Checkerboard DNA-DNA hybridization analysis of endodontic infections

Actinomyces species, streptococci, and Enterococcus faecalis in primary root canal infections

The purpose of this study was to evaluate the prevalence of Actinomyces species, streptococci, and Enterococcus faecalis in primary root canal infections by using a molecular genetic method. Samples were obtained from 53 infected teeth, of which 27 cases were diagnosed as acute periradicular abscesses. DNA was extracted to evaluate the occurrence of 13 bacterial species by using whole genomic DNA probes and checkerboard DNA-DNA hybridization. Polymerase chain reaction using an ubiquitous bacterial primer was undertaken to check the presence of bacterial DNA in clinical samples. All root canal samples contained bacteria as demonstrated by polymerase chain reaction. The checkerboard DNA-DNA hybridization assay allowed the detection of streptococci in 22.6% of the samples, Actinomyces species in 9.4%, and E. faecalis in 7.5%. The most prevalent species were members of the Streptococcus anginosus group. With regard to the asymptomatic lesions, the most prevalent species were S. intermedius (11.5% of the cases), E. faecalis (11.5%), and S. anginosus (7.7%). S. constellatus was the most prevalent species in pus samples (25.9% of the cases). The other most prevalent species in abscessed teeth were A. gerencseriae (14.8%), S. gordonii (11.1%), S. intermedius (11.1%), A. israelii (7.4%), S. anginosus (7.4%), and S. sanguis (7.4%). S. constellatus was the only species positively associated with acute periradicular abscess (p < 0.01).

Patterns of microbial colonization in primary root canal infections

OBJECTIVE

The purpose of this study was to investigate the patterns of microbial infection of root canals in untreated teeth associated with chronic periradicular lesions by use of scanning electron microscopy.

STUDY DESIGN

Fifteen extracted teeth with extensive carious lesions, radiolucent lesions of varying sizes, and attached periradicular lesions after extraction were selected for study. After fixation, lesions were removed and the teeth were split into 2 halves. The teeth were then dehydrated, sputter-coated with gold, and then examined for the patterns of microbial colonization of the root canal system by using a scanning electron microscope.

RESULTS

All examined root canals were infected, and bacterial cells were seen in practically all areas of the root canal system. The pattern of colonization was not uniform between specimens and even within the same specimen. Most of the root canal walls of all specimens were heavily colonized by a root canal microbiota consisting of cocci and/or rods, often forming mixed communities. Spirilla were occasionally observed as single cells or as small clusters between other bacterial forms. Bacteria were often observed penetrating the dentinal tubules. Although a shallow penetration was the most common finding, bacterial cells could be observed reaching approximately 300 microm in some specimens. Yeastlike cells were observed in 1 specimen together with bacteria.

CONCLUSIONS

The root canals of teeth associated with periradicular lesions were heavily infected by bacteria and occasionally by fungi. The pattern of colonization of the root canal microbiota often showed the characteristic of a climax community, which may require special considerations regarding its elimination and prevention of clinical problems. In addition, the observed propagation of the infection to the entire root canal system in teeth associated with periradicular lesions suggests that proper therapeutic measures may be necessary to eliminate the root canal infection completely.

Microbiological evaluation of acute periradicular abscesses by DNA-DNA hybridization

OBJECTIVE

The purpose of the present investigation was to examine the microbiota of acute periradicular abscesses of endodontic origin by using a molecular genetic method.

STUDY DESIGN

Pus was collected by aspiration from 27 cases diagnosed as acute abscesses of endodontic origin, and DNA was extracted to evaluate the occurrence of 49 bacterial species by using whole genomic DNA probes and checkerboard DNA-DNA hybridization. The presence of bacterial DNA in clinical samples was confirmed by polymerase chain reaction with ubiquitous bacterial 16S rRNA gene primers.

RESULTS

The results of the checkerboard DNA-DNA hybridization analysis revealed that 37 of the 49 DNA probes tested were reactive with one or more samples. The number of bacterial species in the pus samples ranged from 1 to 33 (mean, 5.9). Eighteen of the 27 pus samples were positive for at least one DNA probe. The most prevalent species found were: Bacteroides forsythus (29.6% of the cases); Porphyromonas gingivalis (29.6%); Streptococcus constellatus (25.9%), Prevotella intermedia (22.2%), Prevotella nigrescens (22.2%), Fusobacterium periodonticum (18.5%), Fusobacterium nucleatum subspecies nucleatum (18.5%), and Eikenella corrodens (18.5%).

CONCLUSIONS

The microbiologic data of the present investigation indicated that molecular genetic methods could provide additional knowledge regarding the microbiota of acute periradicular abscesses by detecting bacterial species that are difficult--or even impossible--to grow.

Endodontic infection caused by localized aggressive periodontitis: a case report and bacteriologic evaluation

A rare case of a periodontally induced endodontic lesion in a systemically healthy subject of 28 years is described. The patient, having presented with severe attachment loss on the palatal and distal aspects of his maxillary right second premolar, was diagnosed with localized aggressive periodontitis. He had never received periodontal treatment. The tooth was nonvital and showed all signs of symptomatic apical periodontitis. It was also free of any restoration. All clinical findings clearly suggested that the endodontic problem was caused by the aggressive periodontal disease. Bacteriologic screening of the pocket and the root canal, by using "checkerboard" DNA-DNA hybridization analysis, revealed diverse flora in the periodontal lesion. The sample obtained from the root canal exhibited DNA from a limited number of species, including black-pigmented anaerobic rods. No bacterial DNA was found in the root canal that was not also recovered from the periodontal pocket.

Molecular identification of microorganisms from endodontic infections

A relatively wide range of bacteria have been isolated from root canals using standard culture techniques. However, only 50% of the bacteria in the oral cavity are cultivable (S. S. Socransky et al., Arch. Oral Biol. 8:278-280, 1963); hence, bacterial diversity in endodontic infections is underestimated. This study used a PCR-based 16S rRNA gene assay, followed by cloning and sequencing of 16S rRNA amplicons from a small subset of samples to assess the diversity of bacteria present in infected root canals. A total of 41 clinical samples from 15 de novo and 26 refractory cases of endodontic infections were assessed. Of these samples, 44% were positive by culture and 68% were positive by PCR. Eight samples were selected for further analysis. Of these, the two de novo cases yielded sequences related to those of the genera Enterococcus, Lactobacillus, Propionibacterium, and Streptococcus and two clones were related to previously uncultivated bacteria, while the sinus-associated, de novo case yielded sequences related to those of the genera Lactobacillus, Pantoea, Prevotella, and Selenomonas. The five refractory cases produced clones which were related to the genera Capnocytophaga, Cytophaga, Dialister, Eubacterium, Fusobacterium, Gemella, Mogibacterium, Peptostreptococcus, Prevotella, Propionibacterium, Selenomonas, Solobacterium, Streptococcus, and Veillonella and two clones representing previously uncultivated bacteria. The phylogenetic positions of several clones associated with the Clostridiaceae and Sporomusa subgroups of the Firmicutes grouping are also shown. This study demonstrates that molecular techniques can detect the presence of bacteria in endodontic infections when culture techniques yield a negative result and can be used to identify a wider range of endodontic-infection-related bacteria including the presence of previously unidentified or unculturable bacteria.

Identification of oral spirochetes at the species level and their association with other bacteria in endodontic infections

OBJECTIVES

Recent molecular approaches have revealed that fastidious organisms such as Bacteroides forsythus and oral treponemes were frequently found in root canals with apical periodontitis. The purpose of this study was to identify the isolates of oral spirochetes at the species level in endodontic infections and to determine their association with B forsythus and Porphyromonas gingivalis.

STUDY DESIGN

Seventy-nine teeth with apical periodontitis were selected for this study. After sampling from the root canals aseptically, polymerase chain reaction amplification for the 16S rRNA gene was performed with eubacterial universal primers. Subsequently, dot-blot hybridization was performed with 8 species-specific oligonucleotide probes. The microbial associations were analyzed by using the odds ratio.

RESULTS

The most frequently found species was P gingivalis (27.4%), followed by Treponema maltophilum (26%), B forsythus (16.4%), and Treponema socranskii (2.7%). Other treponemes, including Treponema denticola, were not detected in our samples. Significant microbial associations were identified between T maltophilum, B forsythus, and P gingivalis by performing analysis with the odds ratio.

CONCLUSION

Our results indicate that T maltophilum should be included in etiologic studies of endodontic diseases.

"Red complex" (Bacteroides forsythus, Porphyromonas gingivalis, and Treponema denticola) in endodontic infections: a molecular approach

OBJECTIVE

The "red complex," composed of Bacteroides forsythus, Porphyromonas gingivalis, and Treponema denticola, is implicated in severe forms of periodontal diseases. The purpose of this study was to assess the occurrence of the red complex in root canal infections through the use of a sensitive technique-the 16S rDNA-directed polymerase chain reaction (PCR).

STUDY DESIGN

Samples were obtained from 50 necrotic pulps with periradicular pathosis. Ten cases were diagnosed as acute periradicular abscesses. DNA was extracted from the samples and analyzed with a PCR-based identification assay.

RESULTS

At least 1 member of the red complex was found in 33 of 50 cases. T denticola, P gingivalis, and B forsythus were detected in 44%, 30%, and 26% of the cases, respectively. The red complex was found in 4 of 50 cases. No particular signs or symptoms were associated with the presence of these bacterial species.

CONCLUSIONS

Despite what is indicated in reports with respect to marginal periodontitis, red complex bacteria-either singularly or collectively-was not associated with any particular pattern of clinical symptoms. However, because the bacterial species from the red complex are recognized oral pathogens, their occurrence in root canal infections suggests that they may play a role in the pathogenesis of periradicular diseases.

Prevalence OfPrevotella IntermediaAndPrevotella NigrescensIn Infected Root Canals From A Brazilian Population

The purpose of the present study was to evaluate the prevalence of Prevotella intermedia and Prevotella nigrescens in symptomatic and asymptomatic endodontic infections from a Brazilian population. DNA extracted from samples obtained from 28 cases of endodontic infection were examined by the 16S rDNA-directed Polymerase Chain Reaction (PCR) method. PCR detected P. intermedia in 7.1% of the cases (2 out of 28 teeth) and P. nigrescens in only one sample (3.6%). The low prevalence of P. intermedia and P. nigrescens as reported in the present study is probably justified for geographical reasons.