Antibiotic Resistance and Capacity for Biofilm Formation of Different Bacteria Isolated from Endodontic Infections Associated with Root-filled Teeth

Antimicrobial efficacy of alternative root canal disinfection strategies: An evaluation on multiple working models

Researching disinfection strategies is pivotal because effectively eliminating bacteria and their byproducts during root canal treatment (RCT) remains a challenge. This study investigated the antimicrobial efficacy of natural antimicrobial compounds, propolis (PRO) and copaiba oil-resin (COR), compared to conventional agents in Endodontics. Antimicrobials were tested against endodontic pathogens via macrodilution with standardized inoculums to determine the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC). Biofilm killing efficacy were performed using two dual-species biofilms: Enterococcus faecalis (ATCC 29212) and Streptococcus mutans (ATCC 20523) and Streptococcus oralis (J22) and Actinomyces naeslundii (T14V-J1) grown on dentine discs. At the intratubular level (dentine cylinders), dentine tubule contamination was performed with E. faecalis and S. mutans. The specimens were exposed to antimicrobials to simulate their use at different sets of RCT and bacterial viability was quantified using Live/Dead staining via confocal laser scanning microscopy (CLSM). Biofilm characteristics and immediate removal of S. oralis and A. naeslundii biofilm model were evaluated employing optical coherence tomography (OCT) and CFU/mL counting. Statistical tests were applied according to data distribution for each analysis (α=0.05). Macrodilutions showed different effects against endodontic pathogens. Direct contact and intratubular analysis showed that PRO and COR promoted disinfection like conventional agents (p > 0.05). According to OCT analysis, PRO and COR showed similar biofilm reduction after immediate contact (p < 0.05). CFU/mL counting showed decontamination (p < 0.05) after using natural and conventional agents. PRO and COR showed antimicrobial effects, indicating their suitability as complementary approaches in RCT to eliminate as much microbial load as possible.

Targeted metabolomics analysis approach to unravel the biofilm formation pathways of Enterococcus faecalis clinical isolates

AIM

(i) To characterize Enterococcus faecalis biofilm formation pathways by semi-targeted metabolomics and targeted nitrogen panel analysis of strong (Ef63) and weak (Ef 64) biofilm forming E. faecalis clinical isolates and (ii) to validate the identified metabolic markers using targeted inhibitors.

METHODOLOGY

Previous proteomics profiling of E. faecalis clinical isolates with strong and weak biofilm formation revealed that differences in metabolic activity levels of small molecule, nucleotide and nitrogen compound metabolic processes and biosynthetic pathways, cofactor metabolic process, cellular amino acid and derivative metabolic process and lyase activity were associated with differences in biofilm formation. Hence, semi-targeted analysis of Ef 63, Ef 64 and ATC control strain Ef 29212 was performed by selecting metabolites that were part of both the previously identified pathways and a curated library with confirmed physical and chemical identity, followed by confirmatory targeted nitrogen panel analysis. Significantly regulated metabolites (p < .05) were selected based on fold change cut-offs of 1.2 and 0.8 for upregulation and downregulation, respectively, and subjected to pathway enrichment analysis. The identified metabolites and pathways were validated by minimum biofilm inhibitory concentration (MBIC) and colony forming unit (CFU) assays with targeted inhibitors.

RESULTS

Metabolomics analysis showed upregulation of betaine, hypoxanthine, glycerophosphorylcholine, tyrosine, inosine, allantoin and citrulline in Ef 63 w.r.t Ef 64 and Ef 29212, and thesemetabolites mapped to purinemetabolism, urea cycle and aspartate metabolism pathways. MBIC and CFU assays using compounds against selected metabolites and metabolic pathways, namely glutathione against hypoxanthine and hydroxylamine against aspartate metabolism showed inhibitory effects against E. faecalis biofilm formation.

CONCLUSIONS

The study demonstrated the importance of oxidative stress inducers such as hypoxanthine and aspartate metabolism pathway in E. faecalis biofilm formation. Targeted therapeutics against these metabolic markers can reduce the healthcare burden associated with E. faecalis infections.

The use of medicaments in the management of symptomatic irreversible pulpitis: A community-based cohort study

AIM

To investigate patient outcomes from either pulpotomy or pulpectomy for the management of symptomatic irreversible pulpitis, with and without application of antibiotic/corticosteroid pastes in urgent primary dental care settings in the United Kingdom.

METHODOLOGY

All patients receiving intervention for symptomatic irreversible pulpitis in three different primary care settings were invited to participate. Pre-operatively, data regarding patients' numerical ratings scale (NRS), pain score (0-10), analgesic use, oral-health impact profile-14 (OHIP-14) and need for time away from work were collected. For 7 days post-operatively, participants recorded their NRS pain score, global rating of change score, medication use and their ability to work. Analysis used a mixed-effects model with post hoc Tukey's multiple comparisons test for continuous data and chi-squared or Fisher's exact test for categorical data. To test the effect of the corticosteroid/antibiotic paste, pulpectomy and pulpotomy groups were combined following Mantel-Haenszel stratified analysis or a weighted average of the difference between pulpotomy and pulpectomy with and without the use of corticosteroid/antibiotic paste. A binary composite score was constructed using pre- and post-operative data, whereby overall treatment success was defined as: (i) patients did not return for treatment due to pain by day seven; (ii) at day three, there was a 33% (or 2-points) reduction in NRS pain score; (iii) there was a change score of +3 in global rating; (iv) the patient was no longer using analgesia and able to return to work.

RESULTS

Eighty-five participants were recruited, with 83 completing follow up. Overall treatment success was 57%, with 25% of participants returning for more treatment due to inadequate pain relief. Overall treatment success did not differ between the two groups (p = .645), although patients self-reported greater improvement with an antibiotic/corticosteroid dressing for global rating of change (p = .015).

CONCLUSIONS

This study identified limited evidence of improved outcomes using antibiotic/corticosteroid dressings in the management of symptomatic irreversible pulpitis in the emergency setting. Further clinical research is needed to understand if these medications are beneficial in affording pain relief, above that of simple excision of irreversibly inflamed pulp tissue.

Antibiotic Resistance Profile of Clinical Strains of Enterococci from Secondary/Persistent Endodontic Infections: What do We Know? A Systematic Review of Clinical Studies

INTRODUCTION

Enterococcus faecalis is the most common enterococcal species associated with infective endocarditis and 1 of the most commonly detected bacteria in cases of secondary/persistent endodontic infection (SPEI). Antimicrobial resistance is a global public health concern. This review aimed to answer the following research question: "Is there a change in the antibiotic resistance profile in clinical strains of E. faecalis over the years?". P (population) - patients with SPEI, I (intervention) -endodontic retreatment, C (comparison) -not included, O (outcome) - profile of Enterococci resistance and susceptibility to systemic antibiotics used.

METHODS

Two authors independently performed study selection, data extraction, and risk of bias assessment. The literature search was conducted using the following electronic databases: PubMed, Scopus, EMBASE, Web of Science, and Medline. Clinical studies in which Enterococci strains were isolated to assess their antimicrobial resistance were included.

RESULTS

Eleven clinical trials were included. Overall, E. faecalis isolated from teeth with SPEI presented an intermediate resistance to 16 antibiotics. In recent years, E. faecalis showed a little resistance to amoxicillin (without clavulanate) and benzylpenicillin. Erythromycin and rifampicin presented an increase in the intermediate-resistance status between the first and the last studies. E. faecium presented intermediate-resistance results.

CONCLUSION

The most effective drugs remain the combination of amoxicillin and clavulanate, followed by amoxicillin and benzylpenicillin. In patients allergic to penicillin derivatives, moxifloxacin and azithromycin may be indicated with caution. The antibiotics with the highest pattern of resistance against E. faecalis are clindamycin, gentamicin, metronidazole, and rifampicin and are therefore, contraindicated in cases of SPEI. Very few clinical studies using a microbiological approach in teeth with endodontic failure have been carried out to improve the efficacy of prophylactic regimens. However, as bacteria periodically develop resistance to the main drugs used, regular studies should be carried out on the action of these drugs in infection control.

Effects of natural antimicrobial compounds propolis and copaiba on periodontal ligament fibroblasts, molecular docking, and in vivo study in Galleria mellonella

Root canal treatment addresses infectious processes that require control. Occasionally, the radicular pulp is vital and inflamed, presenting a superficial infection. To preserve pulpal remnants, conservative procedures have gained favor, employing anti-inflammatory medications. This study investigated the effects of propolis (PRO), and copaiba oil-resin (COR) associated with hydrocortisone (H) and compared their impact to that of Otosporin® concerning cytotoxic and genotoxic activity, cytokine detection, and toxicity in the Galleria mellonella model. Human periodontal ligament fibroblasts (PDLFs) were exposed to drug concentrations and evaluated by the MTT assay. Associations were tested from concentrations that did not compromise cell density. Genotoxicity was evaluated through micronucleus counting, while cytokines IL-6 and TGF-β1 were detected in the cell supernatant using ELISA. Molecular docking simulations were conducted, considering the major compounds identified in PRO, COR, and H. Increasing concentrations of PRO and COR were assessed for acute toxicity in Galleria mellonella model. Cellular assays were analyzed using one-way ANOVA followed by Tukey tests, while larval survivals were evaluated using the Log-rank (Mantel-Cox) test (α = 0.05). PRO and COR promoted PDLFs proliferation, even in conjunction with H. No changes in cell metabolism were observed concerning cytokine levels. The tested materials induce the release of AT1R, proliferating the PDFLs through interactions. PRO and COR had low toxicity in larvae, suggesting safety at tested levels. These findings endorse the potential of PRO and COR in endodontics and present promising applications across medical domains, such as preventive strategies in inflammation, shedding light on their potential development into commercially available drugs.

Association between oral microbial dysbiosis and poor functional outcomes in stroke-associated pneumonia patients

BACKGROUND

Despite advances in our understanding of the critical role of the microbiota in stroke patients, the oral microbiome has rarely been reported to be associated with stroke-associated pneumonia (SAP). We sought to profile the oral microbial composition of SAP patients and to determine whether microbiome temporal instability and special taxa are associated with pneumonia progression and functional outcomes.

METHODS

This is a prospective, observational, single-center cohort study that examined patients with acute ischemic stroke (AIS) who were admitted within 24 h of experiencing a stroke event. The patients were divided into three groups based on the occurrence of pneumonia and the use of mechanical ventilation: nonpneumonia group, SAP group, and ventilator-associated pneumonia (VAP) group. We collected oral swabs at different time points post-admission and analyzed the microbiota using 16 S rRNA high-throughput sequencing. The microbiota was then compared among the three groups.

RESULTS

In total, 104 nonpneumonia, 50 SAP and 10 VAP patients were included in the analysis. We found that SAP and VAP patients exhibited significant dynamic differences in the diversity and composition of the oral microbiota and that the magnitude of this dysbiosis and instability increased during hospitalization. Then, by controlling the potential effect of all latent confounding variables, we assessed the changes associated with pneumonia after stroke and explored patients with a lower abundance of Streptococcus were more likely to suffer from SAP. The logistic regression analysis revealed that an increase in specific taxa in the phylum Actinobacteriota was linked to a higher risk of poor outcomes. A model for SAP patients based on oral microbiota could accurately predict 30-day clinical outcomes after stroke onset.

CONCLUSIONS

We concluded that specific oral microbiota signatures could be used to predict illness development and clinical outcomes in SAP patients. We proposed the potential of the oral microbiota as a non-invasive diagnostic biomarker in the clinical management of SAP patients.

CLINICAL TRIAL REGISTRATION

NCT04688138. Registered 29/12/2020, https://clinicaltrials.gov/ct2/show/NCT04688138 .

Antimicrobial resistance in patients with endodontic infections: A systematic scoping review of observational studies

The aim of this study was to assess the prevalence and proportions of antimicrobial-resistant species in patients with endodontic infections. A systematic scoping review of scientific evidence was accomplished involving different databases. Nine investigations were selected including 651 patients. Enterococcus faecalis was resistant to tetracycline (30%-70%), clindamycin (100%), erythromycin (10%-20%), ampicillin (9%) and azithromycin (60%). On the contrary, Prevotella spp., Fusobacterium spp., Peptostreptococcus spp. and Streptococcus spp. were resistant to penicillin, tetracycline, doxycycline, ciprofloxacin, amoxicillin, erythromycin, metronidazole and clindamycin in different proportions. Fusobacterium nucleatum showed high resistance to amoxicillin, amoxicillin plus clavulanate and erythromycin. Prevotella oralis presented a predisposition to augment its resistance to clindamycin over time. Tanerella forsythia exhibited resistance to ciprofloxacin and rifampicin. Lactococcus lactis presented robust resistance to cephalosporins, metronidazole, penicillin, amoxicillin and amoxicillin-clavulanic acid. It was observed high levels of resistance to antimicrobials that have been utilised in the local and systemic treatment of oral cavity infections.

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

BACKGROUND

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

RESULTS

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

CONCLUSIONS

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

Use of a Cellulase from Trichoderma reesei as an Adjuvant for Enterococcus faecalis Biofilm Disruption in Combination with Antibiotics as an Alternative Treatment in Secondary Endodontic Infection

Apical periodontitis is an inflammation leading to the injury and destruction of periradicular tissues. It is a sequence of events that starts from root canal infection, endodontic treatment, caries, or other dental interventions. Enterococcus faecalis is a ubiquitous oral pathogen that is challenging to eradicate because of biofilm formation during tooth infection. This study evaluated a hydrolase (CEL) from the fungus Trichoderma reesei combined with amoxicillin/clavulanic acid as a treatment against a clinical E. faecalis strain. Electron microscopy was used to visualize the structure modification of the extracellular polymeric substances. Biofilms were developed on human dental apices using standardized bioreactors to evaluate the antibiofilm activity of the treatment. Calcein and ethidium homodimer assays were used to evaluate the cytotoxic activity in human fibroblasts. In contrast, the human-derived monocytic cell line (THP-1) was used to evaluate the immunological response of CEL. In addition, the secretion of the pro-inflammatory cytokines IL-6 and TNF-α and the anti-inflammatory cytokine IL-10 were measured by ELISA. The results demonstrated that CEL did not induce the secretion of IL-6 and TNF-α when compared with lipopolysaccharide used as a positive control. Furthermore, the treatment combining CEL with amoxicillin/clavulanic acid showed excellent antibiofilm activity, with a 91.4% reduction in CFU on apical biofilms and a 97.6% reduction in the microcolonies. The results of this study could be used to develop a treatment to help eradicate persistent E. faecalis in apical periodontitis.

Antibiotic Resistance of Selected Bacteria after Treatment of the Supragingival Biofilm with Subinhibitory Chlorhexidine Concentrations

Due to increasing rates of antibiotic resistance and very few novel developments of antibiotics, it is crucial to understand the mechanisms of resistance development. The aim of the present study was to investigate the adaptation of oral bacteria to the frequently used oral antiseptic chlorhexidine digluconate (CHX) and potential cross-adaptation to antibiotics after repeated exposure of supragingival plaque samples to subinhibitory concentrations of CHX. Plaque samples from six healthy donors were passaged for 10 days in subinhibitory concentrations of CHX, while passaging of plaque samples without CHX served as control. The surviving bacteria were cultured on agar plates and identified with Matrix-assisted Laser Desorption/Ionization-Time of Flight-Mass spectrometry (MALDI-TOF). Subsequently, the minimum inhibitory concentrations (MIC) of these isolates toward CHX were determined using a broth-microdilution method, and phenotypic antibiotic resistance was evaluated using the epsilometertest. Furthermore, biofilm-forming capacities were determined. Repeated exposure of supragingival plaque samples to subinhibitory concentrations of CHX led to the selection of oral bacteria with 2-fold up to 4-fold increased MICs toward CHX. Furthermore, these isolates showed up to 12-fold increased MICs towards some antibiotics such as erythromycin and clindamycin. Conversely, biofilm-forming capacity was decreased. In summary, this study shows that oral bacteria are able to adapt to CHX, while also decreasing their susceptibility to antibiotics.

Phenotypic Adaptation to Antiseptics and Effects on Biofilm Formation Capacity and Antibiotic Resistance in Clinical Isolates of Early Colonizers in Dental Plaque

Despite the wide-spread use of antiseptics in dental practice and oral care products, there is little public awareness of potential risks associated with antiseptic resistance and potentially concomitant cross-resistance. Therefore, the aim of this study was to investigate potential phenotypic adaptation in 177 clinical isolates of early colonizers of dental plaque (Streptococcus, Actinomyces, Rothia and Veillonella spp.) upon repeated exposure to subinhibitory concentrations of chlorhexidine digluconate (CHX) or cetylpyridinium chloride (CPC) over 10 passages using a modified microdilution method. Stability of phenotypic adaptation was re-evaluated after culture in antiseptic-free nutrient broth for 24 or 72 h. Strains showing 8-fold minimal inhibitory concentration (MIC)-increase were further examined regarding their biofilm formation capacity, phenotypic antibiotic resistance and presence of antibiotic resistance genes (ARGs). Eight-fold MIC-increases to CHX were detected in four Streptococcus isolates. These strains mostly exhibited significantly increased biofilm formation capacity compared to their respective wild-type strains. Phenotypic antibiotic resistance was detected to tetracycline and erythromycin, consistent with the detected ARGs. In conclusion, this study shows that clinical isolates of early colonizers of dental plaque can phenotypically adapt toward antiseptics such as CHX upon repeated exposure. The underlying mechanisms at genomic and transcriptomic levels need to be investigated in future studies.

Synergistic effects of silver ions and metformin against enterococcus faecalis under high-glucose conditions in vitro

Background

This study aimed to evaluate the synergistic antibacterial activities of silver ions (Ag⁺) and metformin hydrochloride (Met) against Enterococcus faecalis (E. faecalis) under normal or high-glucose conditions.

Results

The minimum inhibitory concentration, minimum bactericidal concentration, growth curves, and colony-forming units were used to evaluate the antibacterial effects of Ag⁺ and Met on planktonic E. faecalis in Brain Heart Infusion broth with or without additional glucose. The influences of Ag⁺ and Met on four weeks E. faecalis biofilm on human dentin slices was also tested. Cytotoxicity was tested on MC3T3-E1 osteoblastic cells using CCK-8 assays. The results indicated that E. faecalis showed higher resistance to drug treatment under high-glucose conditions. Ag⁺ (40 μg/mL) plus Met (3.2% or 6.4%) showed enhanced antibacterial activities against both planktonic E. faecalis and biofilm on dentin slices, with low cytotoxicity.

Conclusions

Met enhanced the bactericidal effects of Ag⁺ against both planktonic and biofilm E. faecalis under normal or high-glucose conditions with low cytotoxicity. Further molecular studies are needed to be conducted to understand the mechanisms underlying the synergistic activity between Met and Ag⁺.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12866-021-02291-2.

How is carious pulp exposure and symptomatic irreversible pulpitis managed in UK primary dental care?

AIM

To investigate attitudes and approaches of UK primary care dentists to carrying out vital pulp treatment (VPT) after carious exposure and with additional signs and symptoms indicative of irreversible pulpitis.

METHODOLOGY

An electronic questionnaire was openly distributed via publicly funded (NHS) local dental committees, corporate dental service-providers, professional societies and social media. Principally NHS practitioners and those from mixed and private practice were targeted, in addition to community and military dental officers, and dental therapists. Participants were asked questions relating to several clinical scenarios, with responses analysed using descriptive statistics. χ² tests with sequential Bonferroni correction were used to explore variables including the method of remuneration, practitioner type (dentist/therapist), postgraduate qualification(s), place of graduation and years since qualification. Variables with a relationship p ≤ .2 were selected for backwards likelihood ratio logistic modelling.

RESULTS

In total, 648 primary care practitioners were included for analysis. Calcium hydroxide (CH) was most frequently used for direct pulp caps (DPCs) (398/600; 66.3%) with calcium silicate cements (CSCs) less frequently used (119/600; 19.8%). Rubber dam was used by 222/599 (37.1%) practitioners. A definitive pulpotomy for the management of teeth with signs and symptoms indicative of irreversible pulpitis was selected by 65/613 (10.6%) dentists. The principal barrier for the provision of definitive pulpotomies was a lack of training (602/612; 98.4%). Regression analysis identified NHS practitioners as a good predictor for using CH for DPCs, having shorter emergency appointments, limited access to magnification and not using rubber dam. Non-UK graduates were more likely to select CSCs, appropriately control pulpal haemorrhage, undertake appropriate postoperative evaluation and use rubber dam.

CONCLUSIONS

Practitioners deviated from evidence-based guidelines in a number of aspects including material selection, asepsis and case selection. A number of other challenges exist in primary care in providing predictable VPTs, including lack of time and access to magnification. These were most evident in NHS practice, potentially exacerbating existing social health inequalities. Possible inconsistencies in the UK undergraduate curriculum were supported by a lack of association between years since qualification and technique employed as well as the fact that non-UK graduates and dentists with postgraduate qualifications adhered more to evidence-based VPT guidelines.

Antibacterial and antibiofilm efficacy of k21-E in root canal disinfection

OBJECTIVES

The aim of the current project was to study the antimicrobial efficacy of a newly developed irrigant, k21/E against E. faecalis biofilm.

METHODS

Root canals were instrumented and randomly divided into the following groups: irrigation with saline, 6% NaOCl (sodium hypochlorite), 6% NaOCl+2% CHX (Chlorhexidine), 2% CHX, 0.5% k21/E (k21 - quaternary ammonium silane) and 1% k21/E. E. faecalis were grown (3-days) (1×10⁷CFU mL^-1), treated, and further cultured for 11-days. Specimens were subjected to SEM, confocal and Raman analysis and macrophage vesicles characterized along with effect of lipopolysaccharide treatment. 3T3 mouse-fibroblasts were cultured for alizarin-red with Sortase-A active sites and Schrödinger docking was performed. TEM analysis of root dentin substrate with matrix metalloproteinases profilometry was also included. A cytotoxic test analysis for cell viability was measured by absorbance of human dental pulp cells after exposure to different irrigant solutions for 24h. The test percentages have been highlighted in Table 1.

RESULTS

Among experimental groups, irrigation with 0.5% k21/E showed phase separation revealing significant bacterial reduction and lower phenylalanine 1003cm^-1 and Amide III 1245cm^-1 intensities. Damage was observed on bacterial cell membrane after use of k21/E. No difference in exosomes distribution between control and 0.5%k21/E was observed with less TNFα (*p<0.05) and preferential binding of SrtA. TEM images demonstrated integrated collagen fibers in control and 0.5%k21/E specimens and inner bacterial membrane damage after k21/E treatment. The k21 groups appeared to be biocompatible to the dental pulpal cells grown for 24h.

SIGNIFICANCE

Current investigations highlight potential advantages of 0.5% k21/E as irrigation solution for root canal disinfection.

Subinhibitory Antibiotic Concentrations Enhance Biofilm Formation of Clinical Enterococcus faecalis Isolates

Enterococcus faecalis is a microorganism that can be found in the oral cavity, especially in secondary endodontic infections, with a prevalence ranging from 24-70%. The increase in the ability to form biofilms in the presence of subinhibitory antibiotic concentrations is a phenomenon that is observed for a wide variety of bacterial pathogens and is associated with increased resistance. In this study, therefore, six E. faecalis isolates from an endodontic environment and two control strains were exposed to subinhibitory concentrations of Penicillin G, Amoxicillin, Doxycycline, Fosfomycin, Tetracycline and Vancomycin and examined for their biofilm formation abilities. The minimum inhibitory concentration (MIC) was determined for all E. faecalis isolates. A culture of the isolate was mixed with a serial dilution series of the respective antibiotic, incubated overnight and the biofilm formation was analyzed using a microtiter plate assay. All isolates were able to form biofilms in the absence of an antibiotic. A significant increase in biofilm formation of up to more than 50% was found in the isolates exposed to subinhibitory concentrations of various antibiotics. Most isolates showed a significant increase in Fosfomycin (7/8), Doxycycline (6/8) and Tetracycline (6/8). Three endodontic isolates showed a significant increase in five of the antibiotics examined at the same time. On exposure to Vancomycin, three endodontic isolates and the two control strains showed an increase. The increase in the ability to form biofilms extended over a concentration range from 1/2 to 1/64 of the MIC concentration. Antibiotics may reach certain niches in the oral cavity at subinhibitory concentrations only. This can increase the biofilm formation by enterococci, and in turn lead to decreased susceptibility of these taxa to antibiotics.

Antimicrobial Resistance and Virulence Factor Gene Profiles of Enterococcus spp. Isolated from Giant Panda Oral Cavities

Introduction

The objective of this study was to determine the prevalence and characteristics of antimicrobial-resistant Enterococcus faecalis and E. faecium isolated from the oral cavities of captive giant pandas in China.

Material and Methods

The virulence-associated determinant and antimicrobial resistance genes were detected and antimicrobial susceptibility tests were performed on 54 strains of each bacterium.

Results

All isolates showed 100% multidrug resistance. E. faecalis isolates showed a higher percentage of strains resistant to gentamicin (48.1%), vancomycin (55.6%), linezolid (100%), and streptomycin (33.3%) than E. faecium isolates. The resistance genes of Enterococcus spp. were present to highly varying extents according to antibiotic type, their presence breaking down for E. faecalis and E. faecium respectively as aac(6')/aph(2″) 5.56% and 5.56%; aph(3')-Ⅲ 0% and 14.81%; ant(6)-I 0% and 3.7%; ant(4')-Ia 0% and 64.81%; tetL 20.37% and 100%; vanA 92.59% and 46.3%; vanB 0% and 0%; cfr 0% and 90.74%; optrA 96.3% and 3.7%; blaZ 0% and 1.85%; blaTEM 0% and 0%; tetA 20.37% and 0%; tetC 24.07% and 100%; tetM 0% and 0%; ermA 12.96% and 100%; ermB 5.56% and 3.7%; and ermC 0% and 1.85%.Virulence-associated determinants were detected in this research, which typically include efaA, gelE, asa1, ace, cylA, esp and hyl; however, the latter three were not detected. High proportions of the isolates carried the efaA, gelE, asa1, and ace genes. Respectively for E. faecalis and E. faecium their detection was efaA 98.1% and 85.2%; gelE 98.1% and 87%; asa1 92.6% and 87%; and ace 87% and 85.2%.

Conclusion

This is the first study on the potential disease risk and antimicrobial-resistant characteristics of E. faecalis and E. faecium isolates in giant panda oral cavities. The results of this study show that the antimicrobial resistance rate of Enterococcus spp. isolated from the oral cavity of captive pandas is very high, and thus needs to be monitored.

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

BACKGROUND AND OBJECTIVES

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

MATERIALS AND METHODS

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

RESULTS

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

CONCLUSIONS

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

Evaluation of the efficacy of a novel antibiotic-steroid paste versus conventionally used intracanal antibiotic pastes and irrigating solutions against a 3-week-old biofilm of Enterococcus faecalis

Introduction

Intracanal medicaments have been used during endodontic regenerative procedures to eradicate endodontic pathogens.

Aims

The aim of our study was (1) to evaluate the antimicrobial efficacy of a novel antibiotic-steroid paste over the regularly used calcium hydroxide (Ca (OH)₂), double antibiotic paste (DAP), and modified triple antibiotic paste (M-TAP) and (2) to check the antimicrobial efficacy of irrigating solutions, Chlorhexidine (CHX), and sodium hypochlorite (NaOCl) against a 3-week-old Enterococcus faecalis (E. faecalis) biofilm.

Materials and Methods

A total of 112 human extracted teeth were contaminated with E. faecalis for a period of 21 days. A novel antibiotic-steroid paste, Ca (OH) ₂, DAP, M-TAP, and a placebo were placed inside the canal, sealed, and incubated in an aerobic environment at 37°C. For irrigating solutions, each prepared sample was immersed in 1 ml of sterile saline for 1 min, followed by irrigating and immersion with 1.5% NaOCl and 2% CHX for 5 min. An antimicrobial assessment was performed at the end of 2 days and 7 days, with seven teeth from each group, for each time interval. Dentin debris collected was transferred to the respective medium for culture. After 24 h, colonies were counted using classical bacterial counting technique as colony-forming units.

Results

Statistical analysis revealed that the novel antibiotic-steroid paste showed a statistically insignificant difference when compared to DAP, which had the highest antimicrobial properties.

Conclusion

This novel functional paste has antimicrobial efficacy comparable with that of DAP.

Molecular characterization and antibacterial activity of oral antibiotics and copper nanoparticles against endodontic pathogens commonly related to health care-associated infections

OBJECTIVE

To carry out molecular characterization and determine the antibacterial activity of oral antibiotics and copper nanoparticles (Cu-NPs) against endodontic strains isolated from persistent infections.

MATERIALS AND METHODS

Root canal samples from 24 teeth in different patients with persistent endodontic infections were obtained. The isolated strains were identified by biochemical tests and 16S rDNA sequencing. Genotyping was achieved by molecular methods. The antibacterial activity of antibiotics and copper nanostructures was determined by using minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values. Furthermore, a time-kill kinetics assay was evaluated. Nonparametric tests (Kruskal-Wallis ANOVA) were performed (p value <0.05).

RESULTS

Twenty-one isolated strains were identified. Six isolates of Enterococcus faecalis were grouped into two clusters of three isolates each, two of which were clones. All were clarithromycin-resistant and erythromycin. Eight Pseudomonas putida presented two clusters, two Pseudomonas spp. were not clonal, and all were resistant to the tested antibiotics except tetracycline. Two of five strains of Cutibacterium acnes were clonal, and all were resistant only to metronidazole. The lowest MIC and MBC values were obtained with Cu-NPs. Time-kill kinetics using Cu-NPs showed a significant decrease in all tested species within 4 h and reached 100% in 2 h for C. acnes.

CONCLUSION

In this study, in relation to health care-associated infections, endodontic strains of each species isolated at least in one patient were polyclonal. In Pseudomonas spp., at least one clone was shared between patients. E. faecalis and C. acnes strains were susceptible to low Cu-NP concentrations, while Pseudomonas spp. strains were resistant.

CLINICAL RELEVANCE

Assessing and keeping track of the susceptibility of clinical strains to antimicrobial compounds is important for the clinical outcome. Based on our results, Cu-NPs could be an alternative for endodontic treatment, in order to avoid selection of resistant strains.

Presence of non-oral bacteria in the oral cavity

A homeostatic balance exists between the resident microbiota in the oral cavity and the host. Perturbations of the oral microbiota under particular conditions can contribute to the growth of non-oral pathogens that are hard to kill because of their higher resistance to antimicrobials, raising the probability of treatment failure and reinfection. The presence of these bacteria in the oral cavity has been proven to be associated with several oral diseases such as periodontitis, caries, and gingivitis, and systemic diseases of importance in clinical medicine such as cystic fibrosis, HIV, and rheumatoid arthritis. However, it is still controversial whether these species are merely transient members or unique to the oral cavity. Mutualistic and antagonistic interactions between the oral microbiota and non-oral pathogens can also occur, though the mechanisms used by these bacteria are not clear. Therefore, this review presents an overview of the current knowledge about the presence of non-oral bacteria in the oral cavity, their relationship with systemic and oral diseases, and their interactions with oral bacteria.

In vitro and in vivo research of atmosphere pressure nonequilibrium plasmas on root canal disinfection: implication for alternative strategy for irrigation

OBJECTIVE

To investigate an intracanal disinfection methodology of APNPs (atmosphere pressure nonequilibrium plasmas) or modified APNPs in root canal treatment and evaluate the antimicrobial efficiency against in vitro infected dentinal tubules and in vivo experimental apical periodontitis.

MATERIALS AND METHODS

Dentine specimens were centrifugated with Enterococcus faecalis to generate 1-day-old and 3-week-old biofilms, and were treated with 2% chlorhexidine (Chx), APNP or modified APNP for 3 and 10 min (n=4). LIVE/DEAD staining was employed to analyze the ratio of deactivated bacteria. Experimental apical periodontitis in beagles was induced. Root canal therapy with APNPs or modified APNPs was performed and the antimicrobial effect was evaluated by histological and radiographical analyses.

RESULTS

APNP deactivated 1-day-old and 3-week-old E. feacalis in dentinal tubules as much as 2% Chx irrigating. Modified APNP significantly deactivated more E. faecalis biofilms in dentinal tubules for 3-min and 10-min treatments, without thermal damage or dentinal destruction being observed. In beagles' apical periodontitis, significantly increased BV/TV and decreased lesion volume of apical bone were found in modified APNP group than 2% Chx irrigation group according to μCT. Fewer inflammatory cells and bacterial residual in dentine were observed in modified APNP-treated apical tissue by histology staining compared with those in the 2% Chx irrigation group.

CONCLUSION

The antimicrobial effect of APNP jet irradiation was comparable to that of 2% Chx irrigation. No structural damage in dentine or tissue necrosis at the periapical region was induced upon treatment. The modified APNP demonstrated an increased antimicrobial efficacy compared with 2% Chx irrigation both in vitro and in vivo.

CLINICAL RELEVANCE

The modified APNPs can be used as an alternative intracanal disinfection strategy.

Quaternary ammonium silane (k21) based intracanal medicament triggers biofilm destruction

BACKGROUND

Compare antimicrobial efficacy of a quarternary ammonium silane (QAS)/k21 as an intracanal medicament against E. faecalis and C. albicans biofilms formed on root dentin.

METHODOLOGY

Dentin blocks were sterilized and E. faecalis and C. albicans microbial colonies were counted for colony-forming-units against 2%k21, 2%CHX and Ca(OH)2 medicaments. Biofilm colonies after 7 days on dentin were analysed using confocal laser scanning microscopy with live/dead bacterial viability staining. TEM was done to study dentin collagen matrix. Dentin discs from 3rd day and 7th day well plate was used for Raman spectra and observed under fluorescent-microscope. Docking studies were carried out on MMP-2 S1 binding-domain with k21.

RESULTS

There was reduction of E. faecalis/C. albicans when k21, chlorhexidine and calcium hydroxide were used with highest percentage in 2%k21 treated specimens. 2%k21 showed dense and regular collagen network with intact cross-banding and decreased Raman intensity for 2%k21 on 3rd day. NaOCl + k21 showed least adherence, whereas saline groups showed highest adherence of E. faecalis and C. albicans to root-canal dentin. Alizarin red staining of hDPSCs revealed calcium deposition in all groups with significant difference seen amongst 2%k21 groups. MMP-2 ligand binding was seen accurately indicating possible target sites for k21 intervention.

CONCLUSION

2%k21 can be considered as alternative intracanal medicament.

Root canal microorganisms and their antibiotic susceptibility in patients with persistent endodontic infections, with and without clinical symptoms

Secondary/persistent infections are present in teeth with previous root canal treatment, and a great variety of anaerobic microorganisms has been observed in these infections. The antibiotics prescription is occasional; however, in some cases, it is essential, particularly when the general health condition of the patient is compromised. The aims of this study were to identify the associated microorganisms in diagnosis of persistent or secondary apical periodontitis and to evaluate the susceptibility level to the antibiotics most used. Fifteen patients with persistent or secondary apical periodontitis requiring endodontic re-treatment were included. Microbiological samples were taken from the root canals and incubated in thioglycollate under anaerobic conditions. Anaerobic CDC agar (formulated by the Center for Disease Control and Prevention) was employed as a culture medium and the microorganisms were identified using the API system. The microorganisms were subjected to antibiograms with three different antibiotics. Twenty-six microorganisms were identified, the most common genus was Enterococcus (26.8%), Streptococcus (19.22%), Aerococcus (19.1%), and Clostridium (11.4%). 48% of them were susceptible to amoxicillin, with 28% of resistance. For clavulanic acid/amoxicillin, the susceptibility occurred in 32%, with 28% of resistance; and for clindamycin, the susceptibility was present in 40%, with 52% of resistance. The most frequently detected associated microorganism for secondary infections was genus Enterococcus, which exhibited high resistance to the studied antibiotics.

Antibiotic prescribing practices of dentists for endodontic infections; a cross-sectional study

Objective

The indiscriminate prescription of antibiotics has led to the emergence of resistance microbes worldwide. This study aimed to investigate the antibiotic prescribing practices amongst general dental practitioners and specialists in managing endodontic infections in the United Arab Emirates (UAE).

Design

General dental practitioners and specialists in the UAE were invited to participate in an online questionnaire survey which included questions on socio-demographics, practitioner’s antibiotic prescribing preferences for various pulpal and periapical diseases, and their choice, in terms of the type, dose and duration of the antibiotic. The link to the survey questionnaire was sent to 250 invited dentists. Data were analyzed by descriptive statistics and chi-square tests for independence and level of significance was set at 0.05.

Results

A total of 174 respondents participated in the survey (response rate = 70%). The respondents who prescribed antibiotics at least once a month were 38.5% while 17.2% did so, more than three times a week; amoxicillin 500 mg was the antibiotic of choice for patients not allergic to penicillin (43.7%), and in cases of penicillin allergies, erythromycin 500 mg (21.3%). There was a significant difference in the antibiotic prescribing practices of GDPs compared to endodontists and other specialties especially in clinical cases such as acute apical abscesses with swelling and moderate to severe pre-operative symptoms and retreatment of endodontic cases (p<0.05). Approximately, three quarters of the respondents (78.7%) did not prescribe a loading dose when prescribing antibiotics. About 15% respondents prescribed antibiotics to their patients if they were not accessible to patients due to a holiday/weekend.

Conclusions

In general, the antibiotic prescribing practices of UAE dentists are congruent with the international norms. However, there were occasions of inappropriate prescriptions such as in patients with irreversible pulpitis, necrotic pulps with no systemic involvement and/or with sinus tracts.

Limited antimicrobial efficacy of oral care antiseptics in microcosm biofilms and phenotypic adaptation of bacteria upon repeated exposure

Objectives

The aims of this study were to investigate the antimicrobial efficacy of antiseptics in saliva-derived microcosm biofilms, and to examine phenotypic adaption of bacteria upon repeated exposure to sub-inhibitory antiseptic concentrations.

Methods

Saliva-derived biofilms were formed mimicking caries- or gingivitis-associated conditions, respectively. Microbial compositions were analyzed by semiconductor-based 16S rRNA sequencing. Biofilms were treated with CHX, CPC, BAC, ALX, and DQC for 1 or 10 min, and colony forming units (CFU) were evaluated. Phenotypic adaptation of six selected bacterial reference strains toward CHX, CPC, and BAC was assessed by measuring minimum inhibitory concentrations (MICs) over 10 passages of sub-inhibitory exposure. Protein expression profiles were investigated by SDS-PAGE.

Results

Both biofilms showed outgrowth of streptococci and Veillonella spp., while gingivitis biofilms also showed increased relative abundances of Actinomyces, Granulicatella, and Gemella spp. Antiseptic treatment for 1 min led to no relevant CFU-reductions despite for CPC. When treated for 10 min, CPC was most effective followed by BAC, ALX, CHX, and DQC. Stable adaptations with up to fourfold MIC increases were found in E. coli toward all tested antiseptics, in E. faecalis toward CHX and BAC, and in S. aureus toward CPC. Adapted E. coli strains showed different protein expression as compared with the wildtype strain.

Conclusion

Antiseptics showed limited antimicrobial efficacy toward mature biofilms when applied for clinically relevant treatment periods. Bacteria showed phenotypic adaptation upon repeated sub-inhibitory exposure.

Clinical relevance

Clinicians should be aware that wide-spread use of antiseptics may pose the risk of inducing resistances in oral bacteria.

Properties of a modified quaternary ammonium silane formulation as a potential root canal irrigant in endodontics

OBJECTIVES

Evaluate a new modified quaternary ammonium silane irrigant solution for its antimicrobial, cytotoxic and mechanical properties of dentine substrate.

METHODS

Root canal preparation was performed using stainless steel K-files™ and F4 size protaper with irrigation protocols of 6% NaOCl + 2% CHX; 3.5% QIS; 2% QIS and sterile saline. Biofilms were prepared using E. faecalis adjusted and allowed to grow for 3 days, treated with irrigants, and allowed to grow for 7 days. AFM was performed and surface free energy calculated. MC3T3 cells were infected with endo irrigant treated E. faecalis biofilms. Raman spectroscopy of biofilms were performed after bacterial re-growth on root dentine and exposed to different irrigation protocols and collagen fibers analysed collagen fibers using TEM. Antimicrobial potency against E. faecalis biofilms and cytoxicity against 3T3 NIH cells were also. Resin penetration and MitoTracker green were also evaluated for sealer penetration and mitochondrial viability. Data were analysed using One-way ANOVA, principal component analysis and post-hoc Fisher's least-significant difference.

RESULTS

Elastic moduli were maintained amongst control (5.5 ± 0.9) and 3.5% QIS (4.4 ± 1.1) specimens with surface free energy higher in QIS specimens. MC3T3 cells showed reduced viability in 6%NaOCl+2%CHX specimens compared to QIS specimens. DNA/purine were expressed in increased intensities in control and 6% NaOCl + 2% CHX specimens with bands around 480-490 cm^-1 reduced in QIS specimens. 3.5% QIS specimens showed intact collagen fibrillar network and predominantly dead bacterial cells in confocal microscopy. 3.5% QIS irrigant formed a thin crust-type surface layer with cytoplasmic extensions of 3T3NIH spread over root dentine. Experiments confirmed MitoTracker accumulation in 3.5% treated cells.

SIGNIFICANCE

Novel QIS root canal irrigant achieved optimum antimicrobial protection inside the root canals facilitating a toxic effect against the Enterococcus faecalis biofilm. Root dentine substrates exhibited optimum mechanical properties and there was viability of fibroblastic mitochondria.

Antibacterial efficacy and discolouration potential of antibiotic pastes with macrogol for regenerative endodontic therapy

This study aimed to evaluate the antibacterial efficacy and discolouration potential of antibiotic pastes containing macrogol. Seventy single-rooted teeth were contaminated with a culture of Enterococcus faecalis for 30 days. Double (DAP) and triple antibiotic pastes (TAP) containing propylene glycol or macrogol as vehicles were applied. After 15 days, bacterial viability was compared. Change in teeth coronal colour was measured by a spectrophotometer. Statistical analysis was performed using anova and Tukey's test (P < 0.05). TAP containing clindamycin and propylene glycol was the only medicament that led to the presence of contamination, while the same combination of antibiotics containing macrogol did not result in bacterial growth (P < 0.05). Only the pastes containing minocycline in formulation resulted in coronal discolouration (P < 0.05). Both DAPs evaluated and the TAP containing clindamycin and macrogol showed to be the preferable options for regenerative endodontic therapy, as they were effective against E. faecalis biofilm and did not promote tooth discolouration.

Identification and Morphological Characterization of Biofilms Formed by Strains Causing Infection in Orthopedic Implants

Objectives: For a better understanding of the mechanisms involved in biofilm formation, we performed a broad identification and characterization of the strains affecting implants by evaluating the morphology of biofilms formed in vitro in correlation with tests of the strains' antibiotic susceptibility in planktonic form. The ability of the strains to form biofilms in vitro was evaluated by means of colony forming units counting, metabolic activity tests of biofilm cells, and scanning electron microscopy. Methods: A total of 140 strains were isolated from patients with orthopedic implant-related infections during the period of 2015 to 2018. The identification of the isolates was carried out through microbiological cultures and confirmed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. Antibiotic susceptibility rates of the isolates were accessed according to EUCAST (European Committee on Antimicrobial Susceptibility Testing). The ability of all isolates to form biofilms in vitro was evaluated by counting the colony forming units, by measuring the metabolic activity of biofilm cells, and by analyzing the morphology of the formed biofilms using scanning electron microscopy. Results: From all the isolates, 41.84% (62 strains) were Staphylococcus epidermidis and 15.60% (22 strains) were Staphylococcus aureus. A significant difference in the capacity of biofilm formation was observed among the isolates. When correlating the biofilm forming capacity of the isolates to their antibiotic susceptibility rates, we observed that not all strains that were classified as resistant were biofilm producers in vitro. In other words, bacteria that are not good biofilm formers can show increased tolerance to multiple antibiotic substances. Conclusion: From 2015 until 2018, Staphylococcus epidermidis was the strain that caused most of the orthopedic implant-related infections in our hospital. Not all strains causing infection in orthopedic implants are able to form biofilms under in vitro conditions. Differences were observed in the number of cells and morphology of the biofilms. In addition, antibiotic resistance is not directly related to the capacity of the strains to form biofilms in vitro. Further studies should consider the use of in vitro culture conditions that better reproduce the joint environment and the growth of biofilms in humans.

Cetylpyridinium Chloride: Mechanism of Action, Antimicrobial Efficacy in Biofilms, and Potential Risks of Resistance

Antimicrobial resistance is a serious issue for public health care all over the world. While resistance toward antibiotics has attracted strong interest among researchers and the general public over the last 2 decades, the directly related problem of resistance toward antiseptics and biocides has been somewhat left untended. In the field of dentistry, antiseptics are routinely used in professional care, but they are also included in lots of oral care products such as mouthwashes or dentifrices, which are easily available for consumers over-the-counter. Despite this fact, there is little awareness among the dental community about potential risks of the widespread, unreflected, and potentially even needless use of antiseptics in oral care. Cetylpyridinium chloride (CPC), a quaternary ammonium compound, which was first described in 1939, is one of the most commonly used antiseptics in oral care products and included in a wide range of over-the-counter products such as mouthwashes and dentifrices. The aim of the present review is to summarize the current literature on CPC, particularly focusing on its mechanism of action, its antimicrobial efficacy toward biofilms, and on potential risks of resistance toward this antiseptic as well as underlying mechanisms. Furthermore, this work aims to raise awareness among the dental community about the risk of resistance toward antiseptics in general.

Incidence of retrograde peri-implantitis in sites with previous apical surgeries: A retrospective study

BACKGROUND

Retrograde peri-implantitis (RPI) is a rapidly progressing periapical infection that forms around the implant apex. It is usually associated with sites adjacent to teeth with apical lesions; previous endodontic failures, retained root fragments, etc. This study aimed to study the incidence of RPI in sites with a history of apical surgeries.

METHODS

Patients with sites treated for both apicoectomy and implant placement presenting to the University of Michigan School of Dentistry from 2001 to 2016 were screened. A total of 502 apicoectomies were performed, only 25 of these fit the predetermined eligibility criteria and were thus included in this retrospective analysis.

RESULTS

Implants that were placed in sites with a previous apical surgery had a cumulative survival rate of 92%. The incidence of peri-implantitis was 8%, while the incidence of RPI was 20%. There was an increased trend for RPI in cases where the cause of extraction was persistent apical periodontitis (35.7%), but this increase didn't reach the level of statistical significance (P = 0.061).

CONCLUSION

Implants placed in sites with previous apical surgery are not at an increased risk of implant failure or RPI.

Correlation between biofilm formation and carbapenem resistance among clinical isolates of Klebsiella pneumoniae

Background

Klebsiella pneumoniae is a Gram-negative enteric bacterium that causes nosocomial infections; this bacterium has survived from harsh condition using biofilm formation in hospital equipment and cause severe infection. In the other hand, the emergence and extension of carbapenem resistance burden among K. pneumonia producing biofilm is the current concern of public health services. There are controversial findings about this subject. The aim of this study was to evaluate the correlation between biofilm formation and resistance to carbapenem among clinical isolates of K. pneumoniae.

Methods

A total of 160 K. pneumoniae isolates were collected from various infections of hospitalized patients. The Carba NP test and molecular methods were used for detection of carbapenem resistance isolates of K. pneumonia. Subsequently, the ability for biofilm production was performed from all isolates. Finally, Correlation of biofilm formation among carbapenem resistant isolates was calculated using χ2 and Fisher's exact tests.

Results

Among K. pneumoniae isolates 42.5% have carbapenemase activity by Carba NP test, while carbapenemase genes were detected in 35.6% of isolates in amplification assay. Moreover, there are 52.5% (n= 84) of all isolates were formed a strong biofilm, while 38.1% (n= 61) and 9.3% (n= 15) of isolates were middle and weak biofilm producer, respectively. Among carbapenem resistant cases (n= 68), there are 77.9% (n= 53) and 22% (n= 15) of isolates were reported as strong and middle biofilm producer, respectively. We see a significant correlation was seen between biofilm formation ability and carbapenem resistant isolates (p-value < 0.00001).

Conclusion

The increase of carbapenem resistance burden in biofilm producing isolates of K. pneumoniae is considered as serious alert and the basic measures to combat this phenomenon is imperative.

Antimicrobial peptide GH12 as root canal irrigant inhibits biofilm and virulence of Enterococcus faecalis

AIM

The objectives of this laboratory-based study were to investigate the effects of GH12 on Enterococcus faecalis biofilm and virulence.

METHODOLOGY

Minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of GH12 against E. faecalis were first determined. A time-kill assay was further conducted. The effects of GH12 on the expression of virulence and stress genes in E. faecalis were evaluated by RT-qPCR. Crystal violet stain was used to investigate the effects of GH12 on E. faecalis biofilm formation and 1-day-old biofilm. Finally, an ex vivo tooth model contaminated with E. faecalis was used to evaluate the antimicrobial activity of GH12 as an irrigant by CFU counting, SEM and CLSM. One-way anova and Tukey's multiple comparisons test were used to compare the differences amongst groups (α = 0.05).

RESULTS

The MICs and MBCs of GH12 against E. faecalis were 8.0 ± 0.0 and 16.0 ± 0.0 mg L^-1 , respectively, and GH12 at 32.0 mg L^-1 reduced the bacterial numbers by more than 99.9% within 1 min. Various virulence genes (efaA, esp and gelE) and stress genes (dnaK, groEL, ctsR and clpPBCEX) in E. faecalis were significantly downregulated by GH12 at sub-MIC levels (P < 0.05). Additionally, both E. faecalis biofilm formation and the biomass of 1-day-old E. faecalis biofilm were significantly reduced by GH12 (P < 0.05). Elimination of E. faecalis in biofilms from root canal walls was achieved through irrigation with 64.0 mg L^-1 GH12 for 30 min. CLSM analysis revealed that GH12 at 64.0 mg L^-1 was most effective in eliminating bacteria within dentinal tubules (P < 0.05).

CONCLUSION

In a laboratory setting, and when used as an irrigant, GH12 suppressed E. faecalis, downregulated specific virulence and stress-associated genes, eliminated intracanal E. faecalis protected by biofilms and killed bacteria in dentinal tubules. These results emphasize the need for preclinical and clinical studies to explore the potential of GH12 as an antimicrobial agent during root canal treatment.

Antibiotic Susceptibility Patterns of Aggregatibacter actinomycetemcomitans and Porphyromonas gingivalis Strains from Different Decades

The aim of this study was to determine the antibiotic susceptibility patterns of 57 Aggregatibacter actinomycetemcomitans and 56 Porphyromonas gingivalis strains isolated from subgingival biofilm samples of periodontitis patients in Switzerland from 1980 to 2017. The minimal inhibitory concentrations (MIC) of the most commonly used antibiotics in periodontal therapy (amoxicillin, metronidazole, azithromycin, and doxycycline) or in severe body infections (amoxicillin/clavulanic acid, clindamycin, ertapenem, and moxifloxacin) were determined. Furthermore, all the strains were screened for beta-lactamase activity and the presence of selected resistance genes (cfxA, ermF, and tetQ). Overall, there was no significant increase in MIC values over the 37‑year period. Two of the most recent P. gingivalis isolates yielded the highest MIC values. The first isolate was ermF-positive with MIC values >8 µg/mL, 2 µg/mL, and 0.25 µg/mL for clindamycin, azithromycin, and moxifloxacin, respectively. The second isolate showed a high MIC value of 4 µg/mL for moxifloxacin, which was associated with a confirmed single-point mutation in the quinolone resistance-determining region (QRDR) of the gyrA gene. Although there was no significant increase in the antibiotic resistance among the oral bacterial isolates tested, the detection of resistant P. gingivalis isolates underlines the need to optimize the antibiotic therapeutic protocols in dentistry.

Evidence-based clinical practice guideline on antibiotic use for the urgent management of pulpal- and periapical-related dental pain and intraoral swelling: A report from the American Dental Association

BACKGROUND

An expert panel convened by the American Dental Association Council on Scientific Affairs and the Center for Evidence-Based Dentistry conducted a systematic review and formulated clinical recommendations for the urgent management of symptomatic irreversible pulpitis with or without symptomatic apical periodontitis, pulp necrosis and symptomatic apical periodontitis, or pulp necrosis and localized acute apical abscess using antibiotics, either alone or as adjuncts to definitive, conservative dental treatment (DCDT) in immunocompetent adults.

TYPES OF STUDIES REVIEWED

The authors conducted a search of the literature in MEDLINE, Embase, the Cochrane Library, and the Cumulative Index to Nursing and Allied Health Literature to retrieve evidence on benefits and harms associated with antibiotic use. The authors used the Grading of Recommendations Assessment, Development and Evaluation approach to assess the certainty in the evidence and the Evidence-to-Decision framework.

RESULTS

The panel formulated 5 clinical recommendations and 2 good practice statements, each specific to the target conditions, for settings in which DCDT is and is not immediately available. With likely negligible benefits and potentially large harms, the panel recommended against using antibiotics in most clinical scenarios, irrespective of DCDT availability. They recommended antibiotics in patients with systemic involvement (for example, malaise or fever) due to the dental conditions or when the risk of experiencing progression to systemic involvement is high.

CONCLUSION AND PRACTICAL IMPLICATIONS

Evidence suggests that antibiotics for the target conditions may provide negligible benefits and probably contribute to large harms. The expert panel suggests that antibiotics for target conditions be used only when systemic involvement is present and that immediate DCDT should be prioritized in all cases.

Evaluation of Drug Susceptibility of Microorganisms in Odontogenic Inflammations and Dental Surgery Procedures Performed on an Outpatient Basis

Bacterial infections are the most common cause of purulent soft tissue inflammations in the head and neck area. These bacteria are also responsible for the majority of inflammatory complications after third molar removal. The key to success of antibacterial treatment in both cases is the use of an appropriate antibacterial agent. The aim of the study was to evaluate the susceptibility profile of bacteria isolated from material collected from patients with intraoral odontogenic abscesses. The test material consisted of swabs taken from the odontogenic abscesses, after their incision and drainage. Another swab was collected from the lesion area, 10 days after the initial visit. Results were compared with an identical study conducted on a control group of healthy patients, who had undergone third molar removal. Bacteria identified in this study consisted of aerobic and anaerobic strains, both Gram-positive and Gram-negative. According to the EUCAST guidelines, none of the tested antibiotics was recommended for all identified bacteria. The percentage of bacterial strains sensitive to amoxicillin and clavulanic acid was 78.13% and 81.48% in the study and control groups, respectively, whereas, the percentage of those sensitive to clindamycin was 96.43% and 80.00%, respectively. For Gram-negative aerobic bacteria, gentamicin and ciprofloxacin were among medications affecting all cultured species. 100.00% of strains were found to be susceptible to these antibiotics. Statistically significant relationship between the presence of Gram-negative aerobic strains and the occurrence of complications was found. In the case of the most frequently occurring bacteria in the study, amoxicillin with clavulanic acid and clindamycin were shown to be very effective. In cases of severe purulent odontogenic inflammations, it is recommended to use a combination of antibiotics. Amoxicillin with ciprofloxacin and clindamycin with cefuroxime seem to be the proper choices based on the results of this study.

The inhibitory effect of quaternary ammonium salt on bacteria in root canal

Persisting apical periodontitis is a primary reason for multiple intervention in root canal. Persisting bacteria in root canal is related with the persisting infection. Despite the advancement in treatment strategies the persisting infection is a major challenge for endodontist. Here we tested two newly developed quaternary ammonium methacrylates (QAMs) against endodontic bacteria and their biofilms. Their antibacterial and antibiofilm efficiency were compared with chlorhexidine (CHX) and sodium hypochlorite (NaOCl). We measured the MIC, MBC and MBIC of DMADDM and DMAHDM respectively. We also detected the ratio of live/dead bacteria and bacterial composition in the biofilms treated by DMADDM and DMAHDM. We found that DMADDM and DMAHDM could inhibit the growth of bacteria and biofilms formation. The result showed that novel QAMs were remarkably efficient than CHX against biofilms. In addition, we found that Streptococcus gordonii (S. gordonii) and Enterococcus faecalis (E. faecalis) were frequent isolates after treatment with antimicrobial compounds.

Prevention of infective endocarditis and bacterial resistance to antibiotics: A brief review

The purpose of this statement is to debate the recommendations of the American Heart Association (AHA) for the prevention of infective endocarditis through an antibiotic prophylaxis protocol and its relation with bacterial resistance to antibiotics. Since dental infections involve biofilms that include several bacterial species (Gram-negative and Gram-positive), it is essential, from the dental point of view, to consider the frequency, magnitude, and duration of bacteremia associated with active dental infections before applying antibiotic prophylaxis. The actual guidelines for antibiotic prophylaxis should be revised according to recent evidence of bacterial resistance. Amoxicillin/clavulanic acid and moxifloxacin should be considered due to their effectiveness against bacteria associated with oral, GU, and GI infections and the low rates of antibiotic resistance associated with these antibiotics, instead of the actual protocol, which includes amoxicillin (2 g) or clindamycin (600 mg) administered an hour before the dental procedures. The breaking point to test the antibiotic bacterial resistance (ABR) had a wide range in the different studies that were analyzed, which could explain the widely varied ABR percentages reported for the various antibiotics used for antibiotic prophylaxis.

Antibacterial Additives in Epoxy Resin-Based Root Canal Sealers: A Focused Review

Dental materials used in root canal treatment have undergone substantial improvements over the past decade. However, one area that still remains to be addressed is the ability of root canal fillings to effectively entomb, kill bacteria, and prevent the formation of a biofilm, all of which will prevent reinfection of the root canal system. Thus far, no published review has analysed the literature on antimicrobial additives to root canal sealers and their influence on physicochemical properties. The aim of this paper was to systematically review the current literature on antimicrobial additives in root canal sealers, their anti-fouling effects, and influence on physicochemical properties. A systematic search was performed in two databases (PubMed and Scopus) to identify studies that investigated the effect of antimicrobial additives in epoxy resin-based root canal sealers. The nature of additives, their antimicrobial effects, methods of antimicrobial testing are critically discussed. The effects on sealer properties have also been reviewed. A total of 31 research papers were reviewed in this work. A variety of antimicrobial agents have been evaluated as additives to epoxy resin-based sealers, including quaternary ammonium compounds, chlorhexidine, calcium hydroxide, iodoform, natural extracts, antibiotics, antifungal drugs, and antimicrobial agent-functionalised nanoparticles. Antimicrobial additives generally improved the antimicrobial effect of epoxy resin-based sealers mainly without deteriorating the physicochemical properties, which mostly remained in accordance with ISO and ANSI/ADA specifications.

An in vitro study of a novel quaternary ammonium silane endodontic irrigant

OBJECTIVE

To analyze effect of NaOCl+2% quaternary ammonium silane (QAS)-containing novel irrigant against bacteria impregnated inside the root canal system, and to evaluate its antimicrobial and mechanical potential of dentine substrate.

METHODS

Root canal was prepared using stainless steel K-files™ and ProTaper™ and subjected to manual and ultrasonic irrigation using 6% NaOCl+2% CHX, 6% NaOCl+2% QAS and saline as control. For confocal-microscopy, Raman spectroscopy and SEM analysis before and after treatment, Enterococcus faecalis cultured for 7 days. Raman spectroscopy analysis was done across cut section of gutta percha/sealer-dentine to detect resin infiltration. Indentation of mechanical properties was evaluated using a Berkovich indenter. The contact angle of irrigants and surface free energy were evaluated. Mineralization nodules were detected through Alazarin red after 14 days.

RESULTS

Control biofilms showed dense green colonies. Majority of E. faecalis bacteria were present in biofilm fluoresced red in NaOCl+2% QAS group. There was reduction of 484cm^-1 Raman band and its intensity reached lowest with NaOCl+2% QAS. There was an increase in 1350-1420cm^-1 intensity in the NaOCl+2% CHX groups. Gradual decrease in 1639cm^-1 and 1609cm^-1 Raman signal ratios were seen in the resin-depth region of 17μm>, 14.1μm> and 13.2μm for NaOCl+2% QAS, NaOCl+2% CHX and control groups respectively. All obturated groups showed an intact sealer/dentine interface with a few notable differences. 0.771 and 83.5% creep indentation distance for NaOCl+2% QAS ultrasonic groups were observed. Highest proportion of polar component was significantly found in the NaOCl+2% QAS groups which was significantly higher as compared to other groups. Mineralized nodules were increased in NaOCl+2% QAS.

SIGNIFICANCE

Favorable antimicrobial and endodontic profile of the NaOCl+2% QAS solution might suggest clinical use for it for more predictable reduction of intracanal bacteria.

Inspection of the Microbiota in Endodontic Lesions

The primary objective of endodontic therapy is to create a biologically acceptable environment within the root canal system that allows for the healing and maintenance of the health of the peri-radicular tissue. Bacteria are one of the main causes of pulp problems, and they have different methods of penetrating and invading the endodontic space such as through carious lesions, traumatic pulp exposures, and fractures. The types of bacteria found range from facultative anaerobes to aerobes, up to the most resistant species able to survive in nutrient-free environments; the bacterial species Enterococcus faecalis belongs to this last group. Enterococcus faecalis is considered one of the main causes of recurring apical periodontal lesions following endodontic treatment, with persistent lesions occurring even after re-treatment. The review presented in this paper was performed in accordance with the PRISMA protocol and covers articles from the related scientific literature that were sourced from PubMed, Scopus, and Google Scholar using the following terms as keywords: “endodontic treatment”, “endodontic bacteria”, “microbial endodontic”, and “endodontic failure”. Only the articles considered most relevant for the purposes of this paper were read in full and taken into consideration for the following review. The results show that Enterococcus faecalis, Actinomycetes, and Propionibacterium propionicum are the species most frequently involved in persistent radicular and extra-radicular infections.

Resistance Toward Chlorhexidine in Oral Bacteria - Is There Cause for Concern?

The threat of antibiotic resistance has attracted strong interest during the last two decades, thus stimulating stewardship programs and research on alternative antimicrobial therapies. Conversely, much less attention has been given to the directly related problem of resistance toward antiseptics and biocides. While bacterial resistances toward triclosan or quaternary ammonium compounds have been considered in this context, the bis-biguanide chlorhexidine (CHX) has been put into focus only very recently when its use was associated with emergence of stable resistance to the last-resort antibiotic colistin. The antimicrobial effect of CHX is based on damaging the bacterial cytoplasmic membrane and subsequent leakage of cytoplasmic material. Consequently, mechanisms conferring resistance toward CHX include multidrug efflux pumps and cell membrane changes. For instance, in staphylococci it has been shown that plasmid-borne qac ("quaternary ammonium compound") genes encode Qac efflux proteins that recognize cationic antiseptics as substrates. In Pseudomonas stutzeri, changes in the outer membrane protein and lipopolysaccharide profiles have been implicated in CHX resistance. However, little is known about the risk of resistance toward CHX in oral bacteria and potential mechanisms conferring this resistance or even cross-resistances toward antibiotics. Interestingly, there is also little awareness about the risk of CHX resistance in the dental community even though CHX has been widely used in dental practice as the gold-standard antiseptic for more than 40 years and is also included in a wide range of oral care consumer products. This review provides an overview of general resistance mechanisms toward CHX and the evidence for CHX resistance in oral bacteria. Furthermore, this work aims to raise awareness among the dental community about the risk of resistance toward CHX and accompanying cross-resistance to antibiotics. We propose new research directions related to the effects of CHX on bacteria in oral biofilms.

Antimicrobial action of photodynamic therapy in root canals using LED curing light, curcumin and carbopol gel

AIM

To evaluate the capacity of carbopol gel to maintain the intensity of a LED curing light (blueLED) along the length of prepared root canals in bovine teeth, and to assess the antimicrobial capacity of curcumin photoactivated by a LED curing light in the presence of carbopol gel.

METHODOLOGY

Experiment 1: Eight straight roots of bovine incisors were standardized to a length of 15 mm, and the root canals instrumented up to a size 120 K-file. The LED curing light was irradiated inside the root canals using an aluminium collimator (1.5 mm in diameter) placed at the orifice (n = 8). Initially, the irradiation was performed in empty root canals and then repeated with the root canals filled with carbopol gel. Simple standardized photographs of the roots were taken with a digital camera in the mesial perspective during the irradiation procedure and the images analysed in OriginLab software to verify the light intensity along the length of the root. Experiment 2: Twenty dentine blocks were obtained from the cervical third of bovine incisors using a trephine bur. Biofilms were induced for 21 days on the blocks using Enterococcus faecalis (ATCC 4083) at 10⁹ cells mL^-1 . The blocks were treated according to the groups (n = 5): positive control; standard PDT (methylene blue + diode Laser); curcumin; LED curing light; and curcumin + LED curing light. After the treatment, the samples were dyed with Live/Dead BacLight Bacterial Viability solution and fluorescence images were obtained by Confocal Scanning Laser Microscopy (CSLM). Experiment 3: Thirty-two roots of bovine incisors were prepared as described in experiment 1. Their dentinal tubules were contaminated and the root canals treated according to the groups (n = 8): positive control; standard PDT; curcumin + LED curing light; curcumin + carbopol gel + LED curing light. The specimens were sectioned longitudinally and the split roots were treated with the Live/Dead dye to obtain fluorescence images by CSLM. All images were processed using BioImageL software to measure the percentage of viable bacteria and the data analysed statistically using the nonparametric Kruskal-Wallis test (α < 0.05).

RESULTS

In Experiment 1, carbopol gel did not improve the intensity of LED light transmission along the root canal. In Experiment 2, a significant decrease (P < 0.05) in bacterial viability occurred in the following order: positive control < only LED curing light < only curcumin < curcumin + LED curing light = standard PDT; and in Experiment 3 positive control = curcumin + LED curing light ≤ curcumin + gel + LED curing light ≤ standard PDT.

CONCLUSION

Similar disinfection effectiveness was obtained using curcumin + LED curing light and methylene blue + 660 nm LASER (standard PDT). The use of carbopol gel did not favour a greater transmission of LED light along the root canal and also resulted in less bacterial killing when used in endodontic PDT.

Compounds from Olea europaea and Pistacia lentiscus inhibit oral microbial growth

BACKGROUND

In view of the increasing antibiotic resistance, the introduction of natural anti-infective agents has brought a new era in the treatment of bacterially derived oral diseases.

METHODS

The aim of this study was to investigate the antimicrobial potential of five natural constituents of Olea europaea (oleuropein, maslinic acid, hydroxytyrosol, oleocanthal, oleacein) and three compounds of Pistacia lentiscus (24Z-isomasticadienolic acid, oleanolic acid, oleanonic aldehyde) against ten representative oral bacterial species and a Candida albicans strain. After the isolation and quality control of natural compounds, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) assay were performed.

RESULTS

Among all O. europaea-derived constituents, maslinic acid was the most active (MIC = 4.9-312 μg mL^- 1, MBC = 9.8-25 μg mL^- 1) one against oral streptococci and anaerobic pathogenic bacteria (Porphyromonas gingivalis, Fusobacterium nucleatum, Parvimonas micra), while oleuropein, hydroxytyrosol, oleocanthal and oleacein showed milder, yet significant effects against P. gingivalis and F. nucleatum. Among all P. lentiscus compounds, oleanolic acid was the most effective one against almost all microorganisms with MIC values ranging from 9.8 μg mL^- 1 (P. gingivalis) to 625 μg mL^- 1 (F. nucleatum, P. micra). In the presence of 24Z-isomasticadienolic acid, a mean inhibitory concentration range of 2.4 μg mL^- 1 to 625 μg mL^- 1 was observed for strict anaerobia. The MIC value for 24Z-isomasticadienolic acid was estimated between 39 μg mL^- 1 (Streptococcus sobrinus, Streptococcus oralis) and 78 μg mL^- 1 (Streptococcus mutans). All tested compounds showed no effects against Prevotella intermedia.

CONCLUSIONS

Overall, maslinic acid and oleanolic acid exerted the most significant inhibitory activity against the tested oral pathogens, especially streptococci and anaerobic oral microorganisms.

A comparative evaluation of antimicrobial efficacy and flow characteristics of two epoxy resin-based sealers-AH plus and Perma Evolution: An in vitro study

Aim of the Study

Bacteria that persist at the time of obturation increase the possibility of persistent apical periodontitis. An ideal sealer should be able to kill these remaining bacteria that are present on the dentinal walls as well as inside the dentinal tubules. This could be possible if a sealer has antimicrobial properties with optimum flow characteristics. Hence, the aim of this in vitro study was to assess the antimicrobial efficacy of epoxy resin-based sealer: AH Plus and Perma Evolution against Enterococcus faecalis on the 1^st, 3^rd, 5^th, and 7^th day and also to compare the flow characteristics of both epoxy resin-based sealers.

Materials and Methods

E. faecalis ATCC 35550 strain was used to assess the antibacterial efficacy of sealers by agar-diffusion test (ADT) and direct-contact test (DCT). Flow characteristics of sealers were measured according to the ADA specification no. 57.

Results

In ADT, Perma Evolution sealer showed larger zone of inhibition than AH plus on the 1^st, 3^rd, 5^th, and 7^th day, and in DCT, both sealers were equally effective in inhibiting E. faecalis growth on the 1^st, 3^rd, 5^th, and 7^th day. Flow test showed no significant difference between Perma Evolution and AH Plus sealer.

Conclusion

Both the tested sealers were equally effective against E. faecalis up to 7 days of incubation period. Considering flow properties, both the tested sealers showed optimum flow as per the ADA specification no. 57.

Resistance profile to antimicrobial agents in the main circulating bacteria isolated from acute periodontal and endodontic infections in Latin America (MICROBE- DENT): A systematic review protocol

BACKGROUND

Antimicrobial resistance is currently considered the main risk to global health. A variety of microbial species have been isolated from endodontic and periodontal infections. However, clinical endodontic and periodontics bacterial isolates have not been sufficiently characterized with regard to their capacity for antibiotic resistance. We aim to assess the existing evidence to estimate the prevalence of the main antimicrobial resistance and multidrug resistant organisms in endodontics and periodontics and to describe their geographic distribution in Latin America.

METHODS

All types of designs and will be restricted to Latin American studies will be included in this systematic review. MEDLINE, Embase, CINAHL, BVS (LILACS, BBO - bvsalud.org), IBECS (bases.bireme.br), Google Scholar, Cochrane Central Register of Controlled Trials, and Web of Science databases will be searched from 2013 to December 31, 2018 for all types of study designs that report microbial infection in endodontics and periodontics and their resistance and that define the microbiological methods used to identify microorganisms. The selection of articles for inclusion will be performed by 2 reviewers using predefined eligibility criteria. The Cochrane and ROBINS-I risk of bias assessment tools will be used to assess the methodological quality of randomized control trials. The Newcastle-Ottawa scale will be used to assess the quality of methodology in observational studies. The overall quality of evidence will be assessed using Grading of Recommendations Assessment, Development and Evaluation (GRADE) using the same principles and domains applied in the quality assessment of prognostic studies. The heterogeneity of the findings will be assessed using both the χ test and the I statistic. Sensitivity analysis will be performed by subgroup analyses and meta-regression to investigate the effect of study-level characteristics, such as age, gender, and methodological quality score, whenever possible. Publication bias across studies will be evaluated by visual inspection of the funnel plots and Begg's test for the results covered in 10 or more studies.

RESULTS

The evidence derived by this study will inform best practices for patients with endodontic and periodontal problems receiving antimicrobial agents.

CONCLUSION

Successful completion will significantly impact clinical practice and contribute to improved prescribing competency.

PROTOCOL REGISTRATION

PROSPERO-CRD42018077810.

Suppressing inflammation and enhancing osteogenesis using novel CS-EC@Ca microcapsules

The aim of this study was to investigate the suppression of inflammation and enhancement of osteogenesis using chitosan-coated calcium hydroxide-loaded microcapsules (CS-EC@Ca microcapsules) in vivo. Circular defects were created in the mandibular bones of rabbits and filled with Ca(OH)₂ , Bio-oss, or CS-EC@Ca microcapsules, and rabbits without drug implantation served as the controls. Lipopolysaccharides were injected in situ daily in all groups for 7 days. Mandibular bones were investigated at 4 and 12 weeks after surgery using micro-CT, histological observations, and real-time PCR analysis. At the postoperation, there was more substantial nascent bone in the microcapsule and Bio-oss groups than in the control group. The recovery of the rabbits in the Ca(OH)₂ group was slower than the control group, as determined using micro-CT and histological staining. Osteocalcin and collagen type I production was not significantly different between the microcapsule and Bio-oss groups (p > 0.05), but the expression levels of the two molecules were significantly increased compared to the control and Ca(OH)₂ groups at postoperation (p < 0.05). The mRNA transcript levels of inflammatory factors in the microcapsule group had the most reduced expression of IL-6 and TNF-α (p < 0.05). The microcapsules significantly reduced inflammation and promoted osteogenesis in this rabbit model of inflammatory bone destruction. Our findings indicate that CS-EC@Ca microcapsules hold potential for use in apical periodontitis treatment. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 3222-3230, 2018.

Pharmacological Evaluation of Selected Medicinal Plants Used in the Management of Oral and Skin Infections in Ebem-Ohafia District, Abia State, Nigeria

Oral and skin infections contribute significantly to the global health challenges responsible for the current trend of increased morbidity and premature death. The purpose of this study was to document medicinal plants used in the management of oral and skin infections in Ebem-Ohafia Local Government Area (LGA), Abia State, and to characterize the in vitro antioxidant and antibacterial activity. The thin layer chromatography (TLC) profiling of ten of the selected folklore medicine was carried out using a various solvent system of different polarity index. The antioxidant capacity of the plant extracts was evaluated using chemical-based methods, and its antibacterial effect was investigated using disc diffusion and microdilution methods. Sixty-one plant species belonging to 26 families were discovered, and the most frequently cited species are Euphorbiaceae (18.03%), Fabaceae (11.47%), and Asteraceae (11.47%). All the plant extracts showed a promising free radical scavenging activity and efficient ferric reducing antioxidant power in a concentration-dependent manner possibly due to their richness in polyphenol with TLC profiling showing maximum three bands of phytochemicals. Also, the plant extracts exhibited a mild to weak antibacterial activity against our panel of bacterial strains having MIC values ranging from 256 to > 512 μg/ mL reflected in their zone of inhibition at 10 μg/disc. The data obtained for Breynia nivosa (BN), Eleusine indica (EI), Cassia alata (CA), Chromolaena odorata (CO), and Acalypha hispida (AH) extracts substantiate the traditional use of these herbal remedies in the region and open the possibility for the development of cheaper and affordable drugs in the treatment of oral and skin infections. Further studies are needed to identify active ingredient with strong antibacterial and antioxidant capacities along with their molecular mechanisms.