this review highlights the underutilized potential of clinical microbiology in periodontology, spotlighting the clinical areas most conductive to its diagnostic implementation for enhancing prevention, treatment predictability, and addressing global antibiotic resistance.

Profiling Antibiotic Susceptibility among Distinct Enterococcus faecalis Isolates from Dental Root Canals

Enterococcus faecalis, a leading multi-resistant nosocomial pathogen, is also the most frequently retrieved species from persistently infected dental root canals, suggesting that the oral cavity is a possible reservoir for resistant strains. However, antimicrobial susceptibility testing (AST) for oral enterococci remains scarce. Here, we examined the AST profiles of 37 E. faecalis strains, including thirty-four endodontic isolates, two vanA-type vancomycin-resistant isolates, and the reference strain ATCC-29212. Using Etest gradient strips and established EUCAST standards, we determined minimum inhibitory concentrations (MICs) for amoxicillin, vancomycin, clindamycin, tigecycline, linezolid, and daptomycin. Results revealed that most endodontic isolates were susceptible to amoxicillin and vancomycin, with varying levels of intrinsic resistance to clindamycin. Isolates exceeding the clindamycin MIC of the ATCC-29212 strain were further tested against last-resort antibiotics, with 7/27 exhibiting MICs matching the susceptibility breakpoint for tigecycline, and 1/27 reaching that of linezolid. Both vanA isolates confirmed vancomycin resistance and demonstrated resistance to tigecycline. In conclusion, while most endodontic isolates remained susceptible to first-line antibiotics, several displayed marked intrinsic clindamycin resistance, and MICs matched tigecycline's breakpoint. The discovery of tigecycline resistance in vanA isolates highlights the propensity of clinical clone clusters to acquire multidrug resistance. Our results emphasize the importance of implementing AST strategies in dental practices for continued resistance surveillance.

Deciphering the Role of WWTPs in Cold Environments as Hotspots for the Dissemination of Antibiotic Resistance Genes

Cold environments are the most widespread extreme habitats in the world. However, the role of wastewater treatment plants (WWTPs) in the cryosphere as hotspots in antibiotic resistance dissemination has not been well established. Hence, a snapshot of the resistomes of WWTPs in cold environments, below 5 °C, was provided to elucidate their role in disseminating antibiotic resistance genes (ARGs) to the receiving waterbodies. The resistomes of two natural environments from the cold biosphere were also determined. Quantitative PCR analysis of the aadA, aadB, ampC, blaSHV, blaTEM, dfrA1, ermB, fosA, mecA, qnrS, and tetA(A) genes indicated strong prevalences of these genetic determinants in the selected environments, except for the mecA gene, which was not found in any of the samples. Notably, high abundances of the aadA, ermB, and tetA(A) genes were found in the influents and activated sludge, highlighting that WWTPs of the cryosphere are critical hotspots for disseminating ARGs, potentially worsening the resistance of bacteria to some of the most commonly prescribed antibiotics. Besides, the samples from non-disturbed cold environments had large quantities of ARGs, although their ARG profiles were highly dissimilar. Hence, the high prevalences of ARGs lend support to the fact that antibiotic resistance is a common issue worldwide, including environmentally fragile cold ecosystems.

The Distribution of Eight Antimicrobial Resistance Genes in Streptococcus oralis, Streptococcus sanguinis, and Streptococcus gordonii Strains Isolated from Dental Plaque as Oral Commensals

It has been proposed that oral commensal bacteria are potential reservoirs of a wide variety of antimicrobial resistance genes (ARGs) and could be the source of pathogenic bacteria; however, there is scarce information regarding this. In this study, three common streptococci of the mitis group (S. oralis, S. sanguinis, and S. gordonii) isolated from dental plaque (DP) were screened to identify if they were frequent reservoirs of specific ARGs (blaTEM, cfxA, tetM, tetW, tetQ, ermA, ermB, and ermC). DP samples were collected from 80 adults; one part of the sample was cultured, and from the other part DNA was obtained for first screening of the three streptococci species and the ARGs of interest. Selected samples were plated and colonies were selected for molecular identification. Thirty identified species were screened for the presence of the ARGs. From those selected, all of the S. sanguinis and S. oralis carried at least three, while only 30% of S. gordonii strains carried three or more. The most prevalent were tetM in 73%, and blaTEM and tetW both in 66.6%. On the other hand, ermA and cfxA were not present. Oral streptococci from the mitis group could be considered frequent reservoirs of specifically tetM, blaTEM, and tetW. In contrast, these three species appear not to be reservoirs of ermA and cfxA.

Mouthwash Effects on the Oral Microbiome: Are They Good, Bad, or Balanced?

This narrative review describes the oral microbiome, and its role in oral health and disease, before considering the impact of commonly used over-the-counter (OTC) mouthwashes on oral bacteria, viruses, bacteriophages, and fungi that make up these microbial communities in different niches of the mouth. Whilst certain mouthwashes have proven antimicrobial actions and clinical effectiveness supported by robust evidence, this review reports more recent metagenomics evidence, suggesting that mouthwashes such as chlorhexidine may cause "dysbiosis," whereby certain species of bacteria are killed, leaving others, sometimes unwanted, to predominate. There is little known about the effects of mouthwashes on fungi and viruses in the context of the oral microbiome (virome) in vivo, despite evidence that they "kill" certain viral pathogens ex vivo. Evidence for mouthwashes, much like antibiotics, is also emerging with regards to antimicrobial resistance, and this should further be considered in the context of their widespread use by clinicians and patients. Therefore, considering the potential of currently available OTC mouthwashes to alter the oral microbiome, this article finally proposes that the ideal mouthwash, whilst combatting oral disease, should "balance" antimicrobial communities, especially those associated with health. Which antimicrobial mouthwash best fits this ideal remains uncertain.

The oral microbiota is a reservoir for antimicrobial resistance: resistome and phenotypic resistance characteristics of oral biofilm in health, caries, and periodontitis

BACKGROUND

Antimicrobial resistance (AMR) is an ever-growing threat to modern medicine and, according to the latest reports, it causes nearly twice as many deaths globally as AIDS or malaria. Elucidating reservoirs and dissemination routes of antimicrobial resistance genes (ARGs) are essential in fighting AMR. Human commensals represent an important reservoir, which is underexplored for the oral microbiota. Here, we set out to investigate the resistome and phenotypic resistance of oral biofilm microbiota from 179 orally healthy (H), caries active (C), and periodontally diseased (P) individuals (TRN: DRKS00013119, Registration date: 22.10.2022). The samples were analysed using shotgun metagenomic sequencing combined, for the first time, with culture technique. A selection of 997 isolates was tested for resistance to relevant antibiotics.

RESULTS

The shotgun metagenomics sequencing resulted in 2,069,295,923 reads classified into 4856 species-level OTUs. PERMANOVA analysis of beta-diversity revealed significant differences between the groups regarding their microbiota composition and their ARG profile. The samples were clustered into three ecotypes based on their microbial composition. The bacterial composition of H and C samples greatly overlapped and was based on ecotypes 1 and 2 whereas ecotype 3 was only detected in periodontitis. We found 64 ARGs conveying resistance to 36 antibiotics, particularly to tetracycline, macrolide-lincosamide-streptogramin, and beta-lactam antibiotics, and a correspondingly high prevalence of phenotypic resistance. Based on the microbiota composition, these ARGs cluster in different resistotypes, and a higher prevalence is found in healthy and caries active than in periodontally diseased individuals. There was a significant association between the resistotypes and the ecotypes. Although numerous associations were found between specific antibiotic resistance and bacterial taxa, only a few taxa showed matching associations with both genotypic and phenotypic analyses.

CONCLUSIONS

Our findings show the importance of the oral microbiota from different niches within the oral cavity as a reservoir for antibiotic resistance. Additionally, the present study showed the need for using more than one method to reveal antibiotic resistance within the total oral biofilm, as a clear mismatch between the shotgun metagenomics method and the phenotypic resistance characterization was shown.

Relationship between Phenotypic and Genotypic Resistance of Subgingival Biofilm Samples in Patients with Periodontitis

The phenotypic expression of antibiotic resistance genes (ARGs) can hamper the use of antibiotics as adjuncts to subgingival instrumentation in the treatment of periodontitis patients. The aim of the study was to analyze the relationship between the phenotypic and genotypic resistance against ampicillin-sulbactam, clindamycin, doxycycline and metronidazole of subgingival biofilm samples from 19 periodontitis patients. Samples were analyzed with shotgun sequencing and cultivated anaerobically for 7 days on microbiological culture media incorporating antibiotics. All growing isolates were identified to the species level using MALDI-TOF-MS and sequence analysis of the 16S ribosomal RNA (rRNA) gene. Phenotypic resistance was determined using EUCAST-breakpoints. The genetic profile of eight patients matched completely with phenotypical resistance to the tested antibiotics. The positive predictive values varied from 1.00 for clindamycin to 0.57 for doxycycline and 0.25 for ampicillin-sulbactam. No sample contained the nimI gene. It can be concluded that antibiotic resistance may be polygenetic and genes may be silent. Every biofilm sample harboring erm genes was phenotypic resistant. The absence of cfx and tet genes correlated to 100%, respectively, to 75%, with the absence of phenotypic resistance. The absence of nimI genes leads to the assumption that constitutive resistance among several species could explain the resistance to metronidazole.

Managing Oral Health in the Context of Antimicrobial Resistance

The oral microbiome plays a major role in shaping oral health/disease state; thus, a main challenge for dental practitioners is to preserve or restore a balanced oral microbiome. Nonetheless, when pathogenic microorganisms install in the oral cavity and are incorporated into the oral biofilm, oral infections, such as gingivitis, dental caries, periodontitis, and peri-implantitis, can arise. Several prophylactic and treatment approaches are available nowadays, but most of them have been antibiotic-based. Given the actual context of antimicrobial resistance (AMR), antibiotic stewardship in dentistry would be a beneficial approach to optimize and avoid inappropriate or even unnecessary antibiotic use, representing a step towards precision medicine. Furthermore, the development of new effective treatment options to replace the need for antibiotics is being pursued, including the application of photodynamic therapy and the use of probiotics. In this review, we highlight the advances undergoing towards a better understanding of the oral microbiome and oral resistome. We also provide an updated overview of how dentists are adapting to better manage the treatment of oral infections given the problem of AMR.

Analysis of Antimicrobial Resistance and Genetic Correlations of Escherichia Coli in Dairy Cow Mastitis

Introduction

Escherichia coli is a widespread environmental pathogen frequently causing dairy cow mastitis. This bacterium is particularly capable of acquiring antimicrobial resistance, which can have severe impacts on animal food safety and human health. The objective of the study was to investigate antimicrobial resistance and genetic correlations of E. coli from dairy cow mastitis cases in northern China.

Material and Methods

Forty strains of E. coli from 196 mastitis milk samples were collected, susceptibility to 13 common antibiotics and the prevalence of resistance genes were tested in these strains, and the genetic characteristics were identified by multilocus sequence typing.

Results

The results showed that most isolates were multidrug resistant (MDR) (75%), and the resistance rates to cefazolin, trimethoprim-sulfamethoxazole and ampicillin were 77.5%, 55.0%, and 52.5%, respectively. The representative genes of the isolates were aadA (62.5%) and tet(B) (60.0%). Multilocus sequence typing showed 19 different sequence types (STs) and 5 clonal complexes (CCs) in the 40 isolates, mainly represented by ST10 and CC10. The strains of the same ST or CC showed a high level of genetic relatedness, but the characteristics of their antimicrobial resistance were markedly different.

Conclusion

Most E. coli isolates in the study were MDR strains. Some strains of the same ST or CC showed diverse resistance characteristics to common antimicrobials. Therefore, E. coli from dairy cow mastitis in northern China should be investigated to elucidate its antimicrobial resistance and genotypes.

Oral Health, Antimicrobials and Care for Patients With Chronic Oral Diseases – A Review of Knowledge and Treatment Strategies

Periodontal and chronic oral mucosal diseases are significant life impacting conditions which may co-exist and synergistically act to cause more severe and widespread oral pathology with enhanced challenges in effective management. Clinicians regularly observe these effects and struggle to effectively manage both problems in many patients. There is limited understanding of many basic and applied scientific elements underpinning potentially shared aetiopathological features and management. Recent developments in translational science provide an opportunity to greater improve knowledge and subsequently care for patients with these problems.

Antimicrobial Resistance Profile by Metagenomic and Metatranscriptomic Approach in Clinical Practice: Opportunity and Challenge

The burden of bacterial resistance to antibiotics affects several key sectors in the world, including healthcare, the government, and the economic sector. Resistant bacterial infection is associated with prolonged hospital stays, direct costs, and costs due to loss of productivity, which will cause policy makers to adjust their policies. Current widely performed procedures for the identification of antibiotic-resistant bacteria rely on culture-based methodology. However, some resistance determinants, such as free-floating DNA of resistance genes, are outside the bacterial genome, which could be potentially transferred under antibiotic exposure. Metagenomic and metatranscriptomic approaches to profiling antibiotic resistance offer several advantages to overcome the limitations of the culture-based approach. These methodologies enhance the probability of detecting resistance determinant genes inside and outside the bacterial genome and novel resistance genes yet pose inherent challenges in availability, validity, expert usability, and cost. Despite these challenges, such molecular-based and bioinformatics technologies offer an exquisite advantage in improving clinicians’ diagnoses and the management of resistant infectious diseases in humans. This review provides a comprehensive overview of next-generation sequencing technologies, metagenomics, and metatranscriptomics in assessing antimicrobial resistance profiles.

Metagenomic analysis of microbial communities and antibiotic resistance genes in spoiled household chemicals

Numerous attempts have been utilized to unveil the occurrences of antibiotic resistance genes (ARGs) in human-associated and non-human-associated samples. However, spoiled household chemicals, which are usually neglected by the public, may be also a reservoir of ARGs because of the excessive and inappropriate uses of industrial drugs. Based upon the Comprehensive Antibiotic Research Database, a metagenomic sequencing method was utilized to detect and quantify Antibiotic Resistance Ontology (AROs) in six spoiled household chemicals, including hair conditioner, dishwashing detergent, bath shampoo, hand sanitizer, and laundry detergent. Proteobacteria was found to be the dominant phylum in all the samples. Functional annotation of the unigenes obtained against the KEGG pathway, eggNOG and CAZy databases demonstrated a diversity of their functions. Moreover, 186 types of AROs that were members of 72 drug classes were identified. Multidrug resistance genes were the most dominant types, and there were 17 AROs whose resistance mechanisms were categorized into the resistance-nodulation-cell division antibiotic efflux pump among the top 20 AROs. Moreover, Proteobacteria was the dominant carrier of AROs with the primary resistance mechanism of antibiotic efflux. The maximum temperature of the months of collection significantly affected the distributions of AROs. Additionally, the isolated individual bacterium from spoiled household chemicals and artificial mixed communities of isolated bacteria demonstrated diverse resistant abilities to different biocides. This study demonstrated that there are abundant microorganisms and a broad spectrum profile of AROs in spoiled household chemicals that might induce a severe threat to public healthy securities and merit particular attention.

Functional screening of a human saliva metagenomic DNA reveal novel resistance genes against sodium hypochlorite and chlorhexidine

Objective

Many sections of the health care system are facing a major challenge making infectious disease problematic to treat; antimicrobial resistance (AMR). Identification and surveillance of the resistome have been highlighted as one of the strategies to overcome the problem. This study aimed to screen for AMR genes in an oral microbiota, a complex microbial system continuously exposed to antimicrobial agents commonly used in dental practice.

Materials and methods

As a significant part of the oral microbiome cannot be conventionally cultured, a functional metagenomic approach was chosen. The human oral metagenomic DNA was extracted from saliva samples collected from 50 healthy volunteers in Norway. The oral metagenomic library was then constructed by ligating partially digested oral metagenome into pSMART BAC vector and introducing into Escherichia coli. The library was screened against antimicrobials in dental practices. All resistant clones were selected and analyzed.

Results

Screening of the oral metagenomic library against different antimicrobials detected multiple clones with resistance against chlorhexidine, triclosan, erythromycin, tetracycline, and sodium hypochlorite. Bioinformatic analysis revealed both already known resistance genes, including msr, mef(A), tetAB(46), and fabK, and genes that were not previously described to confer resistance, including recA and accB conferring resistance to sodium hypochlorite and chlorhexidine, respectively.

Conclusion

Multiple clones conferring resistance to antimicrobials commonly used in dental practices were detected, containing known and novel resistant genes by functional-based metagenomics. There is a need for more studies to increase our knowledge in the field.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12903-021-02000-5.

Antimicrobial photodynamic therapeutic effects of cationic amino acid-porphyrin conjugate 4i on Porphyromonas gingivalis in vitro

BACKGROUND

Porphyromonas gingivalis (P. gingivalis) is considered to be among the principal pathogens in periodontal disease. The present study aimed to investigate the effect of antimicrobial photodynamic therapy (aPDT) mediated by cationic amino acid-porphyrin conjugate 4i on P. gingivalis METHODS: The uptake of 4i by P. gingivalis over different times of incubation was evaluated by optical density using a microplate reader. Laser radiation at λ=650nm-660nm with I =50 mW/cm² at doses of 0, 3.0, 6.0, 9.0, and 12 J/cm² was used for aPDT. A colony-counting method and confocal laser scanning microscopy (CLSM) were used to observe the neutralization of P. gingivalis. The fluorescent molecular probe 3'(p-hydroxyphenyl)-fluorescein and the reagent Singlet Oxygen Sensor Green were used to measure the quantities of •OH and ¹O₂ produced by 4i after irradiation with different light energies.

RESULTS

The 4i conjugate was absorbed gradually by P. gingivalis, reaching a maximum at 30 min. A clear cytotoxic effect on P. gingivalis was observed with aPDT using 62.5 µM 4i, with colony counts dropping by a factor of 3.35 log₁₀, indicating a sterilization rate of 99.95%. Light irradiation resulted principally in the production of • OHby 4i. A live/dead viability assay demonstrated substantial red fluorescence in P. gingivalis treated with aPDT.

CONCLUSIONS

The results suggest that 4i-aPDT caused substantial cytotoxicity in P. gingivalis.

Dental Plaque Microbial Resistomes of Periodontal Health and Disease and Their Changes after Scaling and Root Planing Therapy

The human oral microbial community has been considered a reservoir of antibiotic resistance. Currently, the effects of periodontitis and the scaling and root planing (SRP) treatment on the performance of antibiotic-resistant genes (ARGs) and metal-resistant genes (MRGs) in the dental plaque microbiota are not well characterized. To explore this issue, we selected 48 healthy-state (HS), 40 periodontitis-state (PS; before treatment), and 24 resolved-state (RS; after SRP treatment) metagenomic data of dental plaque samples from the Sequence Read Archive (SRA) database. NetShift analysis identified Fretibacterium fastidiosum, Tannerella forsythia, and Campylobacter rectus as key drivers during dental plaque microbiota alteration in the progression of periodontitis. Periodontitis and SRP treatment resulted in an increase in the number of ARGs and MRGs in dental plaque and significantly altered the composition of ARG and MRG profiles. Bacitracin, beta-lactam, macrolide-lincosamide-streptogramin (MLS), tetracycline, and multidrug resistance genes were the main classes of ARGs with high relative abundance, whereas multimetal, iron, chromium, and copper resistance genes were the primary types of MRGs in dental plaque microbiota. The cooccurrence of ARGs, MRGs, and mobile genetic elements (MGEs) indicated that a coselection phenomenon exists in the resistomes of dental plaque microbiota. Overall, our data provide new insights into the standing of the distribution of ARGs and MRGs in oral microbiota of periodontitis patients, and it was possible to contribute to the understanding of the complicated correlations among microorganisms, resistomes, and MGEs. IMPORTANCE The emergence and development of resistance to antibiotics in periodontal pathogens have affected the success rate of treatment for periodontitis. The development of new antibacterial strategies is urgently needed to help control and treat periodontal disease, and dental plaque microbiome studies offer a promising new angle of attack. In this study, we investigated the dental plaque microbiota and resistomes in periodontal health and disease states and their changes after SRP therapy. This is the first analysis of the profile of the microbial community and antibiotic and metal resistance genes in dental plaque by the metagenomic approach, to the best of our knowledge. Monitoring the profile of these resistomes has huge potential to provide reference levels for proper antibiotics use and the development of new antimicrobial strategies in periodontitis therapy and thereby improve actual efficacy of the treatment regimens.

How does the early life environment influence the oral microbiome and determine oral health outcomes in childhood?

The first 1000 days of life, from conception to 2 years, are a critical window for the influence of environmental exposures on the assembly of the oral microbiome, which is the precursor to dental caries (decay), one of the most prevalent microbially induced disorders worldwide. While it is known that the human microbiome is susceptible to environmental exposures, there is limited understanding of the impact of prenatal and early childhood exposures on the oral microbiome trajectory and oral health. A barrier has been the lack of technology to directly measure the foetal "exposome", which includes nutritional and toxic exposures crossing the placenta. Another barrier has been the lack of statistical methods to account for the high dimensional data generated by-omic assays. Through identifying which early life exposures influence the oral microbiome and modify oral health, these findings can be translated into interventions to reduce dental decay prevalence.

From Simple Mouth Cavities to Complex Oral Mucosal Disorders-Curcuminoids as a Promising Therapeutic Approach

Oral diseases are among the most common encountered health issues worldwide, which are usually associated with anomalies of the oral cavity, jaws, and salivary glands. Despite the availability of numerous treatment modalities for oral disorders, a limited clinical response has been observed because of the inefficacy of the drugs and countless adverse side effects. Therefore, the development of safe, efficacious, and wide-spectrum therapeutics is imperative in the battle against oral diseases. Curcumin, extracted from the golden spice turmeric, is a well-known natural polyphenol that has been extensively studied for its broad pleiotropic attributes and its ability to modulate multiple biological processes. It is well-documented to target pro-inflammatory mediators like NF-κB, ROS, COX-2, IL-1, IL-2, TGF-β, growth factors, apoptotic proteins, receptors, and various kinases. These properties make curcumin a promising nutraceutical in the treatment of many oral diseases like oral submucous fibrosis, oral mucositis, oral leukoplakia, oral erythroplakia, oral candidiasis, aphthous stomatitis, oral lichen planus, dental caries, periodontitis, and gingivitis. Numerous in vitro and in vivo studies have shown that curcumin alleviates the symptoms of most of the oral complications, including the inhibition of the progression of oral cancer. In this regard, many clinical trials have been completed, and many are ongoing to investigate the "curcumin effect" in oral maladies. Therefore, the current review delineates the mechanistic framework of curcumin's propensity in curbing oral diseases and present outcomes of the clinical trials of curcumin-based therapeutics that can provide a breakthrough in the clinical management of these diseases.

Prevalence, diversity and transferability of the Tn916-Tn1545 family ICE in oral streptococci

Background: The Tn916-Tn1545 family of Integrative Conjugative Elements (ICE) are mobile genetic elements (MGEs) that play a role in the spread of antibiotic resistance genes. The Tn916 harbors the tetracycline resistance gene tet(M) and it has been reported in various bacterial species. The increase in the levels of tetracycline resistance among oral streptococci is of great concern primarily due to the abundance of these species in the oral cavity and their ability to act as reservoirs for antibiotic resistance genes.Methods: In the current study, we screened 100 Norwegian clinical oral streptococcal isolates for the presence and diversity of the Tn916-Tn1545 family. In addition, we investigated the transferability the elements, and the associated transfer frequencies.Results: We observed that 21 isolates harboured the Tn916-Tn1545 family and that two of these elements were the novel Tn6815 and Tn6816. The most prevalent member of the Tn916 -Tn1545 family observed in the Norwegian clinical oral streptococcal isolates was the wild type Tn916.Conclusion: The detection of other members of this family of ICE and varying transfer frequencies suggests high versatility of the Tn916 element in oral streptococci in Norway.

Functional Metagenomic Screening for Antimicrobial Resistance in the Oral Microbiome

A large proportion of bacteria, from a multitude of environments, are not yet able to be grown in the laboratory, and therefore microbiological and molecular biological investigations of these bacteria are challenging. A way to circumvent this challenge is to analyze the metagenome, the entire collection of DNA molecules that can be isolated from a particular environment or sample. This collection of DNA molecules can be sequenced and assembled to determine what is present and infer functional potential, or used as a PCR template to detect known target DNA and potentially unknown regions of DNA nearby those targets; however assigning functions to new or conserved hypothetical, functionally cryptic, genes is difficult. Functional metagenomics allows researchers to determine which genes are responsible for selectable phenotypes, such as resistance to antimicrobials and metabolic capabilities, without the prerequisite needs to grow the bacteria containing those genes or to already know which genes are of interest. It is estimated that a third of the resident species of the human oral cavity is not yet cultivable and, together with the ease of sample acquisition, makes this metagenome particularly suited to functional metagenomic studies. Here we describe the methodology related to the collection of saliva samples, extraction of metagenomic DNA, construction of metagenomic libraries, as well as the description of functional assays that have previously led to the identification of new genes conferring antimicrobial resistance.

Healthcare Challenges and Future Solutions in Dental Practice: Assessing Oral Antibiotic Resistances by Contemporary Point-Of-Care Approaches

Antibiotic resistance poses a global threat, which is being acknowledged at several levels, including research, clinical implementation, regulation, as well as by the World Health Organization. In the field of oral health, however, the issue of antibiotic resistances, as well as of accurate diagnosis, is underrepresented. Oral diseases in general were ranked third in terms of expenditures among the EU-28 member states in 2015. Yet, the diagnosis and patient management of oral infections, in particular, still depend primarily on empiric means. On the contrary, on the global scale, the field of medical infections has more readily adopted the integration of molecular-based systems in the diagnostic, patient management, and antibiotic stewardship workflows. In this perspective review, we emphasize the clinical significance of supporting in the future antibiotic resistance screening in dental practice with novel integrated and point-of-care operating tools that can greatly support the rapid, accurate, and efficient administration of oral antibiotics.

Bacterial diversity and prevalence of antibiotic resistance genes in the oral microbiome

OBJECTIVES

This study aims to describe the oral microbiome diversity and prevalence of ARGs in periodontal health and disease.

BACKGROUND

The human oral cavity harbors a complex microbial community known as the oral microbiome. These organisms are regularly exposed to selective pressures, such as the usage of antibiotics, which drive evolution and acquisition of antibiotic resistance genes (ARGs). Resistance among oral bacteria jeopardizes not only antibiotic therapy for oral infections, but also extra-oral infections caused by bacterial translocation.

METHODS

We carried out a cross-sectional investigation. Saliva and subgingival plaque samples were collected during a clinical exam. 16S rRNA gene sequencing was performed to assess microbial diversity. Resistance genes were identified through PCR assays.

RESULTS

Of the 110 participants, only 22.7% had healthy periodontium, while the majority was diagnosed with gingivitis (55.4%) and chronic periodontitis (21.8%). The composition of the oral microbiota differed from healthy and diseased samples, being Streptococcus spp. and Rothia spp. predominant in periodontal disease. Regarding ARGs, 80 (72.7%) samples were positive for at least one of genes screened, erm being the most frequent variant (58.2%), followed by blaTEM (16.4%), mecA (2.7%), pbp2b and aac(6 ') (1.8%). Neither genes coding resistance to carbapenems nor metronidazole were detected.

CONCLUSIONS

Our findings indicate that there are no significant differences in terms of taxonomic enrichment between healthy and diseased oral microbiomes. However, samples retrieved from healthy patients had a more diverse microbial community, whereas diseased samples have lower taxonomic diversity. We have also identified clinically relevant ARGs, providing baseline information to guide antibiotic prescription in dentistry.

Distribution of Antibiotic Resistance Genes in the Saliva of Healthy Omnivores, Ovo-Lacto-Vegetarians, and Vegans

Food consumption allows the entrance of bacteria and their antibiotic resistance (AR) genes into the human oral cavity. To date, very few studies have examined the influence of diet on the composition of the salivary microbiota, and even fewer investigations have specifically aimed to assess the impact of different long-term diets on the salivary resistome. In this study, the saliva of 144 healthy omnivores, ovo-lacto-vegetarians, and vegans were screened by nested PCR for the occurrence of 12 genes conferring resistance to tetracyclines, macrolide-lincosamide-streptogramin B, vancomycin, and β-lactams. The tet(W), tet(M), and erm(B) genes occurred with the highest frequencies. Overall, no effect of diet on AR gene distribution was seen. Some differences emerged at the recruiting site level, such as the higher frequency of erm(C) in the saliva of the ovo-lacto-vegetarians and omnivores from Bologna and Turin, respectively, and the higher occurrence of tet(K) in the saliva of the omnivores from Bologna. A correlation of the intake of milk and cheese with the abundance of tet(K) and erm(C) genes was seen. Finally, when the occurrence of the 12 AR genes was evaluated along with geographical location, age, and sex as sources of variability, high similarity among the 144 volunteers was seen.

Resistencia a antibióticos β-lactámicos y eritromicina en bacterias de la cavidad oral

Introducción. La microbiota humana como fuente de bacterias y genes de resistencia constituyen un problema de salud pública. En este estudio se investigó la prevalencia de bacilos entéricos Gram negativos resistentes a β-lactámicos y de los Streptococcus del grupo viridans (EGV) con resistencia a eritromicina en la cavidad oral. Métodos. Se realizó un estudio descriptivo de corte transversal con 193 aislamientos de la cavidad oral sana de 178 adultos que asistieron a una Clínica Odontológica de la ciudad de Cali durante el 2018. La evaluación de la sensibilidad antimicrobiana se realizó en 59 bacilos entéricos y 134 EGV y se identificó por PCR los genes que confieren resistencia a β-lactámicos y eritromicina. El análisis estadístico se realizó mediante el empleo del paquete SPSS vs 23. Resultados. El 84,7% de los bacilos entéricos fueron multirresistentes y presentaron genes bla, siendo blaTEM-1 (49,2%) y blaVIM-2 (30,5%,) los más prevalentes. Los EGV fueron resistentes a eritromicina (38,8%) y clindamicina (28,4%). El 18,7% presentaron el fenotipo cMLSβ, 4,5% el iMLSβ y el 14,9% fueron M.  El gen ermB se detectó en los cMLSβ, (13,4%) y el gen mef  en los M (9,7%). Conclusión. En este estudio se demostró la presencia de EGV y bacilos entéricos resistentes a los antibióticos y portadores de genes de resistencia a eritromicina y genes bla en la cavidad oral sana. La presencia de estas bacterias representa un riesgo para la salud de los individuos portadores y contribuyen a la creciente epidemia de resistencia bacteriana.

Characteristics of oral methicillin-resistant Staphylococcus epidermidis isolated from dental plaque

The oral microbial community is widely regarded as a latent reservoir of antibiotic resistance genes. This study assessed the molecular epidemiology, susceptibility profile, and resistance mechanisms of 35 methicillin-resistant Staphylococcus epidermidis (MRSE) strains isolated from the dental plaque of a healthy human population. Broth microdilution minimum inhibitory concentrations (MICs) revealed that all the isolates were nonsusceptible to oxacillin and penicillin G. Most of them were also resistant to trimethoprim (65.7%) and erythromycin (54.3%). The resistance to multiple antibiotics was found to be largely due to the acquisition of plasmid-borne genes. The mecA and dfrA genes were found in all the isolates, mostly dfrG (80%), aacA-aphD (20%), aadD (28.6%), aphA3 (22.9%), msrA (5.7%), and the ermC gene (14.3%). Classical mutational mechanisms found in these isolates were mainly efflux pumps such as qacA (31.4%), qacC (25.7%), tetK (17.1%), and norA (8.6%). Multilocus sequence type analysis revealed that sequence type 59 (ST59) strains comprised 71.43% of the typed isolates, and the eBURST algorithm clustered STs into the clonal complex 2-II(CC2-II). The staphyloccoccal cassette chromosome mec (SCCmec) type results showed that 25 (71.43%) were assigned to type IV. Moreover, 88.66% of the isolates were found to harbor six or more biofilm-associated genes. The aap, atlE, embp, sdrF, and IS256 genes were detected in all 35 isolates. This research demonstrates that biofilm-positive multiple-antibiotic-resistant ST59-SCCmec IV S. epidermidis strains exist in the dental plaque of healthy people and may be a potential risk for the transmission of antibiotic resistance.

Antimicrobial Photoinactivation Using Visible Light Plus Water-Filtered Infrared-A (VIS + wIRA) and Hypericum Perforatum Modifies In Situ Oral Biofilms

Due to increasing antibiotic resistance, the application of antimicrobial photodynamic therapy (aPDT) is gaining increasing popularity in dentistry. The aim of this study was to investigate the antimicrobial effects of aPDT using visible light (VIS) and water-filtered infrared-A (wIRA) in combination with a Hypericum perforatum extract on in situ oral biofilms. The chemical composition of H. perforatum extract was analyzed using ultra-high-performance liquid chromatography coupled with high resolution mass spectrometry (UPLC-HRMS). To obtain initial and mature oral biofilms in situ, intraoral devices with fixed bovine enamel slabs (BES) were carried by six healthy volunteers for two hours and three days, respectively. The ex situ exposure of biofilms to VIS + wIRA (200 mWcm^-2) and H. perforatum (32 mg ml^-1, non-rinsed or rinsed prior to aPDT after 2-min preincubation) lasted for five minutes. Biofilm treatment with 0.2% chlorhexidine gluconate solution (CHX) served as a positive control, while untreated biofilms served as a negative control. The colony-forming units (CFU) of the aPDT-treated biofilms were quantified, and the surviving microorganisms were identified using MALDI-TOF biochemical tests as well as 16 S rDNA-sequencing. We could show that the H. perforatum extract had significant photoactivation potential at a concentration of 32 mg ml^-1. When aPDT was carried out in the presence of H. perforatum, all biofilms (100%) were completely eradicated (p = 0.0001). When H. perforatum was rinsed off prior to aPDT, more than 92% of the initial viable bacterial count and 13% of the mature oral biofilm were killed. Overall, the microbial composition in initial and mature biofilms was substantially altered after aPDT, inducing a shift in the synthesis of the microbial community. In conclusion, H. perforatum-mediated aPDT using VIS + wIRA interferes with oral biofilms, resulting in their elimination or the substantial alteration of microbial diversity and richness. The present results support the evaluation of H. perforatum-mediated aPDT for the adjunctive treatment of biofilm-associated oral diseases.

Think before you prescribe: how dentistry contributes to antibiotic resistance

Antibiotic resistance presents a daunting challenge to health professionals worldwide and has the potential to create major problems for modern health care, resulting in more medical expenditure, extended hospital stays and increased morbidity and mortality. Advanced genome sequencing technologies present a complex picture of resistance, extending our understanding beyond the pharmacotherapeutic interface between pathogens and antibiotics. This review discusses the global scope and scale of antibiotic resistance and contextualizes it for the dental practitioner, emphasizing the role we must play in limiting the progression of resistance through antibiotic stewardship and disease prevention.

Streptococcal peptides that signal Enterococcus faecalis cells carrying the pheromone-responsive conjugative plasmid pAM373

Pheromone-mediated conjugative transfer of enterococcal plasmids can contribute to the dissemination of genes involved in antibiotic resistance, fitness, and virulence among co-residents of mixed microbial communities. We have previously shown that intergeneric signaling by the Streptococcus gordonii strain Challis heptapeptide s.g.cAM373 (SVFILAA) induces an aggregation substance-mediated mating response and facilitates plasmid transfer from Enterococcus faecalis cells carrying the pheromone-responsive plasmid pAM373 to both pheromone-producing and non-pheromone-producing oral streptococcal recipients. To further investigate the streptococcal pheromone-like peptides, s.g.cAM373-like sequences were identified in the signal sequences of streptococcal CamG lipoproteins and their abilities to induce a mating response in E. faecalis/pAM373 cells were examined. Synthetic heptamers with the consensus sequence (A/S)-(I/V)-F-I-L-(A/V/T)-(S/A) induced AS-mediated clumping. The conserved pheromone ABC transporter encoded by S. gordonii genome loci SGO_RS02660 and SGO_RS02665 was identified and confirmed to be required for s.g.cAM373 activity. Functional assays of culture supernatants from representative oral and blood isolates of S. gordonii showed that in addition to strains encoding s.g.cAM373, strain SK120, encoding the newly identified pheromone s.g.cAM373-V (SVFILVA), was able to induce enterococcal clumping, whereas strains SK6, SK8, SK9, and SK86 which encoded s.g.cAM373-T (SVFILTA) did not elicit a detectable mating response. Absence of pheromone activity in supernatants of heterologous hosts encoding its CamG precursor suggested that s.g.cAM373-T was not effectively processed and/or transported. Overall, these studies demonstrated the distribution of active pheromone peptides among strains of S. gordonii, and support a potential role for enterococcal-streptococcal communication in contributing to genetic plasticity in the oral metagenome.

Use of synthesized double-stranded gene fragments as qPCR standards for the quantification of antibiotic resistance genes

Pollution of various environmental matrices by antibiotic resistance genes (ARGs) has become a growing threat to human health. For the quantitative analysis of the presence of ARGs, there is a need for sensitive and robust qPCR assays which can detect various genes from different types of DNA extracts. Fourteen ARGs were selected as target genes in this study including: bla_TEM, bla_OXA-1 and bla_CTX-M coded for resistance to β-lactams; ermB for macrolides; tetA, tetG, tetM, tetQ, tetW and tetX for tetracyclines; sul I and sul II for sulfonamides; drfA1 and drfA12 d for trimethoprim; and integron gene intI 1 and intI 2. Chemically synthesized double-stranded gene fragments were modified using molecular biology methods and used as real-time PCR standards as well as to establish in-house qPCR assays. The ermB gene from a naturally occurring plasmid was used to compare the performance of qPCR assay with the chemically synthesized ermB. Additionally, environmental water, soil and faeces samples were used to validate the established qPCR assays. Importantly, the study proves the usefulness of rapidly synthesized oligonucleotides serving as qPCR standards for ARG analysis and provides comparable sensitivity and reliability to a traditional amplicon standard.

The Photomodulation Activity of Metformin Against Oral Microbiome

Periodontitis is one of the most common inflammatory diseases of the periodontium, which results in the inflammatory destruction of supporting structures around teeth and is closely associated with the development of systemic disease. Due to a wide variety of antibiotic resistance periodontopathic bacteria, photodynamic therapy (PDT) is a non-invasive adjunctive therapeutic modality that is capable of destroying the whole range of microbes. Metformin (Metf) is an antidiabetic drug, and recent studies suggest that cancer patients who receive Metf and are exposed to radiotherapy and chemotherapy show better outcomes. Our surveys in this review introduce Metf as a potent stimulus in increasing the efficacy of PDT in the induction of destruction in microbial cells.

The oral microbiome - friend or foe?

The microbiome and the human body constitute an integrated superorganism, which is the result of millions of years of coevolution with mutual adaptation and functional integration, and confers significant benefits for both parties. This evolutionary process has resulted in a highly diverse oral microbiome, which covers the full spectrum of acidogenic, aciduric, inflammatory, and anti-inflammatory properties. The relative proportions of members of the microbiome are affected by factors associated with modern life, such as general diet patterns, sugar consumption, tobacco smoking, oral hygiene, use of antibiotics and other antimicrobials, and vaccines. A perturbed balance in the oral microbiome may result in caries, periodontal disease, or candidiasis, and oral bacteria passively transferred to normally sterile parts of the body may cause extra-oral infections. Nevertheless, it should never be our goal to eliminate the oral microbiome, but rather we have to develop ways to re-establish a harmonious coexistence that is lost because of the modern lifestyle. With regard to oral diseases, this goal can normally be achieved by optimal oral hygiene, exposure to fluoride, reduction of sucrose consumption, stimulation of our innate immune defense, smoking cessation, and control of diabetes.

Rapid molecular detection of macrolide resistance

BACKGROUND

Emerging antimicrobial resistance is a significant threat to human health. However, methods for rapidly diagnosing antimicrobial resistance generally require multi-day culture-based assays. Macrolide efflux gene A, mef(A), provides resistance against erythromycin and azithromycin and is known to be laterally transferred among a wide range of bacterial species.

METHODS

We use Recombinase Polymerase Assay (RPA) to detect the antimicrobial resistance gene mef(A) from raw lysates without nucleic acid purification. To validate these results we performed broth dilution assays to assess antimicrobial resistance to erythromycin and ampicillin (a negative control).

RESULTS

We validate the detection of mef(A) in raw lysates of Streptococcus pyogenes, S. pneumoniae, S. salivarius, and Enterococcus faecium bacterial lysates within 7-10 min of assay time. We show that detection of mef(A) accurately predicts real antimicrobial resistance assessed by traditional culture methods, and that the assay is robust to high levels of spiked-in non-specific nucleic acid contaminant. The assay was unaffected by single-nucleotide polymorphisms within divergent mef(A) gene sequences, strengthening its utility as a robust diagnostic tool.

CONCLUSIONS

This finding opens the door to implementation of rapid genomic diagnostics in a clinical setting, while providing researchers a rapid, cost-effective tool to track antibiotic resistance in both pathogens and commensal strains.

Anaerobes in cystic fibrosis patients' airways

Anaerobes are known to constitute an important part of the airway microbiota in both healthy subjects and cystic fibrosis (CF) patients. Studies on the potential role of anaerobic bacteria in CF and thus their involvement in CF pathophysiology have reported contradictory results, and the question is still not elucidated. The aim of this study was to summarize anaerobe diversity in the airway microbiota and its potential role in CF, to provide an overview of the state of knowledge on anaerobe antibiotic resistances (resistome), and to investigate the detectable metabolites produced by anaerobes in CF airways (metabolome). This review emphasizes key metabolites produced by strict anaerobic bacteria (sphingolipids, fermentation-induced metabolites and metabolites involved in quorum-sensing), which may be essential for the better understanding of lung disease pathophysiology in CF.

Genetics of sanguinis-Group Streptococci in Health and Disease

With the application of increasingly advanced "omics" technologies to the study of our resident oral microbiota, the presence of a defined, health-associated microbial community has been recognized. Within this community, sanguinis-group streptococci, comprising the closely related Streptococcus sanguinis and Streptococcus gordonii, together with Streptococcus parasanguinis, often predominate. Their ubiquitous and abundant nature reflects the evolution of these bacteria as highly effective colonizers of the oral cavity. Through interactions with host tissues and other microbes, and the capacity to readily adapt to prevailing environmental conditions, sanguinis-group streptococci are able to shape accretion of the oral plaque biofilm and promote development of a microbial community that exists in harmony with its host. Nonetheless, upon gaining access to the blood stream, those very same colonization capabilities can confer upon sanguinis-group streptococci the ability to promote systemic disease. This article focuses on the role of sanguinis-group streptococci as the commensurate commensals, highlighting those aspects of their biology that enable the coordination of health-associated biofilm development. This includes the molecular mechanisms, both synergistic and antagonistic, that underpin adhesion to substrata, intercellular communication, and polymicrobial community formation. As our knowledge of these processes advances, so will the opportunities to exploit this understanding for future development of novel strategies to control oral and extraoral disease.

Dental biofilm: ecological interactions in health and disease

BACKGROUND

The oral microbiome is diverse and exists as multispecies microbial communities on oral surfaces in structurally and functionally organized biofilms.

AIM

To describe the network of microbial interactions (both synergistic and antagonistic) occurring within these biofilms and assess their role in oral health and dental disease.

METHODS

PubMed database was searched for studies on microbial ecological interactions in dental biofilms. The search results did not lend themselves to systematic review and have been summarized in a narrative review instead.

RESULTS

Five hundred and forty-seven original research articles and 212 reviews were identified. The majority (86%) of research articles addressed bacterial-bacterial interactions, while inter-kingdom microbial interactions were the least studied. The interactions included physical and nutritional synergistic associations, antagonism, cell-to-cell communication and gene transfer.

CONCLUSIONS

Oral microbial communities display emergent properties that cannot be inferred from studies of single species. Individual organisms grow in environments they would not tolerate in pure culture. The networks of multiple synergistic and antagonistic interactions generate microbial inter-dependencies and give biofilms a resilience to minor environmental perturbations, and this contributes to oral health. If key environmental pressures exceed thresholds associated with health, then the competitiveness among oral microorganisms is altered and dysbiosis can occur, increasing the risk of dental disease.

Determination and identification of antibiotic-resistant oral streptococci isolated from active dental infections in adults

OBJECTIVE

To determine and identify antibiotic-resistant bacteria (ARB) of oral streptococci from active dental infections in adults and its association with age and gender.

MATERIAL AND METHODS

This cross-sectional study included 59 subjects from 18 to 62 years old. Ninety-eighth samples obtained from the subjects were cultivated in agar plates containing antibiotics amoxicillin/clavulanic acid (A-CA), clindamycin, and moxifloxacin (concentrations of 16, 32 or 64 µg/ml). PCR assay was performed to identify bacterial species.

RESULTS

The bacterial species that showed more antibiotic-resistance (AR) was S. mutans (45.9%), followed by S. gordonii (21.6%), S. oralis (17.6%), S. sanguinis (9.5%), S. salivarius (5.4%) and S. sobrinus (0%). Moreover, clindamycin (59.4%) showed the highest frequency of AR. Moxifloxacin and A-CA showed an susceptibility >99.1%, while clindamycin showed the lowest efficacy (93.3%); there was a significant statistically difference (p < .01). The age group between 26 and 50 years old (32.2%) and females (28.8%) showed more multiresistance. Clindamycin showed a statistical difference (p < .05) when comparing groups by gender.

CONCLUSIONS

Clindamycin was the antibiotic with the highest frequency of ARB and lower bactericidal effect. Moxifloxacin and A-CA showed the highest efficacy and the lowest ARB frequency. Streptococcus mutans was the bacterial specie that showed an increased frequency of AR.

Application of Metagenomic Analyses in Dentistry as a Novel Strategy Enabling Complex Insight into Microbial Diversity of the Oral Cavity

The composition of the oral microbiome in healthy individuals is complex and dynamic, and depends on many factors, such as anatomical location in the oral cavity, diet, oral hygiene habits or host immune responses. It is estimated at present that worldwide about 2 billion people suffer from diseases of the oral cavity, mainly periodontal disease and dental caries. Importantly, the oral microflora involved in local infections may spread and cause systemic, even life-threatening infections. In search for etiological agents of infections in dentistry, traditional approaches are not sufficient, as about 50% of oral bacteria are not cultivable. Instead, metagenomic analyses are particularly useful for studies of the complex oral microbiome - both in healthy individuals, and in patients with oral and dental diseases. In this paper we review the current and future applications of metagenomic studies in evaluation of both the composition of the oral microbiome as well as its potential pathogenic role in infections in dentistry.

Exploring the microbiome in health and disease

The analysis of human microbiome is an exciting and rapidly expanding field of research. In the past decade, the biological relevance of the microbiome for human health has become evident. Microbiome comprises a complex collection of microorganisms, with their genes and metabolites, colonizing different body niches. It is now well known that the microbiome interacts with its host, assisting in the bioconversion of nutrients and detoxification, supporting immunity, protecting against pathogenic microbes, and maintaining health. Remarkable new findings showed that our microbiome not only primarily affects the health and function of the gastrointestinal tract but also has a strong influence on general body health through its close interaction with the nervous system and the lung. Therefore, a perfect and sensitive balanced interaction of microbes with the host is required for a healthy body. In fact, growing evidence suggests that the dynamics and function of the indigenous microbiota can be influenced by many factors, including genetics, diet, age, and toxicological agents like cigarette smoke, environmental contaminants, and drugs. The disruption of this balance, that is called dysbiosis, is associated with a plethora of diseases, including metabolic diseases, inflammatory bowel disease, chronic obstructive pulmonary disease, periodontitis, skin diseases, and neurological disorders. The importance of the host microbiome for the human health has also led to the emergence of novel therapeutic approaches focused on the intentional manipulation of the microbiota, either by restoring missing functions or eliminating harmful roles. In the present review, we outline recent studies devoted to elucidate not only the role of microbiome in health conditions and the possible link with various types of diseases but also the influence of various toxicological factors on the microbial composition and function.

Streptococcus gordonii pheromone s.g.cAM373 may influence the reservoir of antibiotic resistance determinants of Enterococcus faecalis origin in the oral metagenome

Streptococcus gordonii produces a pheromone heptapeptide, s.g.cAM373, which induces a conjugative mating response in Enterococcus faecalis cells carrying the responsive plasmid, pAM373. We investigated the extent of this intergeneric signaling on DNA acquisition by streptococcal species likely to cohabit oral biofilms. E. faecalis/pAM373/pAMS470 cells were incubated with synthetic s.g.cAM373, reverse peptide s.g.cAM373-R, or peptide-free medium and examined for their abilities to transfer plasmid DNA to streptococcal species in the presence of DNase. Preinduction of E. faecalis donors with s.g.cAM373 resulted in transconjugation frequencies in non-pheromone producing strains of Streptococcus mutans, Streptococcus sanguinis, Streptococcus anginosus, and Streptococcus suis that were significantly higher than frequencies when donors were preincubated with s.g.cAM373-R or medium alone. Peptide-mediated communication between commensal streptococci and E. faecalis carrying pheromone-responsive plasmids may facilitate conjugative DNA transfer to bystander species, and influence the reservoir of antibiotic resistance determinants of enterococcal origin in the oral metagenome.

Use of ethanol extracts of Terminalia chebula to prevent periodontal disease induced by dental plaque bacteria

BACKGROUND

The fruit of the Terminalia chebula tree has been widely used for the treatment of various disorders. Its anti-diabetic, anti-mutagenic, anti-oxidant, anti-bacterial, anti-fungal, and anti-viral effects have been studied. Dental plaque bacteria (DPB) are intimately associated with gingivitis and periodontitis. In the quest for materials that will prove useful in the treatment and prevention of periodontal disease, we investigated the preventive effects of an ethanol extract of Terminalia chebula (EETC) on DPB-induced inflammation and bone resorption.

METHODS

The anti-bacterial effect of EETC was analyzed using the disc diffusion method. The anti-inflammatory effect of EETC was determined by molecular biological analysis of the DPB-mediated culture cells. Prevention of osteoclastic bone resorption by EETC was explored using osteoclast formation and pit formation assays.

RESULTS

EETC suppressed the growth of oral bacteria and reduced the induction of inflammatory cytokines and proteases, abolishing the expression of PGE2 and COX-2 and inhibiting matrix damage. By stimulating the DPB-derived lipopolysaccharides, EETC inhibited both osteoclast formation in osteoclast precursors and RANKL expression in osteoblasts, thereby contributing to the prevention of bone resorption.

CONCLUSIONS

EETC may be a beneficial supplement to help prevent DPB-mediated periodontal disease.

Translational metagenomics and the human resistome: confronting the menace of the new millennium

The increasing threat of antimicrobial resistance poses one of the greatest challenges to modern medicine. The collection of all antimicrobial resistance genes carried by various microorganisms in the human body is called the human resistome and represents the source of resistance in pathogens that can eventually cause life-threatening and untreatable infections. A deep understanding of the human resistome and its multilateral interaction with various environments is necessary for developing proper measures that can efficiently reduce the spread of resistance. However, the human resistome and its evolution still remain, for the most part, a mystery to researchers. Metagenomics, particularly in combination with next-generation-sequencing technology, provides a powerful methodological approach for studying the human microbiome as well as the pathogenome, the virolume and especially the resistome. We summarize below current knowledge on how the human resistome is shaped and discuss how metagenomics can be employed to improve our understanding of these complex processes, particularly as regards a rapid translation of new findings into clinical diagnostics, infection control and public health.