Quantitative real-time PCR detection of oral Enterococcus faecalis in humans

Genetic modifications to temperate Enterococcus faecalis phage Ef11 that abolish the establishment of lysogeny and sensitivity to repressor, and increase host range and productivity of lytic infection

Ef11 is a temperate bacteriophage originally isolated by induction from a lysogenic Enterococcus faecalis strain recovered from an infected root canal, and the Ef11 prophage is widely disseminated among strains of E. faecalis. Because E. faecalis has emerged as a significant opportunistic human pathogen, we were interested in examining the genes and regulatory sequences predicted to be critical in the establishment/maintenance of lysogeny by Ef11 as a first step in the construction of the genome of a virulent, highly lytic phage that could be used in treating serious E. faecalis infections. Passage of Ef11 in E. faecalis JH2-2 yielded a variant that produced large, extensively spreading plaques in lawns of indicator cells, and elevated phage titres in broth cultures. Genetic analysis of the cloned virus producing the large plaques revealed that the variant was a recombinant between Ef11 and a defective FL1C-like prophage located in the E. faecalis JH2-2 chromosome. The recombinant possessed five ORFs of the defective FL1C-like prophage in place of six ORFs of the Ef11 genome. Deletion of the putative lysogeny gene module (ORFs 31-36) and replacement of the putative cro promoter from the recombinant phage genome with a nisin-inducible promoter resulted in no loss of virus infectivity. The genetic construct incorporating all the aforementioned Ef11 genomic modifications resulted in the generation of a variant that was incapable of lysogeny and insensitive to repressor, rendering it virulent and highly lytic, with a notably extended host range.

Real-time PCR surveillance of vanA for vancomycin-resistant Enterococcus faecium

In Korea, the incidence of vancomycin-resistant enterococci (VRE) infection has recently been increasing, with a clinical isolation rate of up to 25%. We evaluated the clinical usefulness of real-time PCR for the detection of the vanA gene over conventional culture in patients confirmed as being VRE-colonized. During the evaluation stage, 100 consecutive clinical specimens were analyzed for the presence of the vanA gene via real-time PCR, for which 4 specimen preparations were used. During the application stage, 1,115 specimens from 82 patients were monitored for 20 months by vanA real-time PCR. For isolates prepared via incubation in broth for 24 h, the PCR results were concordant with those of the conventional method. The median value of the time spent in isolation and the number of test repeats from detection to release from isolation was 71 days and 5.5, respectively. The optimal negative test number for the release from isolation was ≥3. In conclusion, the real-time PCR method is more sensitive than, and is expected to replace, the conventional VRE surveillance method.

Prevalence of Enterococcus faecalis in saliva and filled root canals of teeth associated with apical periodontitis

To investigate the prevalence of Enterococcus faecalis in saliva and filled root canals of patients requiring endodontic retreatment for apical periodontitis. Patients with apical periodontitis who were referred for endodontic retreatment were examined. The type and quality of the restoration, symptoms, quality of obturation were recorded. During retreatment, an oral rinse sample and root canal sample were cultured using brain-heart infusion agar and bile esculinazide agar to select for E. faecalis. The 16S rRNA technique was used to identify E. faecalis. A total of 32 women and 22 men (mean age: 38 years; s.d.: 11 years) and 58 teeth were studied. The prevalence of E. faecalis was 19% in the saliva and 38% in the root canals. The odds that root canals harbored E. faecalis were increased if the saliva habored this bacterium (odds ratio=9.7; 95% confidence interval=1.8–51.6; P<0.05). Teeth with unsatisfactory root obturation had more cultivable bacterial species in root canals than teeth with satisfactory root obturation (P<0.05). E. faecalis is more common in root canals of teeth with apical periodontitis than in saliva. The prevalence of E. faecalis in root canals is associated with the presence of E. faecalis in saliva.

Effect of vanadium chloroperoxidase on Enterococcus faecalis biofilms

INTRODUCTION

The aim of this study was to explore the antimicrobial effect of vanadium chloroperoxidase (VCPO) reaction products on Enterococcus faecalis biofilms of 4 different strains.

METHODS

Twenty-four-hour biofilms of E. faecalis strains V583, ER5/1, E2, and OS-16 were incubated in mixtures with VCPO, halide (either bromide or chloride), and hydrogen peroxide. The antibacterial efficacy was assessed by colony-forming unit counts.

RESULTS

The VCPO reaction products had a similar efficacy in reducing the viability of the 4 strains of E. faecalis (94%; range, 87%-100%). Bromide as the halogen of choice was more effective on E. faecalis strains E2 and OS-16, as compared with chloride (Mann-Whitney U test; P < .05). Despite different quantities of produced biofilms by the 4 strains, VCPO treatment was similarly effective toward all strains (Kruskal-Wallis test; P < .05).

CONCLUSIONS

VCPO treatment results in an antimicrobial effect toward in vitro E. faecalis biofilms and might provide an addition to current endodontic treatment, possibly as an antimicrobial dressing.

Impact of erosion and accretion on the distribution of enterococci in beach sands

Bacterial pathogens in coastal sediments may pose a health risk to users of beaches. Although recent work shows that beach sands harbor both indicator bacteria and potential pathogens, it is not known how deep within beach sands the organisms may persist nor if they may be exposed during natural physical processes. In this study, sand cores of approximately 1 m depth were collected at three sites across the beach face in Kitty Hawk, North Carolina before, during and after large waves from an offshore hurricane. The presence of DNA from the fecal indicator bacterium Enterococci was detected in subsamples at different depths within the cores by PCR amplification. Erosion and accretion of beach sand at the three sites also was determined for each sampling day. The results indicate that ocean beach sands with persisting enterococci signals could be exposed and redistributed when wind, waves, and currents cause beach erosion or accretion.

Antibiotic resistance and adhesion properties of oral Enterococci associated to dental caries

BACKGROUND

Enterococci are increasingly associated with opportunistic infections in Humans but the role of the oral cavity as a reservoir for this species is unclear. This study aimed to explore the carriage rate of Enterococci in the oral cavity of Tunisian children and their antimicrobial susceptibility to a broad range of antibiotics together with their adherence ability to abiotic and biotic surfaces.

RESULTS

In this study, 17 E. faecalis (27.5%) and 4 E. faecium (6.5%) were detected. The identified strains showed resistance to commonly used antibiotics. Among the 17 isolated E. faecalis, 12 strains (71%) were slime producers and 5 strains were non-producers. Among the 4 E. faecium, 2 strains were slime producers. All the tested strains were able to adhere to at least one of the two tested cell lines. Our result showed that 11 E. faecalis and 2 E. faecium strains adhered strongly to Hep-2 as well as to A549 cells.

CONCLUSIONS

Drugs resistance and strong biofilm production abilities together with a high phenotypic adhesion to host cells are important equipment in E. faecalis and E. faecium which lead to their oral cavity colonization and focal infections.

Real-time polymerase chain reaction of "red complex" (Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola) in periradicular abscesses

OBJECTIVE

The red complex bacteria (Porphyromonas gingivalis, Tannerella forsythia, and Treponema denticola) have been implicated, either singly or in combination, in the development of various forms of periodontal diseases. The aim of this study was to investigate the presence of "red complex" in acute periradicular abscesses by real-time polymerase chain reaction (PCR) method.

STUDY DESIGN

Microbial samples were collected by aspiration from 32 cases diagnosed as acute periradicular abscess. DNA was extracted from the samples by using a QIAamp DNA mini-kit and analyzed with real-time PCR.

RESULTS

At least 1 member of the red complex was found in 84% of the cases. In general T. denticola, P. gingivalis, and T. forsythia were detected in 65.6%, 43.7%, and 40.6% of the cases, respectively. Red complex was detected in 15.6% of samples taken from acute periradicular abscesses.

CONCLUSIONS

Our findings suggest that "red complex" can participate in the pathogenesis of acute periradicular abscesses.

Association of red complex, A. actinomycetemcomitans and non-oral bacteria with periodontal diseases

OBJECTIVE

Pathogens related to systemic infections have been detected in the periodontal microbiota. The relationship amongst these pathogens, periodontal bacteria and periodontal clinical status is poorly understood. This study evaluated the association amongst red complex, A. actinomycetemcomitans (A.a) and non-oral pathogenic bacteria in subjects with good periodontal health (PH), gingivitis (G), chronic (CP) and aggressive (AP) periodontitis.

METHODS

Subgingival biofilm samples were obtained from 51 PH, 42 G, 219 CP and 90 AP subjects. The presence and levels of A.a, red complex (Porphyromonas gingivalis, Tannerella forsythia, Treponema denticola), Acinetobacter baumannii, Escherichia coli, Enterococcus faecalis, Pseudomonas aeruginosa, and Staphylococcus aureus were determined by DNA probes and DNA-DNA hybridization technique.

RESULTS

CP and AP subjects presented significantly higher prevalence and levels of A.a, red complex and A. baumannii than G and PH individuals (p<0.01), whereas S. aureus was detected in lower frequency and counts in AP as compared to the other groups (p<0.001). The predictor variables age, prevalence of red complex, and the presence of A. baumannii and P. aeruginosa were strongly associated with the frequency of sites with PD and CAL ≥5 mm. Increasing age (OR 1.08), high frequency of red complex (OR 6.10), and the presence of A.a with P. aeruginosa (OR 1.90) were associated with periodontal disease (p<0.001). Subjects harbouring a high prevalence of A.a, A. baumannii, and red complex with P. aeruginosa were more likely to have AP than CP (p<0.001).

CONCLUSION

Putative periodontal pathogens and non-oral bacteria alone or in association were strongly associated with periodontitis.

Enterococcus faecalis infection in root canals - host-derived or exogenous source?

AIMS

Enterococcus faecalis is associated with a significant number of refractory endodontic infections. Previous studies report a prevalence of Ent. faecalis ranging from 24% up to 77% in teeth with failed endodontic treatment. The origin of the micro-organism remains unclear, as enterococci do not belong to the normal oral microflora. The aim of this study was to determine whether these enterococci were of endogenous or exogenous origin.

METHODS AND RESULTS

Fifty consecutive patients with apical periodontitis in need of endodontic orthograde re-treatment were included. Samples were collected from root canals, saliva and faeces and subjected to microbiological culturing. The genetic relationship between Ent. faecalis from root canals and isolates from the different host sources was determined using pulsed-field gel electrophoresis. In 16% (8/50) of the patients, enterococci were collected from the root canal samples. The genetic analysis showed that the isolates from the root canals were not related to those from the normal gastrointestinal microflora. None of these patients had enterococci in their saliva samples.

CONCLUSIONS

Endodontic infections with Ent. faecalis are probably not derived from the patient's own normal microflora, which indicates that these infections ent. faecalis are of exogenous origin.

SIGNIFICANCE AND IMPACT OF THE STUDY

This is the first study to genetically compare endodontic infectious Ent. faecalis isolates with isolates from the hosts' own normal microflora.

A genetic determinant in Streptococcus gordonii Challis encodes a peptide with activity similar to that of enterococcal sex pheromone cAM373, which facilitates intergeneric DNA transfer

Enterococcus faecalis strains secrete multiple peptides representing different sex pheromones that induce mating responses by bacteria carrying specific conjugative plasmids. The pheromone cAM373, which induces a response by the enterococcal plasmid pAM373, has been of interest because a similar activity is also secreted by Streptococcus gordonii and Staphylococcus aureus. The potential to facilitate intergeneric DNA transfer from E. faecalis is of concern because of extensive multiple antibiotic resistance, including vancomycin resistance, that has emerged among enterococci in recent years. Here, we characterize the related pheromone determinant in S. gordonii and show that the peptide it encodes, gordonii-cAM373, does indeed induce transfer of plasmid DNA from E. faecalis into S. gordonii. The streptococcal determinant camG encodes a lipoprotein with a leader sequence, the last 7 residues of which represent the gordonii-cAM373 heptapeptide SVFILAA. Synthetic forms of the peptide had activity similar to that of the enterococcal cAM373 AIFILAS. The lipoprotein moiety bore no resemblance to the lipoprotein encoded by E. faecalis. We also identified determinants in S. gordonii encoding a signal peptidase and an Eep-like zinc metalloprotease (lspA and eep, respectively) similar to those involved in processing certain pheromone precursors in E. faecalis. Mutations generated in camG, lspA, and eep each resulted in the ablation of gordonii-cAM373 activity in culture supernatants. This is the first genetic analysis of a potential sex pheromone system in a commensal oral streptococcal species, which may have implications for intergeneric gene acquisition in oral biofilms.

Analysis of Enterococcus faecalis in samples from Turkish patients with primary endodontic infections and failed endodontic treatment by real-time PCR SYBR green method

Objective:

The aims of this study were to investigate the presence of Enterococcus faecalis in primary endodontic infections and failed endodontic treatments using real-time PCR and to determine the statistical importance of the presence of E. faecalis in a Turkish population with endodontic infections.

Material and Methods:

E. faecalis was investigated from 79 microbial samples collected from patients who were treated at the Endodontic Clinic of the Dental School of Atatürk University (Erzurum, Turkey). Microbial samples were taken from 43 patients (Group 1) with failed endodontic treatments and 36 patients (Group 2) with chronic apical periodontitis (primary endodontic infections). DNA was extracted from the samples by using a QIAamp^® DNA mini-kit and analyzed with real-time PCR SYBR Green.

Results:

E. faecalis was detected in 41 out of 79 patients, suggesting that it exists in not less than 61% of all endodontic infections when the proportion test (z= -1.645, <x= 0.05) was applied. Real-time PCR SYBR Green allowed for the detection of E. faecalis in 32 out of 43 (74.4%) in Group 1, and in 9 out of 36 (25%) in Group 2.

Conclusions:

These results suggest that E. faecalis is a frequent isolate for endodontic infections in Turkish patients, and is more often associated with failed endodontic treatments than primary endodontic infections.

Analysis ofSalmonellaand enterococci isolated from rendered animal products

The objectives of this study were to determine the current status of bacterial contamination in rendered animal products and to analyze Salmonella and enterococci isolates from the samples. One hundred and fifty samples were provided by various rendering companies across the United States, including the following meal types: feather, meat, meat and bone, meat and bone from poultry, poultry, and blood meals. The average pH of the meals ranged from 6.16 to 7.36, and the moisture content ranged from 1.9% to 11.5%. The total bacterial counts were in the range of 1.7 to 6.68 log10CFU/g, with the highest in blood meal and the lowest in meat meal. Enterococcus species were detected in 81.3% of the samples and accounted for up to 54% of the total bacterial counts in some samples. Both blood meal and feather meal were more contaminated (P < 0.05) with enterococci than other meal types, although all blood meals were from a single company. Salmonella was detected in 8.7% of the samples. Escherichia coli was not detected in any of the samples, but coliforms were detected in four samples. Among enterococci isolates, three were vancomycin resistant. Thirteen serotypes of Salmonella displayed 16 pulsed-field gel electrophoresis patterns. Pulsed-field gel electrophoresis analysis has indicated that Salmonella contamination was not persistent in the plant environment over time. The D-values for the Salmonella isolates at 55, 60, and 65 °C were in the ranges of 9.27–9.99, 2.07–2.28, and 0.35–0.40 min, respectively. These results suggest that the presence of Salmonella in the finished products may be due to postprocessing contamination. This study has also revealed that the rendering industry has microbiologically improved its products since earlier studies were conducted.

Prevalence of putative virulence factors and antimicrobial susceptibility of Enterococcus faecalis isolates from patients with dental Diseases

Background

This study investigated the prevalence of Enterococcus faecalis, its putative virulence factors and antimicrobial susceptibility in individuals with and without dental diseases. A total of 159 oral rinse specimens were collected from patients (n = 109) suffering from dental diseases and healthy controls (n = 50).

Results

E. faecalis was detected using only culture in 8/109 (7.3%) of the patients with various types of dental diseases, whereas no E. faecalis was found in the healthy controls weather using both culture and PCR. Phenotype characterizations of the 8 E. faecalis isolates indicated that 25% of the isolates produced haemolysin and 37.5% produced gelatinase. Most important virulence genes; collagen binding protein (ace) and endocarditis antigen (efaA) were present in all 8 E. faecalis isolates, while haemolysin activator gene (cylA) was detected only in 25% of isolates, and all isolates were negative for esp gene. All E. faecalis isolates were 100% susceptible to ampicillin, chloramphenicol, ciprofloxacin, vancomycin, and teicoplanin, and to less extent to erythromycin (62.5%).

Conclusion

This study shows that all E. faecalis isolates were recovered only from patients with dental diseases especially necrotic pulps, and all isolates carried both collagen binding protein and endocarditis antigen genes and highly susceptible to frequently used antimicrobial drugs in Jordan.

Prevalence of Enterococcus faecalis in subgingival biofilm and saliva of subjects with chronic periodontal infection

BACKGROUND AND AIMS

Enterococci are increasingly associated with nosocomial and opportunistic infections in humans. The role of the oral cavity as a reservoir for this species is unclear, particularly in the presence of oral infection. This study investigated the prevalence of Enterococcus faecalis in subgingival biofilm and saliva of patients with periodontal disease.

METHODS

Samples were obtained from 56 periodontally healthy and 169 chronic periodontitis subjects. DNA was extracted from the samples and detection of E. faecalis was carried out by polymerase chain reaction.

RESULTS

In general, E. faecalis was detected in 34.9% of all samples evaluated. No significant difference in the prevalence of this species between subgingival biofilm (34.6%) and saliva (35.1%) samples was observed. E. faecalis was detected significantly more often in saliva and subgingival samples of periodontitis patients (40.5% and 47.8%, respectively) compared to controls (14.6% and 17.1%, respectively; p<0.05). Moreover, significant positive correlations were observed between the presence of E. faecalis and clinical parameters of probing depth, clinical attachment level, bleeding on probing and plaque accumulation (p<0.001).

CONCLUSION

The present data showed that E. faecalis is frequently detected in the oral microbiota of periodontitis patients suggesting that periodontal infection may favour the colonization by this species. Close attention should be given to these patients regarding the risk for development of E. faecalis infection in other sites of the body.

Recovery of Enterococcus faecalis from cheese in the oral cavity of healthy subjects

INTRODUCTION

Enterococci are rarely found in the healthy human oral cavity, yet they are strongly associated with filled root canals. The origin of these enterococci remains unknown. Our hypothesis is that they are transient food-born colonizers under healthy conditions. This pilot study reinvestigated the prevalence of enterococci in the oral cavity of healthy volunteers, screened cheese samples for enterococci and investigated colonization of the oral cavity after ingestion of an enterocci-positive cheese.

METHOD

Concentrated oral rinse samples were collected from a cohort of 50 dental students and proved negative for viable enterococci. Twenty cheese samples were obtained from local supermarkets. Enterococci were cultured and identified using standard methods.

RESULTS

Viable enterococci were detected in one of five specimens of Swiss Tilsiter, three of five samples of French soft cheese, one of five Mozzarella samples and one of five Feta samples. Eight volunteers from the cohort consumed 10 g of a cheese with high Enterococcus faecalis load. Oral rinse samples were collected before and 1, 10 and 100 min after cheese ingestion. One minute after ingestion, a median of 5,480 E. faecalis colony-forming units was recovered from the oral rinse samples. Bacterial counts were reduced after 10 min, had dropped after 100 min to levels that were significantly (P < 0.005) different from the 1-min and 10-min scores and were below the detection limit after 1 week.

CONCLUSIONS

These findings suggest that colonization of the healthy oral cavity by enterococci is transitional, but at the same time add weight to our hypothesis that enterococcal root canal infections could be food-borne.

Effects of prolonged exposure to alkaline pH on Enterococcus faecalis survival and specific gene transcripts

INTRODUCTION

The persistence of Enterococcus faecalis in treated root canals has been attributed to its resistance to the high pH of antimicrobial agents used during treatment, but the specific mechanisms are not clear. We investigated the survival and gene expression of E. faecalis maintained in alkaline media.

METHODS

E. faecalis JH2-2 was maintained in media at pH 7, 10, 11 and 12 at either 25 degrees C or 37 degrees C for 1 week (168 h). At 24, 48, 72, 120 and 168 h, cell viability was determined in parallel with real-time quantitative polymerase chain reaction analyses of stress response genes (dnaK, fba, ftsZ, GroEL, napA, pbp5, tsf and tuf).

RESULTS

After 1 week the E. faecalis showed survival levels of 100% in pH 7, 1% in pH 10, 0.001% in pH 11 and 0.00001% in pH 12 media. At 37 degrees C increased levels of gene transcripts occurred between 72 and 120 h in pH 7 media for ftsZ and dnaK, and in pH 10 media for ftsZ, pbp5, dnaK, napA, tsf, fba and GroEL. No increase in transcripts was observed at 37 degrees C in media at pH 11 or pH 12, nor at 25 degrees C in any media.

CONCLUSION

Transcripts of ftsZ, a gene involved in cell division, increased by 37-fold after 120 h at pH 10 at 37 degrees C. Overall, the greatest increase in levels of gene transcripts occurred in cultures maintained in pH 10 media at 37 degrees C. These data may assist in understanding the survival strategies of E. faecalis following prolonged exposure to alkaline pH levels.

The Influence of Root Canal Sealer on Extended Intracanal Survival of Enterococcus faecalis With and Without Gelatinase Production Ability in Obturated Root Canals

Enterococcus faecalis can survive for extended periods in obturated root canals. In this study, the hypotheses tested were that long-term survival of E. faecalis is dependent on (1) the type of endodontic sealer and (2) the capacity for microbial gelatinase activity, a potential "virulence" trait identified previously in clinical isolates. Root canals of extracted human canines (n=95) were inoculated with either E. faecalis OG1RF or its gelatinase-negative mutant E. faecalis TX5128. After 48 hours of incubation at 37 degrees C, canals were obturated with gutta-percha and either the epoxy-resin-based AH-Plus (Dentsply, De Trey, Konstanz, Germany), the silicone-based RoekoSeal (Coltène/Whaledent, Langenau, Germany), or zinc oxide eugenol-based Roth's sealer (Root Canal Cement Type 801; Roth International Ltd, Chicago, IL). Access cavities were sealed. After 8 months of incubation at 37 degrees C, viable E. faecalis was recovered from more teeth sealed with RoekoSeal (95%) compared with AH-Plus (40%) (p=0.0004, Fisher's exact test) and Roth's sealer (45%) (p=0.0012, Fisher's exact test). In the RoekoSeal groups, viable counts of E. faecalis OG1RF were higher than E. faecalis TX5128 (p=0.03, Mann-Whitney U test) suggesting that gelatinase activity plays a role in long-term survival of E. faecalis in obturated root canals.

Real-time PCR for detection of the Aspergillus genus

Aspergillus is a genus of mold that has strong indoor sources, including several species capable of acting as opportunistic pathogens. Previous studies suggest that Aspergillus could serve as an indicator for abnormal mold growth or moisture, making it an important genus for environmental monitoring. Here, a quantitative polymerase chain reaction (qPCR, or real-time PCR) assay is presented for Aspergillus. The assay shows good specificity for the genus, detecting all Aspergillus species tested, although a few non-Aspergillus species are also amplified. Sensitivity testing demonstrates that DNA representing one conidium can be detected. A validation study compared qPCR results against direct microscopy counts using A. fumigatus conidia aerosolized into a laboratory chamber. The assay was then used to quantify Aspergillus in indoor air samples, demonstrating its utility for environmental monitoring. Analysis of a small number of clinical sputum samples showed complete agreement with culturing results.

Primer sensitivity: can it influence the results in Enterococcus faecalis prevalence studies?

BACKGROUND/OBJECTIVE

Recent polymerase chain reaction (PCR)-based studies have shown significant variability in the prevalence of Enterococcus faecalis cases with nonhealing endodontic infections. This variability may be, at least in part, due to the differences in sensitivities of the primers used. The purpose of this study was to compare the sensitivity of 3 sets of PCR primers which have been reported in the endodontic literature.

METHODS

The 3 primers sets used were: group 1) tuf gene-based primers with genus-level specificity; and groups 2 and 3) 16S rDNA-based primers that were E. faecalis specific. Three strains of E. faecalis at concentrations of 10(2)-10(8) cells/mL were included in this study.

RESULTS

The PCR amplification of E. faecalis strains with the 3 primer pairs showed that group 1 primers consistently had the highest sensitivity, followed by group 2 and group 3 (P<.0001).

CONCLUSION

A tuf-based PCR identification assay followed by direct sequencing would yield accurate and consistent prevalence rates of E. faecalis in endodontic infections.

Coaggregation interactions between oral and endodontic Enterococcus faecalis and bacterial species isolated from persistent apical periodontitis

Interactions between Enterococcus faecalis and other species found in root canal infections might be important for the development and persistence of periapical disease. The aim of this study was to investigate the coaggregation interactions between E. faecalis clinical isolates and species previously shown to survive and induce apical periodontitis in monkeys: Peptostreptococcus anaerobius, Prevotella oralis, Fusobacterium nucleatum, and Streptococcus anginosus. Intergeneric coaggregation assays were conducted in duplicate with observations scored immediately at 0 h, 1 h and 24 h after mixing of combinations of strains. All E. faecalis strains (n = 53) coaggregated with F. nucleatum; E. faecalis did not coaggregate with P. anaerobius or S. anginosus. One strain, E. faecalis E1, coaggregated with P. oralis, with aggregates visible at 1 h. Coaggregation interactions between E. faecalis and F. nucleatum observed in this study suggest a potential role for this combination in endodontic infections.

Increased levels of CK19 mRNA in oral squamous cell carcinoma tissue detected by relative quantification with real-time polymerase chain reaction

Oral squamous cell carcinoma (OSCC) is the most common malignant tumour in the oral and maxillofacial region and has a poor prognosis. Cytokeratin 19 (CK19) is a component of cytoskeleton protein. Previous studies have reported abnormal expression of CK19 protein in OSCC tissue. This study is to investigate the quantitative level of CK19 gene transcript in OSCC tissue as well as its clinical significance. Thirty-one OSCC patients (26 males and 5 females) took part in the present study, aged 34-78 years (mean 58.2 years). The level of CK19 mRNA was detected using fluorescent quantitative real-time reverse transcriptase polymerase chain reaction (RT-PCR) in cancerous and paracancerous tissues. The relative quantification in cancerous tissue compared with paracancerous tissue was calculated using the 2(-DeltaDeltaCt) equation. The level of CK19 mRNA in cancerous tissue from OSCC patients was 2.21-fold higher than that in paracancerous tissue (P=0.020), and the amplicon was specific without genomic DNA contamination. The level of CK19 mRNA correlated significantly with the pathological differentiation grade of OSCC tissue (P=0.025), with poorer differentiation indicating a higher level of CK19 mRNA. These results suggest that fluorescent quantitative real-time RT-PCR is accurate and reliable for the detection of CK19 gene transcript levels in OSCC tissue. The level of CK19 mRNA was increased in OSCC tissue, and this was significantly correlated with the pathological differentiation grade.

Detection and quantitation of E. faecalis by real-time PCR (qPCR), reverse transcription-PCR (RT-PCR), and cultivation during endodontic treatment

Enterococcus faecalis is frequently recovered from refractory endodontic infections and has been implicated in endodontic treatment failures. This study compared real-time quantitative PCR (qPCR) assay to cultivation for E. faecalis detection and quantitation during endodontic treatment. A reverse-transcription PCR (RT-PCR) assay was also developed to detect the bacterium clinically in the viable but nonculturable (VBNC) state. Intra-canal samples (n = 87) were collected upon access, post-instrumentation/irrigation and postcalcium hydroxide treatment from 15 primary and 14 refractory infections involving 29 single-rooted teeth, and analyzed by the three methods. The bacterium was up to three times more prevalent in refractory than primary infections at each collection step. Overall, qPCR detected significantly more E. faecalis-positive teeth and samples than cultivation (p < 0.001). VBNC E. faecalis was detected by RT-PCR in four samples that were negative by cultivation. These findings support qPCR and RT-PCR as more sensitive methods than cultivation for detecting E. faecalis in endodontic infections.

Real-time Quantitative Polymerase Chain Reaction and Culture Analyses of Enterococcus faecalis in Root Canals

Reports on the prevalence of Enterococcus faecalis in root canals vary considerably, potentially because of variations in clinical sampling and sample analysis methods. This study compared culture and real-time quantitative polymerase chain reaction (qPCR) to detect and quantify E. faecalis in the same root canal sample. Consecutive root canal samples obtained from primary infection (n = 40) and retreatment (n = 48) cases were divided into two equal aliquots that were independently analyzed using culture and qPCR by investigators blinded to the analysis results of the other sample. E. faecalis was detected in 10.2% and 79.5% of samples by culture and qPCR, respectively (p < 0.0001; McNemar's test). E. faecalis was detected in more retreatment than primary infection samples (89.6% versus 67.5%; p = 0.01, Fisher's exact test). qPCR reported a significantly higher prevalence of E. faecalis in endodontic samples than culture techniques.

Survival of Enterococcus faecalis in root canals ex vivo

AIM

The hypotheses tested in this study were that: (i) Enterococcus faecalis can survive long-term entombment in root filled teeth without additional nutrients, (ii) initial cell density influences the survival of E. faecalis in instrumented root canals and (iii) gelatinase-production capacity influences the survival of E. faecalis in root canals.

METHODOLOGY

The root canals of 150 extracted single canal teeth were instrumented to apical size 60 and divided into six groups of 25. Within each group 10 canals were inoculated with either gelatinase-producing E. faecalis OG1-S and the other 10 with its gelatinase-defective mutant E. faecalis OG1-X. Five canals per group were kept as uninoculated controls. The root canals in groups 1 and 2 were inoculated with 10(6) bacteria, incubated for 48 h at 37 degrees C then filled with gutta-percha and zinc-oxide eugenol sealer. Root canals were inoculated with 10(6), 10(5), 10(4) and 10(3) bacteria in groups 3-6, respectively, and left unfilled. All teeth were sealed coronally with glass-ionomer cement. After 6- (groups 1, 3-6) and 12-month (group 2) incubation at 37 degrees C in 100% humidity, root fragments were analysed for presence of E. faecalis, using culture, polymerase chain reaction and histological methods.

RESULTS

Viable E. faecalis was recovered from all root filled teeth and from 95-100% of unfilled inoculated teeth. Initial cell density and gelatinase production did not influence the recovery of viable E. faecalis (P > 0.05; chi-square test). Enterococcus faecalis 16S rRNA gene products were present in all inoculated teeth and absent in all noninoculated controls. Dentinal tubule infection was evident under light microscopy in sections from inoculated teeth after 48-h, 6- and 12-month incubation.

CONCLUSIONS

Enterococcus faecalis inoculated into root canals maintained viability for 12-months ex vivo. The clinical implications are that viable E. faecalis entombed at the time of root filling could provide a long-term nidus for subsequent infection.