Association of Enterococcus faecalis with different forms of periradicular diseases

Microbiology of Root Canal Infections

Inflammatory reaction in the periapical tissues is induced by microbial infection in the root canal system. The aim of root canal treatment is to preserve healthy periapical tissues or to provide healing of them in restorable teeth, which have sufficient periodontal support. The amount of microbial cells in the root canal system and their virulence as well as host responses influence on the degree of periapical inflammation and symptoms. Microbial biofilm formation is typically seen on root canal walls but some microbial species are able to invade the dentine tubules to varying depth. In prolonged and complicated infections, or in case of risk of systemic spread of infection, root canal sampling for microbiological diagnostics is recommended. Anaerobic gram-negative rods are commonly isolated organisms in primary infections. In post-treatment disease, the microflora is dominated by facultatively anaerobic gram-positive cocci and rods such as Streptococcus, Enterococcus, Peptostreptococcus and Actinomyces species. Instrumentation, disinfection and interappointment medication in strict aseptic conditions are essential steps for eradication of microbial species from the infected root canal system. During past decades, Enterococcus faecalis and Candida albicans have been commonly associated organisms in treatment-resistant infections. Novel microbial detection methods are giving increasing knowledge about microbial species associated with endodontic infections and their roles in them.

Relevance of the clustered regularly interspaced short palindromic repeats of Enterococcus faecalis strains isolated from retreatment root canals on periapical lesions, resistance to irrigants and biofilms

A high prevalence of Enterococcus faecalis (E. faecalis) is observed in teeth with root canal treatment failures. Clustered regularly interspaced short palindromic repeats (CRISPR) are widely distributed in prokaryotes that have adaptive immune systems against mobile elements, including pathogenic genes. The present study investigated the relevance of the CRISPR in E. faecalis strains isolated from retreated root canals on biofilms, periapical lesions and drug resistance. A total of 20 E. faecalis strains were extracted from the root canals of teeth referred for root canal retreatment. CRISPR-Cas loci were identified by two pairs of relevant primers and polymerase chain reaction. The susceptibility of the 20 isolated strains to intracanal irrigants was evaluated by 1- and 5-minute challenges with a mixture of a tetracycline isomer, an acid and a detergent (MTAD), 2% chlorhexidine (CHX) and 5.25% sodium hypochlorite (NaOCl). The microtiter plate assay and crystal violet staining were used to compare the biofilm formation of the E. faecalis isolate strains. Out of the 20 E. faecalis isolate strains, 5 strains that lacked CRISPR-cas determinants exhibited significant periapical lesions. Among the 15 strains containing CRISPR-cas determinants, 8 were isolated from root canals with inadequate fillings and 7 were isolated from root canals without any fillings. The five strains lacking CRISPR-cas loci were observed to be more resistant to MTAD and 2% CHX than the 15 strains that had CRISPR-cas loci. All of the strains exhibited the same susceptibility to 5.25% NaOCl. Furthermore, the 5 strains lacking CRISPR-cas determinants generated more biofilm than the other 15 strains. Thus, the results of the present study suggested that E. faecalis root canal isolates lacking CRISPR-cas exhibit higher resistance to intracanal irrigants, stronger biofilm formation and generate significant periapical lesions.

Proinflammatory MG-63 cells response infection with Enterococcus faecalis cps2 evaluated by the expression of TLR-2, IL-1β, and iNOS mRNA

OBJECTIVE

We have previously demonstrated that unencapsulated Enterococcus faecalis cps2 inhibits biofilm formation of Candida albicans, a fungus commonly found with E. faecalis in periapical lesion. In this study, we compared encapsulated and unencapsulated E. faecalis cps2 strains relationship with osteoblastic (MG-63) cells, whereas E. faecalis ATCC 29212 were used as a reference strain.

RESULTS

The binding capacity of E. faecalis to MG-63 cells as shown by each tested strain was comparable, but the unencapsulated strain was less invasive compared to the encapsulated and the reference strains. Moreover, quantitative real time-PCR (qPCR) results showed that infecting unencapsulated E. faecalis cps2 is a stronger stimulator for toll like receptor 2 (TLR2) and interleukin-1β (IL-1β) mRNAs, but not for inducible nitric oxide synthase (iNOS) mRNA in osteoblastic cells. In conclusion, the performance of unencapsulated E. faecalis cps2 when the bacterium interacts with osteoblastic cells is quite different from that of encapsulated E. faecalis cps2 and reference strains. It appears that the unencapsulated strain might contribute to the persistence of the periapical inflammatory response, depending on down-regulation of iNOS mRNA expression.

Can the Enterococcus faecalis identified in the root canals of primary teeth be a cause of failure of endodontic treatment?

OBJECTIVE

This study investigated the presence of Enterococcus faecalis in primary teeth with primary root canal infections and related to the possible failure of pulpectomy outcome after 36 months.

MATERIAL AND METHODS

Root canal samples were obtained from 25 out of 244 patients using the sterile paper cone method. The identification of E. faecalis was done with culture and molecular tests using species-specific 16S rRNA gene-based polymerase chain reaction (PCR). After 36 months, the pulpectomy outcome was evaluated.

RESULTS

Enterococcus faecalis was found in five (20%) samples, and dental caries were the cause of primary infection in all of them. Pulpectomy outcome was evaluated only in teeth that completed the entire clinical protocol and were followed up to 36 months (n = 8). From these, 75% (n = 6) were successful and 25% (n = 2) failed. E. faecalis was present in 50% of both successful and failed cases.

CONCLUSIONS

Enterococcus faecalis was not related to the failure of endodontic treatment of primary teeth.

Antibacterial activity of different root canal sealers against Enterococcus faecalis

BACKGROUND

The aim of the present study was to compare in vitro the antimicrobial activity of different root canal sealers against Enterococcus faecalis, prior and subsequent to setting.

MATERIAL AND METHODS

Agar diffusion test (ADT) was used for evaluating the antibacterial activity of non-set sealer while the direct contact test (DCT) was used for after setting.

RESULTS

ADT: Except for TotalFill BC Sealer all the others sealers tested showed antibacterial activity. BioRoot™RCS, MTA Fillapex and Sealapex Root Canal Sealer showed the lowest antibacterial activity, a significant increase in antibacterial effect for both Pulp Canal Sealer™ and AH plus sealers were found. Significantly higher were the mean diameters of the bacterial inhibition zone by both EasySeal or N2 sealers. DCT: AH plus and Sealapex Root Canal Sealer doesn't show any bactericidal effect after 6 min of contact. After 15 and 60 min of contact a significant increment for AH plus and for Sealapex Root Canal Sealer of the bactericidal effect was found. Significantly much higher was the antibacterial effect of Sealapex Root Canal Sealer compare to that observed for AH plus. BioRootTMRCS, MTA Fillapex, Pulp Canal Sealer™ and N2 showed at least means of the number of colonies formed in milliliter after 6 min of contact. Except for N2, a significant increase in bactericidal effect after 15 and 60 min for the other compared sealers (BioRootTMRCS, MTA Fillapex and Pulp Canal Sealer™).

CONCLUSIONS

For every contact times considered, both TotalFill BC Sealer and EasySeal were bactericidal against E. faecalis and killed all bacteria. Key words:Agar diffusion test, antibacterial activity, direct contact test, Enterococcus faecalis, root canal sealer.

Comparative evaluation of micron- and nano-sized intracanal medicaments on penetration and fracture resistance of root dentin - An in vitro study

Intracanal medicaments play a vital role in disinfection of root canal system. The aim of this study was to evaluate intratubular penetration and fracture resistance of roots filled with micron- and nano-sized intracanal medicaments: calcium hydroxide (CH), nanocalcium hydroxide (NCH), chitosan (CS) and nanochitosan (NCS). Their antibacterial effect on E. faecalis was tested using agar diffusion method. NCH and NCS were prepared by precipitation method and ionic crosslinking respectively. NCH and NCS particles were spherical, with an average particle size of 102±11.3nm and 130±17.6nm respectively. The medicaments were filled in extracted human teeth. Depth of penetration of the medicaments into dentinal tubules at coronal (C), middle (M) and apical (A) thirds was measured. Fracture resistance of the teeth was evaluated after 1 week and 1-month intervals. NCH showed the highest depth of penetration (C ∼746.98μm, M ∼700.30μm, A ∼134.69μm). CS showed the highest fracture resistance, whereas no significant difference was found between other medicaments, at both the time intervals. NCH (8.07±0.06) and NCS (8.13±0.06) showed significantly higher zone of inhibition than CH (7.7±0.17) and CS (7.37±0.15). Under the conditions of this study, it can be concluded that NCH and NCS can be used as potential intracanal medicaments.

Effects of Diode Laser, Gaseous Ozone, and Medical Dressings on Enterococcus faecalis Biofilms in the Root Canal Ex Vivo

The objective was to compare the antibacterial effects of adjunctive disinfection using diode laser and gaseous ozone compared to the medical dressings calcium hydroxide (Ca(OH)₂) and chlorhexidine gel (CHX-Gel) on Enterococcus faecalis biofilms in human root canals ex vivo. Root canals of 180 human extracted teeth were infected by E. faecalis and divided into 3 main groups (G): G1, control; G2, instrumentation and irrigation using 0.9% NaCl; G3, instrumentation and irrigation using 1% NaOCl. In each main group, the following treatments were applied: gaseous ozone, diode laser, and medical dressings of Ca(OH)₂ or CHX-Gel for 7 days (n = 15). Reduction of colony forming units (CFUs) inside the root canal of planktons and frequencies of adherent bacteria after treatment were calculated. Bacterial reduction was significantly affected by the irrigation protocol (p < 0.0005) and the disinfection method (p < 0.0005), and a significant interaction between both factors could be observed (p < 0.0005; ANOVA). In G3 (instrumentation using 1% NaOCl), no significant effect of disinfection methods could be demonstrated on planktonic bacteria (p = 0.062; ANOVA) and frequencies of adherent bacteria (p > 0.05; chi-square test). Instrumentation and irrigation using NaOCl combined with ozone or laser application resulted in comparable bacterial reduction on E. faecalis to the application of medical dressings.

Evaluation of Antimicrobial and Antifungal efficacy of Chitosan as endodontic irrigant against Enterococcus Faecalis and Candida Albicans Biofilm formed on tooth substrate

Background

Bacterial biofilms formed on the root canal wall are often difficult to remove. This study aimed to evaluate the cytotoxic effect and antibacterial efficacy of chitosan when used as root canal irrigant against E. Faecalis and Candida albicans biofilm formed on tooth substrate.

Material and Methods

The present study evaluated antibacterial effect of 0.25% Chitosan, 0.5% Chitosan, 2% chlorhexidine and 3% sodium hypochlorite against Enterococcus faecalis and Candida Albicans. Agar-well diffusion methods, minimal inhibitory concentration tests and biofilm susceptibility assays were used to determine antibacterial activity. Teeth specimens were sectioned to obtain a standardized tooth length of 12mm. Specimens were inoculated with 10 mL of the freshly prepared E. Faecalis suspension and Candida albicans for 4 weeks. The specimens were then instrumented with ProTaper rotary files F3 size. After irrigation with test solution, three sterile paper points were placed into one canal, left for 60 s and transferred to a test tube containing 1 mL of reduced transport fluid. The number of CFU in 1 mL was determined.

Results

3-week biofilm qualitative assay showed complete inhibition of bacterial growth with 3% Sodium hypochlorite, 2% Chlorhexidine and Chitosan except saline, which showed presence of bacterial growth. Significant reduction of colony forming units (CFU)/mL was observed for the chitosan groups and the antibacterial activity of the chitosan groups was at par with 3% NaOCl and 2% Chlorhexidine. It was observed that the chitosan showed no cytotoxicity at 3mg/ml and 10% cytotoxicity at 6mg/ml.

Conclusions

The use of chitosan as a root canal irrigant might be an alternative considering the various undesirable properties of NaOCl and chlorhexidine.

Key words:Biofilm, Candida albicans, Chitosan, Cytotoxicity, Enterococcus faecalis.

Antibacterial efficacy of several intracanal medicaments for endodontic therapy

The antibacterial efficacy of intracanal medicaments for 2 and 7 days, in open apex root canals contaminated with Enterococcus faecalis biofilms was compared. One hundred and thirty-eight standardized uniradicular human roots were inoculated with E. faecalis. Colony forming units (CFU) were recorded before and after medication. Samples were divided in two (2/7 days), and subdivided (n=8/group): triple antibiotic paste (TAP); double antibiotic paste (DAP); dental base paste (DBP), consisting of calcium hydroxide, propylene glycol and calcium carbonate; DBP+0.2% chlorhexidine (CHX); DBP+0.2% cetrimide (CTR); DBP+0.2% CHX+0.2% CTR; 2.5% sodium hypochlorite (NaOCl); and distilled water. At both periods TAP, DAP, DBP+0.2% CHX, DBP+0.2% CTR and DBP+0.2% CHX+0.2% CTR exhibited no growth (NG) of E. faecalis. Distilled water and 2.5% NaOCl obtained the lowest CFU reduction. No growth with DBP was reached only at 7 days. CHX and/or CTR pastes were as effective as DAP and TAP. A 2-day period provided an effective disinfection.

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.

The Effect of Diode Laser on Planktonic Enterococcus faecalis in Infected Root Canals in an Ex Vivo Model

OBJECTIVE

This study examined the bactericidal effect of diode laser irradiation against intracanal Enterococcus faecalis.

METHODS AND MATERIALS

m total of 128 extracted single-rooted and single-canal teeth were treated with ProTaper instruments (Dentsply Maillefer, Ballaigues, Switzerland). A total of 120 root canals were inoculated with E. faecalis for 21 days, and the samples were randomly divided into five groups: Group 1 (n = 24) samples were irrigated with only saline solution (positive controls); Group 2 (n = 24) was treated with only 5.25% sodium hypochlorite; Group 3 (n = 24) was irrigated with saline solutions activated by diode laser; Group 4 (n = 24) was treated with 5.25% sodium hypochlorite activated by diode laser; and Group 5 (n = 24) was irrigated with saline solution with methylene blue dye activated by the diode laser Fox (Sweden & Martina, Padova, Italy); additionally, eight teeth were not contaminated and their canals were irrigated with saline solution and used as a negative control. The Uro-Quick system was used to determine the microbial residual charge. The data were analyzed using Pearson's chi-square test (p < 0.001).

RESULTS

A statistically significant reduction in bacterial count was observed in Group 2 and Group 4 (p < 0.001). There were no statistically significant differences among the other groups (p > 0.001).

CONCLUSIONS

Evidence indicates that the diode laser was not more effective than sodium hypochlorite in reducing free bacteria.

In vitro evaluation of the antibacterial activity of five sealers used in root canal therapy

BACKGROUND

Antibacterial activity is one of the important characteristics of an ideal root canal sealer. The aim of this study was to investigate the antibacterial activity of five different sealers against Enterococcus faecalis using two different methods.

MATERIALS AND METHODS

The mineral trioxide aggregate (MTA) Fillapex, Tg-sealer, Endomethasone, AH-26, and RoekoSeal sealers were placed into the brain heart infusion (BHI) culture medium containing E. faecalis (PTCC1393). The diameter of the bacterial zone of inhibition was measured. In the direct contact test, a suspension containing grinded set sealers and E. faecalis bacteria was cultured in BHI after 6, 15, and 60 min. The number of colonies in milliliter was calculated. Data were subjected to one-way ANOVA and Tukey's multiple comparisons test (P < 0.05).

RESULTS

In the agar diffusion test, Endomethasone had the highest antibacterial activity against E. faecalis compared to other sealers (P < 0.001). In the direct test, the antibacterial effect of MTA Fillapex was significantly higher than that of all other sealers (P < 0.001).

CONCLUSION

The technique and components of the tested sealers affect the antibacterial activity results. This study showed that all of sealers had antimicrobial effect.

Antibacterial Efficacy of Super-Oxidized Water on Enterococcus faecalis Biofilms in Root Canal

Background

The success of endodontic treatment depends on a few crucial factors. One of these factors is the complete chemomechanic preparation of root canal against various bacteria. In particular, the effect of resistant bacteria may cause intense pain with flare-up and formation of periapical lesions. Therefore, the strong effect of irrigants plays an important role in terms of the complete elimination of these bacteria to achieve long-term successful treatment.

Objectives

The aim of this study was to investigate the antibacterial effects of super-oxidized water (SPO) in root canals infected with Enterococcus faecalis biofilms.

Methods

One hundred twenty single-root, premolar teeth were selected. Initially, the teeth were prepared and then disinfected. E. faecalis were inoculated and kept at 37°C for 24 hours in the root canals. The re-inoculation procedure was repeated on the first, fourth, seventh, and tenth days. The infected root canals were divided into one negative (saline) and one positive (sodium hypochlorite) control group and four experimental groups (super-oxidized water: 1, 2, 3, or 5 minutes) (n = 20). Paper points were placed in the root canals to control and evaluate the biofilm formation. Biofilms were counted on blood agar plates, and data was evaluated and statistically analyzed using one-way ANOVA and Tukey’s test.

Results

Although sodium hypochlorite (NaOCl) showed no statistically significant difference when compared with three and five minutes of SPO irrigation (P > 0.05), NaOCl showed statistically significant differences among all other groups (P < 0.05).

Conclusions

Super-oxidized water indicated a remarkable and similar bactericidal effect to that of traditional NaOCl against E. faecalis biofilms. In terms of successful endodontic treatment approaches, super-oxidized water may be used as an effective irrigation solution in clinics.

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.

Bacteria in the apical root canals of teeth with apical periodontitis

BACKGROUND/PURPOSE

Bacteria in the tooth root canal may cause apical periodontitis. This study examined the bacterial species present in the apical root canal of teeth with apical periodontitis. Antibiotic sensitivity tests were performed to evaluate whether these identified bacterial species were susceptible to specific kinds of antibiotics.

METHODS

Selective media plating and biochemical tests were used first to detect the bacterial species in samples taken from the apical portion of root canals of 62 teeth with apical periodontitis. The isolated bacterial species were further confirmed by matrix-assisted laser desorption ionization-time of flight mass spectrometry.

RESULTS

We found concomitant presence of two (32 teeth) or three species (18 teeth) of bacteria in 50 (80.6%) out of 62 tested teeth. However, only 34 bacterial species were identified. Of a total of 118 bacterial isolates (83 anaerobes and 35 aerobes), Prophyromonas endodontalis was detected in 10; Bacteroides, Dialister invisus or Fusobacterium nucleatum in 9; Treponema denticola or Enterococcus faecalis in 8; Peptostreptococcus or Olsenella uli in 6; and Veillonella in 5 teeth. The other 25 bacterial species were detected in fewer than five teeth. Approximately 80-95% of bacterial isolates of anaerobes were sensitive to ampicillin/sulbactam (Unasyn), amoxicillin/clavulanate (Augmentin), cefoxitin, and clindamycin. For E. faecalis, 85-90% of bacterial isolates were sensitive to gentamicin and linezolid.

CONCLUSION

Root canal infections are usually caused by a mixture of two or three species of bacteria. Specific kinds of antibiotic can be selected to control these bacterial infections after antibiotic sensitivity testing.

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.

Microbiome in the Apical Root Canal System of Teeth with Post-Treatment Apical Periodontitis

INTRODUCTION

Bacteria present in the apical root canal system are directly involved with the pathogenesis of post-treatment apical periodontitis. This study used a next-generation sequencing approach to identify the bacterial taxa occurring in cryopulverized apical root samples from root canal-treated teeth with post-treatment disease.

METHODS

Apical root specimens obtained during periradicular surgery of ten adequately treated teeth with persistent apical periodontitis were cryogenically ground. DNA was extracted from the powder and the microbiome was characterized on the basis of the V4 hypervariable region of the 16S rRNA gene by using paired-end sequencing on Illumina MiSeq device.

RESULTS

All samples were positive for the presence of bacterial DNA. Bacterial taxa were mapped to 11 phyla and 103 genera composed by 538 distinct operational taxonomic units (OTUs) at 3% of dissimilarity. Over 85% of the sequences belonged to 4 phyla: Proteobacteria, Firmicutes, Fusobacteria and Actinobacteria. In general, these 4 phyla accounted for approximately 80% of the distinct OTUs found in the apical root samples. Proteobacteria was the most abundant phylum in 6/10 samples. Fourteen genera had representatives identified in all cases. Overall, the genera Fusobacterium and Pseudomonas were the most dominant. Enterococcus was found in 4 cases, always in relatively low abundance.

CONCLUSIONS

This study showed a highly complex bacterial community in the apical root canal system of adequately treated teeth with persistent apical periodontitis. This suggests that this disease is characterized by multispecies bacterial communities and has a heterogeneous etiology, because the community composition largely varied from case to case.

Phage therapy against Enterococcus faecalis in dental root canals

Antibiotic resistance is an ever-growing problem faced by all major sectors of health care, including dentistry. Recurrent infections related to multidrug-resistant bacteria such as methicillin-resistant Staphylococcus aureus, carbapenem-resistant Enterobacteriaceae, and vancomycin-resistant enterococci (VRE) in hospitals are untreatable and question the effectiveness of notable drugs. Two major reasons for these recurrent infections are acquired antibiotic resistance genes and biofilm formation. None of the traditionally known effective techniques have been able to efficiently resolve these issues. Hence, development of a highly effective antibacterial practice has become inevitable. One example of a hard-to-eradicate pathogen in dentistry is Enterococcus faecalis, which is one of the most common threats observed in recurrent root canal treatment failures, of which the most problematic to treat are its biofilm-forming VRE strains. An effective response against such infections could be the use of bacteriophages (phages). Phage therapy was found to be highly effective against biofilm and multidrug-resistant bacteria and has other advantages like ease of isolation and possibilities for genetic manipulations. The potential of phage therapy in dentistry, in particular against E. faecalis biofilms in root canals, is almost unexplored. Here we review the efforts to develop phage therapy against biofilms. We also focus on the phages isolated against E. faecalis and discuss the possibility of using phages against E. faecalis biofilm in root canals.

In vitro model of production of antibodies; a new approach to reveal the presence of key bacteria in polymicrobial environments

Background

There is a rapid emergence of multiple resistant gram-negative bacteria due to overuse of antibiotics in the treatment of infections. Biofilms consist of polymicrobial communities that survive the host’s defense system. The key bacteria in biofilms are slow growing and support an attachment and rapid growth of other microorganisms. Current antimicrobial strategies often fail due to poor diagnosis of key pathogens in biofilms.

The study aims to develop anti-bacterial human antibodies in vitro from patients who had recently undergone a systemic infection by pathogenic bacteria and to use these antibodies as a tool for detecting bacteria in biofilms.

Methods

Lymphocytes were separated from whole blood of patients (n = 10) and stimulated with heat-killed bacteria to produce antibodies in vitro. The specificity of antibodies in recognizing the bacteria against which they were directed was evaluated by surface plasmon resonance system (SPR) and electron microscopy. The ulcer secretions from patients with chronic and acute leg ulcers and healthy controls were analyzed by the SPR system and the results were compared with culture studies.

Results

The produced antibodies recognized bacteria with high sensitivity (SPR). The antibodies against Enterococcus fecalis bound specifically to the microorganism in a bacterial co-culture that was visualized by electron microscopy.

Conclusion

In the present work, a method for producing specific antibodies against bacteria is introduced to recognize bacterial components in body fluids of patients suffering from pathogenic biofilms. This diagnostic technique may be most useful in clinical microbiology and in the choice of antibiotics in the treatment of serious infections.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-016-0821-5) contains supplementary material, which is available to authorized users.

Antibacterial Activity of Leaf Extract of Annona muricata and Simarouba glauca on Enterococcus faecalis

AIM

To determine the antimicrobial effect of water extracts of leaves of Annona muricata and Simarouba glauca on Enterococcus faecalis using agar diffusion method.

MATERIALS AND METHODS

Dried leaves of A. muricata and S. glauca were powdered and extracted in a soxhlet apparatus. Enterococcus faecalis was grown overnight in Trypticase soy agar plates. About 10 μl of each extract was placed on agar plates and incubated overnight. The zone of inhibition was measured after 24 hours. About 1% sodium hypochlorite and distilled water were used as positive and negative controls.

RESULTS

The leaf extract of A. muricata showed similar effectiveness as that of sodium hypochlorite, whereas the leaf extract of S. glauca showed only a slight reduction in growth of E. faecalis.

CONCLUSION

Leaf extract of A. muricata can be developed as an alternative to sodium hypochlorite for root canal irrigants.

CLINICAL SIGNIFICANCE

Success of endodontic treatment depends on complete disinfection of the root canals. Root canal irrigants have a major role in complete disinfection of the root canals. Chemical root canal irrigants are more or less toxic to the oral environment. In this study, naturally derived leaf extracts of A. muricata and S. glauca are compared with sodium hypochlorite for its effectiveness against E. faecalis - the most common pathogen found in the root canals.

Assessment of Correlation between Clinical Parameters and Pulp Canal Pathogens in Endodontic Pathologies: A Microbiological Study

INTRODUCTION

Success and failure of root canal therapy is largely dependent on the clinician and the patient. Once the tooth is restored into its functional and esthetic place, the root canal therapy is considered to be complete. It is a well-known fact that root canal space acts as a rich reservoir for microorganisms. Past studies show that root canal harbors an array of different microorganisms. Streptococcus mitis and Enterococcus faecalis have been found to be the most prevalent microorganisms isolated from the infected pulp canal space. Hence, we evaluated the association of endodontic signs and symptoms with root canal pathogens.

MATERIALS AND METHODS

A total of 120 patients were selected for the study and divided broadly into two groups: Group I containing patients with primary infection and group II containing patients in which retreatment was required. Both groups contained 60 patients each. Clinical parameters recorded for the study are pain, tenderness on percussion, swelling, periapical radiolucency on radiographic analysis, caries, sinus formation, and tooth mobility. After assessment, opening, and initial filing, sterile paper points were inserted into the root canal space for collection of microbiological sample, which was further send to laboratory for cultural analysis. All the results were analyzed by Statistical Package for the Social Sciences (SPSS) software. Student's t-test and Fisher's exact test were used to evaluate the level of significance.

RESULTS

While comparing the mean age of the patients in the two groups, no significant association was seen. Statistically significant results were obtained while comparing the association between pain and S. mitis. Positive correlation was seen on comparing the association between tenderness on percussion and E. faecalis. Also, a positive association was seen between periapical radiolucency and S. mitis.

CONCLUSION

Strong positive correlation exists between S. mitis and E. faecalis and endodontic signs and symptoms.

CLINICAL SIGNIFICANCE

Sound knowledge regarding the association of microbes of root canal and specific endodontic signs and symptoms could help therapeutic management of root canal infections effectively.

Microbial Ecosystem Analysis in Root Canal Infections Refractory to Endodontic Treatment

INTRODUCTION

The purpose of this study was to combine multiple displacement amplification and checkerboard DNA-DNA hybridization to qualitatively and quantitatively evaluate the microbiota present in infections refractory to endodontic treatment.

METHODS

The subjects of this study were 40 patients presenting with periapical lesions refractory to endodontic treatment. Samples were taken by scraping or filing root canal walls with a #10 K-type hand file. Sample DNA was amplified by multiple displacement amplification, and the levels of 107 bacterial taxa were analyzed by checkerboard DNA-DNA hybridization. The taxa were divided into 3 distinct microbial populations depending on their mean proportion in samples (% DNA probe counts ± standard error of the mean) as follows: dominant (≥3.0%), subdominant (>1.6%-3.0%), and residual (≤1.6%) populations. The significance of differences was determined using the Mann-Whitney test.

RESULTS

The taxa present with the highest mean proportions (constituting the dominant population) were Corynebacterium diphtheriae (8.03 ± 0.98), Porphyromonas gingivalis (5.42 ± 2.09), Streptococcus sobrinus (5.33 ± 0.69), and Stenotrophomonas maltophilia (4.72 ± 1.73). Among the subdominant population were Eubacterium saphenum (3.85 ± 1.06), Helicobacter pylori (3.16 ± 0.62), Dialister pneumosintes (3.12 ± 1.1), Clostridium difficile (2.74 ± 0.41), Enterobacter agglomerans (2.64 ± 0.54), Salmonella enterica (2.51 ± 0.52), Mobiluncus mulieris (2.44 ± 0.6), and Klebsiella oxytoca (2.32 ± 0.66). In the population of bacteria present at the lowest mean proportions (the residual population), Bacteroides ureolyticus (0.04 ± 0.01), Haemophilus influenzae (0.04 ± 0.02), and Prevotella oris (0.01 ± 0.01) were found at the lowest mean proportions. Enterococcus faecalis was detected in the residual population (0.52 ± 0.26).

CONCLUSIONS

The microbial climax community in teeth refractory to endodontic treatment not only harbors medically important species but also contains distinct microbial consortia present with different population levels.

Comparative evaluation of antimicrobial efficacy of three herbal irrigants in reducing intracanal E. faecalis populations: An in vitro study

Background

The present study aimed to evaluate the intracanal bacterial reduction promoted by chemomechanical preparation using three different herbal extracts named Ocimum sanctum (OS), Cinnamomum zeylanicum (CZ), Syzygium aromaticum (SA) against Enterococcus faecalis.

Material and Methods

Root canals from extracted teeth were contaminated with Enterococcus faecalis ATCC 29212 for 7 days and then randomly distributed into 3 experimental groups of 10 teeth each: which includes conventional irrigation with OS, CZ and SA. The control groups included 5 teeth each consisting of NaOCl (positive control) and distilled water (negative control). Samples taken before and after chemomechanical procedures were cultured, and the colony-forming units (CFUs) were counted. Bacterial identification was performed using Polymerase chain reaction technique. The statistical analyses were performed with various tests.

Results

Reduction in the intracanal bacterial populations was highly significant for all the experimental groups. CZ and SA showed 80 to 85% intracanal bacterial reduction while O. Sanctum revealed only 70 to 75 % reduction. NaOCl showed 96 to 100 % bacterial reduction on the other hand distilled water showed very minimal bacterial reduction i.e 10 to 16%.

Conclusions

Cinnamomum zeylanicum, Syzygium aromaticum and Ocimum sanctum showed intracanal bacterial reduction against Enterococcus faecalis. The 3 experimental groups were less effective in terms of intracanal bacterial reduction as compare to NaOCl but more effective than distilled water.

Key words:Antimicrobial activity, Cinnamomum zeylanicum, Enterococcus faecalis, Ocimum sanctum, Syzygium aromaticum, herbal extracts.

Enterococcus faecalis promotes osteoclast differentiation within an osteoblast/osteoclast co-culture system

OBJECTIVE

To investigate the effects of heat-killed Enterococcus faecalis ATCC 29212 and P25RC clinical strain (derived from an obturated root canal with apical periodontitis) on osteoclast differentiation within an osteoblast/osteoclast co-culture system.

RESULTS

Heat-killed E. faecalis significantly increased the proportion of multinucleated osteoclastic cells (MNCs) within the co-culture system. The IL-6 level was significantly increased upon exposure to heat-killed E. faecalis. Gene expression levels of NFATc1 and cathepsin K were significantly up-regulated compared to the untreated control. EphrinB2 and EphB4 expressions at both the mRNA and protein levels were also significantly upregulated compared to the untreated control.

CONCLUSIONS

Heat-killed E. faecalis can induce osteoclast differentiation within the osteoblast/osteoclast co-culture system in vitro, possibly through ephrinB2-EphB4 bidirectional signaling.

Ions Release and pH of Calcium Hydroxide-, Chlorhexidine- and Bioactive Glass-Based Endodontic Medicaments

Abstract This study evaluated pH and release of calcium, sodium and phosphate ions from different medications in human dentin. Fifty premolars were prepared and randomly divided into groups: (CHX) - 2% chlorhexidine gel; (CHX + CH) - CHX + calcium hydroxide PA; (CH) - CH + propylene glycol 600; (NPBG) - experimental niobium phosphate bioactive glass + distilled water; (BG) - bioactive glass (Bio-Gran) + distilled water. The specimens were immersed in deionized water and the pH variations were measured. The quantification of ions in the solutions was made by inductively coupled plasma - atomic emission spectroscopy (ICP/AES) at 10 min, 24 h, 7, 14, 21 and 30 days. The results were analyzed by ANOVA and Tukey`s test, with a significance level of 5%. CH had the highest level of calcium ions release at 30 days, while CHX and BG released more sodium ions. BG, NPBG and CHX released a higher amount of phosphate ions. The pH of CH was significantly higher compared with the other groups. CH favored the greatest increase of pH and calcium ions release. The bioactive glasses released more sodium and phosphate ions and presented an alkaline pH immediately and after 30 days.

Bactericidal Effect of Strong Acid Electrolyzed Water against Flow Enterococcus faecalis Biofilms

INTRODUCTION

This study evaluated the bactericidal effect of strong acid electrolyzed water (SAEW) against flow Enterococcus faecalis biofilm and its potential application as a root canal irrigant.

METHODS

Flow E. faecalis biofilms were generated under a constant shear flow in a microfluidic system. For comparison, static E. faecalis biofilms were generated under a static condition on coverslip surfaces. Both the flow and static E. faecalis biofilms were treated with SAEW. Sodium hypochlorite (NaOCl, 5.25%) and normal saline (0.9%) were included as the controls. Bacterial reductions were evaluated using confocal laser scanning microscopy and the cell count method. Morphological changes of bacterial cells were observed using scanning electron microscopy.

RESULTS

The confocal laser scanning microscopic and cell count results showed that SAEW had a bactericidal effect similar to that of 5.25% NaOCl against both the flow and static E. faecalis biofilms. The scanning electron microscopic results showed that smooth, consecutive, and bright bacteria surfaces became rough, shrunken, and even lysed after treated with SAEW, similar to those in the NaOCl group.

CONCLUSIONS

SAEW had an effective bactericidal effect against both the flow and static E. faecalis biofilms, and it might be qualified as a root canal irrigant for effective root canal disinfection.

Evaluation of the Antibacterial Efficacy of Azadirachta Indica, Commiphora Myrrha, Glycyrrhiza Glabra Against Enterococcus Faecalis using Real Time PCR

AIM

To compare the antibacterial efficacy of Azadirachta indica (Neem), Commiphora myrrha (Myrrh), Glycyrrhiza glabra (Liquorice) with 2% Chlorhexidine (CHX) against E. faecalis by using Real Time PCR.

MATERIALS AND METHODS

A total of fifty teeth specimens (n=50) were inoculated with E. faecalis for 21 days. Specimens were divided into five groups (Group 1: Myrrh, Group 2: Neem, Group 3: Liquorice, Group 4: 2% CHX and Group 5: Saline (negative control)). The intracanal medicaments were packed inside the tooth. After 5 days, the remaining microbial load was determined by using real time PCR.

RESULTS

Threshold cycle (Ct) values of Myrrh extract, Neem extract, Liquorice Extract, 2% CHX and saline were found to be 30.94, 23.85, 21.38, 30.93 and 17.8 respectively.

CONCLUSION

Myrrh extract showed inhibition of E.faecalis equal to that of 2% CHX followed by Neem, Liquorice and Saline.

Comparison of the Antimicrobial Efficacy of Two Antibiotics Sparfloxacin and Augmentin as Experimental Root Canal Irrigating Solutions against Enterococcus faecalis - An Invitro Study

INTRODUCTION

One of the main goals of endodontic treatment is root canal disinfection and to prevent subsequent chances of reinfection. Adjuvant to instrumentation, root canal irrigants are required to eliminate the bacteria found on the root canal walls and lateral canals within the dentinal tubules.

AIM

To measure and compare the antibacterial efficacy of two antibiotics as experimental root canal irrigating solutions against Enterococcus faecalis (E. faecalis).

MATERIALS AND METHODS

Fifteen Brain Heart Infusion agar plates were inoculated with Enterococcus faecalis-American Type Culture Collection (ATCC) 29212. 5 micrograms (mcg) Sparfloxacin discs, 30mcg Augmentin discs, and sterile paper test discs saturated with 2% Chlorhexidine (CHX), 3% Sodium Hypochlorite (NaOCl) and 5% NaOCl solutions were placed on agar plates. Sodium Chloride 0.9% (NaCl) paper discs were used as controls. Fifteen plates were incubated aerobically at 37°C. Results were expressed as per the terms of the diameter of the inhibition zone.

RESULTS

Results suggested a statistically significant difference in the zones of inhibition between five irrigating solutions (p < 0.001).

CONCLUSION

Although, zones of inhibition were found in all the groups, 5mcg Sparfloxacin and 30mcg Augmentin showed maximum antimicrobial activity against E.faecalis.

Antibacterial effects of N-acetylcysteine against endodontic pathogens

The success of endodontic treatment depends on the eradication of microorganisms from the root canal system and the prevention of reinfection. The purpose of this investigation was to evaluate the antibacterial and antibiofilm efficacy of N-acetylcysteine (NAC), an antioxidant mucolytic agent, as an intracanal medicament against selected endodontic pathogens. Minimum inhibitory concentrations (MICs) of NAC for Actinomyces naeslundii, Lactobacillus salivarius, Streptococcus mutans, and Enterococcus faecalis were determined using the broth microdilution method. NAC showed antibacterial activity, with MIC values of 0.78-1.56 mg/ml. The effect of NAC on biofilm formation of each bacterium and a multispecies culture consisting of the four bacterial species was assessed by crystal violet staining. NAC significantly inhibited biofilm formation by all the monospecies and multispecies bacteria at minimum concentrations of 0.78-3.13 mg/ml. The efficacy of NAC for biofilm disruption was evaluated by scanning electron microscopy and ATP-bioluminescence quantification using mature multispecies biofilms. Preformed mature multispecies biofilms on saliva-coated hydroxyapatite disks were disrupted within 10 min by treatment with NAC at concentrations of 25 mg/ml or higher. After 24 h of treatment, the viability of mature biofilms was reduced by > 99% compared with the control. Moreover, the biofilm disrupting activity of NAC was significantly higher than that of saturated calcium hydroxide or 2% chlorhexidine solution. Within the limitations of this in vitro study, we conclude that NAC has excellent antibacterial and antibiofilm efficacy against endodontic pathogens and may be used as an alternative intracanal medicament in root canal therapies.

Oral microbiota species in acute apical endodontic abscesses

Background and objectives

Acute apical abscesses are serious endodontic diseases resulting from pulpal infection with opportunistic oral microorganisms. The objective of this study was to identify and compare the oral microbiota in patients (N=18) exhibiting acute apical abscesses, originating from the demographic region in Portland, Oregon. The study hypothesis is that abscesses obtained from this demographic region may contain unique microorganisms not identified in specimens from other regions.

Design

Endodontic abscesses were sampled from patients at the Oregon Health & Science University (OHSU) School of Dentistry. DNA from abscess specimens was subjected to polymerase chain reaction amplification using 16S rRNA gene-specific primers and Cy3-dCTP labeling. Labeled DNA was then applied to microbial microarrays (280 species) generated by the Human Oral Microbial Identification Microarray Laboratory (Forsyth Institute, Cambridge, MA).

Results

The most prevalent microorganisms, found across multiple abscess specimens, include Fusobacterium nucleatum, Parvimonas micra, Megasphaera species clone CS025, Prevotella multisaccharivorax, Atopobium rimae, and Porphyromonas endodontalis. The most abundant microorganisms, found in highest numbers within individual abscesses, include F. nucleatum, P. micra, Streptococcus Cluster III, Solobacterium moorei, Streptococcus constellatus, and Porphyromonas endodontalis. Strong bacterial associations were identified between Prevotella multisaccharivorax, Acidaminococcaceae species clone DM071, Megasphaera species clone CS025, Actinomyces species clone EP053, and Streptococcus cristatus (all with Spearman coefficients >0.9).

Conclusions

Cultivable and uncultivable bacterial species have been identified in endodontic abscesses obtained from the Portland, Oregon demographic region, and taxa identifications correlated well with other published studies, with the exception of Treponema and Streptococcus cristae, which were not commonly identified in endodontic abscesses between the demographic region in Portland, Oregon and other regions.

Cysteamine Enhances Biofilm Eradication Efficacy of Calcium Hydroxide

INTRODUCTION

Calcium hydroxide (Ca[OH]2) is a widely used interappointment dressing, but its antibacterial property is compromised by dentin. Hence, the addition of chlorhexidine (CHX) with Ca(OH)2 has been proposed. However, the antimicrobial efficacy of this mixture compared with Ca(OH)2 alone is currently still debatable. Cysteamine is a mucolytic agent used to reduce the viscosity of mucus through the disruption of proteins, which are also important components of the extracellular matrix of biofilms. The aims of this study were to determine the efficacy of cysteamine alone and in combination with Ca(OH)2 to eradicate Enterococcus faecalis biofilm compared with CHX with Ca(OH)2, and to determine if this effect is affected by dentin.

METHODS

The biofilm eradication efficacies of Ca(OH)2 alone and with cysteamine were determined using 7-day E. faecalis biofilm cultured on dentin discs and compared with Ca(OH)2 with 2% CHX. The effects of dentin on the efficacies of Ca(OH)2 alone and with either cysteamine or CHX were examined.

RESULTS

Cysteamine alone completely abolished E. faecalis biofilm at 200 mg/mL. The combination of Ca(OH)2 with either cysteamine at 10 mg/mL or 2% CHX completely obliterated E. faecalis biofilm. Cysteamine with Ca(OH)2 completely eradicated E. faecalis biofilm despite preincubation with dentin, whereas CHX with Ca(OH)2 was less effective.

CONCLUSIONS

Cysteamine effectively eliminated E. faecalis biofilm and showed synergistic effects in combination with Ca(OH)2, which were unaffected by dentin. Hence, our findings support the use of cysteamine as a potential adjunct to Ca(OH)2 as an interappointment dressing.

Expression of Alzheimer-Type Neurofibrillary Epitopes in Primary Rat Cortical Neurons Following Infection with Enterococcus faecalis

The neurofibrillary tau pathology and amyloid deposits seen in Alzheimer’s disease (AD) also have been seen in bacteria-infected brains. However, few studies have examined the role of these bacteria in the generation of tau pathology. One suggested link between infection and AD is edentulism, the complete loss of teeth. Edentulism can result from chronic periodontal disease due to infection by Enterococcus faecalis. The current study assessed the ability to generate early Alzheimer-like neurofibrillary epitopes in primary rat cortical neurons through bacterial infection by E. faecalis. Seven-day old cultured neurons were infected with E. faecalis for 24 and 48 h. An upward molecular weight shift in tau by Western blotting (WB) and increased appearance of tau reactivity in cell bodies and degenerating neurites was found in the 48 h infection group for the antibody CP13 (phospho-Serine 202). A substantial increase in reactivity of Alz-50 was seen at 24 and 48 h after infection. Furthermore, extensive microtubule-associated protein 2 (MAP2) reactivity also was seen at 24 and 48 h post-infection. Our preliminary findings suggest a potential link between E. faecalis infection and intracellular changes that may help facilitate early AD-like neurofibrillary pathology.

Highlights

Enterococcus faecalis used in the generation of AD neurofibrillary epitopes in rat.

Infection increases Alz-50, phospho-Serine 202 tau, and MAP2 expression.

Infection by Enterococcus may play a role in early Alzheimer neurofibrillary changes.

Antibacterial efficacy of Azadirachta indica, Mimusops elengi and 2% CHX on multispecies dentinal biofilm

Aims:

To check the antimicrobial activity of Azadirachta indica (Neem), Mimusops elengi (Bakul), and Chlorhexidine gluconate (CHX) on multispecies biofilm of common endodontic pathogens such as Streptococcus mutans, Enterococcus faecalis, Staphylococcus aureus and Candida albicans.

Settings and Design:

In vitro dentin disinfection model used to check the antimicrobial efficacy of herbal extracts.

Materials and Methods:

The in vitro dentin disinfection model was used to check the antimicrobial activity of the methanolic extracts of the medicinal plants along with Chlorhexidine gluconate. The polymicrobial biofilm was allowed to grow on extracted teeth sections for a period of 21 days. Remaining microbial load in the form of CFU/ml after the antimicrobial treatment was tabulated, and data were statistically analyzed using ANOVA and Bonferroni post-hoc tests.

Statistical Analysis Used:

SPSS version 17, one-way ANOVA, Bonferroni post-hoc test.

Results:

Both the plant extracts showed considerable antimicrobial efficacy as compared to negative control. 2% CHX was the most effective antimicrobial agent having statistically significant difference against plant extracts and negative control (saline).

Conclusion:

The methanolic extract of A. Indica, M. elengi, and Chlorhexidine Gluconate has considerable antimicrobial activity against polymicrobial dentinal biofilm of S. mutans, E. faecalis, S. aureus and C. albicans.

Confocal microscopy evaluation of the effect of irrigants on Enterococcus faecalis biofilm: An in vitro study

The purpose of this study was to evaluate in vitro the effectiveness of two endodontic irrigants and their association against Enterococcus faecalis (E. faecalis) by confocal laser scanning microscope (CLSM). Twenty-four bovine incisors were inoculated in a monoculture of E. faecalis for 21 days. After this period, the teeth were divided into three test groups (n = 5) according to the chemical used. Group 1: 2.5% sodium hypochlorite (NaOCl), group 2: 2% chlorhexidine gel (CHX), group 3: 2.5% NaOCl + 2% CHX gel, and two control groups (n = 3): negative control group (NCG)-sterile and without root canals preparation and positive control group (PCG)-saline. Then, the samples were stained with SYTO9 and propidium iodide and subjected to analysis by CLSM. Bacterial viability was quantitatively analyzed by the proportions of dead and live bacteria in the biofilm remnants. Statistical analysis was performed by the One-way ANOVA test (p = 0.05). No statistical differences were observed to bacterial viability. According to CLSM analysis, none of the tested substances could completely eliminate E. faecalis from the root canal space. Until now, there are no irrigant solutions able to completely eliminate E. faecalis from the root canal. In this regard, the search for irrigants able to intensify the antimicrobial action is of paramount importance.

Enterococcus faecalis attenuates osteogenesis through activation of p38 and ERK1/2 pathways in MC3T3-E1 cells

AIM

To explore the role of Enterococcus faecalis in the proliferation, apoptosis and differentiation of osteoblasts.

METHODOLOGY

Pre-osteoblastic MC3T3-E1 cells were treated with heat-killed E. faecalis ATCC 29212 and clinical E. faecalis P25RC strains, respectively. Cell proliferation, mineralized calcium deposition, alkaline phosphatase (ALP) activity and apoptosis were assessed at various time-points. The expression levels of osteogenic-related genes including ALP, osteocalcin (OC), runt-related protein 2 (Runx2) and collagen type 1 (COL1) were also analysed throughout the duration of the experiment. Additionally, the involvement of mitogen-activated protein kinases (MAPKs) signalling pathways was analysed by Western blotting. In the presence of culture supernatant from E. faecalis-treated murine macrophages, apoptosis of MC3T3-E1 cells was detected with flow cytometry. Data were analysed using analysis of variance (anova), and P < 0.05 was considered significantly different.

RESULTS

E. faecalis significantly inhibited proliferation (P < 0.05) and also significantly induced apoptosis of MC3T3-E1 cells (P < 0.05), whilst differentiation seemed to be unaffected after 7 days of E. faecalis treatment. However, osteogenic differentiation was significantly inhibited with 21-day E. faecalis treatment (P < 0.05). The p38 and ERK1/2 phosphorylation pathways associated with mineral deposition and apoptosis were significantly activated in MC3T3-E1 cells. The culture supernatants from E. faecalis-treated macrophages induced osteoblast apoptosis.

CONCLUSIONS

E. faecalis exerted an inhibitory effect on osteogenesis in pre-osteoblastic MC3T3-E1 cells via phosphorylation of p38 and ERK1/2.

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.

Effect of gaseous ozone on Enterococcus faecalis biofilm-an in vitro study

OBJECTIVES

The aim of this study was to evaluate the antimicrobial effect of gaseous ozone compared to conventional methods against Enterococcus faecalis.

MATERIALS AND METHODS

One hundred twenty-five teeth were infected by E. faecalis and were incubated for 72 h to form biofilm. Teeth were distributed among five groups. In the first group, ozone was used; in the second group, teeth were rinsed with 20 % ethylenediaminetetraacetic acid (EDTA); in the third group, with 3 % sodium hypochlorite (NaOCl). Group 4 combined 20 % EDTA with ozone. NaOCl and ozone were combined in group 5. After treatment, the samples with paper points were taken, followed by dentin samples taken with K-file, and cultured for 24 h. Then bacterial colonies were counted.

RESULTS

All treatments reduced significantly (p < 0.05) the bacteria. Paper points' samples showed 85.38 % reduction after ozone. The highest reduction was observed in NaOCl group (99.98 %). EDTA reduced bacteria by 80.64 %. Combination of NaOCl and ozone eradicated 99.95 % of the bacteria. Combination of EDTA and ozone reduced E. faecalis up to 91.33 %. The dentin chips showed the following: the highest CFU counts were observed in EDTA group, followed by ozone and NaOCl group. The lowest CFU counts were found in NaOCl-ozone group and EDTA-ozone group.

CONCLUSIONS

Ozone reduced E. faecalis, even organised in a biofilm, however, lower than NaOCl. No treatment reduced totally the bacteria.

CLINICAL RELEVANCE

Used as an adjuvant, ozone can increase the efficacy of conventional rinsing like EDTA and presents an alternative treatment when NaOCl cannot be used e.g. in teeth with a wide-open apical foramen.

In vitro comparison of antimicrobial effectiveness of QMix and other final irrigants in human root canals

Final root canal irrigation stands as an effective strategy for eliminating the dentin infection. This study aimed to investigate and compare the antibacterial efficacy of QMix and other four final irrigation regimens in reducing Enterococcus faecalis within human root canals. Single-canal human teeth contaminated with E. faecalis for 4 weeks were prepared chemomechanically with sodium hypochlorite (NaOCl). Then, the teeth were randomly assigned into six groups according to the final irrigation protocols: (1) EDTA/NaOCl, 17% EDTA followed by 5.25% NaOCl; (2) EDTA/chlorhexidine (CHX), 17% EDTA followed by 2% CHX; (3) EDTA/cetrimide (CTR), 17% EDTA followed by 2% CTR; (4) MTAD; (5) QMix; and (6) control, 0.9% saline. Bacterial samples collected before instrumentation and after final irrigation were cultured and the colony-forming units (CFUs) were counted. The CFUs in the QMix, EDTA/CHX, and EDTA/CTR groups were significantly lower than those in the EDTA/NaOCl group. No significant differences were observed between the QMix, EDTA/CHX, and EDTA/CTR groups. MTAD showed weaker ability than QMix and EDTA/CHX to eliminate E. faecalis, but it caused a greater reduction in CFU than EDTA/NaOCl. Hence, the antimicrobial activity of QMix was comparable to that of EDTA/CHX and EDTA/CTR and more effective than that of EDTA/NaOCl against intracanal E. faecalis.

Implant Placement in Failed Endodontic Sites: A Review

Dental implants may fail to osseointegrate in sites of endodontic failure. This may occur as a result colonization by various anaerobic and facultative bacterial species. If an implant is placed in a site where vegetative bacteria are residing, the implant may fail to integrate if a bacterial colonization proceeds coronally. If the implant apical cortical bone is thin or if there is an apical fenestration, the colonization may proceed through the thin or nonexistent bone through the covering mucosa, relieving inflammatory pressure to create an apical (retrograde) peri-implantitis. Enterococcus faecalis may be the prime culprit in these types of implant failures. After thorough debridement, the implant may be immediately placed after extraction of an endodontically failed tooth, and the patient treated with an appropriate antibiotic. Alternatively waiting for postextraction healing and subsequent implant placement can be done. Nevertheless, either way may allow for the formation of bacterial vegetative forms or biofilms. The implant surface may be colonized when the surface is exposed to the bacteria. Thorough debridement is crucial. Nonetheless, organisms may persist. Randomized controlled trials are needed to elucidate this issue.

Comparative evaluation of effect of different irrigation solutions against Enterococcus faecalis: A polymerase chain reaction-based study

Enterococcus faecalis is the most isolated or detected species from oral infections including marginal periodontitis, infected root canals, periradicular abscesses and also detected in cases of failed endodontic therapy. To prevent endodontic treatment failure irrigation is mandatory for the effective removal of smear layer, pulp tissue, and microorganisms. Cultivation and other traditional identification methods have been demonstrated to have several limitations when it comes to microbiological identification. Polymerase chain reaction was selected because it has an added advantage over traditional microbiological methods.