Virulence factors of Enterococcus faecalis: relationship to endodontic disease. ACTA ACUST UNITED AC. 2004;15:308-320. [PMID: 15470268 DOI: 10.1177/154411130401500506]

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.

The Identification of Novel Diagnostic Marker Genes for the Detection of Beer Spoiling Pediococcus damnosus Strains Using the BlAst Diagnostic Gene findEr

As the number of bacterial genomes increases dramatically, the demand for easy to use tools with transparent functionality and comprehensible output for applied comparative genomics grows as well. We present BlAst Diagnostic Gene findEr (BADGE), a tool for the rapid prediction of diagnostic marker genes (DMGs) for the differentiation of bacterial groups (e.g. pathogenic / nonpathogenic). DMG identification settings can be modified easily and installing and running BADGE does not require specific bioinformatics skills. During the BADGE run the user is informed step by step about the DMG finding process, thus making it easy to evaluate the impact of chosen settings and options. On the basis of an example with relevance for beer brewing, being one of the oldest biotechnological processes known, we show a straightforward procedure, from phenotyping, genome sequencing, assembly and annotation, up to a discriminant marker gene PCR assay, making comparative genomics a means to an end. The value and the functionality of BADGE were thoroughly examined, resulting in the successful identification and validation of an outstanding novel DMG (fabZ) for the discrimination of harmless and harmful contaminations of Pediococcus damnosus, which can be applied for spoilage risk determination in breweries. Concomitantly, we present and compare five complete P. damnosus genomes sequenced in this study, finding that the ability to produce the unwanted, spoilage associated off-flavor diacetyl is a plasmid encoded trait in this important beer spoiling species.

Collagen degradation and MMP9 activation by Enterococcus faecalis contribute to intestinal anastomotic leak

Even under the most expert care, a properly constructed intestinal anastomosis can fail to heal, resulting in leakage of its contents, peritonitis, and sepsis. The cause of anastomotic leak remains unknown, and its incidence has not changed in decades. We demonstrate that the commensal bacterium Enterococcus faecalis contributes to the pathogenesis of anastomotic leak through its capacity to degrade collagen and to activate tissue matrix metalloproteinase 9 (MMP9) in host intestinal tissues. We demonstrate in rats that leaking anastomotic tissues were colonized by E. faecalis strains that showed an increased collagen-degrading activity and also an increased ability to activate host MMP9, both of which contributed to anastomotic leakage. We demonstrate that the E. faecalis genes gelE and sprE were required for E. faecalis-mediated MMP9 activation. Either elimination of E. faecalis strains through direct topical antibiotics applied to rat intestinal tissues or pharmacological suppression of intestinal MMP9 activation prevented anastomotic leak in rats. In contrast, the standard recommended intravenous antibiotics used in patients undergoing colorectal surgery did not eliminate E. faecalis at anastomotic tissues nor did they prevent leak in our rat model. Finally, we show in humans undergoing colon surgery and treated with the standard recommended intravenous antibiotics that their anastomotic tissues still contained E. faecalis and other bacterial strains with collagen-degrading/MMP9-activating activity. We suggest that intestinal microbes with the capacity to produce collagenases and to activate host metalloproteinase MMP9 may break down collagen in the intestinal tissue contributing to anastomotic leak.

Antimicrobial efficacy of different root canal sealers by using real-time polymerase chain reaction: An ex vivo study

Background:

Root canal sealers help to minimize leakage, provides antimicrobial activity to reduce the possibility of residual bacteria, and to resolve periapical lesion.

Aim:

To compare five different root canal sealers against Enterococcus faecalis in an infected root canal model by using real-time polymerase chain reaction (RT-PCR).

Settings and Design:

Sixty human mandibular premolars were sectioned to standardize a uniform length of 14 mm. Fifty microliters of the inoculum containing E. faecalis were transferred into each microcentrifuge tube (n = 60). The samples were divided into six groups Tubli-Seal, Apexit Plus, Fillapex, AH Plus, RoekoSeal, and Positive control, respectively.

Materials and Methods:

Five groups after the incubation with the microorganism E. faecalis were coated with different root canal sealers and obturated using F3 ProTaper Gutta-percha point. The dentinal shavings were collected and analyzed for RT-PCR.

Statistical Analysis:

The mean difference between six groups was calculated using analysis of variance and post-hoc test.

Results:

The highest antibacterial activity was achieved with Tubli-Seal (1938.13 DNA in pictogram [pg]) and least by RoekoSeal (3034.54 DNA in pg).

Conclusion:

The maximum antimicrobial activity was achieved AH Plus and Tubli-Seal. RT-PCR can be used as a valuable and accurate tool for testing antimicrobial activity.

Enterococcus faecalis from Food, Clinical Specimens, and Oral Sites: Prevalence of Virulence Factors in Association with Biofilm Formation

Enterococci have gained significance as the cause of nosocomial infections; they occur as food contaminants and have also been linked to dental diseases. E. faecalis has a great potential to spread virulence as well as antibiotic resistance genes via horizontal gene transfer. The integration of food-borne enterococci into the oral biofilm in-vivo has been observed. Therefore, we investigated the virulence determinants and antibiotic resistance of 97 E. faecalis isolates from the oral cavity, food, and clinical specimens. In addition, phenotypic expression of gelatinase and cytolysin were tested, in-vitro biofilm formation was quantified and isolates were compared for strain relatedness via pulsed field gel electrophoresis (PFGE). Each isolate was found to possess two or more virulence genes, most frequently gelE, efaA, and asa1. Notably, plaque/saliva isolates possessed the highest abundance of virulence genes, the highest levels of phenotypic gelatinase and hemolysin activity and concurrently a high ability to form biofilm. The presence of asa1 was associated with biofilm formation. The biofilm formation capacity of clinical and plaque/saliva isolates was considerably higher than that of food isolates and they also showed similar antibiotic resistance patterns. These results indicate that the oral cavity can constitute a reservoir for virulent E. faecalis strains possessing antibiotic resistance traits and at the same time distinct biofilm formation capabilities facilitating exchange of genetic material.

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.

Tumor Necrosis Factor Receptor-associated Factor 6 Plays a Role in the Inflammatory Responses of Human Periodontal Ligament Fibroblasts to Enterococcus faecalis

INTRODUCTION

Enterococcus faecalis is a frequently isolated microorganism in persistent periapical lesion or secondary infection. However, no evidence has demonstrated that E. faecalis induced inflammation directly in the apical area. This study aimed to explore the mechanism of the inflammatory responses of human periodontal ligament fibroblasts (PDLs) to E. faecalis.

METHODS

PDLs were stimulated with heat-killed E. faecalis (HKEF) or lipoteichoic acid from E. faecalis (LTA) with or without silencing of tumor necrosis factor receptor-associated factor 6 (TRAF6). The expressions of toll-like receptor 2/4, nucleotide-binding oligomerization domain 1/2, and TRAF6 were detected by using quantitative real-time polymerase chain reaction and Western blot. The secretions of proinflammatory cytokines, including interleukin-1β, interleukin-6, interleukin-8, and tumor necrosis factor-α, were determined in the cell supernatants with enzyme-linked immunosorbent assay.

RESULTS

Both HKEF and LTA stimulated the expression of toll-like receptor 2 and TRAF6 in a time-dependent manner. The secretions of proinflammatory cytokines were also increased. After silencing TRAF6, the upregulations of proinflammatory cytokines induced by HKEF or LTA were attenuated.

CONCLUSIONS

TRAF6 plays a pivotal role in inflammation induced by E. faecalis or its LTA in PDLs.

Identification of Enterococcus faecalis antigens specifically expressed in vivo

Objectives

Molecular mechanism of the pathogenicity of Enterococcus faecalis (E. faecalis), a suspected endodontic pathogen, has not yet been adequately elucidated due to limited information on its virulence factors. Here we report the identification of in vivo expressed antigens of E. faecalis by using a novel immunoscreening technique called change-mediated antigen technology (CMAT) and an experimental animal model of endodontic infection.

Materials and Methods

Among 4,500 E. coli recombinant clones screened, 19 positive clones reacted reproducibly with hyperimmune sera obtained from rabbits immunized with E. faecalis cells isolated from an experimental endodontic infection. DNA sequences from 16 of these in vivo-induced (IVI) genes were determined.

Results

Identified protein antigens of E. faecalis included enzymes involved in housekeeping functions, copper resistance protein, putative outer membrane proteins, and proteins of unknown function.

Conclusions

In vivo expressed antigens of E. faecalis could be identified by using a novel immune-screening technique CMAT and an experimental animal model of endodontic infection. Detailed analysis of these IVI genes will lead to a better understanding of the molecular mechanisms involved in the endodontic infection of E. faecalis.

Chitosan nanoparticles enhance the antibacterial activity of chlorhexidine in collagen membranes used for periapical guided tissue regeneration

Endodontic failure is mainly associated with the persistence of microbial infection in the root canal system and/or the periradicular area. Microorganisms and their toxins located in the root canal system may trigger apical periodontitis and tissue destruction. Tissue regeneration in periapical surgery by using membrane barriers has shown an improved healing and bone closure. However, bacterial membrane contamination is a main reason of failure. In this in vitro study, different brands of chlorhexidine, a combination of chitosan nanoparticles containing chlorhexidine were tested against Enterococcus faecalis on agar plate's cultures and infected collagen membranes. Our results indicated that chitosan nanoparticles acted synergistically with chlorhexidine, inhibiting and eliminating significantly a greater amount of colony former units in both BHI-agar cultures and infected collagen membranes. These results suggested that chitosan nanoparticles could be used to improve regenerative procedures in periapical surgery.

In vitro effectiveness of Brazilian brown propolis against Enterococcus faecalis

The aim of this study was to evaluate the in vitro antimicrobial activity of Brazilian brown propolis as an intracanal medication against Enterococcus faecalis. Thirty dentin discs prepared from intact freshly extracted bovine maxillary central incisors were infected with E. faecalis for 21 days. The specimens were distributed into six groups according to the medicament used as follows: G1- calcium hydroxide paste; G2- Carbowax 400 (control group); G3- 20% brown propolis paste; G4- 40% brown propolis paste; G5- 20% brown propolis paste + calcium hydroxide paste; and G6- 40% brown propolis paste + calcium hydroxide paste. The experimental pastes were placed into the canal lumen and left for 14 days. After each period, irrigation was performed with sterile saline to remove the medicament, and the canals were dried with sterile paper points. The dentin chips were removed from the canals with sequential sterile round burs at low speed and were immediately collected in separate test tubes containing BHI broth. The tubes were incubated at 37°C, and microbial growth was analyzed by spectrophotometry after 15 days. All the experimental medications significantly reduced the number of viable bacteria. The G4 and G5 pastes were more effective than the G1 paste, with 35.8%, 41%, and 21.3% antibacterial activity, respectively. Brazilian brown propolis shows antibacterial capacity against E. faecalis.

Lipoteichoic acid from an Enterococcus faecalis clinical strain promotes TNF-α expression through the NF-κB and p38 MAPK signaling pathways in differentiated THP-1 macrophages

To study the immune-inflammatory response and signaling mechanism of macrophages to purified Enterococcus faecalis (E. faecalis) lipoteichoic acid (LTA), intact LTA was obtained from an E. faecalis clinical strain P25RC using the butanol method and hydrophobic interaction chromatography purification. The fractions containing LTA were determined using phosphate detection. Contaminations with lipopolysaccharide and proteins were excluded using the Limulus amoebocyte lysate assay and sodium dodecyl sulfate-polyacrylamide gel electrophoresis, respectively. LTA was analyzed using nuclear magnetic resonance. Prior to LTA stimulation assays, THP-1 monocytes were pretreated with phorbol 12-myristate 13-acetate to differentiate into macrophages. Macrophages were treated with LTA in concentration gradients and cells without LTA treatment as the control. Gene expression of TLR2, CD14 and MyD88 were evaluated by quantitative polymerase chain reaction. Tumor necrosis factor-α (TNF-α) and interleukin (IL)-10 were quantified using ELISA. The activated and total nuclear factor-κB (NF-κB) p65 and three mitogen-activated protein kinases (p38, ERK1/2 and JNK) were assessed using western blot analysis. E. faecalis LTA induced the gene expression of TLR2 and MyD88 whilst it downregulated CD14, suggesting a TLR2-dependent and CD14-independent immune-inflammatory activity. LTA stimulated the expression of pro-inflammatory cytokine TNF-α (P<0.05), but not the anti-inflammatory cytokine IL-10. In conclusion, E. faecalis LTA stimulated the expression of TNF-α in macrophages possibly through the NF-κB and p38 pathways.

Combined Antibacterial Effect of Sodium Hypochlorite and Root Canal Sealers against Enterococcus faecalis Biofilms in Dentin Canals

INTRODUCTION

The present study aimed to evaluate the antibacterial effect of the combined use of sodium hypochlorite (NaOCl) and root canal sealers on Enterococcus faecalis biofilms using a dentin infection model.

METHODS

Cells of E. faecalis were introduced into the dentinal tubules by centrifugation and incubated in brain-heart infusion for 3 weeks. The biofilms in dentin were first subjected to 5% NaOCl or sterile water for 10 minutes followed by an equal thickness of AH Plus (Dentsply International Inc, York, PA), Endosequence BC Sealer (Brasseler USA, Savannah, GA), or MTA Fillapex (Angelus Indústria de Produtos Odontológicos S/A, Londrina, Brazil) placed on the root canal wall of the dentin specimens for 7, 30, and 60 days. Gutta-percha and water were used in a similar manner as controls. The proportions of dead and live bacteria inside the dentinal tubules were assessed by confocal laser scanning microscopy and viability staining.

RESULTS

The combined use of NaOCl and sealers (30 and 60 days) killed significantly more bacteria than NaOCl or sealers alone (P < .05). NaOCl + MTA Fillapex was the most effective antibacterial combination by killing 83% bacteria in dentin tubules in 60 days. Thirty and 60 days of exposure to the sealers resulted in significantly more dead bacteria in dentin biofilms than 7-day exposures (P < .05).

CONCLUSIONS

The placement of root canal sealer after NaOCl treatment enhanced antibacterial effects against E. faecalis in the dentinal tubules. Little additional effect was obtained after 30 days of exposure to sealers.

Comparing the Coronal Seal of Different Thicknesses of MTA with Gutta-Percha after Post Space Preparation

INTRODUCTION

The aim of this study was to compare the coronal seal of different thicknesses of MTA with gutta-percha after post space preparation.

MATERIALS AND METHODS

A total of 50 maxillary central incisors randomly divided into 5 experimental groups (n = 8). After preparation of the root canals with step back technique, in groups 1 and 2, post spaces were prepared and 4 or 5 mm gutta-percha remained in the apical, respectively. In groups 3, 4, and 5, there was 1-2 and 3 mm MTA in the apical, respectively. The ten teeth serve as control groups. The teeth were connected to a bacterial microleakage evaluation system. The study period was 120 days and the samples were evaluated on ten-day intervals; Meier-Kaplan technique was used for estimation of the mean time of microleakage to occur. Log-rank test was used for comparison of microleakage.

RESULTS

Number of samples exhibiting microleakage in MTA was less than those of gutta-percha at all intervals. Means of days with no microleakage were maximum and minimum with 3 mm MTA and 4 mm gutta-percha, respectively.

CONCLUSION

Obturation of root canals using the MTA technique provides a proper seal with the minimum thickness of MTA in teeth requiring post space preparation.

Antibiotic susceptibilities of enterococcus species isolated from hospital and domestic wastewater effluents in alice, eastern cape province of South Africa

Background: Antimicrobial resistance in microorganisms are on the increase worldwide and are responsible for substantial cases of therapeutic failures. Resistance of species of Enterococcus to antibiotics is linked to their ability to acquire and disseminate antimicrobial resistance determinants in nature, and wastewater treatment plants (WWTPs) are considered to be one of the main reservoirs of such antibiotic resistant bacteria. We therefore determined the antimicrobial resistance and virulence profiles of some common Enterococcus spp that are known to be associated with human infections that were recovered from hospital wastewater and final effluent of the receiving wastewater treatment plant in Alice, Eastern Cape. Methods: Wastewater samples were simultaneously collected from two sites (Victoria hospital and final effluents of a municipal WWTP) in Alice at about one to two weeks interval during the months of July and August 2014. Samples were screened for the isolation of enterococci using standard microbiological methods. The isolates were profiled molecularly after targeted generic identification and speciation for the presence of virulence and antibiotic resistance genes. Results: Out of 66 presumptive isolates, 62 were confirmed to belong to the Enterococcus genusof which 30 were identified to be E. faecalis and 15 E. durans. The remaining isolates were not identified by the primers used in the screening procedure. Out of the six virulence genes that were targeted only three of them; ace, efaA, and gelE were detected. There was a very high phenotypic multiple resistance among the isolates and these were confirmed by genetic analyses. Conclusions: Analyses of the results obtained indicated that hospital wastewater may be one of the sources of antibiotic resistant bacteria to the receiving WWTP. Also, findings revealed that the final effluent discharged into the environment was contaminated with multi-resistant enterococci species thus posing a health hazard to the receiving aquatic environment as these could eventually be transmitted to humans and animals that are exposed to it.

In vitro study of beneficial properties and safety of lactic acid bacteria isolated from Portuguese fermented meat products

Many lactic acid bacteria produce bacteriocins with a rather broad spectrum of inhibition, which could offer potential applications in food preservation. Bacteriocin production by starter cultures may bring advantage to these strains in competitive interactions with pathogenic bacteria from the food matrix. The objective of this study was to determine the safety of beneficial strains (Lactobacillus plantarum ST202Ch and ST216Ch, Enterococcus faecium ST211Ch, and Lactobacillus sakei ST22Ch, ST153Ch and ST154Ch) previously isolated from fermented meat products and characterised as bacteriocin producers. Auto-aggregation was strain-specific, and values of 28.97, 27.86 and 28.56% were recorded for L. sakei ST22Ch, ST153Ch and ST154Ch, respectively, 16.95 and 14.58% for L. plantarum ST202Ch and ST216Ch, respectively, and 12.77% for E. faecium ST211Ch. Various degrees of co-aggregation between 28.85 and 44.76% for Listeria monocytogenes 211 and 409, and between 23.60 to 34.96% for E. faecium ATCC 19443 were observed. According to the results of the diffusion method, the studied strains demonstrated susceptibility to penicillin G, ampicillin, amoxicillin, amoxicillin/clavulonic acid, imipenem, linezolid, and tetracycline. In addition, the susceptibility of the six strains to various non-antibiotic commercial drugs was examined. Production of β-galactosidase by L. sakei ST22Ch, ST153Ch and ST154Ch, L. plantarum ST202Ch and ST216Ch, and E. faecium ST211Ch was confirmed by employing sterile filter paper discs impregnated with o-nitrophenyl-β-D-galactopyranose. A statistically significant (P<0.001) inhibition of Mycobacterium tuberculosis growth by bacteriocins produced by L. plantarum ST202Ch (38.3%) and ST216Ch (48.6%), L. sakei ST153Ch (16.2%) and ST154Ch (16.1%), and E. faecium ST211Ch (21.7%) was observed. As determined by the polymerase chain reaction, the tested strains showed a low virulence gene profile.

Matrix Metalloproteinase Inhibitor as an Antimicrobial Agent to Eradicate Enterococcus faecalis Biofilm

INTRODUCTION

Successful endodontic treatment outcomes require new strategies for the complete eradication of microbial biofilms in the root canal system. Matrix metalloproteinases (MMPs) are essential enzymes in microbial cell growth and homeostasis, and they require transition metal ion cofactors to function. Targeting MMP activity also preserves dentin collagen integrity. In this study, 1,10-phenanthroline-5,6-dione (Phendione), a metal chelator, was tested as a potentially novel antimicrobial agent against Enterococcus faecalis and inhibitor of human MMP in the root canal.

METHODS

Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of Phendione on E. faecalis were determined. The antimicrobial properties of Phendione in the presence of dentin powder and various transition metal ions were examined. The ability of Phendione to inhibit human MMP-2 was subsequently tested. The efficacy of Phendione against E. faecalis biofilm was determined by exposure of 7-day-old E. faecalis biofilms to Phendione.

RESULTS

The MIC and MBC of Phendione were 2.0 μg/mL and 16 μg/mL, respectively, whereas 64 μg/mL was required to kill E. faecalis biofilm. Phendione completely eradicated E. faecalis despite dentin preincubation. The presence of Zn(2+), and to a lesser extent Fe(2+), abrogated the antimicrobial effect of Phendione. In addition, Phendione at MIC and MBC significantly inhibited human MMP-2 activity.

CONCLUSIONS

Phendione effectively eradicated E. faecalis biofilms and significantly inhibited human MMP-2 through its ability to chelate metal ions. The antibacterial property of Phendione was preserved in the presence of dentin. Phendione can potentially be applied in endodontic treatment as both an antimicrobial agent and MMP inhibitor.

Safety, beneficial and technological properties of Enterococcus faecium isolated from Brazilian cheeses

This study aimed to characterize the safety and technological properties of Enterococcus faecium strains isolated from Brazilian Coalho cheeses. High levels of co-aggregation were observed between Enterococcus faecium strains EM485 and EM925 and both Escherichia coli and Clostridium perfringens . Both strains presented low levels of hydrophobicity. E. faecium EM485 and EM925 were both able to grow in the presence of 0.5% of the sodium salts of taurocholic acid (TC), taurodeoxycholic acid (TDC), glycocholic acid (GC), and glycodeoxycholic acid (GDC), although they showed the ability to deconjugate only GDC and TDC. Both strains showed good survival when exposed to conditions simulating the gastro intestinal tract (GIT). When tested for the presence of virulence genes, only tyrosine decarboxylase and vancomycin B generated positive PCR results.

Antimicrobial activity of seven essential oils from Iranian aromatic plants against common causes of oral infections

Background:

Over the past two decades, there has been a growing trend in using oral hygienic products originating from natural resources such as essential oils (EOs) and plant extracts. Seven aromatic plants used in this study are among popular traditional Iranian medicinal plants with potential application in modern medicine as anti-oral infectious diseases.

Objectives:

This study was conducted to determine the chemical composition and antimicrobial activities of essential oils from seven medicinal plants against pathogens causing oral infections.

Materials and Methods:

The chemical compositions of EOs distilled from seven plants were analyzed by gas chromatography/mass spectrometry (GC/MS). These plants included Satureja khuzestanica, S. bachtiarica, Ocimum sanctum, Artemisia sieberi, Zataria multiflora, Carum copticum and Oliveria decumbens. The antimicrobial activity of the essential oils was evaluated by broth micro-dilution in 96 well plates as recommended by the Clinical and Laboratory Standards Institute (CLSI) methods.

Results:

The tested EOs inhibited the growth of examined oral pathogens at concentrations of 0.015-16 µL/mL. Among the examined oral pathogens, Enterococcus faecalis had the highest Minimum Inhibitory Concentrations (MICs) and Minimum Microbicidal Concentrations (MMCs). Of the examined EOs, S. khuzestanica, Z. multiflora and S. bachtiarica, showed the highest antimicrobial activities, respectively, while Artemisia sieberi exhibited the lowest antimicrobial activity.

Conclusions:

The excellent antimicrobial activities of the tested EOs might be due to their major phenolic or alcoholic monoterpenes with known antimicrobial activities. Hence, these EOs can be possibly used as an antimicrobial agent in treatment and control of oral pathogens.

Enterococcus faecalis attenuates the differentiation of macrophages into osteoclasts

INTRODUCTION

Enterococcus faecalis is closely associated with refractory apical periodontitis, manifesting periapical lesions and alveolar bone loss. Macrophages playing an important role in the induction of inflammation can differentiate into bone-resorbing osteoclasts. In the present study, we investigated the effect of E. faecalis on the differentiation and function of macrophages as osteoclast precursors.

METHODS

Bone marrow-derived macrophages (BMMs) were differentiated into osteoclasts with macrophage colony-stimulating factor and receptor activator of nuclear factor kappa B ligand in the presence or absence of heat-killed E. faecalis (HKEF). Tartrate-resistant acid phosphatase-positive multinucleated giant cells were analyzed to determine osteoclast differentiation. Western blotting was performed to examine the expression of c-Fos and NFATc1 transcription factors. Phagocytic capacity was analyzed by measuring uptake of carboxyfluorescein succinimidyl ester-labeled E. faecalis. Secretion of tumor necrosis factor-α, interleukin-6, keratinocyte-derived chemokine, and monocyte chemotactic protein-1 was determined by enzyme-linked immunosorbent assay.

RESULTS

Differentiation of BMMs into osteoclasts was attenuated in the presence of HKEF, and expression of c-Fos and NFATc1 was inhibited. HKEF exposure also prevented a reduction in the phagocytic capacity of BMMs after differentiation into osteoclasts. Concomitantly, HKEF induced the expression of chemokines monocyte chemotactic protein-1 and keratinocyte-derived chemokine and proinflammatory cytokines tumor necrosis factor-α and interleukin-6.

CONCLUSIONS

E. faecalis attenuated macrophages from differentiating into osteoclasts, allowing them to keep their ability to phagocytose and kill pathogens and to induce proinflammatory cytokine and chemokine secretion.

Effects of Fixed and Removable Space Maintainers on Plaque Accumulation, Periodontal Health, Candidal and Enterococcus Faecalis Carriage

OBJECTIVE

To evaluate the effects of space maintainers on plaque accumulation, periodontal health and oral microflora.

SUBJECTS AND METHODS

The study participants comprised 38 patients aged 4-10 years requiring either fixed or removable space maintainers. Plaque index, gingival index, bleeding on probing index, candidal colonization and Enterococcus faecalis were recorded just before the application of space maintainers (T0) and during treatment at the 1st (T1), 3rd (T2) and 6th (T3) month.

RESULTS

The gingival and bleeding on probing index scores increased significantly (gingival index from 0.20 ± 0254 to 0.54 ± 0417 and bleeding on probing index from 7.18 ± 9.946 to 18.07 ± 14.074) in the regions with fixed space maintainers at T3 (p < 0.01). The mean Candida counts also increased (for removable appliances from 1.90 ± 3.638 to 1.98 ± 3.318, p < 0.05, and for fixed appliances from 4.25 ± 4.587 to 4.52 ± 4.431, p < 0.001). The salivary E. faecalis counts at T3 also increased significantly with the use of fixed and removable appliances (for removable appliances from 5.93 ± 2.65 to 85.53 ± 34.1 and for fixed appliances from 4.95 ± 2.94 to 123.59 ± 29.51, p < 0.001). A positive correlation was found between the plaque (r = 0.67), gingival (r = 0.76) and bleeding on probing index scores (r = 0.76) and the candidal colonization for the fixed space maintainers (p < 0.01, p < 0.001).

CONCLUSIONS

In this study, both fixed and removable space maintainers led to an increase in the number of microorganisms in the oral cavity as well as to increases in the periodontal index scores. Patients should be informed that space maintainers may serve as a source of infection and that special attention must be given to their oral hygiene.

Proteome reactivity profiling for the discrimination of pathogenic bacteria

Diverse proteome reactivity profiles were obtained using small-molecule electrophiles. Based on the cross-reactivity profile, each protein generated a unique reactivity fingerprint. Here, we report the first proteome reactivity signature-based discrimination of 11 bacteria. Perfect differentiation of 11 bacteria can be achieved using 2 benzyl-halide probes.

Effects of Epigallocatechin gallate against Enterococcus faecalis biofilm and virulence

OBJECTIVE

Epigallocatechin-3-gallate (EGCG), the most abundant polyphenol in green tea (Camellia sinesis) has been shown to exert antimicrobial effects on numerous bacterial pathogens. However its efficacy against Enterococcus faecalis biofilm, which is associated with persistent root canal infection is unknown. The aims of this study were to investigate the effects of EGCG against E. faecalis biofilm and virulence.

DESIGN

Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of EGCG on E. faecalis were determined. The efficacy of EGCG on E. faecalis biofilms was tested by exposing 7-day old E. faecalis biofilm to EGCG. Flow cytometry analysis of hydroxyphenyl fluorescein (HPF) labelled E. faecalis was used to determine if EGCG induced intracellular hydroxyl radical formation. Co-treatment of EGCG with the iron chelator 2,2-dipyridyl (DIP) was carried out to determine if hydroxyl radical generated through Fenton reaction played a role in EGCG-mediated killing of E. faecalis. Furthermore, the effects of EGCG on the expression of virulence genes in E. faecalis were evaluated by quantitative polymerase chain reaction.

RESULTS

EGCG exhibited a MIC and MBC of 5 μg/mL and 20 μg/mL respectively and effectively eradicated E. faecalis biofilms. EGCG induced the formation of hydroxyl radicals in E. faecalis. The addition of DIP protected E. faecalis against EGCG-mediated antibacterial effects. At sub-MIC, EGCG induced significant down-regulation of E. faecalis virulence genes.

CONCLUSIONS

EGCG is an effective antimicrobial agent against both the planktonic and biofilm forms of E. faecalis, inhibiting bacterial growth and suppressing the expression of specific genes related to virulence and biofilm formation. The antimicrobial action of EGCG on E. faecalis occurred through the generation of hydroxyl radical.

Antibacterial activity of various root canal sealers and root-end filling materials in dentin blocks infected ex vivo with Enterococcus faecalis

OBJECTIVE

The aim was to investigate the antibacterial activity of the root-end filling materials MTA and IRM, different endodontic sealers and calcium hydroxide [Ca(OH)₂] in experimentally infected dentinal tubules.

MATERIALS AND METHODS

Ninety-four human root segments were prepared and the root canals were enlarged to ISO size 90. After smear removal, the specimens were infected with Enterococcus faecalis for 3 weeks. The roots were divided into eight groups and filled either with MTA, IRM, Ca(OH)₂, gutta-percha and EndoRez (ER)/GuttaFlow (GF)/AH Plus (AH+) or with Resilon and Epiphany (EpRe). One group of specimens was left unfilled for control. Half of the specimens were treated for 1 day and the other half for 7 days in humid conditions at 37°C. Dentin samples from each canal were collected by enlarging the canals to ISO size 150; thus a dentinal depth of 300 µm was sampled. The number of cultivable bacteria was determined for each specimen. Statistical significance was set to 5%.

RESULTS

After 1-day or 7-days of treatment, compared to control, all materials (except ER and GF at day 7) significantly reduced the number of bacteria. At day 1 and day 7, no significant difference was found between ER and GF and between Ca(OH)₂, AH+, EpRe, IRM and MTA. However, a significant difference was found between these two groups of materials (except between GF and EpRe at day 7). Significantly more bacteria were cultured in the ER, GF, EpRe and IRM groups at day 7 compared to day 1.

CONCLUSIONS

All materials exerted varying degrees of antibacterial activity which generally tended to decrease with time. The most stable antibacterial effect throughout the 7-day period was for Ca(OH)₂, AH+ and MTA.

In vitro activity of Amazon plant extracts against Enterococcus faecalis

Previous studies analyzing 2,200 plant extracts indicated anti-enterococcal activity in 25 extracts obtained from Brazilian forests’ plants. In the present study, these extracts were subjected to microdilution broth assay (MDBA) and disk diffusion assay (DDA) using planktonic Enterococcus faecalis ATCC^® 29212™ and were submitted to phytochemical analysis in TLC and HPLC. Three extracts obtained from Ipomoea alba (MIC < 40 μg/mL), Diclinanona calycina (MIC ≤ 40 μg/mL) and Moronobea coccinea (40 < MIC < 80 μg/mL; MBC = 80 μg/mL) showed significant bactericidal activity in the MDBA and four extracts obtained from I. alba (14.04 ± 0.55 mm diameter) S. globulifera (14.43 ± 0.33 mm and 12.18 ± 0.28 mm diameter) and Connarus ruber var. ruber (13.13 ± 0.18 mm diameter) were active in DDA. Residues H₂O obtained from Psidium densicomum (mean of 16.78 mm diameter) and from Stryphnodendron pulcherrimum (mean of 15.97 mm diameter) have shown an improved antibacterial activity after fractionation if compared to that obtained from the respective crude extracts. Antioxidant activity was observed in some residues of the active extracts. TLC analysis showed that phenolic compounds are likely to be found in active extracts. Three molecules were isolated from S. globulifera and were identified by ¹³C NMR lupeol, α-amyrin and 3β-hydroxyglutin-5-ene. The present chemical and biological findings suggest that these extracts are a potential source of new anti-Enterococcus compounds to be introduced in endodontic therapy.

Antimicrobial activity of some essential oils against oral multidrug-resistant Enterococcus faecalis in both planktonic and biofilm state

OBJECTIVE

To evaluate some essential oils in treatment of intractable oral infections, principally caused by biofilm of multidrug-resistant Enterococcus faecalis (E. faecalis), such as persistent endodontic infections in which their treatment exhibits a real challenge for dentists.

METHODS

Ten chemically analyzed essential oils by gas chromatography-mass spectrometry were evaluated for antimicrobial activity against sensitive and resistant clinical strains of E. faecalis in both planktonic and biofilm state using two methods, disk diffusion and broth micro-dilution.

RESULTS

Studied essential oils showed a good antimicrobial activity and high ability in E. faecalis biofilm eradication, whether for sensitive or multidrug-resistant strains, especially those of Origanum glandulosum and Thymbra capitata with interesting minimum inhibitory concentration, biofilm inhibitory concentration, and biofilm eradication concentration values which doesn't exceed 0.063%, 0.75%, and 1.5%, respectively.

CONCLUSIONS

Findings of this study indicate that essential oils extracted from aromatic plants can be used in treatment of intractable oral infections, especially caused by biofilm of multidrug-resistant E. faecalis.

New insights into the antimicrobial effect of mast cells against Enterococcus faecalis

Enterococcus faecalis has emerged as an important cause of life-threatening multidrug-resistant bacterial infections in the hospital setting. The pathogenesis of enterococcal infections has remained a relatively neglected field despite their obvious clinical relevance. The objective of this study was to characterize the interactions between mast cells (MCs), an innate immune cell population abundant in the intestinal lamina propria, and E. faecalis. This study was conducted with primary bone marrow-derived murine MCs. The results demonstrated that MCs exerted an antimicrobial effect against E. faecalis that was mediated both by degranulation, with the concomitant discharge of the antimicrobial effectors contained in the granules, and by the release of extracellular traps, in which E. faecalis was snared and killed. In particular, the cathelicidin LL-37 released by the MCs had potent antimicrobial effect against E. faecalis. We also investigated the specific receptors involved in the recognition of E. faecalis by MCs. We found that Toll-like receptors (TLRs) are critically involved in the MC recognition of E. faecalis, since MCs deficient in the expression of MyD88, an adaptor molecule required for signaling by most TLRs, were significantly impaired in their capacity to degranulate, to reduce E. faecalis growth as well as to release tumor necrosis factor alpha (TNF-α) and interleukin 6 (IL-6) after encountering this pathogen. Furthermore, TLR2 was identified as the most prominent TLR involved in the recognition of E. faecalis by MCs. The results of this study indicate that MCs may be important contributors to the host innate immune defenses against E. faecalis.

3D analysis of D-RaCe and self-adjusting file in removing filling materials from curved root canals instrumented and filled with different techniques

The aim of this study was to compare the efficacy of D-RaCe files and a self-adjusting file (SAF) system in removing filling material from curved root canals instrumented and filled with different techniques by using microcomputed tomography (micro-CT). The mesial roots of 20 extracted mandibular first molars were used. Root canals (mesiobuccal and mesiolingual) were instrumented with SAF or Revo-S. The canals were then filled with gutta-percha and AH Plus sealer using cold lateral compaction or thermoplasticized injectable techniques. The root fillings were first removed with D-RaCe (Step 1), followed by Step 2, in which a SAF system was used to remove the residual fillings in all groups. Micro-CT scans were used to measure the volume of residual filling after root canal filling, reinstrumentation with D-RaCe (Step 1), and reinstrumentation with SAF (Step 2). Data were analyzed using Wilcoxon and Kruskal-Wallis tests. There were no statistically significant differences between filling techniques in the canals instrumented with SAF (P = 0.292) and Revo-S (P = 0.306). The amount of remaining filling material was similar in all groups (P = 0.363); all of the instrumentation techniques left filling residue inside the canals. However, the additional use of SAF was more effective than using D-RaCe alone.

Single consumption of Bryndza cheese temporarily affects oral microbiota and salivary markers of oxidative stress

Several oral diseases are associated with changes in oral microbiota and higher oxidative stress. Enterococcus faecalis has been hypothesized to directly contribute to the oxidative stress in oral cavity. The aim of this study was to examine the effect of single consumption of unpasteurized Bryndza cheese containing enterococci on changes of microbiota and oxidative status in saliva. Fourteen healthy volunteers aged 23-30 years were asked to eat 100 g of Bryndza cheese. Saliva samples were collected before and 1, 10, 100 min, and 24 h after Bryndza cheese consumption. Species-specific PCR and terminal restriction fragment length polymorphism (T-RFLP) analysis were used to characterize oral microbiota. Markers of oxidative stress and antioxidant status were measured in saliva. PCR identified E. faecium in 36 % of probands saliva up to 1 day after consumption of enterococci containing Bryndza cheese. E. faecalis was detected in 57 % of probands saliva up to 10 min and in one proband up to 100 min after Bryndza cheese consumption. T-RFLP analysis confirmed short-term changes in composition of oral microbiota after Bryndza cheese ingestion. Nevertheless, the microbiota was completely restored after 24 h. One minute after ingestion of Bryndza cheese, salivary advanced oxidation protein products were significantly increased (by 74.6 %, P < 0.001), and total antioxidant capacity was decreased (by 22.0 %, P < 0.05). This study shows that single consumption of enterococci containing Bryndza cheese can temporally affect the composition of oral microbiota and oxidative stress in saliva. Further studies should identify the impact of these changes to the pathogenesis of oral diseases.

The antimicrobial activity of Azadirachta indica, Mimusops elengi, Tinospora cardifolia, Ocimum sanctum and 2% chlorhexidine gluconate on common endodontic pathogens: An in vitro study

Objective:

To check the antimicrobial activity of Azadirachta indica (Neem), Ocimum sanctum (Tulsi), Mimusops elelngi (Bakul), Tinospora cardifolia (Giloy) and Chlorhexidine Gluconate (CHX) on common endodontic pathogens like Streptococcus mutans, Enterococcus faecalis and staphylococcus aureus.

Materials and Methods:

The agar diffusion test was used to check the antimicrobial activity of the Methanolic extracts of the medicinal plants along with CHX. Six different concentrations of the tested agents were used for the study. The values of Zone of Inhibition were tabulated according to the concentration of the tested agent and data was statistically analyzed using ANOVA and Bonferroni post- hoc tests. The Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentrations (MBC) values were also recorded.

Results:

All the plants extracts showed considerable antimicrobial activity against selected endodontic pathogens. At 3mg. concentration, O.sanctum was the most effective against S. mutans, M. elengi showed highest zone of inhibition against E.faecalis, whereas CHX was the most effective agent against S.aureus. CHX was also the most consistent of all the medicaments testes, showing inhibitory effect against all the tree pathogens at all the selected concentrations.

Conclusions:

The Methanolic extract of A.Indica, O.sanctum, M. Elengi, T.cardifolia and Chlorhexidine Gluconate has considerable antimicrobial activity against S. mutans, E. faecalis and S. aureus.

Clonal diversity in biofilm formation by Enterococcus faecalis in response to environmental stress associated with endodontic irrigants and medicaments

AIM

To determine whether clonal diversity within E. faecalis affects biofilm formation when exposed to antimicrobial compounds found in endodontic medicaments and irrigants.

METHODOLOGY

Five human isolates of E. faecalis were compared; biofilms were grown in microtitre trays in the presence of sodium hypochlorite, calcium hydroxide, chlorhexidine, tetracycline or clindamycin. Biofilms were quantified by staining with crystal violet and optical density determined with a microplate reader. Slime production (an amorphous extracellular matrix comprising polysaccharides, glycoproteins and glycolipids loosely attached to the cell surface) was determined qualitatively by growth on Congo red agar plates. Linear mixed models were used to examine whether medicaments affected biofilm growth of the isolates in the presence of the medicaments or irrigants.

RESULTS

Overall, different endodontic antimicrobials significantly altered biofilm growth in E. faecalis isolates. Two E. faecalis isolates significantly (P < 0.0001) increased biofilm formation in the presence of tetracycline and one in the presence of NaOCl (P = 0.018). Qualitatively, slime production also varied between isolates and correlated with biofilm production.

CONCLUSIONS

When subjected to sub-minimum inhibitory concentration (MIC) levels of antimicrobial compounds found in endodontic medicaments, E. faecalis isolates demonstrated significant clonal variation in their capacity to form biofilms. Interestingly, there was a correlation between slime production and the ability of isolates to form a biofilm in the presence of antimicrobials. The results indicate that isolates of E. faecalis that form biofilms in response to endodontic medicaments may be more likely to survive endodontic treatment.

Effective analysis of the use of peracetic acid after instrumentation of root canals contaminated with Enterococcus faecalis

INTRODUCTION

The aim of this study was to evaluate the effectiveness of peracetic acid (PAA) in cleaning root canals contaminated with Enterococcus faecalis.

METHODS

Sixty first and second mandibular molars were used. Their mesiobuccal canals were prepared with the Reciproc System (VDW, Munich, Germany). The canals were irrigated with 10 mL saline during instrumentation. The teeth were randomly divided into 3 groups (n = 20), according to the irrigation solution to be used after instrumentation: group PAA (5 mL 1% PAA), group EDTA/sodium hypochlorite (NaOCl) (5 mL 17% EDTA followed by 5 mL 2.5% sodium hypochlorite), and group S (5 mL saline). Microbiological samples were collected before instrumentation and after final irrigation. Bacterial quantification was performed by counting the number of colony-forming units (CFUs/mL). The results were analyzed by the nonparametric Wilcoxon and Kruskal-Wallis tests.

RESULTS

The 3 groups showed a significant reduction (P < .05) in CFUs/mL after final irrigation. PAA and NaOCl associated with EDTA produced a significantly higher reduction in CFUs/mL (P < .05) compared with saline. There was no statistically significant difference between PAA and EDTA + 2.5% NaOCl (P > .05).

CONCLUSIONS

According to the results of the present study, the effectiveness of 1% PAA was similar to that of 17% EDTA + 2.5% NaOCl in cleaning curved root canals contaminated with E. faecalis.

Effects of intracanal irrigant MTAD Combined with nisin at sub-minimum inhibitory concentration levels on Enterococcus faecalis growth and the expression of pathogenic genes

Exposure to antibiotics is considered to be the major driver in the selection of antibiotic-resistant bacteria and may induce diverse biological responses in bacteria. MTAD is a common intracanal irrigant, but its bactericidal activity remains to be improved. Previous studies have indicated that the antimicrobial peptide nisin can significantly improve the bactericidal activity of MTAD against Enterococcus faecalis. However, the effects of MTAD and its modification at sub-minimum inhibitory concentration (sub-MIC) levels on Enterococcus faecalis growth and the expression of pathogenic genes still need to be explored. In this study, the results of post-antibiotic effects (PAE) and post-antibiotic sub-MIC effects (PASME) showed that MTADN (nisin in combination with MTAD) had the best post-antibiotic effect. E. faecalis after challenge with MTAD was less sensitive to alkaline solutions compared with MTAN (nisin in place of doxycycline in MTAD) and MTADN. E. faecalis induced with sub-MIC of MTAD generated resistance to the higher concentration, but induction of E. faecalis with MTAN did not cause resistance to higher concentrations. Furthermore, real-time polymerase chain reaction (RT-PCR) showed that the stress caused by sub-MIC exposure to MTAD, MTAN, or MTADN resulted in up- or down-regulation of nine stress genes and four virulence-associated genes in E. faecalis and resulted in different stress states. These findings suggested that nisin improved the post-antibacterial effect of MTAD at sub-MIC levels and has considerable potential for use as a modification of MTAD.

Enterococcus infection biology: lessons from invertebrate host models

The enterococci are commensals of the gastrointestinal tract of many metazoans, from insects to humans. While they normally do not cause disease in the intestine, they can become pathogenic when they infect sites outside of the gut. Recently, the enterococci have become important nosocomial pathogens, with the majority of human enterococcal infections caused by two species, Enterococcus faecalis and Enterococcus faecium. Studies using invertebrate infection models have revealed insights into the biology of enterococcal infections, as well as general principles underlying host innate immune defense. This review highlights recent findings on Enterococcus infection biology from two invertebrate infection models, the greater wax moth Galleria mellonella and the free-living bacteriovorous nematode Caenorhabditis elegans.

Safety of the surrogate microorganism Enterococcus faecium NRRL B-2354 for use in thermal process validation

Enterococcus faecium NRRL B-2354 is a surrogate microorganism used in place of pathogens for validation of thermal processing technologies and systems. We evaluated the safety of strain NRRL B-2354 based on its genomic and functional characteristics. The genome of E. faecium NRRL B-2354 was sequenced and found to comprise a 2,635,572-bp chromosome and a 214,319-bp megaplasmid. A total of 2,639 coding sequences were identified, including 45 genes unique to this strain. Hierarchical clustering of the NRRL B-2354 genome with 126 other E. faecium genomes as well as pbp5 locus comparisons and multilocus sequence typing (MLST) showed that the genotype of this strain is most similar to commensal, or community-associated, strains of this species. E. faecium NRRL B-2354 lacks antibiotic resistance genes, and both NRRL B-2354 and its clonal relative ATCC 8459 are sensitive to clinically relevant antibiotics. This organism also lacks, or contains nonfunctional copies of, enterococcal virulence genes including acm, cyl, the ebp operon, esp, gelE, hyl, IS16, and associated phenotypes. It does contain scm, sagA, efaA, and pilA, although either these genes were not expressed or their roles in enterococcal virulence are not well understood. Compared with the clinical strains TX0082 and 1,231,502, E. faecium NRRL B-2354 was more resistant to acidic conditions (pH 2.4) and high temperatures (60°C) and was able to grow in 8% ethanol. These findings support the continued use of E. faecium NRRL B-2354 in thermal process validation of food products.

Efficacy of endodontic applications of ozone and low-temperature atmospheric pressure plasma on root canals infected with Enterococcus faecalis

This study aimed to compare the antimicrobial efficacy of low-temperature atmospheric pressure plasma (LTAPP) design and gaseous ozone delivery system with 2.5% NaOCl on Enterococcus faecalis in root canal walls and dentine tubules. The samples were divided into LTAPP (n = 12), ozone (n = 12), NaOCl (positive control, n = 12) and saline (negative control, n = 6) groups. Microbial samples were collected using paper points and dentin chips from root canals. Antimicrobial efficacy was assessed by counting the colony-forming units of Ent. faecalis before and after each irrigation protocol. Data were analysed using Kruskal-Wallis, Wilcoxon signed-rank, Friedman and Bonferroni t (Dunn's test)-tests (P = 0.05). The microbial sampling with paper points showed antibacterial efficacy of NaOCl, LTAPP, ozone and saline in descending order, respectively (P < 0.05). The microbial sampling with dentin chips demonstrated a superior efficacy of LTAPP compared with NaOCl in the middle third (P < 0.05), while both had similar effects in coronal and apical thirds (P > 0.05). NaOCl and LTAPP were better than ozone at the coronal and middle parts of the root canals (P < 0.05). These findings led us to suggest that LTAPP, which has no thermal and chemical effects, may be of great aid in endodontic treatment.

SIGNIFICANCE AND IMPACT OF THE STUDY

The present study handles different perspectives on chemomechanical preparation of root canals. Ozone and low-temperature atmospheric pressure plasma (LTAPP) were investigated to determine whether they could be an alternative for NaOCl. Up to now, chemical solutions (NaOCl, chlorhexidine digluconate, etc...) have been used to disinfect the root canals. When the reported effects of LTAPP on biological and chemical decontamination were taken into consideration, a question rose whether it has antimicrobial efficacy in root canals infected with E. faecalis. According to the findings of the present study, LTAPP may constitute a promising aid in endodontics in disinfection of root canals.