Influence of Enterococcus faecalis proteases and the collagen-binding protein, Ace, on adhesion to dentin

A Comparative Evaluation of Antimicrobial and Cytotoxic Efficacy of Biosynthesized Silver Nanoparticles and Chemically Synthesized Silver Nanoparticles Against Enterococcus faecalis: An In Vitro Study

Introduction Effective root canal cleaning and sealing are essential for a successful endodontic procedure. For the purpose of disinfecting root canals, both herbal and non-herbal medications are recommended. This study aimed to analyze the antimicrobial and cytotoxic properties of biosynthesized silver nanoparticles (AgNPs) synthesized from Azadirachta indica/neem and chemically synthesized AgNPs from trisodium citrate (TSC) against oral pathogens to be further used as an irrigant in endodontic treatment. Materials and methods To synthesize A. indica AgNPs, powdered fresh A. indica leaves were weighed, added to double distilled water, heated for 30 minutes, and then combined with silver nitrate solution. TSC was also used to create TSC AgNPs. X-ray diffraction (XRD), scanning electron microscopy (SEM), ocular observation, and the ultraviolet-visible light (UV-vis) spectrum were used to characterize the AgNPs. Studies were conducted on the extract's characteristics, including its cytotoxicity and antibacterial activity. Results The hue shift and peak on the UV-vis spectrophotometer were signs that AgNPs were forming. The XRD pattern showed that the sample included crystalline AgNPs, mostly spherical ones. By using SEM, the presence of AgNPs was also verified. AgNPs that were synthesized showed antimicrobial efficacy against Enterococcus faecalis. Compared to chemically synthesized AgNPs, A. indica AgNPs showed lower minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values, a bigger zone of inhibition (ZOI), and less cytotoxic action. Conclusion This study demonstrates the minimal cytotoxicity and antibacterial activity of A. indica AgNPs against E. faecalis. This suggests that they might also be employed as root canal cleaners. Before experimenting with animals or cell lines in clinical trials for endodontic treatment, further research should be done.

Enterococcus faecalis in secondary apical periodontitis: Mechanisms of bacterial survival and disease persistence

Enterococcus faecalis is a commensal bacterium commonly found in the human gastrointestinal tract. However, in individuals with compromised immune systems, the pathogen can lead to severe illness. This opportunistic pathogen is associated with secondary apical diseases and is adept at resisting antibiotics and other forms of treatment because of its numerous virulence factors. Enterococcus faecalis is capable of disrupting the normal functions of immune cells, thereby hindering the body's ability to eradicate the infection. However, intensive research is needed in further understanding the adverse immunomodulatory effects of E. faecalis. Potential strategies specific for eradicating E. faecalis have proven beneficial in the treatment of persistent secondary apical periodontitis.

Collagen adhesin protein and necrotic enteritis B-like toxin as biomarkers for early diagnosis of necrotic enteritis in commercial broiler chickens

Mouse monoclonal antibodies (mAbs) reactive with Clostridium perfringens collagen adhesin protein (CNA) and necrotic enteritis B-like toxin (NetB) were developed. The best capture/detection mAb pairs for CNA and NetB were selected based on their affinity and specificity to develop sandwich enzyme-linked immunosorbent assays (ELISAs) to detect CNA and NetB proteins, respectively, in jejunal digesta samples from commercial broiler farms in the United States. Prior to the analysis of samples from commercial broiler flocks, the specificity and sensitivity of the CNA and NetB ELISAs were validated using sera, jejunal digesta, and fecal samples from chickens coinfected with Eimeria maxima and CNA+/NetB+C. perfringens in an animal model of necrotic enteritis (NE). Subsequently, a total of 251 field samples were collected from 74 commercial poultry farms. Among these, 18 samples were from 6 broiler farms that used certified organics (CO), and 155 samples were from 42 farms with nonantibiotics (NA). In jejunal digesta samples, CNA levels ranged from 0.02 to 0.59 ng/mL and NetB levels ranged from 0.09 to 1.91 ng/mL. CNA and NetB levels showed a positive correlation with each other (Pearson correlation coefficient r = 0.772, P < 0.001). CNA and NetB levels in jejunal digesta were significantly decreased in CO farms compared with those from NA farms (P < 0.001). In conclusion, these new C. perfringens antigen-specific sandwich ELISAs offer a sensitive and specific means to detect C. perfringens CNA and NetB proteins as biomarkers of early NE occurrence in field samples from commercial broiler chickens.

A small molecule II-6s inhibits Enterococcus faecalis biofilms

Background

Limitations of current intracanal irrigants such as sodium hypochlorite (NaOCl) and chlorhexidine (CHX) necessitate the development of novel antimicrobial agents to control endodontic infection.

Aim

This study investigated the antimicrobial activities of a small molecule II-6s against Enterococcus faecalis associated with endodontic diseases.

Methods

The susceptibility of E. faecalis to II-6s was evaluated by the microdilution method and time-kill assay. Microbial resistance was assessed by repeated exposure of E. faecalis to II-6s. Cytotoxicity of II-6s was evaluated by CCK-8 assay. Virulence gene expression of the II-6s-treated E. faecalis cells was measured by RT-qPCR. Bacterial reductions in the dentinal tubules were further assessed by confocal laser scanning microscopy.

Results

II-6s exhibited potent antimicrobial activity against E. faecalis and down-regulated virulence-associated genes in E. faecalis. II-6s induced no drug resistance in E. faecalis with lower cytotoxicity as compared to NaOCl and CHX. More importantly, 0.003125% II-6s exhibited significant bactericidal effect against E. faecalis residing in the dentinal tubules, which was comparable to 5.25% NaOCl and 2% CHX.

Conclusions

II-6s has excellent antimicrobial activity, moderate cytotoxicity and induces no drug resistance, and thus is a promising agent for the treatment of endodontic infection.

Synergistic Effect of Plant Extracts on Endodontic Pathogens Isolated from Teeth with Root Canal Treatment Failure: An In Vitro Study

BACKGROUND AND OBJECTIVES

This study aimed to evaluate the synergistic antimicrobial activity of extracts obtained from Salvadora persica (Miswak), Commiphora molmol (myrrh) and Azadirachta indica (neem) in combination with commercially available antimicrobial agents: penicillin, tetracycline, ofloxacin and fluconazole on endodontic pathogens such as Enterococcus faecalis, Streptococcus mitis,Actinomyces naeslundii and Candida albicans.

MATERIALS AND METHODS

Microbiological samples from the root canals of the teeth undergoing retreatment were taken using sterile paper points kept at full length in the canal for 30 s. The disc diffusion method was used to check the susceptibility of microbes to the plant extracts and antimicrobials by measuring the diameter of the inhibition zones. Against the microbes, minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC)/minimum fungicidal concentration (MFC) of the plant extracts were assessed. The fractional inhibitory concentration index (FICI) was used to estimate the synergistic effect of plant extracts combined with antimicrobials against the resistant endodontic microbes.

RESULTS

The findings clearly indicate the effectiveness of all the three plant extracts, Commiphora molmol, Azadirachta indica, Salvadora persica, against all the experimental pathogenic microorganisms except for the ineffectiveness of Azadirachta indica, Salvadora persica against Candidaalbicans. Maximum antimicrobial activity was displayed by Azadirachta indica against Enterococcusfaecalis (MIC = 0.09 ± 1.2 mg/mL, MBC = 0.78 ± 1.25 mg/mL) and the minimum antimicrobial activity was displayed by Commiphora molmol against Actinomyces naeslundii (MIC = 12.5 ± 3.25 mg/mL, MBC = 100 ± 3.75 mg/mL). The best synergy was displayed by Commiphora molmol with fluconazole against Candidaalbicans (FICI = 0.45).

CONCLUSIONS

The current study delineates the variable antimicrobial activity of plant extracts against the experimental endodontic pathogenic microorganisms. Plant extracts in conjunction with various antimicrobials can be valuable aids in combating relatively resistant endodontic microorganisms that have been the cause of worry in recent years, leading to failure even in treatment procedures following all required protocols.

Phenotypic and Genotypic Characterization of Streptococcus mutans Strains Isolated from Endodontic Infections

Streptococcus mutans plays an important role in caries etiology and eventually in systemic infections. However, it is often found in infected root canals, but the pathophysiological characteristics of strains residing in this site are largely unknown. Here, we characterized strains of S. mutans isolated from root canals of primary (PI) and secondary/persistent (SI) endodontic infections in relation to serotype and genotype; presence of genes coding for collagen binding proteins (CBPs); collagen binding activity and biofilm formation capacity; ability to withstand environmental stresses; systemic virulence in Galleria mellonella; and invasion of human coronary artery endothelial cells and human dental pupal fibroblasts. Samples from 10 patients with PI and 10 patients with SI were collected, and a total of 14 S. mutans isolates, belonging to 3 genotypes, were obtained. Of these, 13 were serotype c, and 1 was serotype k. When compared with the reference strains, the clinical isolates were hypersensitive to hydrogen peroxide. Remarkably, all 14 strains harbored and expressed the CBP-encoding gene cbm, showing increased binding to collagen, enhanced systemic virulence in G. mellonella, and ability to invade human coronary artery endothelial cells and human dental pupal fibroblasts when compared with CBP-negative strains. Whole genome sequence analysis of PI and SI isolates revealed that these strains are phylogenetically related but genetically distinct from each other. Our findings highlight the importance of CBPs in facilitating colonization and persistence of S. mutans in collagenous substrates such as root canals and their potential role in the pathogenesis of endodontic infections.

The enterococcal PASTA kinase: A sentinel for cell envelope stress

Enterococci are Gram-positive, opportunistic pathogens that reside throughout the gastrointestinal tracts of most terrestrial organisms. Enterococci are resistant to many antibiotics, which makes enterococcal infections difficult to treat. Enterococci are also particularly hardy bacteria that can tolerate a variety of environmental stressors. Understanding how enterococci sense and respond to the extracellular environment to enact adaptive biological responses may identify new targets that can be exploited for development of treatments for enterococcal infections. Bacterial eukaryotic-like serine/threonine kinases (eSTKs) and cognate phosphatases (STPs) are important signaling systems that mediate biological responses to extracellular stimuli. Some bacterial eSTKs are transmembrane proteins that contain a series of extracellular repeats of the penicillin-binding and Ser/Thr kinase-associated (PASTA) domain, leading to their designation as "PASTA kinases." Enterococcal genomes encode a single PASTA kinase and its cognate phosphatase. Investigations of the enterococcal PASTA kinase revealed its importance in resistance to antibiotics and other cell wall stresses, in enterococcal colonization of the mammalian gut, clues about its mechanism of signal transduction, and its integration with other enterococcal signal transduction systems. In this review, we describe the current state of knowledge of PASTA kinase signaling in enterococci and describe important gaps that still need to be addressed to provide a better understanding of this important signaling system.

Genotype, biofilm formation ability and specific gene transcripts characteristics of endodontic Enterococcus faecalis under glucose deprivation condition

OBJECTIVE

To study the relationship between the specific gene and biofilm formation ability of seven wild type Enterococcus faecalis (E. faecalis) under glucose deprivation conditions.

DESIGN

Wild type E. faecalis (3RC, 5RC, 25RC, 31RC, 33RC, 37RC, 58RC) extracted from the teeth with persistent apical periodontitis were cultured under glucose deprivation conditions and then resequenced. The biofilm formation ability was compared using primary adherence assay, confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM). The transcriptional level of biofilm formation-related genes (ace, gelE, efa, esp and fsrB) were detected.

RESULTS

Genomic resequencing showed that 3RC and 58RC (Class B) were similar, while 5RC, 25RC, 31RC, 33RC and 37RC (Class A) were similar. Based on primary adherence assay, CLSM and SEM results, biofilm formation ability of Class B strains was lower, while Class A strains were higher when compared with control group (0.25 % glucose). Furthermore, compared with control group (0.25 % glucose), the transcriptional levels of ace, efa and fsrB genes were upregulated in all strains; the transcriptional levels of gelE were downregulated in Class B strains, upregulated in Class A strains; the transcriptional levels of esp of Class B strains were downregulated, while upregulated in 25RC, 31RC and 37RC (Class A), and not observed in 5RC and 33RC.

CONCLUSION

The genotypes of wild type E. faecalis of different persistent periapical periodontitis teeth are different. The genotype differences and the transcription levels of related virulence genes (ace, gelE, efa, esp and fsrB) are related to the biological phenotype.

Pathogenicity of Enterococci

Enterococci are unusually well adapted for survival and persistence in a variety of adverse environments, including on inanimate surfaces in the hospital environment and at sites of infection. This intrinsic ruggedness undoubtedly played a role in providing opportunities for enterococci to interact with other overtly drug-resistant microbes and acquire additional resistances on mobile elements. The rapid rise of antimicrobial resistance among hospital-adapted enterococci has rendered hospital-acquired infections a leading therapeutic challenge. With about a quarter of a genome of additional DNA conveyed by mobile elements, there are undoubtedly many more properties that have been acquired that help enterococci persist and spread in the hospital setting and cause diseases that have yet to be defined. Much remains to be learned about these ancient and rugged microbes, particularly in the area of pathogenic mechanisms involved with human diseases.

Assessment of Nitrofurantoin as an Experimental Intracanal Medicament in Endodontics

Background and Objectives. Multiple antibacterial agents have been mixed and used as an intracanal medicament-like modified triple antibiotic paste (MTAP) to eliminate Enterococcus faecalis (EF), which has been most frequently identified in the cases of failed root canal treatment and periapical lesions. This study is aimed at using a single antibacterial agent, nitrofurantoin (Nit), as an experimental intracanal medicament paste against different clinical isolates of EF), which has been most frequently identified in the cases of failed root canal treatment and periapical lesions. This study is aimed at using a single antibacterial agent, nitrofurantoin (Nit), as an experimental intracanal medicament paste against different clinical isolates of Materials and Methods. Three strains of EF), which has been most frequently identified in the cases of failed root canal treatment and periapical lesions. This study is aimed at using a single antibacterial agent, nitrofurantoin (Nit), as an experimental intracanal medicament paste against different clinical isolates of n = 90), group M (MTAP) (n = 90), group M (MTAP) (n = 90), group M (MTAP) (EF), which has been most frequently identified in the cases of failed root canal treatment and periapical lesions. This study is aimed at using a single antibacterial agent, nitrofurantoin (Nit), as an experimental intracanal medicament paste against different clinical isolates of n = 90), group M (MTAP) (n = 90), group M (MTAP) (n = 90), group M (MTAP) (EF), which has been most frequently identified in the cases of failed root canal treatment and periapical lesions. This study is aimed at using a single antibacterial agent, nitrofurantoin (Nit), as an experimental intracanal medicament paste against different clinical isolates of

Mixed aerobic-anaerobic incubation conditions induce proteolytic activity from in vitro salivary biofilms

Oral biofilms have not been studied using both metabolome and protein profiling concurrently. Bacteria produce proteases that lead to degradation of functional salivary proteins. The novel protocol described here allows for complete characterisation of in vitro oral biofilms, including proteolytic, metabolic, and microbiome analysis.

Biofilms were grown on hydroxyapatite discs from whole mouth saliva, using sterilised saliva as a growth-medium, in different growth environments. Salivary protein degradation was assessed from spent saliva growth-medium using SDS-polyacrylamide gel electrophoresis (SDS-PAGE), and metabolic activity by nuclear magnetic resonance (NMR). Discs were assessed for depth and coverage of biofilms by confocal laser scanning microscopy (CLSM), and biofilms were collected at the end of the experiment for 16S rRNA gene sequence analysis.

There was a significant difference in biofilm viability, salivary protein degradation, and metabolites identified between biofilms grown aerobically and biofilms exposed to an anaerobic environment. Bacterial 16S rRNA gene sequencing showed the predominant genus in the 7-day aerobic biofilms was Streptococcus, in aerobic-anaerobic and anaerobic 7-day biofilms Porphyromonas, and in aerobic-anaerobic and anaerobic 13-day biofilms Fusobacterium.

This data suggests new growth requirements and capabilities for analysing salivary biofilms in vitro, which can be used to benefit future research into oral bacterial biofilms.

Influence of Endodontic Procedure on the Adherence of Enterococcus faecalis

INTRODUCTION

The purpose of this study was to investigate the effects of instrumentation and irrigation on the initial adherence of Enterococcus faecalis to root canal dentin and to explore initial microbial adhesion to root filling materials.

METHODS

The following specimens were prepared: instrumented and uninstrumented dentin, dentin treated with different irrigation protocols, and root filling materials. The number of E. faecalis cells adhered on dentin was measured. The adhesion force of E. faecalis cells on different materials and the roughness of different surfaces were measured. The contact angle of the surfaces was recorded. The results were analyzed using the t test.

RESULTS

Instrumented dentin specimens had a significantly higher amount of E. faecalis adherence than uninstrumented dentin. There were higher numbers of adhering bacteria on the dentin when EDTA was used alone (P < .05) compared with other irrigants alone. The use of chlorhexidine (CHX) as the last irrigant for a certain time resulted in a reduced number of adhering bacteria when the specimens were first exposed to sodium hypochlorite (NaOCl) followed by EDTA. EDTA used alone had the highest adhesion force followed by NaOCl alone and CHX alone (P < .05). Dentin treated with EDTA alone had the highest roughness and contact angle followed by NaOCl alone and CHX alone (P < .05). CHX added as the final irrigant after NaOCl with EDTA irrigation reduced the contact angle (P < .05). Larger amounts of adhering bacteria and higher adhesion force were detected on the surface of gutta-percha and sealer than on the dentin surface (P < .05).

CONCLUSIONS

Instrumentation and irrigation alter the initial adherence of E. faecalis to root canal dentin and the surface properties of the dentin as well.

Evaluation of Phage Therapy in the Context of Enterococcus faecalis and Its Associated Diseases

Bacteriophages (phages) or bacterial viruses have been proposed as natural antimicrobial agents to fight against antibiotic-resistant bacteria associated with human infections. Enterococcus faecalis is a gut commensal, which is occasionally found in the mouth and vaginal tract, and does not usually cause clinical problems. However, it can spread to other areas of the body and cause life-threatening infections, such as septicemia, endocarditis, or meningitis, in immunocompromised hosts. Although E. faecalis phage cocktails are not commercially available within the EU or USA, there is an accumulated evidence from in vitro and in vivo studies that have shown phage efficacy, which supports the idea of applying phage therapy to overcome infections associated with E. faecalis. In this review, we discuss the potency of bacteriophages in controlling E. faecalis, in both in vitro and in vivo scenarios. E. faecalis associated bacteriophages were compared at the genome level and an attempt was made to categorize phages with respect to their suitability for therapeutic application, using orthocluster analysis. In addition, E. faecalis phages have been examined for the presence of antibiotic-resistant genes, to ensure their safe use in clinical conditions. Finally, the domain architecture of E. faecalis phage-encoded endolysins are discussed.

Novel anti-biofouling bioactive calcium silicate-based cement containing 2-methacryloyloxyethyl phosphorylcholine

Calcium silicate-based cements (CSCs) are commonly used for endodontic procedures; however, their antibacterial effects are limited. The objective of this study was to develop a 2-methacryloyloxyethyl phosphorylcholine (MPC)-incorporated CSC with improved antibacterial properties, while maintaining the original advantageous features of CSC. MPC was incorporated into a commercial CSC (Endocem MTA) at 0 wt% (control), 1.5%, 3.0 wt%, 5.0 wt%, 7.5 wt%, and 10 wt%. The setting time, compressive strength, water sorption, and glycerol contact angle were measured. Protein absorption was measured and bacterial adhesion on the surface was evaluated using Enterococcus faecalis. The bactericidal effect was examined by the disc diffusion test. Mineralization ability was assessed based on calcium ion deposition, as assessed by alizarin red staining, after immersion into Hank's balanced salt solution for 7 days. High concentrations of MPC in CSC (7.5 wt% and 10 wt%) increased the setting time, reduced compressive strength, and reduced wettability. MPC (3 wt%) had greater protein repellent and anti-biofouling effects than those of control and test materials (P < 0.001). However, no bactericidal effect was observed for any control or test materials. There was greater calcium ion deposition on the surface of MPC-supplemented CSC than on the control (P < 0.001). The addition of 3 wt% MPC polymer to CSC confers protein-repellent properties and reduced bacterial attachment, with the potential for improved mineralization.

Biofilm model systems for root canal disinfection: a literature review

The aim of this review was to present an overview of laboratory root canal biofilm model systems described in the endodontic literature and to critically appraise the various factors that constitute these models. The electronic databases MEDLINE, Web of Science and EMBASE were searched up to and including December 2016 to identify laboratory studies using endodontic biofilm models. The following search terms were used in various combinations: biofilm, root canal, in vitro, endodontic, bacteria, root canal infection model, colony-forming unit. Only English papers from journals with an impact factor were selected. The records were screened by two reviewers, and full-text articles were assessed according to pre-defined criteria. The following data were extracted from the included studies: the microbial composition of the biofilm, the substrate, growth conditions, validation and quantification. Seventy-seven articles met the inclusion criteria. In the majority (86%) of the studies, a monospecies biofilm was cultured. In two studies, a dual-species biofilm was grown; others cultivated a multispecies biofilm, containing at least three species. Enterococcus faecalis was the most frequently used test species (in 79% of all studies, 92% of the monospecies studies). Four studies used an inoculum derived directly from the oral cavity. Human dentine was the most frequently used substratum (88% of the studies). Incubation times differed considerably, ranging from one to seventy days. The most common quantification method (in 87% of the studies) was bacterial culturing, followed by microscopy techniques. The variation in laboratory root canal biofilm model systems is notable. Because of substantial variation in experimental parameters, it is difficult to compare results between studies. This demonstrates the need for a more standardized approach and a validated endodontic biofilm model.

Evaluation of the mono instrument (Wave One) mechanical action on the bacterial load reduction: In vitro study of 32 permanent human teeth

CONTEXT

Enterococcus faecalis is the most common bacteria found in infected root canals.

AIM

The purpose of this study was to evaluate the effect of the mono instrument (wave-one®) on the reduction of E. faecalis in root canals.

MATERIALS AND METHODS

Thirty-two human monoroot teeth were used. After sterilization by autoclave, the teeth were infected by E. faecalis and incubated for 24 h. Each tooth underwent sampling before and after the root canal shaping. After serial dilution, samples were incubated, and colony-forming units were counted.

RESULTS

The mono instrument technique reduced infection by E. faecalis in root canals of 30 teeth. The mean bacterial load (log10) was 3.98 before treatment and 1.20 after treatment. The paired t-test showed a significant mean difference (log10) of the bacterial load before and after treatment (P < 0.0001).

CONCLUSION

This study found that the mono instrument (Wave One®) significantly decreases bacterial load in root canals. However, the instrument alone is not enough to eradicate infections; thus, the use of a complementary antimicrobial is required.

Root Canal Microflora

Modern day endodontics is undergoing a massive change with the introduction of new molecular based techniques for microbial identification. This review focuses on the microbiota in untreated and root-filled canals. It will also describe briefly the recent developments in microbial identification and the mechanisms by which certain species of microbes are able to invade and establish themselves in the root canal.

Effects of a Peganum harmala (Zygophyllaceae) preparation for root canal disinfection

The aim of this study was to determine the antimicrobial capacity, minimum inhibitory concentration (MIC), and cytotoxic effects of a Peganum harmala seed extract in comparison to 5.25% sodium hypochlorite (NaOCl). The oral pathogen Enterococcus faecalis was used to evaluate the antimicrobial capacity, and the MIC values were determined through serial dilution. Inhibition zones were measured in millimeter, and the data were analyzed statistically by analysis of variance and the Tukey HSD test. For cytotoxicity testing, P. harmala seed extract and 5.25% NaOCl solution were incubated with L929 fibroblast cells. After 1, 24, and 72 hr of incubation, cells were stained and the optical density determined with an enzyme-linked immunosorbent assay (ELISA) reader. Data were analyzed with Chi-Square statistical test. The significance level was set at p < .05. There was no significant difference between the antimicrobial capacity of 5.25% NaOCl and the P. harmala extract (p > .05; MIC 4 μg/ml). The Microculture Tetrazolium (MTT) assay test showed that the cytotoxic effects of the P. harmala extract were significantly lower than 5.25% NaOCl (p < .05). The results show that 5.25% NaOCl and P. harmala seed extract have similar antimicrobial activity against Enterococcus faecalis; but P. harmala, which shows reduced cytotoxicity, should be considered for further investigation as a safe, phytotherapeutic, intracanal irrigant.

Antibacterial Efficacy of Biosynthesized Silver Nanoparticles against Enterococcus faecalis Biofilm: An in vitro Study

Aim

This study aims to evaluate the antibacterial efficacy of biosynthesized silver nanoparticles (AgNPs) produced using the fungi against Enterococcus faecalis biofilm model on root dentin.

Materials and Methods

AgNPs were biosynthesized using the fungi Fusarium semitectum isolated from healthy leaves of Withania somnifera. Minimum inhibitory concentration (MIC) of AgNPs was determined by microbroth dilution method using series of dilutions. MIC dose was standardized to evaluate the antibacterial efficacy. For biofilm model, thirty root dentin blocks prepared using human extracted single-rooted teeth were inoculated with E. faecalis in Trypticase soy agar broth for 2 weeks with alternate day replenishment and randomly divided into three groups (n = 10 each) and treated as: Group I: Sterile distilled water, Group II: AgNPs, and Group III: 2% chlorhexidine gluconate (CHX) and incubated at 37°C for 24 h. Each dentin block was rinsed in saline, vortex shaken for 60 s, and serial decimal dilutions were prepared and plated on trypticase soy agar plates and incubated for 24 h followed by CFU colony counting and statistically analyzed using one-way ANOVA followed by post hoc Tukey honestly significant difference test.

Results

MIC of AgNPs for E. faecalis was determined as 30 mg/ml. No significant difference was seen between AgNPs and 2% CHX when compared to the control group with mean colony counts being 2.4, 2.5, and 6.77 CFU/ml (10⁷), respectively (P < 0.0001), against E. faecalis biofilm.

Conclusion

Biosynthesized AgNPs exhibit effective antimicrobial activity against E. faecalis biofilm on root dentin. Therefore, it can be employed as antimicrobial agent for root canal disinfection.

Effect of ultrasound streaming on the disinfection of flattened root canals prepared by rotary and reciprocating systems

New technical and scientific developments have been advocated to promote the success of the endodontic treatment. In addition to rotary and reciprocating systems, irrigating solution agitation has been suggested and passive ultrasonic irrigation (PUI) is the most used. Objective: To evaluate, in vitro, the effect of ultrasound streaming (US) in the disinfection of flattened root canal systems prepared by the ProTaper, BioRaCe and Reciproc systems, utilizing the microbiological culture. Methodology: Extracted human mandibular incisors (n=84) were used. Suspensions of Enterococcus faecalis (ATCC 29212) were standardized and inserted along with the teeth immersed in brain-heart infusion (BHI) broth. The contamination was made following a protocol during 5 days. The teeth were randomly divided into six groups: G1, ProTaper Universal; G2, ProTaper Universal with US; G3, BioRaCe; G4, BioRaCe with US; G5, Reciproc; and G6, Reciproc with US. Irrigation was performed with saline solution. After biomechanical preparation, microbiological samples were performed with sterilized paper points, which were diluted and spread on BHI agar; after 48 h, the colony forming units (CFU/mL) were counted for each sample. Results: Groups using ultrasonic agitation presented a greater antibacterial effect than the other ones, even using saline solution as irrigant. The ProTaper Universal system showed the best antibacterial activity of the tested systems (median of 0 CFU/mL with and without surfactant or ultrasonic activation [PUI]). Even with PUI, Reciproc (median of 2.5 CFU/mL with PUI and 5 without it) could not reduce as many colonies as ProTaper Universal without US. The BioRaCe system had greater bacterial reduction when using US (median of 0 CFU/mL with PUI and 30 without it). Conclusions: US promoted greater reduction in the number of bacteria in the flattened root canals prepared with nickel-titanium mechanized systems. Regarding the instruments used, the ProTaper Universal system was the most effective in reducing the bacterial number.

Assessment of facultative anaerobes from the root canals of deciduous molars: An in vivo study

Background. The current research aimed to assess the prevalence of facultative anaerobes isolated from the root canals of deciduous molars.

Methods. The present research enrolled 60 children in the 6‒9-year age group based on clinical and radiographic findings. Under aseptic conditions, access cavities were prepared followed by collection of samples from infected root canals with the help of sterile paper points. The samples thus obtained were subjected for microbial assay.

Results. It was found that Enterococcus faecalis was isolated in 30% of cases, Escherichia coli in 28.4%, Staphylococcus aureus in 25%, α-hemolytic Streptococci in 15% and Proteus mirabilis in 1.6% of cases.

Conclusion. It was concluded from the results of the present study that the root canals of deciduous molars had predominance of facultative anaerobes, confirming its polymicrobial nature. This identification of microbes is crucial as it aids in understanding the pathogenesis of pulpal and periradicular diseases to provide effective antimicrobial irrigation and medicament for endodontic treatment.

The effect of gelatinase production of Enterococcus faecalis on adhesion to dentin after irrigation with various endodontic irrigants

Objectives: The aim of this study was to evaluate whether the gelatinase production ability of Enterococcus faecalis provides any advantage on adhesion of this bacterium to dentin treated with various irrigants and their combinations.

Materials and methods: Standardized dentin discs were randomly divided into five groups (n = 20): group 1: 2.5% sodium hypochlorite (NaOCl), group 2: 2% chlorhexidine (CHX), group 3: NaOCl + Saline + CHX, group 4: NaOCl + EDTA + NaOCl, group 5: QMix. After incubation of dentin discs with irrigants, each group was divided into two subgroups (n = 10) according to the bacterial strains used; a gelatinase-producing and a gelatinase-deficient strain of E. faecalis. After incubation of the discs with the bacterial suspensions aerobically for 48 h, XTT assay was conducted for bacterial adherence evaluation. Data were statistically analyzed by ANOVA and Tukey’s HSD tests (p = .05).

Results: Gelatinase-producing E. faecalis adhered to dentin was significantly more than gelatinase-deficient E. faecalis in all test groups (p < .05). Adherence to CHX-treated dentin was lower than to the surfaces treated with other irrigants, alone or in combination (p < .05). These differences were significant except for comparisons with QMix for gelatinase-producing bacteria (p < .05).

Conclusions: Gelatinase production of E. faecalis may be an important factor for bacterial adhesion. The addition of CHX to the irrigation regimen resulted in fewer adhered bacteria to dentin. QMix was not as effective as CHX in terms of bacterial adhesion prevention.

Antibacterial Efficacy of Octenisept, Alexidine, Chlorhexidine, and Sodium Hypochlorite against Enterococcus faecalis Biofilms

INTRODUCTION

The purpose of this study was to evaluate the antibacterial effectiveness of Octenisept (OCT; Schülke & Mayr GmBH, Norderstedt, Germany), 1% alexidine (ALX) (Santa Cruz Biotechnology, Inc, Santa Cruz, CA), and 2% chlorhexidine (CHX) against Enterococcus faecalis biofilm using confocal laser scanning microscopy.

METHODS

Root dentin discs were prepared from extracted human teeth, sterilized, and inoculated with E. faecalis strain (ATCC 29212) to establish 3-week-old biofilm model. Infected dentin discs were exposed to OCT (n = 20), 1% ALX (n = 20), and 2% CHX (n = 20) for 10 minutes. Dentin discs (n = 15) exposed to 5.25% sodium hypochlorite (NaOCl) were used as a positive control, whereas specimens exposed to saline (n = 15) were used as a negative control. After exposure, the dentin discs were stained with fluorescent LIVE/DEAD BacLight dye (Invitrogen Molecular Probes, Eugene, OR) and analyzed with confocal laser scanning microscopy to determine the proportion of dead cells in the biofilm. Statistical analysis was performed using the Kruskal-Wallis and Mann-Whitney U tests (P < .05).

RESULTS

The highest proportion of dead cells was found in the 5.25% NaOCl group (94.14%; range, 92.30%-98.20%) compared with the experimental groups (P < .05). A significantly greater proportion of dead cells was found in the OCT group (74.14%; range, 70.03%-78.96%) compared with the 1% ALX and 2% CHX groups (P < .05). The proportion of dead cells was 43.89% (range, 24.86%-55.63%) and 42.78% (range, 25.45%-55.06%) in the 1% ALX and 2% CHX groups, respectively, with no statistical significant difference between the 2 groups (P > .05).

CONCLUSIONS

NaOCl had significantly greater antimicrobial activity against E. faecalis biofilms compared with OCT, CHX, and ALX. OCT was more effective than CHX and ALX.

Antibacterial effect of urushiol on E. faecalis as a root canal irrigant

Objectives

The purpose of this study was to compare the antibacterial activity of urushiol against Enterococcus faecalis (E. faecalis) to that of NaOCl.

Materials and Methods

The canals of thirty two single rooted human teeth were instrumented with Ni-Ti files (ProTaper Next X1, X2, X3, Dentsply). A pure culture of E. faecalis ATCC 19433 was prepared in sterile brain heart infusion (BHI) broth. The teeth were submerged in the suspension of E. faecalis and were incubated at 37℃ for 7 days to allow biofilm formation. The teeth were randomly divided into three experimental groups according to the irrigant used, and a negative control group where no irrigant was used (n = 8). Group 1 used physiologic normal saline, group 2 used 6% NaOCl, and group 3 used 10 wt% urushiol solution. After canal irrigation, each sample was collected by the sequential placement of 2 sterile paper points (ProTaper NEXT paper points, size X3, Dentsply). Ten-fold serial dilutions on each vials, and 100 µL were cultured on a BHI agar plate for 8 hours, and colony forming unit (CFU) analysis was done. The data were statistically analyzed using Kruskal-Wallis and Mann-whitney U tests.

Results

Saline group exhibited no difference in the CFU counts with control group, while NaOCl and urushiol groups showed significantly less CFU counts than saline and control groups (p < 0.05).

Conclusions

The result of this study suggests 10% urushiol and 6% NaOCl solution had powerful antibacterial activity against E. faecalis when they were used as root canal irrigants.

Effect of a genetically engineered bacteriophage on Enterococcus faecalis biofilms

OBJECTIVE

Enterococcus faecalis is a Gram-positive, facultative anaerobic bacterium that is associated with failed endodontic cases and nosocomial infections. E. faecalis can form biofilms, penetrate dentinal tubules and survive in root canals with scarce nutritional supplies. These properties can make E. faecalis resistant to conventional endodontic disinfection therapy. Furthermore, treatment may be complicated by the fact that many E. faecalis strains are resistant to antibiotics. A potential alternative to antibiotic therapy is phage therapy. ϕEf11 is a temperate phage that infects strains of E. faecalis. It was previously sequenced and genetically engineered to modify its properties in order to render it useful as a therapeutic agent in phage therapy. In the current study, we have further genetically modified the phage to create phage ϕEf11/ϕFL1C(Δ36)PnisA. The aim of this study was to evaluate the efficacy of bacteriophage ϕEf11/ϕFL1C(Δ36)PnisA, to disrupt biofilms of two Enterococcus faecalis strains: JH2-2 (vancomycin-sensitive) and V583 (vancomycin-resistant).

METHODS

24h static biofilms of E. faecalis strains JH2-2(pMSP3535 nisR/K) and V583 (pMSP3535nisR/K), formed on cover slips, were inoculated with bacteriophage ϕEf11/ϕFL1C(Δ36)PnisA. After 24 and 48h incubation, the bacterial biomass was imaged by confocal microscopy and viable cells were quantified by colony forming unit measurement.

RESULTS

The results showed a 10-100-fold decrease in viable cells (CFU/biofilm) after phage treatment, which was consistent with comparisons of treated and untreated biofilm images visualized as max projections of the Z-series.

CONCLUSION

The biomass of both vancomycin-sensitive and vancomycin-resistant E. faecalis biofilms is markedly reduced following infection by bacteriophage ϕEf11/ϕFL1C(Δ36)PnisA.

Enterococcus faecalis and Dental Implants

Enterococcus faecalis appears in many tooth root infections and is not eliminated by root canal therapy. It can reside in tooth root canals and the surrounding bone. This species may vegetate in bone after extraction of an infected tooth and colonize a dental implant after placement in the healed site. A colonization may cause fixture loss or marginal bone loss. These colonizations are generally multibacterial and pathogenic properties can be shared via plasmids. However, E faecalis is not detectable with some culture techniques and thus can be missed. It is usually not a dominant species in these infections. Nonetheless, E faecalis may be a "keystone" player in dental implant bone loss or peri-implantitis. That is, E faecalis may be the pathogenic determinant for any particular peri-implantitis infection of a multiple-species infection.

Microbial complexes levels in conventional and self-ligating brackets

OBJECTIVES

The aims were to evaluate the levels of bacterial species in saliva and in situ and to assess whether the design of brackets influences the risk of developing periodontal disease.

MATERIALS AND METHODS

Twenty patients (13.3 mean age) were bonded with self-ligating brackets and a conventional bracket. Saliva was collected before bonding and 30 and 60 days after bonding. One sample of each bracket was removed 30 and 60 days after bonding. The analysis was determined by checkerboard DNA-DNA hybridization. The data was evaluated by the non-parametric test.

RESULTS

A significant increase in the levels of bacterial species in the saliva occurred in 15 of the 22 analyzed species. The self-ligating brackets presented the highest incidence percentages for the orange and red complexes 60 days after bonding. In situ analyses showed different patterns according to the bracket design. The levels of Campylobacter rectus showed significant differences (p = 0.011) 60 days after bonding among the three brackets; the highest values were observed in the In-Ovation®R bracket.

CONCLUSIONS

The bracket design seems to influence the levels of bacterial species involved in periodontal disease. Considering the wide variety of bacterial species, additional studies are needed to aid in the establishment of effective protocols to prevent the development of periodontal disease during orthodontic treatment.

CLINICAL RELEVANCE

A dynamic alteration in the oral microbiota may lead to inflammatory reactions in the supporting soft and hard tissues. The different types of brackets interfere with bacterial adherence. Bracket design should be considered in orthodontic treatment.

Antimicrobial Susceptibility and Characterization of Virulence Genes of Enterococcus faecalis Isolates from Teeth with Failure of the Endodontic Treatment

INTRODUCTION

The aim of this study was to investigate the prevalence of virulence factors and the antimicrobial resistance of Enterococcus faecalis isolates of teeth with failure of the endodontic treatment.

METHODS

Twenty root canal samples were collected from teeth with apical periodontitis. E. faecalis was firstly identified based on phenotypic features and then by 16S ribosomal RNA gene sequencing. The antimicrobial susceptibility was determined by the minimum inhibitory concentration (MIC) of amoxicillin, amoxicillin + clavulanate, azithromycin, benzylpenicillin, ciprofloxacin, clindamycin, chloramphenicol, doxycycline, erythromycin, gentamicin, metronidazole, moxifloxacin, rifampicin, tetracycline, and vancomycin using the E test method. Virulence factors (ace, asa, asa373, cylA, efaA, esp, and gelE) were detected by polymerase chain reaction assay.

RESULTS

Amoxicillin + clavulanate was effective against all strains. Intermediate and total resistance was found against the majority of the tested antimicrobials. The susceptibility of some microorganisms to some antimicrobial agents changed according to the evaluation time. MIC50 and MIC90 also varied according to the evaluation time. In relation to the virulence factors of the E faecalis isolates, ace was detected in 100% of the strains, asa (60%), asa373 (15%), efaA (95%), esp (70%), and gelE (75%), whereas cylA was not detected.

CONCLUSIONS

It was concluded that E. faecalis isolates from persistent endodontic infections showed varied degrees of intermediate/total resistance to several antimicrobial agents, with amoxicillin + clavulanate being the most effective agent. Moreover, the strains showed different patterns for virulence gene detection.

Effectiveness of N-acetyl cysteine, 2% chlorhexidine, and their combination as intracanal medicaments on Enterococcus faecalis biofilm

Aim:

The purpose of this study was to evaluate the antibacterial efficacies of 2% chlorhexidine (CHX), N-acetyl cysteine (NAC) and assess their synergistic or antagonist action as intracanal medicament.

Materials and Methods:

Agar diffusion test was performed with 2% CHX, NAC, and their combination against E. faecalis planktonic cells. The diameters of the zones of bacterial inhibition were measured and recorded for each solution. The assay was further extended to 2 weeks old E. faecalis dentinal biofilm. Sixteen freshly extracted teeth were vertically sectioned into two halves resulting in a total of 32 samples. The samples were inoculated with bacterial suspension and incubated at 37°C for 2 weeks for biofilm formation. The samples were then divided into four experimental groups with 8 samples in each group. The samples were gently washed in saline and placed in culture wells containing the test solutions, i.e., 2% CHX, NAC, a combination of 2% CHX and NAC in 1:1 ratio, and a control group containing saline. The biofilm formed on the root canal surface were removed with a sterile scalpel and inoculated on blood agar plates to check for the formation of E. faecalis colonies.

Statistical Analysis:

For agar diffusion test, data were analyzed statistically using one-way analysis of variance and then by post-hoc Scheffe's test to compare the antimicrobial efficacy between the groups. Statistical analysis was not done for the cultures obtained from the biofilm as there was no growth in all the three test groups except the control group, i.e., saline.

Results:

In agar diffusion test, among the three groups tested, 2% CHX and NAC showed almost equal zones of inhibition whereas maximum inhibition was shown by a combination of NAC and 2% CHX suggesting a synergistic action. The results obtained were highly significant (P < 0.001) for the combination of medicament when compared to individual test group. In culture analysis, which was done for the biofilm, no growth was observed in all the three test groups. The results obtained were biologically significant but statistically insignificant.

Conclusion:

NAC has almost equal antimicrobial property as 2% CHX whereas their combination showed a synergistic action.

Evaluation of Enterococcus faecalis adhesion, penetration, and method to prevent the penetration of Enterococcus faecalis into root cementum: Confocal laser scanning microscope and scanning electron microscope analysis

Aim:

To ascertain the role of Enterococcus faecalis in persistent infection and a possible method to prevent the penetration of E. faecalis into root cementum.

Methodology:

One hundred and twenty human single-rooted extracted teeth divided into five groups. Group I (control): intact teeth, Group II: no apical treatment done, Group III divided into two subgroups. In Groups IIIa and IIIb, root apex treated with lactic acid of acidic and neutral pH, respectively. Group IV: apical root cementum exposed to lactic acid and roughened to mimic the apical resorption. Group V: apical treatment done same as Group IV and root-end filling done using mineral trioxide aggregate (MTA). Apical one-third of all samples immersed in E. faecalis broth for 8 weeks followed by bone morphogenetic protein and obturation and again immersed into broth for 8 weeks. Teeth split into two halves and observed under confocal laser scanning microscope and scanning electron microscope, organism identified by culture and polymerase chain reaction techniques.

Results:

Adhesion and penetration was observed in Group IIIa and Group IV. Only adhesion in Group II and IIIB and no adhesion and penetration in Group I and V.

Conclusion:

Adhesion and penetration of E. faecalis into root cementum providing a long-term nidus for subsequent infection are the possible reason for persistent infection and root-end filling with MTA prevents the adhesion and penetration.

Antibacterial Activity of Diode Laser and Sodium Hypochlorite in Enterococcus Faecalis-Contaminated Root Canals

Introduction:

The aim of the present in vitro study was to evaluate the disinfection ability of 980-nm diode laser in comparison with sodium hypochlorite (NaOCl) as a common root canal irrigant in canals infected with Enterococcus faecalis (E. faecalis).

Methods and Materials:

The root canals of 18 extracted single-rooted premolars were prepared by rotary system. After decoronation, the roots were autoclaved. One specimen was chosen for the negative control, and the remaining teeth were incubated with E. faecalis suspension for two weeks. Subsequently, one specimen was selected as the positive control and the remaining samples were divided into two groups (n=8). The samples of the first group were irrigated with 5.25% NaOCl and the second group were treated with a 980-nm diode laser. Microbial samples were taken from the root canals and bacterial cultivation was carried out. The average value and the standard deviation of colony-forming units (CFU) of each specimen were measured using descriptive statistics. The student’s t-test was used to compare the reduction in CFU in each group. The equality of variance of CFU was measured by the Levene’s test.

Results:

NaOCl resulted in 99.87% removal of the bacteria and showed significantly more antibacterial effect compared to the 980-nm diode laser which led to 96.56% bacterial reduction (P<0.05).

Conclusion:

Although 5.25% NaOCl seems to reduce E. faecalis more effectively, the diode laser also reduced the bacterial count. Therefore a 980-nm diode laser could be considered as a complementary disinfection method in root canal treatment.

The Effect of Addition of an EPS Degrading Enzyme with and without Detergent to 2% Chlorhexidine on Disruption of Enterococcus faecalis Biofilm: A Confocal Laser Scanning Microscopic Study

BACKGROUND

Enterococcus faecalis is one of the most commonly occurring organisms retrieved from root canal treated teeth that show refractory apical periodontitis. Though it is well known that the ability of E. faecalis to form a matrix-encased biofilm contributes to its pathogenicity, the role of extracellular dextran and DNA in biofilm formation and its effect on the susceptibility of the biofilm to chlorhexidine remains poorly understood. It was hypothesized that the addition of an Extracellular Polymeric Substance (EPS) degrading enzyme along with a detergent to chlorhexidine may increase the susceptibility of the E. faecalis biofilm.

AIM

To evaluate the sensitivity of Enterococcus faecalis biofilms treated with DNase enzyme and their susceptibility to 2% chlorhexidine used alone or in conjunction with a detergent in a dentin disinfection model and examine under confocal laser scanning microscopy (CLSM).

MATERIALS AND METHODS

Semi cylindrical shaped dentin specimens were infected with E. faecalis and incubated for 24 hours. Following incubation, the infected dentin specimens were exposed for 3 minutes to the four disinfecting solutions and grouped accordingly. {Group I- Sterile saline, Group II- 2% Chlorhexidine (CHX), Group III- Dnase1 Enzyme + 2% CHX, Group IV- DNase1 Enzyme + 2% CHX & Tween 80. Bacterial viability was then assessed by staining the specimens and examining under CLSM to analyse the proportion of dead and live bacteria within the dentinal tubules.

RESULTS

The Groups II, III and IV showed statistically significant (p<0.05) percentage of dead bacteria compared to the control (Group I). However there was no significant difference in the killing effectiveness within the experimental groups (II-IV) at (p<0.05).

CONCLUSION

EPS degrading enzyme (DNase I) disrupts the biofilm and increases the susceptibility of E.faecalis when exposed to 2% Chlorhexidine and the use of a surfactant with this combination significantly contributes to improving the antibacterial efficacy.

Histopathological changes induced in an animal model by potentially pathogenic Enterococcus faecalis strains recovered from ready-to-eat food outlets in Osun State, Nigeria

Enterococci have been implicated as an emerging important cause of several diseases and multiple antibiotic resistance. However, there is little information about the prevalence of pathogenic and/or antibiotic-resistant Enterococcus faecalis in ready-to-eat foods in Nigeria. Here we report the pathogenic potential of three selected antibiotic-resistant E. faecalis strains isolated from food canteens and food outlets with different virulence determinant genes, including EFC 12 (with gel⁺, esp⁺, cylA⁺, and asa1⁺), EFT 148 (with gel⁺, ace⁺, and asa1⁺), and EFS 18 (with esp⁺ and cylA⁺) in an animal model. Enterococcemia, hematological parameters, and histopathological changes in organ tissues were examined in experimental animals. The results showed differences in enterococcemia and hematological parameters between the control group and experimental animal group. Enterococcemia was observed for 7 days, and the animal group infected with EFC 12 showed the highest growth rate, followed by EFT 148, with the lowest growth rate seen in the EFS 18-infected group. White blood cell count, packed cell volume, and platelets were significantly reduced (P<0.05) in the experimental animals compared with the controls. White blood cells decreased drastically during the study period in rats challenged with EFC 12 (from 7,800 to 6,120 per mm³) but levels remained higher in the control group (from 9,228 to 9,306 per mm³). Histopathological changes included areas of pronounced hemorrhage, necrosis, and distortion in liver tissues, which were more marked in rats infected with EFC 12, followed by EFT 148, then EFS 18. The results of this study suggest the presence of potentially pathogenic E. faecalis strains in food canteens and food outlets; hence, there is a need for strict adherence to good hygiene practices in the study area owing to the epidemiological significance of foods.

Biofilm in endodontics: A review

Endodontic disease is a biofilm-mediated infection, and primary aim in the management of endodontic disease is the elimination of bacterial biofilm from the root canal system. The most common endodontic infection is caused by the surface-associated growth of microorganisms. It is important to apply the biofilm concept to endodontic microbiology to understand the pathogenic potential of the root canal microbiota as well as to form the basis for new approaches for disinfection. It is foremost to understand how the biofilm formed by root canal bacteria resists endodontic treatment measures. Bacterial etiology has been confirmed for common oral diseases such as caries and periodontal and endodontic infections. Bacteria causing these diseases are organized in biofilm structures, which are complex microbial communities composed of a great variety of bacteria with different ecological requirements and pathogenic potential. The biofilm community not only gives bacteria effective protection against the host's defense system but also makes them more resistant to a variety of disinfecting agents used as oral hygiene products or in the treatment of infections. Successful treatment of these diseases depends on biofilm removal as well as effective killing of biofilm bacteria. So, the fundamental to maintain oral health and prevent dental caries, gingivitis, and periodontitis is to control the oral biofilms. From these aspects, the formation of biofilms carries particular clinical significance because not only host defense mechanisms but also therapeutic efforts including chemical and mechanical antimicrobial treatment measures have the most difficult task of dealing with organisms that are gathered in a biofilm. The aim of this article was to review the mechanisms of biofilms’ formation, their roles in pulpal and periapical pathosis, the different types of biofilms, the factors influencing biofilm formation, the mechanisms of their antimicrobial resistance, techniques to identify biofilms.

Assessment of dentinal tubule invasion capacity of Enterococcus faecalis under stress conditions ex vivo

AIM

To investigate the dentinal tubule invasion capacity of Enterococcus faecalis under alkaline and energy starvation stress conditions.

METHODOLOGY

The root canals from human single-rooted teeth (n = 40) were infected with E. faecalis under alkaline (pH 9, 10, 11 and 12) and energy starvation (no glucose, 0.05% glucose and 0.15% glucose) stress conditions. The root canals were prepared in a standard manner and treated to remove the smear layer before incubation. After 4 weeks of cultivation, the roots were split vertically into two halves: one half was processed for biofilm formation analysis using a scanning electron microscope; the other half was stained with fluorescent DNA-binding reagents, washed thoroughly and sectioned (100 μm thick), and the depth of tubule invasion by the microorganism was examined by confocal laser-scanning microscopy. The extent of dentine tubule invasion was analysed statistically.

RESULTS

The E. faecalis strain resulted in biofilm formation and dentine tubules invasion under all of the stress conditions, except for pH 11 and 12 conditions. However, the tubule penetration distance was markedly reduced in these stress conditions (P < 0.01) compared with in tryptic soy broth (TSB) or pH 7 medium. The invasion depth in the middle root dentine was significantly higher than in the apical sections in TSB and energy starvation medium (P < 0.01).

CONCLUSIONS

Ex vivo E. faecalis formed biofilms and colonized dentine under alkaline and glucose starvation stress conditions, but its ability to invade dentine tubules was significantly decreased.

Evaluation of the presence of Enterococcus Faecalis in root cementum: A confocal laser scanning microscope analysis

Aim:

The aim of this study is to address the cause of persistent infection of root cementum by Enterococcus faecalis.

Materials and Methods:

A sample of 60 human single-rooted teeth were divided into three groups. Group I (control group) had no access opening and one-third of the apical root cementum was sealed using varnish. Group II had no preparation of teeth samples. In group III, apical root cementum was exposed to organic acid and roughened using diamond point to mimic apical resorption. After access opening in groups II and III, all teeth samples were sterilized using gamma irradiation (25 kGy). E. faecalis broth was placed in the root canal and apical one-third of the tooth was immersed in the broth for 8 weeks with alternate day refreshment followed by biomechanical preparation, obturation and coronal seal. Apical one-third of all teeth samples were again immersed in the broth for 8 weeks with alternate day refreshment to mimic secondary infection. The samples were observed under a confocal microscope after splitting the teeth into two halves.

Results:

E. faecalis penetrated 160 μm deep into the root cementum in group III samples and only showed adhesion in group II samples.

Conclusion:

Penetration and survival of E. faecalis deep inside the cementum in extreme conditions could be the reason for persistent infection.

Comparative genome analysis of Lactobacillus rhamnosus clinical isolates from initial stages of dental pulp infection: identification of a new exopolysaccharide cluster

The human oral microbiome has a major role in oral diseases including dental caries. Our studies on progression of caries infection through dentin and more recently, the invasion of vital dental pulp, detected Lactobacillus rhamnosus in the initial stages of infection of vital pulp tissue. In this study employing current high-throughput next generation sequencing technology we sought to obtain insight into genomic traits of tissue invasive L. rhamnosus, to recognise biomarkers that could provide an understanding of pathogenic potential of lactobacilli, generally regarded as safe. Roche GS FLX+ technology was used to generate whole genome sequences of two clinical isolates of L. rhamnosus infecting vital pulp. Detailed genome-wide comparison of the genetic profiles of tissue invasive L. rhamnosus with probiotic L. rhamnosus was performed to test the hypothesis that specific strains of L. rhamnosus possessing a unique gene complement are selected for the capacity to invade vital pulp tissue. Analysis identified 264 and 258 genes respectively, from dental pulp-invasive L. rhamnosus strains LRHMDP2 and LRHMDP3 isolated from two different subjects that were not present in the reference probiotic L. rhamnosus strain ATCC 53103 (GG). Distinct genome signatures identified included the presence of a modified exopolysaccharide cluster, a characteristic confirmed in a further six clinical isolates. Additional features of LRHMDP2 and LRHMDP3 were altered transcriptional regulators from RpoN, NtrC, MutR, ArsR and zinc-binding Cro/CI families, as well as changes in the two-component sensor kinase response regulator and ABC transporters for ferric iron. Both clinical isolates of L. rhamnosus contained a single SpaFED cluster, as in L. rhamnosus Lc705, instead of the two Spa clusters (SpaCBA and SpaFED) identified in L. rhamnosus ATCC 53103 (GG). Genomic distance analysis and SNP divergence confirmed a close relationship of the clinical isolates but segregation from the reference probiotic L. rhamnosus strain ATCC 53103 (GG).

Influence of various herbal irrigants as a final rinse on the adherence of Enterococcus faecalis by fluorescence confocal laser scanning microscope

Aim:

The aim of this study was to assess the antibacterial efficacy of three different herbal irrigants against Enterococcus faecalis.

Materials and Methods:

Single rooted teeth were extracted due to orthodontic and periodontal reasons. The teeth were then inoculated with E. faecalis. The teeth were randomly divided into three experimental groups and two control groups of six samples each. Group 1 specimens were treated with 5.2% sodium hypochlorite (NaOCL) for 30 min followed by 5 mmol/L Ethylenediaminetetraacetic acid (EDTA) for 5 min and saline as final irrigant. Group 2 specimens were treated with and 5.2% NaOCl for 30 min as final irrigant. Group 3 were treated with Morinda citrifolia (MC) for 30 min as final irrigant. Group 4 were treated with Azadiracta indica (AI) as final irrigant. Group 5 were treated with green tea (GT) for 30 min as final irrigant. The dentin specimens were carefully spread onto a microscope slide and stained with BacLight and examined in a confocal laser scanning microscope set to monitor fluorescein isothiocyanate and propidium iodide. A total of nine fields were examined for each treatment and the bacteria presented were counted.

Statistical Analysis:

Using the one-way ANOVA with multiple comparison, significantly less bacteria were found adhering to the samples treated with Neem followed by NaOCL, GT, MC, Saline.

Results:

AI treatment produced the maximum reduction in adherence of E. faecalis to dentin (9.30%) followed by NaOCl (12.50%), GT (27.30%), MC (44.20%) and saline (86.70%).

Conclusion:

Neem is effective in preventing adhesion of E. faecalis to dentin.