Occurrence, population structure, and antimicrobial resistance of enterococci in marginal and apical periodontitis

Microbial Communities in the Extraradicular and Intraradicular Infections Associated With Persistent Apical Periodontitis

Microorganisms in the complex root canal system and the extraradicular regions, including the periapical lesions and extraradicular biofilm may cause root canal treatment failures. However, few studies described the difference between the intraradicular and extraradicular infections from the same tooth associated with persistent apical periodontitis. This study aimed to characterize the microbiome present in the root canal, extraradicular biofilm, and periapical lesions associated with persistent apical periodontitis. The microbial communities in the root canal, extraradicular biofilm, and periapical lesions were investigated by Illumina high-throughput sequencing using Illumina Hiseq 2500 platform. The dominant phyla in the extraradicular and intraradicular infections associated with persistent apical periodontitis were Proteobacteria, Firmicutes, Bacteroidetes, and Actinobacteria, and the genera Fusobacterium, Morganella, Porphyromonas, Streptococcus, and Bifidobacterium dominated across all samples. Although extraradicular infection sites showed higher OTU richness and β-diversity compared to intraradicular samples, the occurrence of sinus tract rather than the sampling sites demarcated the microbial communities in the infections associated with persistent apical periodontitis. PERMANOVA analysis confirmed that the samples with or without sinus tracts contained significantly different microbial communities. Porphyromonas, Eubacterium, Treponema, and Phocaeicola were found in significantly higher levels with sinus tracts, whilst Microbacterium and Enterococcus were more abundant in samples without sinus tracts. In conclusion, diverse bacteria were detected in both intraradicular and extraradicular infections associated with persistent apical periodontitis, which might be influenced by the occurrence of the sinus tract. The results may provide new insight into the pathogenesis of persistent apical periodontitis.

Radiographic and antimicrobial evaluation of enterococcus Faecalis and Actinomyces Israelii micro-organisms after photodynamic therapy (aPDT)

This study evaluated the action of Antimicrobial Photodynamic Therapy (aPDT) on Enterococcus faecalis and Actinomyces israelii. Samples were taken from the root canal system, at different stages of treatment and bacteria were identified through qPCR. Fifty teeth (incisors, canines, and premolars) with pulp necrosis and periapical lesion diagnosis were randomly selected and divided into 2 groups: Group 1 (G1) - Endodontic Therapy with Mechanical Chemical Preparation (MPQ) and intracanal medication; Group 2 (G2) - Endodontic therapy with MPQ, intracanal medication, and 2 applications of aPDT. APDT was performed with application of 0.005% methylene blue, wavelength of 660 nm, and 90 seconds. Follow-up was performed with an initial x-ray and an x-ray 60 days after the end of treatment. The radiographs were scored evaluated by two examiners to classify periapical repair: total repair, partial repair, doubtful repair, or no repair. Enterococcus faecalis was found more frequently in G1 than G2. Actinomyces israelii was found equally in G1 and G2. Evaluation of the two bacteria between collections 1, 2 and 3, showed that there was no difference, both in G1 and in G2. There was association between the variables group and repair classification in radiographs evaluation. APDT did not promote better results in endodontic treatment, being similar to conventional treatment. However, this study pointed out that molecular methods may not be efficient in detecting bacteria after treatment, and colony-forming units may complement, being an effective quantifying method. Therefore, new studies must be carried out to show the possible effectiveness of aPDT.

Antimicrobial susceptibility and virulence of Enterococcus spp. isolated from periodontitis-associated subgingival biofilm

BACKGROUND

This study evaluated the prevalence, virulence and antimicrobial susceptibility of enterococci isolated from the subgingival microbiota of patients with different periodontal status.

METHODS

Subgingival biofilm was obtained from individuals with periodontal health (PH) (n = 139), gingivitis (n = 103), and periodontitis (n = 305) and cultivated on selective media. Isolated strains were identified by mass spectrometry. Antimicrobial sensitivity was determined by disk diffusion, virulence genes by polymerase chain reaction, and the subgingival microbiota by checkerboard. Differences among groups were assessed by Kruskal-Wallis, Mann-Whitney, and Chi-square tests.

RESULTS

Enterococcus spp. were isolated from 7.4% of all samples; 53.7% were Enterococcus faecalis. They were more prevalent in periodontitis (9.8%) and gingivitis (7.8%) than PH (2.2%; P <0.05), but no differences among stages of disease severity were observed. High rates of low susceptibility/resistance (>64%) to at least one antimicrobial were observed. Predominant virulence factors included ace (64.3%), asa (39.3%), and esp (35.7%). Fusobacterium nucleatum was prevalent in the subgingival microbiota of enterococci+ individuals, whereas Dialister pneumosintes was found in low frequency in patients with bopD+ enterococci. Oral streptococci were prevalent (>70%) in patients carrying enterococci susceptible to doxycycline (P <0.05), usually bopD- and esp- (P <0.01).

CONCLUSIONS

E. faecalis is increased in periodontitis-associated biofilm. Oral enterococci carry virulence genes and express resistance to some antibiotics commonly used in dentistry, such as ciprofloxacin and erythromycin. Specific subgingival taxa are associated with oral enterococci, suggesting they may interact with species of the dysbiotic periodontitis biofilm, constituting a potential source of factors to tissue destruction, antibiotic resistance dissemination, and poor response to periodontal therapy.

Improving the Efficiency of Photodynamic Chemotherapy in Root Canals against Enterococcus faecalis In Vitro

The aim of this study was to evaluate the effect of photoactivated chemotherapy (PACT) on Enterococcus faecalis (E. faecalis) biofilms in root canals using an 90% isopropanol (IPA)-based photosensitizer and removing excess photosensitizer before light incubation. Three hundred and seven extracted human teeth with one root canal were infected with E. faecalis for 72 h and treated in groups: IPA irrigation; PACT; PACT and final rinse with IPA; PACT with photosensitizer removal using either 0.9% NaCl solution or sterile paper points or both; PACT using IPA-based photosensitizer with and without a final rinse of IPA. Root canals were sampled using sterile paper points and dentin chips collected from the root canal walls. Additionally, SEM (Scanning Electron Microscopy) images of the specimens were taken to evaluate the root canal walls for residue bacterial contamination. In all antimicrobial treatment groups treatments E. faecalis counts were significantly reduced in the root canals. Using IPA-based photosensitizer the antimicrobial effect of PACT was significantly enhanced. Irrigation with IPA alone or after PACT significantly increased the antimicrobial effect compared to PACT alone. The collected dentin chips revealed the highest amount of culture negative root canals (10%) after PACT using IPA-based photosensitizer. In the other groups, the culture negative samples ranged from only 0–2 specimens of 30 specimens. REM images show remaining E. faecalis cells on the root canal wall and inside dentin tubules. Using IPA-based photosensitizer significantly enhanced the antimicrobial effect of PACT against E. faecalis in the root canals.

Assessment of Nitrofurantoin as an Experimental Intracanal Medicament in Endodontics

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

The effect of smear layer removal on E. faecalis leakage and bond strength of four resin-based root canal sealers

BACKGROUND

The aim of the study was to assess bacterial sealability and bonding ability of methacrylate-based Resilon (RS, SybronEndo), Endo Rez (ER, Ultradent Products Inc), and epoxy-based AH Plus (AH, Dentsply/DeTrey), MTA Fill Apex (MTAF, Angelus Soluções Odontológicas) root canal sealers, and the effect of the smear layer removal on the sealability.

METHODS

One hundred thirty root segments were instrumented up to apical size #60 and rinsed with 2.5% NaOCl. Half of the roots were rinsed with 5ml 17% EDTA to remove the smear layer. All the roots were filled with AH, ER, MTAF sealers and gutta-percha, or RS with Resilon cones. After storage at 37°C for 7 days the samples were mounted into bacterial leakage assay for 50 days. Another 100 roots were instrumented and rinsed as described above, split longitudinally, cut into the cervical, middle and apical parts. The sealers were injected through the plastic mould on the dentin surface. After 7 days of incubation at 37°C, bond strength was tested using a notched-edge test fixture (Crosshead, Ultradent Products Inc.) and a universal testing machine (Lloyd Instruments).

RESULTS

AH revealed the longest mean time for bacterial resistance by 29.4 and 36.8 days (with and without smear layer, respectively) followed by RS (15.1 and 24.7 days, respectively). The difference between materials was significant (p<0.001). Bond strength values ranged from 0.2± 0.1 to 3.5± 0.7 MPa and increased from the apical to the cervical third. In the apical third, AH showed the highest mean (SD) bond values 1.4 (0.4) MPa and 1.7 (0.6) MPa (with and without smear, respectively, followed by RS, 0.5 (0.1) MPa and 0.8 (0.1) MPa, respectively. The difference between materials was significant (p=0.001).

CONCLUSION

The effect of the smear layer removal on the sealability was material-dependent.

Evaluation of the Effect of MTAD on Expression of Enterococcus faecalis Virulence Factors Considering the Role of Different Obturating Materials

OBJECTIVES

The aim of this study was to determine the effect of MTAD on the expression of virulence factors of Enterococcus faecalis (E.faecalis) considering the role of Guttapercha/AH26 or Resilon/RealSeal SE as root canal obturating materials.

MATERIALS AND METHODS

One-hundred and forty-four single-rooted human teeth were instrumented to a standardized apical size. Root canals were infected by E.faecalis (ATCC 29212). Ninety teeth were irrigated with MTAD and randomly divided into three groups. In two groups, root canals were obturated by either Gutta-percha/AH26 or Resilon/RealSeal SE. Root canals were kept unobturated in the third group. The remaining 54 teeth received no final irrigation. All groups were then subdivided into three timepoint subgroups in which dentin powder was obtained from each sample to determine the expression of specific virulence factors of E.faecalis (efa, esp, gel, fsr) using real-time reverse transcription polymerase chain reaction (RT-PCR). Statistical analysis was performed by one-way analysis of variance (ANOVA) and Tukey's post-hoc test. The statistical power was set at P-value ≤0.05.

RESULTS

MTAD was effective against the expression of most of the tested virulence factors, and Gutta-percha/AH26 increased the antibacterial efficacy of MTAD.

CONCLUSIONS

MTAD could inhibit the expression of some known virulence factors of E.faecalis at the majority of tested timepoints. This may partly explain some of the mechanisms of antimicrobial efficacy of MTAD against this resistant microorganism which is known as one of the main causes of failure of root canal treatment.

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

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

Comparative genomics of Enterococcus spp. isolated from bovine feces

Background

Enterococcus is ubiquitous in nature and is a commensal of both the bovine and human gastrointestinal (GI) tract. It is also associated with clinical infections in humans. Subtherapeutic administration of antibiotics to cattle selects for antibiotic resistant enterococci in the bovine GI tract. Antibiotic resistance genes (ARGs) may be present in enterococci following antibiotic use in cattle. If located on mobile genetic elements (MGEs) their dissemination between Enterococcus species and to pathogenic bacteria may be promoted, reducing the efficacy of antibiotics.

Results

We present a comparative genomic analysis of twenty-one Enterococcus spp. isolated from bovine feces including Enterococcus hirae (n = 10), Enterococcus faecium (n = 3), Enterococcus villorum (n = 2), Enterococcus casseliflavus (n = 2), Enterococcus faecalis (n = 1), Enterococcus durans (n = 1), Enterococcus gallinarum (n = 1) and Enterococcus thailandicus (n = 1). The analysis revealed E. faecium and E. faecalis from bovine feces share features with human clinical isolates, including virulence factors. The Tn917 transposon conferring macrolide-lincosamide-streptogramin B resistance was identified in both E. faecium and E. hirae, suggesting dissemination of ARGs on MGEs may occur in the bovine GI tract. An E. faecium isolate was also identified with two integrative conjugative elements (ICEs) belonging to the Tn916 family of ICE, Tn916 and Tn5801, both conferring tetracycline resistance.

Conclusions

This study confirms the presence of enterococci in the bovine GI tract possessing ARGs on MGEs, but the predominant species in cattle, E. hirae is not commonly associated with infections in humans. Analysis using additional complete genomes of E. faecium from the NCBI database demonstrated differential clustering of commensal and clinical isolates, suggesting that these strains may be specifically adapted to their respective environments.

Electronic supplementary material

The online version of this article (doi:10.1186/s12866-017-0962-1) contains supplementary material, which is available to authorized users.

Systemic antibiotics in the treatment of periodontitis

Despite the fact that several clinical studies have shown additional benefits when certain systemic antibiotics are used as adjuncts to periodontal treatment, clear guidelines for the use of these agents in the clinical practice are not yet available. Basic questions concerning the use of systemic antibiotics to treat periodontitis remain unanswered, such as: which drug(s) should be used; which patients would most benefit from treatment; which are the most effective protocols (i.e. doses and durations); and in which phase of the mechanical therapy should the drug(s) be administered? Although not all of those questions have been directly addressed by controlled randomized clinical trials, recent concepts related to the ecology of periodontal diseases, as well as the major advances in laboratory and clinical research methods that have occurred in the past decade, have significantly broadened our knowledge in this field. This article endeavored to provide a 'state of the art' overview on the use of systemic antibiotics in the treatment of periodontitis, based on the most recent literature on the topic as well as on a compilation of data from studies conducted at the Center of Clinical Trials at Guarulhos University (São Paulo, Brazil) from 2002 to 2012.

Biofilm Formation by Drug Resistant Enterococci Isolates Obtained from Chronic Periodontitis Patients

INTRODUCTION

Enterococci are an important cause of opportunistic nosocomial infections and several multidrug resistant strains have emerged. The severity of periodontal diseases is managed by reduction in the pathogenic bacteria. There is a need to assess the prevalence and antibiotic susceptibility of enterococci colonizing the periodontal pocket and correlate its biofilm formation ability because oral biofilms provide a protective environment and are a reservoir of bacterial colonization of the gingival crevice.

AIM

To investigate possible association between antibiotic susceptibility and biofilm formation in enterococci isolates from chronic periodontitis patients.

MATERIALS AND METHODS

This retrospective study was conducted at Dr. Harvansh Singh Judge Institute of Dental Sciences and Hospital, Punjab University, Chandigarh from January 2015 to October 2015. Sterile paper points were inserted in the periodontal pocket of 100 subjects and put in a transport media. Forty -six isolates were identified as enterococci. The isolates were further examined for their ability to form biofilm by microtitre plate assay and antimicrobial susceptibility testing was done by disc diffusion method for clinically relevant antibiotics.

RESULTS

Significant relationship (p<0.001) was found between biofilm production with antibiotic resistance to Vancomycin, Erythromycin, Ciprofloxacin, Tiecoplanin, Amoxycillin and Gentamycin.

CONCLUSION

The study demonstrates a high propensity among the isolates of Enterococci to form biofilm and a significant association of biofilm with multiple drug resistance.

Abutment Coating With Diamond-Like Carbon Films to Reduce Implant-Abutment Bacterial Leakage

BACKGROUND

The influence of diamond-like carbon (DLC) films on bacterial leakage through the interface between abutments and dental implants of external hexagon (EH) and internal hexagon (IH) designs was evaluated.

METHODS

Film deposition was performed by plasma-enhanced chemical vapor deposition. Sets of implants and abutments (n = 30 per group, sets of 180 implants) were divided according to connection design and treatment of the abutment base: 1) no treatment (control); 2) DLC film deposition; and 3) Ag-DLC film deposition. Under sterile conditions, 1 μL Enterococcus faecalis was inoculated inside the implants, and abutments were tightened. The sets were tested for immediate external contamination, suspended in test tubes containing sterile culture broth, and followed for 5 days. Turbidity of the broth indicated bacterial leakage. At the end of the period, the abutments were removed and the internal content of the implants was collected with paper points and plated in Petri dishes. After 24-hour incubation, they were assessed for bacterial viability and colony-forming unit counting. Bacterial leakage was analyzed by χ(2) and Fisher exact tests (α = 5%).

RESULTS

The percentage of bacterial leakage was 16.09% for EH implants and 80.71% for IH implants (P <0.0001). The bacterial load was higher inside IH implants (P = 0.000). The type of implant significantly influenced the results (P = 0.000), whereas the films did not (P = 0.487).

CONCLUSION

IH implants show a higher frequency of bacterial leakage; and DLC and Ag-DLC films do not significantly reduce the frequency of bacterial leakage and bacteria load inside the implants.

Transcription factor Rex in regulation of pathophysiology in oral pathogens

The NAD(+) and NADH-sensing transcriptional regulator Rex is widely conserved across gram-positive bacteria. Rex monitors cellular redox poise and controls the expression of genes/operons involved in diverse pathways including alternative fermentation, oxidative stress responses, and biofilm formation. The oral cavity undergoes frequent and drastic fluctuations in nutrient availability, pH, temperature, oxygen tension, saliva, and shear forces. The oral streptococci are major colonizers of oral mucosa and tooth surfaces and include commensals as well as opportunistic pathogens, including the primary etiological agent of dental caries, Streptococcus mutans. Current understanding of the Rex regulon in oral bacteria is mostly based on studies in S. mutans and endodontic pathogen Enterococcus faecalis. Indeed, other oral bacteria encode homologs of the Rex protein and much is to be gleaned from more in-depth studies. Our current understanding has Rex positioned at the interface of oxygen and energy metabolism. In biofilms, heterogeneous oxygen tension influences the ratio of intracellular NADH and NAD(+) , which is finely tuned through glycolysis and fermentation. In S. mutans, Rex regulates the expression of glycolytic enzyme NAD(+) -dependent glyceraldehyde 3-phosphate dehydrogenase, and NADH-dependent fermentation enzymes/complexes lactate dehydrogenase, pyruvate dehydrogenase, alcohol-acetaldehyde dehydrogenase, and fumarate reductase. In addition, Rex controls the expression of NADH oxidase, a major enzyme used to eliminate oxidative stress and regenerate NAD(+) . Here, we summarize recent studies carried out on the Rex regulators in S. mutans and E. faecalis. This research has important implications for understanding how Rex monitors redox balance and optimizes fermentation pathways for survival and subsequent pathogenicity.

Ultrasonic activation and chemical modification of photosensitizers enhances the effects of photodynamic therapy against Enterococcus faecalis root-canal isolates

BACKGROUND

The aim of this study was to evaluate the effect of photodynamic therapy (PDT) on Enterococcus faecalis biofilms in artificially infected root canals using modified photosensitizers and passive ultrasonic activation.

METHODS

Two hundred and seventy extracted human teeth with one root canal were instrumented utilizing ProTaper files, autoclaved, infected with E. faecalis T9 for 72 h and divided into different groups: irrigation with 3% sodium hypochlorite (NaOCl), 20% ethylenediaminetetraacetic acid (EDTA), or 20% citric acid, PDT without irrigation, PDT accompanied by irrigation with NaOCl, EDTA, or citric acid, PDT using an EDTA-based photosensitizer or a citric-acid-based photosensitizer and PDT with ultrasonic activation of the photosensitizer. A 15 mg/ml toluidine blue served as the photosensitizer, activated by a 100 mW LED light source. Sterile paper points were used for sampling the root canals and dentin chips were collected to assess the remaining contamination after treatment. Samples were cultured on blood agar plates and colony forming units were quantified.

RESULTS

PDT alone achieved a reduction in E. faecalis counts by 92.7%, NaOCl irrigation alone and combined with PDT by 99.9%. The antibacterial effects increased by the combination of irrigation using EDTA or citric acid and PDT compared to irrigation alone. More than 99% of E. faecalis were killed using PDT with the modified photosensitizers and ultrasonic activation.

CONCLUSIONS

NaOCl based disinfection achieved the highest antimicrobial effect. Using PDT with an EDTA-based or citric-acid-based phozosensitizer or activating the photosensitizer with ultrasound resulted in a significantly higher reduction in E. faecalis counts compared to conventional PDT.

Effect of photodynamic therapy (PDT) on Enterococcus faecalis biofilm in experimental primary and secondary endodontic infections

BACKGROUND

To determine the antibacterial effect of photodynamic Therapy on Enterococcus faecalis (E. faecalis) biofilms in experimentally infected human root canals in primary infections and endodontic retreatments.

METHODS

One hundred and sixty single-rooted extracted teeth with one root canal were prepared using ProTaper instruments. Seventy specimens were left without root canal filling and autoclaved. The root canals of another 70 specimens were filled with Thermafil and AH Plus and the root canal fillings were removed after 24 hours using ProTaper D files and plasma sterilized. The specimens were infected with a clinical isolate of E. faecalis for 72 hours. Samples were taken using sterile paper points to determine the presence of E. faecalis in the root canals. The specimens were randomly divided into groups according to their treatment with 20 teeth each and a control. In the PDT group the teeth were treated using PDT, consisting of the photosensitizer toluidine blue and the PDT light source at 635 nm. In the NaOCl (sodium hypochlorite) group the root canals were rinsed with 10 mL of 3% NaOCl. In the NaOCl-PDT group the root canals were rinsed with 10 mL of 3% of sodium hypochlorite and then treated with PDT. Samples were taken after treatments using sterile paper points. Additionally, remaining root canal filling material was recovered from the root canal walls. Survival fractions of the samples were calculated by counting colony-forming units. A one-way analysis of variance (ANOVA) was applied to the data to assess the effect of different treatment techniques.

RESULTS

Antimicrobial treatment of root canals caused a significant reduction of bacterial load in all groups. NaOCl irrigation eliminated E. faecalis most effectively. PDT alone was less effective compared to NaOCl irrigation and the combination of NaOCl irrigation and PDT. CFU levels recovered from the filling material after NaOCl irrigation of the root canals were 10fold higher compared to PDT and the combination of NaOCl irrigation and PDT.

CONCLUSIONS

Photodynamic therapy killed E. faecalis in experimental primary endodontic infections and retreated human root canals. PDT is an effective supplement in root canal disinfection, especially in endodontic retreatments.

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

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

Photodynamic biofilm inactivation by SAPYR--an exclusive singlet oxygen photosensitizer

Prevention and control of biofilm-growing microorganisms are serious problems in public health due to increasing resistances of some pathogens against antimicrobial drugs and the potential of these microorganisms to cause severe infections in patients. Therefore, alternative approaches that are capable of killing pathogens are needed to supplement standard treatment modalities. One alternative is the photodynamic inactivation of bacteria (PIB). The lethal effect of PIB is based on the principle that visible light activates a photosensitizer, leading to the formation of reactive oxygen species, e.g., singlet oxygen, which induces phototoxicity immediately during illumination. SAPYR is a new generation of photosensitizers. Based on a 7-perinaphthenone structure, it shows a singlet oxygen quantum yield ΦΔ of 99% and is water soluble and photostable. Moreover, it contains a positive charge for good adherence to cell walls of pathogens. In this study, the PIB properties of SAPYR were investigated against monospecies and polyspecies biofilms formed in vitro by oral key pathogens. SAPYR showed a dual mechanism of action against biofilms: (I) it disrupts the structure of the biofilm even without illumination; (II) when irradiated, it inactivates bacteria in a polymicrobial biofilm after one single treatment with an efficacy of ≥ 99.99%. These results encourage further investigation on the potential of PIB using SAPYR for the treatment of localized infectious diseases.

Characterisation of the plasmidome within Enterococcus faecalis isolated from marginal periodontitis patients in Norway

The present study aimed to identify and characterize plasmids in a national collection of oral Enterococcus faecalis (n = 106) isolated from patients with marginal periodontitis. Plasmid replicon typing was performed by multiplex-PCR and sequencing with specific primers for 18 rep-families and 1 unique sequence. Additional plasmid analysis by S1-PFGE was performed for comparison. Totally 120 plasmid replicon amplicons of seven rep-families were identified in 93 E. faecalis strains, e.g. rep9 (prototype pCF10), rep6 (prototype pS86), rep2 (prototype pRE25/pEF1), and rep8 (prototype pAM373). Rep9 was the most predominant rep-family being detected in 81 (76.4%) strains. Forty of these strains were tetracycline resistant and three were erythromycin resistant. Rep6 was the second predominant rep-family being detected in 22 (20.8%) strains. Rep2 was detected in eight (7.5%) strains. All rep2-positive strains were resistant to tetracycline and/or erythromycin and six of them contained Tn916/Tn1545 genes. The rep-positive E. faecalis exhibited divergence in multilocus sequence types (STs). There was a significant correlation between rep9 and ST21, while multiple rep-families appeared in ST40. Totally 145 plasmid bands were identified in 95 E. faecalis strains by S1-PFGE, 59 strains carrying one plasmid, 27 carrying two, five carrying three, three carrying four, and one strain carrying five plasmids. Plasmid sizes varied between 5-150 kbp. There was a significant correlation between the number of plasmids identified by PCR rep-typing and by S1-PFGE. The results indicate that the majority of E. faecalis of marginal periodontitis are likely to be a reservoir for diverse mobile genetic elements and associated antimicrobial resistance determinants.

Low-cost periodontal therapy

Periodontitis is a complex infectious disease that affects low-income individuals disproportionately. Periodontitis is associated with specific bacterial species and herpesviruses, and successful prevention and treatment of the disease is contingent upon effective control of these pathogens. This article presents an efficacious, highly safe, minimally invasive, practical and low-cost periodontal therapy that involves professional and patient-administered mechanical therapy and antimicrobial agents. The major components are scaling for calculus removal, periodontal pocket irrigation with potent antiseptics, and treatment with systemic antibiotics for advanced disease. Povidone-iodine and sodium hypochlorite have all the characteristics for becoming the first-choice antiseptics in the management of periodontal diseases. Both agents show excellent antibacterial and antiviral properties, are readily available throughout the world, have been safely used in periodontal therapy for decades, offer significant benefits for individuals with very limited financial resources, and are well accepted by most dental professionals and patients. Four per cent chlorhexidine applied with a toothbrush to the most posterior part to the tongue dorsum can markedly reduce or eliminate halitosis in most individuals. Systemic antibiotics are used to treat periodontopathic bacteria that are not readily reached by topical therapy, such as pathogens within gingival tissue, within furcation defects, at the base of periodontal pockets, and on the tongue, tonsils and buccal mucosae. Valuable antibiotic therapies are amoxicillin-metronidazole (250 mg of amoxicillin and 250 mg of metronidazole, three times daily for 8 days) for young and middle-aged patients, and ciprofloxacin-metronidazole (500 mg of each, twice daily for 8 days) for elderly patients and for patients in developing countries who frequently harbor enteric rods subgingivally. Scaling to remove dental calculus and the prudent use of inexpensive antimicrobial agents can significantly retard or arrest progressive periodontitis in the great majority of patients.

Antibiotic susceptibility of periodontal Enterococcus faecalis

BACKGROUND

Enterococcus faecalis may contribute to periodontal breakdown in heavily infected subgingival sites, particularly in patients responding poorly to mechanical forms of periodontal therapy. Because only limited data are available on the antimicrobial sensitivity of enterococci of subgingival origin, this study evaluates the in vitro antibiotic susceptibility of E. faecalis isolated from periodontitis patients in the United States.

METHODS

Pure cultures of 47 subgingival E. faecalis clinical isolates were each inoculated onto specially prepared broth microdilution susceptibility panels containing vancomycin, teicoplanin, and six oral antibiotics of potential use in periodontal therapy. After incubation in ambient air for 18 to 20 hours, minimal inhibitory drug concentrations were determined using applicable Clinical and Laboratory Standards Institute criteria and interpretative guidelines. The organisms were additionally evaluated for in vitro resistance to metronidazole at 4 μg/mL.

RESULTS

Periodontal E. faecalis exhibited substantial in vitro resistance to tetracycline (53.2% resistant), erythromycin (80.8% resistant or intermediate resistant), clindamycin (100% resistant to 2 μg/mL), and metronidazole (100% resistant to 4 μg/mL). In comparison, the clinical isolates were generally sensitive to ciprofloxacin (89.4% susceptible; 10.6% intermediate resistant) and 100% susceptible in vitro to ampicillin, amoxicillin/clavulanate, vancomycin, and teicoplanin.

CONCLUSIONS

Tetracycline, erythromycin, clindamycin, and metronidazole revealed poor in vitro activity against human subgingival E. faecalis clinical isolates, and would likely be ineffective therapeutic agents against these species in periodontal pockets. Among orally administered antibiotics, ampicillin, amoxicillin/clavulanate, and ciprofloxacin exhibited marked in vitro inhibitory activity against periodontal E. faecalis, and may be clinically useful in treatment of periodontal infections involving enterococci.

Virulence factors and antibiotic susceptibility in enterococci isolated from oral mucosal and deep infections

OBJECTIVE

This study evaluates the presence of virulence factors and antibiotic susceptibility among enterococcal isolates from oral mucosal and deep infections.

METHODS

Forty-three enterococcal strains from oral mucosal lesions and 18 from deep infections were isolated from 830 samples that were sent during 2 years to Oral Microbiology, University of Gothenburg, for analysis. The 61 strains were identified by 16S rDNA, and characterized by the presence of the virulence genes efa A (endocarditis gene), gel E (gelatinase gene), ace (collagen binding antigen gene), asa (aggregation substance gene), cyl A (cytolysin activator gene) and esp (surface adhesin gene), tested for the production of bacteriocins and presence of plasmids. MIC determination was performed using the E-test method against the most commonly used antibiotics in dentistry, for example, penicillin V, amoxicillin and clindamycin. Vancomycin was included in order to detect vancomycin-resistant enterococci (VRE) strains.

RESULTS

Sixty strains were identified as Enterococcus faecalis and one as Enterococcus faecium. All the virulence genes were detected in more than 93.3% (efa A and esp) of the E. faecalis strains, while the presence of phenotypic characteristics was much lower (gelatinase 10% and hemolysin 16.7%). Forty-six strains produced bacteriocins and one to six plasmids were detected in half of the isolates.

CONCLUSIONS

Enterococcal strains from oral infections had a high virulence capacity, showed bacteriocin production and had numerous plasmids. They were generally susceptible to ampicillins but were resistant to clindamycin, commonly used in dentistry, and no VRE-strain was found.

Population biology of Gram-positive pathogens: high-risk clones for dissemination of antibiotic resistance

Infections caused by multiresistant Gram-positive bacteria represent a major health burden in the community as well as in hospitalized patients. Staphylococcus aureus, Enterococcus faecalis and Enterococcus faecium are well-known pathogens of hospitalized patients, frequently linked with resistance against multiple antibiotics, compromising effective therapy. Streptococcus pneumoniae and Streptococcus pyogenes are important pathogens in the community and S. aureus has recently emerged as an important community-acquired pathogen. Population genetic studies reveal that recombination prevails as a driving force of genetic diversity in E. faecium, E. faecalis, S. pneumoniae and S. pyogenes, and thus, these species are weakly clonal. Although recombination has a relatively modest role driving the genetic variation of the core genome of S. aureus, the horizontal acquisition of resistance and virulence genes plays a key role in the emergence of new clinically relevant clones in this species. In this review, we discuss the population genetics of E. faecium, E. faecalis, S. pneumoniae, S. pyogenes and S. aureus. Knowledge of the population structure of these pathogens is not only highly relevant for (molecular) epidemiological research but also for identifying the genetic variation that underlies changes in clinical behaviour, to improve our understanding of the pathogenic behaviour of particular clones and to identify novel targets for vaccines or immunotherapy.

Assessment of antimicrobial susceptibility of Enterococcus faecalis isolated from chronic periodontitis in biofilm versus planktonic phase

BACKGROUND

Enterococci are often associated with chronic and recurrent infectious diseases because of their antimicrobial resistance. The aim of this study is to assess antimicrobial susceptibility of Enterococcus faecalis in chronic periodontitis.

METHODS

Antimicrobial susceptibility was determined on 23 E. faecalis strains isolated from patients with chronic periodontitis. Ampicillin, erythromycin, gentamicin, tetracycline, triclosan, and vancomycin were prepared in two-fold serial dilution up to 8,192 μg/mL. Enterococcal biofilm was established by a biofilm device and observed by confocal laser microscopy and scanning electron microscopy. The minimum inhibitory concentration (MIC), minimum biofilm inhibitory concentration, and minimum biofilm eradication concentration were determined by spectrophotometer at optical density(650).

RESULTS

A few patches of monolayer early biofilm were observed on the surfaces of biofilm device pegs. The colony-forming units of biofilm per peg were 1.2 × 10(3) to 1.7 × 10(4) and 0 to 20 post-triclosan treatment. The MIC(50) was higher than the MIC epidemiologic cut-off for tetracycline and the MIC(90) was higher than the cut-off for erythromycin and tetracycline, respectively. In biofilm, minimum biofilm eradication concentrations were extremely high for all of the drugs except triclosan.

CONCLUSIONS

The E. faecalis strains of chronic periodontitis exhibited weak biofilm formation ability at the early stage. Over 50% of the strains were resistant to tetracycline, and a few strains were highly resistant to erythromycin or gentamicin. E. faecalis cells in biofilm were hardly eradicated by most of the agents, even in high concentrations. Triclosan was effective in inhibiting E. faecalis growth in both biofilm and planktonic phase.

Isolation of Tn1546-like elements in vancomycin-resistant Enterococcus faecium isolated from wood frogs: an emerging risk for zoonotic bacterial infections to humans

AIM

Isolation and characterization of vancomycin-resistant enterococci (VRE), mainly Enterococcus faecium, from the faecal pellet of wood frogs (Rana sylvatica).

METHODS AND RESULTS

The frog VRE isolates were tested for their susceptibility to various antibiotics and were found resistant to ampicillin (Am), chloramphenicol (Cm), erythromycin (Em), gentamicin (Gm), tetracycline (Tc), teicoplanin (Tp) and vancomycin (Vn). The linkage of multiple antibiotic resistances to Em, Tc, Tp and Vn was observed in 84% of resistant Ent. faecium. Inducible antibiotic resistance (MIC ≥ 512 μg ml(-1) ) to Vn was also detected in these isolates. PCR analysis revealed the presence of vanA in all strains, and none of the strains were positive for vanB, indicating the existence of vanA phenotype. Furthermore, the PCR-RFLP analysis of the frog vanA amplicon with PstI, BamHI and SphI generated identical restriction patterns similar to Tn1546-like elements found in human VRE isolates. DNA homoduplex analysis also confirmed that vanA from the frog VRE has DNA sequence homology with the vanA of Tn1546-like elements of human and animal isolates. Blastx analysis of frog vanA sequence showed similarities with protein sequences generated from protein database of Vn-resistant Ent. faecium, Baccilus circulans, Paenibacillus apiarius and Oerskovia turbata isolates. Horizontal transfer of Vn resistance was not detected in frog isolates as revealed by filter mating conjugal experiment.

CONCLUSIONS

In summary, our results demonstrated that wood frogs carry Vn-resistant bacteria, and resistance genes (vanA) are located on Tn1546-like elements.

SIGNIFICANCE AND IMPACT OF THE STUDY

This study highlights a previously less recognized role of amphibians as sentinels for multidrug-resistant bacteria and alerts the public health workers for an emerging risk of zoonotic bacterial infections to humans.