Comparison of sample collection methods for the PCR detection of oral anaerobic pathogens

Effect of nano-crystalline silver membrane on early wound healing after periodontal surgery: A comparative randomized study

Background:

Periodontal dressings are used for wound protection and patient comfort. Nano-silver particles have the ability to promote wound healing through anti-inflammatory properties. Hence, the present study aims to evaluate early wound healing parameters following periodontal surgery using nano-crystalline silver membrane as periodontal dressing.

Materials and Methods:

Forty-two systemically healthy patients diagnosed with chronic periodontitis indicated for periodontal flap surgery were enrolled for the present study. Post surgery, the patients were randomly allocated to either a nano-crystalline silver dressing (Acticoat™) group (test group) or only the noneugenol dressing group (control group). Plaque index (PI) and wound healing index were recorded at the 7^th- and 14^th-day postsurgery. The microbiological analysis and vascular endothelial growth factor (VEGF) levels were evaluated at baseline and 7^th-day postsurgery.

Results:

The healing index was significantly higher in the test group as compared to the control group at days 7 and 14 (P < 0.001; P < 0.001). The colony-forming units/ml count of bacteria were significantly reduced postsurgery in the test group (P = 0.019). VEGF levels increased significantly 7^th-day postsurgery in the test group (P = 0.001). There was no statistically significant difference in the PI on the 7^th-day postsurgery between the two groups (P = 0.173).

Conclusion:

The results of the study revealed that silver can be used as a potent periodontal dressing ingredient that can decrease the microbial colonization beneath the pack and promote faster healing postsurgery due to its antimicrobial activity.

Feasibility of investigating the association between bacterial pathogens and oral leukoplakia in low and middle income countries: A population-based pilot study in India

BACKGROUND

Certain oral bacterial pathogens may play a role in oral carcinogenesis. We assessed the feasibility of conducting a population-based study in India to examine the distributions and levels of Porphyromonas gingivalis, Fusobacterium nucleatum and Prevotella intermedia in relation to oral leukoplakia (a potentially malignant disorder) and other participant characteristics.

METHODS

This exploratory case-control study was nested within a large urban Indian cohort and the data included 22 men and women with oral leukoplakia (cases) and 69 leukoplakia-free controls. Each participant provided a salivary rinse sample, and a subset of 34 participants (9 cases; 25 controls) also provided a gingival swab sample from keratinized gingival surface for quantitative polymerase chain reaction (qPCR).

RESULTS

Neither the distribution nor the levels of pathogens were associated with oral leukoplakia; however, individual pathogen levels were more strongly correlated with each other in cases compared to controls. Among controls, the median level of total pathogens was the highest (7.55×104 copies/ng DNA) among persons of low socioeconomic status. Salivary rinse provided better DNA concentration than gingival swab for qPCR analysis (mean concentration: 1.8 ng/μl vs. 0.2 ng/μl).

CONCLUSIONS

This study confirms the feasibility of population studies evaluating oral microbiome in low-resource settings and identifies promising leads for future research.

Comparison between polymerase chain reaction-based and checkerboard DNA hybridization techniques for microbial assessment of subgingival plaque samples

AIM

To compare polymerase chain reaction (PCR) with subsequent reverse hybridization (micro-IDent test) and checkerboard DNA-DNA hybridization for the identification of 13 bacterial species in subgingival plaque samples.

MATERIAL AND METHODS

Subgingival plaque samples were taken using paper points and curettes from two sites each with pocket depth <4, 4-6 and >6 mm at baseline and 3 months in 25 periodontitis subjects and two sites in 25 periodontally healthy subjects. Samples were analysed for their content of 13 bacterial species using both assays. Similarities for each species between techniques were determined using regression analysis. Differences between health and periodontitis were determined using the Mann-Whitney test.

RESULTS

Three hundred and fifty samples were evaluated using both techniques. Regression analysis indicated that 10/13 test species showed significant positive correlations between the counts determined by checkerboard analysis and levels determined by the PCR-based test after adjusting for 13 comparisons. The highest rank correlations of 0.58, 0.49 and 0.46 were seen for Treponema denticola, Fusobacterium nucleatum and Eubacterium nodatum, respectively (p<0.0001). Both tests could distinguish samples from healthy and periodontitis subjects.

CONCLUSION

Detection patterns of 10/13 test species in subgingival plaque samples from periodontitis and healthy subjects were similar using the two molecular techniques.

Recovery of putative pathogens from paper point sampling at different depths of periodontal lesions

Background

The aim of this study was to compare the recovery of three putative periodontal pathogens from periodontal lesions in samples using paper points inserted to different depths of the lesions.

Methods

Twenty 6–8 mm deep periodontal lesions with bleeding on probing were studied. Microbial samples were obtained using paper points inserted to three different depths of the lesions: orifice of lesion; 2 mm into the lesion; and to the base of lesion. Culturing was used for recovery and identification of Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, and Prevotella intermedia.

Results

The recovery of each of the three putative periodontal pathogens was similar following sampling at the various depths of the lesions.

Conclusions

The findings may be explained by the fact that the paper points become saturated as they pass through the orifice of the lesion. Absorption of microorganisms will therefore primarily occur at the orifice. It is also conceivable that the pathogens may be present in similar proportions throughout the various depths of the periodontal lesions.

The reproducibility of curet sampling of subgingival biofilms

BACKGROUND

Because few studies have examined the critical issue of sampling reproducibility, the purpose of the present study was to examine the reproducibility of curet sampling of subgingival biofilms.

METHODS

Seven subgingival biofilm samples were taken successively, using a curet, from each of 80 sites and individually analyzed for their content of 40 bacterial species using checkerboard DNA-DNA hybridization. One healthy site was sampled in each of 20 periodontally healthy subjects, and one sulcus/pocket of < or =3, 4 to 5, and > or =6 mm was sampled in each of 20 subjects with chronic periodontitis. The significance of differences in counts and proportions of individual species at the seven successive samplings for each probing depth (PD) category was determined using the Kruskal-Wallis test. The reproducibility of species proportions at each PD category was measured using the coefficient of variation (CV), and the consistency of microbial profiles across samples was examined using the minimum similarity coefficient.

RESULTS

There was no significant difference in the mean proportions of the 40 test species in the seven successive samples in each of the four PD categories. The median CV for individual species in the same site was 0.79 (95% confidence interval [CI]: 0.76 to 0.82) compared to 1.76 (95% CI: 1.69 to 1.82) in samples from different sites. The within-site mean minimum similarity coefficient (+/- SEM) was 51.2% +/- 2.2%, and it was 27.9% +/- 0.3% between sites.

CONCLUSION

The proportions of species remained consistent in successive curet samples, indicating that the use of curets provided a reliable and reproducible method to obtain subgingival samples.

Comparison of Curet and Paper Point Sampling of Subgingival Bacteria as Analyzed by Real-Time Polymerase Chain Reaction

BACKGROUND

The outcome of microbiological diagnostics may depend on the sampling technique. It was the aim of the present study to compare two widely used sampling techniques for subgingival bacteria using quantitative real-time polymerase chain reaction.

METHODS

Twenty patients with chronic periodontitis were randomized into two groups. In group A, samples were taken first with a paper point and then with a curet at the same site (single-rooted teeth with probing depth >5 mm) before scaling and root planing and after 10 weeks. The sampling sequence was reversed in group B. The analysis enabled the quantification of Actinobacillus actinomycetemcomitans, Fusobacterium nucleatum, Porphyromonas gingivalis, Prevotella intermedia, Treponema denticola, and Tannerella forsythensis and total bacterial counts (TBCs). Statistical analysis included t test, kappa, and Spearman correlation.

RESULTS

Higher TBC was harvested with curets than by paper points (P = 0.008). The plaque composition with regard to total target pathogens was similar for both sampling techniques. A strong positive correlation was found between curet and paper point samples for TBC and single target bacteria.

CONCLUSIONS

Overall, there was a relatively good agreement for the results of paper point and curet sampling. Thus, both techniques seem to be suitable for microbiological diagnostics.

Quantitative real-time PCR using TaqMan and SYBR Green for Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia, tetQ gene and total bacteria

Accurate quantification of bacterial species in dental plaque is needed for microbiological diagnosis of periodontal diseases. The present study was designed to assess the sensitivity, specificity and quantitativity of the real-time PCR using the GeneAmp Sequence Detection System with two fluorescence chemistries. TaqMan probe with reporter and quencher dye, and SYBR Green dye were used for sources of the fluorescence. Primers and probes were designed for Actinobacillus actinomycetemcomitans, Porphyromonas gingivalis, Prevotella intermedia and total bacteria based on the nucleotide sequences of the respective 16S ribosomal RNA genes. Since spread of antibiotic resistance genes is one of the crucial problems in periodontal therapy, quantitative detection of tetQ gene, which confers resistance to tetracycline, was included in the examination. The detection of P. gingivalis, P. intermedia and A. actinomycetemcomitans was linear over a range of 10-10(7) cells (10-10(7) copies for tetQ gene), while the quantitative range for total bacteria was 10(2)-10(7) cells. Species-specific amplifications were observed for the three periodontal bacteria, and there was no significant difference between the TaqMan and SYBR Green chemistry in their specificity, quantitativity and sensitivity. The SYBR Green assay, which was simpler than TaqMan assay in its manipulations, was applied to the clinical plaque samples. The plaque samples were obtained from eight patients (eight periodontal pockets) before and 1 week after the local drug delivery of minocycline. Although the number of P. gingivalis, P. intermedia and A. actinomycetemcomitans markedly decreased after the antibiotic therapy in most cases, higher copy numbers of the tetQ gene were detectable. The real-time PCR demonstrated sufficient sensitivity, specificity and quantitativity to be a powerful tool for microbiological examination in periodontal disease, and the quantitative monitoring of antibiotic resistance gene accompanied with the antibiotic therapy should be included in the examination.