Development of species-specific primers for detection of Streptococcus mutans in mixed bacterial samples

Antineoplastic therapy is an independent risk factor for dental caries in childhood cancer patients: a retrospective cohort study

PURPOSE

To evaluate the antineoplastic therapy (AT) as a risk factor for dental caries lesions independent of other risk factors such as income, family education, stimulated salivary flow rate, hygiene habits, frequency of sugar intake, and microbiota in childhood cancer (CC) patients.

METHODS

72 individuals were divided into CC patients (n=36) and healthy individuals (control group - CT n=36). Demographic data, hygiene habits, frequency of sugar intake, CC type, and AT were collected. Stimulated salivary flow rate was measured and the presence and concentration of Streptococcus mutans were assessed using a real-time polymerase chain reaction (qPCR) technique. Clinical evaluations included plaque index (PI) and decayed-missing-filled-teeth index (dmft/DMFT). Descriptive statistics, T-test, Mann-Whitney test, chi-square test, Fisher's exact test, and two-way analysis of variance were used for data analysis (p<0.05).

RESULTS

At the time of oral evaluation, both groups exhibited similar ages with means of 12.0±3.9 years old for CC and 12.0±4.0 years old for CT patients. All CC patients underwent chemotherapy with nine also undergoing radiotherapy. Significant differences were observed between the groups in terms of color/race, income, family education, and hygiene habits. However, no statistically significant differences were found between groups regarding the frequency of sugar intake, stimulated salivary flow rate, or the concentration of Streptococcus mutans (qPCR technique). For clinical parameters, the DMF (CC:1.80, CT: 0.75), decayed (CC: 0.88, CT: 0.19), missing (CC: 0.25, CT:0), and PI (CC: 30.5%, CT: 22.6%) were higher in the CC group (p<0.05).

CONCLUSION

Childhood cancer (CC) patients undergoing antineoplastic therapy (AT) exhibit a higher prevalence of dental caries, regardless of income/education, frequency of sugar intake, stimulated salivary flow rate, and microbiota.

Nattokinase, a Subtilisin-like Alkaline-Serine Protease, Reduces Mutacin Activity by Inactivating the Competence-Stimulating Peptide in Streptococcus mutans

Streptococcus mutans is a major cariogenic organism because of its ability to form biofilms on tooth surfaces. Bacteriocins produced by S. mutans (known as mutacins) are indirect pathogenic factors that play a role in the persistence of this microbe in the oral environment. Nattokinase, a subtilisin-like alkaline serine protease, potently inhibits biofilm formation without affecting S. mutans growth. However, effective strategies utilizing nattokinase to control mutacin production by S. mutans are lacking. In this study, we evaluated the effect of nattokinase on mutacin activity in 46 strains of S. mutans with different mutacin genotypes isolated from the dental plaques of pediatric patients with caries. Nattokinase reduced the activity of mutacin against oral streptococci at a concentration of 1 mg/mL in all clinical isolates. Furthermore, nattokinase reduced the expression of non-lantibiotic mutacin structural genes (nlmABCD) and inactivated the extracellular competence-stimulating peptide involved in comDE activation, which regulates non-lantibiotic mutacin gene expression. These results suggest that nattokinase may reduce the virulence of S. mutans and could potentially be used as a new caries-preventive agent as an alternative to conventional drug treatments.

Evaluation of Changes in Oral Microflora in Children with Early Childhood Caries after Full Mouth Rehabilitation

Aim

To evaluate the change in microflora in children suffering from severe early childhood caries (ECC) after full mouth rehabilitation.

Materials and methods

A total of 60 children, aged 3-5 years suffering from severe ECC who fulfilled the inclusion and exclusion criteria were included in the study. Pooled plaque samples were taken and subjected to quantitative reverse transcriptase polymerase chain reaction (PCR) to obtain baseline mean values of Streptococcus mutans (S. mutans), Streptococcus sobrinus (S. sobrinus), Candida albicans (C. albicans), and Candida dubliniensis (C. dubliniensis) before full mouth rehabilitation was done under general anesthesia. Posttreatment samples were collected at 6, 12, and 18 months. Wilcoxon signed-rank test was used to compare the mean values of S. mutans, S. sobrinus, C. albicans, and C. dubliniensis before and after full mouth rehabilitation.

Results

A total of 60 patients recruited for the study were present at the follow-up at 6 and 12 months. At 18 months, 55 patients returned, and five were lost due to follow-up. A statistically significant reduction was seen in all microorganisms at 6, 12, and 18 months compared to baseline values. At 18 months a slight increase in S. mutans, S. sobrinus, and C. albicans was seen. C. dubliniensis was not detected in any cases after full mouth rehabilitation. Caries recurrence was seen in four patients at 18 months.

Conclusion

Significant reduction of S. mutans, S. sobrinus, C. albicans, and C. dubliniensis was seen at 6, 12, and 18 months. A complete reduction of only C. dubliniensis was seen. A significant but not permanent reduction of S. mutans, S. sobrinus, and C. albicans. Caries recurrence was seen in 7.27% of patients at 18 months.

How to cite this article

Mathew MG, Jeevanandan G, Rathod NN. Evaluation of Changes in Oral Microflora in Children with Early Childhood Caries after Full Mouth Rehabilitation. Int J Clin Pediatr Dent 2024;17(1):21-25.

The potential of nano graphene oxide and chlorhexidine composite membranes for use as a surface layer in functionally graded membranes for periodontal lesions

Membranes have been used for treating periodontal defects and play a crucial role in guided bone regeneration applications. Nano graphene oxide have been exploited in tissue engineering due to its biomechanical properties. Its composite formulations with hydroxyapatite and chitosan with controlled degradation could aid in becoming part of a surface layer in a functionally graded membrane. The aim of the study was to synthesize chitosan and composite formulations of nano graphene oxide, hydroxyapatite and chlorhexidine digluconate using solvent casting technique and to characterize the physiochemical, mechanical, water vapor transmission rate (barrier), degradation and antimicrobial potential of the membranes. Altogether four different membranes were prepared (CH, CCG, 3511 and 3322). Results revealed the chemical interactions of hydroxyapatite, chitosan and nanographene oxide due to inter and intra molecular hydrogen bonding. The tensile strength of 3322 (33.72 ± 6.3 MPa) and 3511 (32.06 ± 5.4 MPa) was higher than CH (27.46 ± 9.6 MPa). CCG showed the lowest water vapor transmission rate (0.23 ± 0.01 g/h.m2) but the highest weight loss at day 14 (76.6 %). 3511 showed a higher drug release after 72 h (55.6 %) Significant biofilm growth inhibition was observed for all membranes. 3511 showed complete inhibition against A. actinomycetemcomitans. Detailed characterization of the synthesized membranes revealed that 3511 composite membrane proved to be a promising candidate for use as a surface layer of membranes for guided bone regeneration of periodontal lesions.

Lactobacillus acidophilus novel strain, MJCD175, as a potential probiotic for oral health in dogs

The oral cavity is the second-largest habitat for microorganisms, and a well-balanced oral microbiome contributes to preventing dental disorders caused by pathogenic bacteria. Since humans and dogs have different lifestyles and oral microbiome structures, the present study aimed to develop novel probiotics for dogs. A total 53 Lactobacillus spp. were isolated from healthy dogs, and nine isolates were identified as Lactobacillus acidophilus according to 16S rRNA gene sequencing. According to the high antimicrobial activity against the dental caries-causing bacterium Streptococcus mutans, single or three mixed strains were orally administered to dogs for 4 weeks with concentration of 10⁸-10⁹ CFU/day. Intraoral swab samples were collected before and after the administration, and changes of oral pathogen were analyzed using quantitative PCR. Among them, Porphyromonas gingivalis, a critical factor of periodontitis, was significantly reduced in the single-strain administered group. Based on the acid and bile salts tolerance characteristics of isolates, systemic effects were also analyzed by comparing serum immunoglobulin and reproductive ability before and after the administration. However, no significant changes were observed in the serum IgG level and sperm quality. Overall, these in vitro and in vivo results suggest that L. acidophilus isolates from dogs, especially L. acidophilus MJCD175, could be promising probiotic candidates to support oral health without systemic adverse effects in dogs.

Genotypic and phenotypic characterization of Streptococcus mutans strains isolated from patients with dental caries

Background and Objectives

The oral cavity harbors numerous Streptococcus mutans strains which display remarkable genotypic and phenotypic diversity. This study evaluated the genotypic and phenotypic diversity of 209 S. mutans strains isolated from 336 patients with dental caries and compared with the universal reference strain, UA159.

Materials and Methods

Selective cultivation on mitis-salivaries-bacitracin agar and species-specific polymerase chain reaction (PCR) was carried out to isolate and identify the 209 S. mutans isolates from 336 patients with dental caries. Arbitrarily primed polymerase chain reaction (AP-PCR), PCR amplification of specific gene, acid production and biofilm formation capacity were performed to evaluate the genotypic and phenotypic variation. Student's t-test and Chi-square test were used for analysis of variables and a probability (P) of <0.05 was considered as significant.

Results

Our study revealed a high degree of genotypic and phenotypic variability among the clinical strains. We observed significant differences in colony morphology, generation time, biofilm formation, and acid production while growing in culture medium. All the clinical isolates were able to lower pH while growing in Todd-Hewitt broth. Consistent with phenotypic variations, we also observed genotypic variation by AP-PCR and gene specific PCR. AP-PCR analysis suggested that most of the patients with dental caries have distinct type of S. mutans strains. Genes related to various two component systems were highly conserved among the isolated strains, however, bacteriocin encoding genes such as nlmAB, nlmC were absent in nearly half of the clinical isolates.

Conclusion

Our results support that S. mutans clinical isolates have wide genotypic diversity and show variation in growth kinetics, acid production, acid tolerance and biofilm formation capacity and indicates the presence of diverse mechanism to initiate and establish the biofilm lifestyle which leads to tooth decay.

Quantitative difference of oral pathogen between individuals with gastric cancer and individuals without cancer

The loss of teeth and lack of oral hygiene have been associated with the risk of developing gastric cancer (GC) in several populations evidenced in epidemiological studies. In this study, we quantitatively compared the proportion of oral pathogens in individuals with gastric cancer and individuals without cancer in a referral hospital in the city of Belém, Brazil. This study evaluated 192 patients with GC and 192 patients without cancer. Periodontal clinical examination was performed, and all individuals were submitted to the collection of salivary and dental biofilms. When comparing the median periodontal indexes in the gastric and cancer-free groups, it was statistically significant (p < 0.001) in the gastric cancer group compared to the probing depth of the periodontal pocket. Levels of bacterial DNA were observed in saliva and dental plaque, with a statistically significant difference (p < 0.001) between individuals with cancer and without neoplasia in all the bacteria surveyed. Significant relationships (p < 0.001) between biological agents and GC have been found in bacterial species that cause high rates of periodontal pathology and caries. The results suggest a different quantitative association in the presence of oral pathogens between individuals without cancer and patients with GC. As noted, it cannot be said that the bacteria present in the oral cavity increase the risk of gastric cancer or are aggravating factors of the disease. However, it is worth mentioning that, as it is part of the digestive system, the lack of care for the oral cavity can negatively affect the treatment of patients with gastric cancer.

Association of Candida albicans and Cbp+ Streptococcus mutans with early childhood caries recurrence

Early childhood caries (ECC) recurrence occurs in approximately 40% of treated cases within one year. The association of Streptococcus mutans and Candida albicans with the onset of ECC is well known. Also, S. mutans strains harboring collagen-binding proteins (Cbps) avidly bind to collagen-rich dentin and are linked to increased caries risk. Here, we investigated the presence of Cbp⁺ S. mutans and C. albicans in saliva and dental plaque of children with varying caries statuses, and their salivary microbiome. In this cross-sectional study, 143 children who were caries-free (n = 73), treated for ECC with no signs of recurrence after 6 months (n = 45), or treated for ECC and experiencing recurrence within 6 months following treatment (n = 25) were enrolled. Co-infection with C. albicans and S. mutans, especially Cbp⁺ S. mutans, was strongly associated with caries recurrence. Subjects of the recurrence group infected with Cbp⁺ S. mutans showed a greater burden of Candida spp. and of Mutans streptococci in dentin than those infected with Cbp^- strains. Salivary microbiome analysis revealed that Streptococcus parasanguinis was overrepresented in the caries recurrence group. Our findings indicate that Cbp⁺ S. mutans and C. albicans are intimately associated with caries recurrence, contributing to the establishment of recalcitrant biofilms.

A clinical investigation into the efficacy of miswak chewing sticks as an oral hygiene aid: A crossover randomized trial

OBJECTIVES

This study evaluates the effect of using miswak chewing sticks on dental plaque, selected oral microbiota and gingival inflammation among patients with gingivitis.

METHODS

The study was a single-centre, single-examiner blind, randomized, crossover study. Twenty healthy participants were randomly assigned into two equal groups (n = 10). Group 1 were instructed to use both toothbrush and miswak (TB+M) for the first 2 weeks from baseline (T1) and only toothbrush for the next 2 weeks (T2); and Group 2, only TB during T1 and TB+M during T2. Gingival index (GI), plaque index (PI) and bleeding on probing (BOP) were evaluated at baseline (T0), T1 and T2 visits. Supra-gingival plaque samples were taken at T0, T1 and T2. Quantification of Streptococcus mutans and Aggregatibacter actinomycetemcomitans from the supra-gingival plaque samples were performed by real-time polymerase chain reaction (qPCR).

RESULTS

The scores of GI, PI and BOP had significantly improved for both groups between T0 and T1. A significantly greater reduction in the percentage of sites with BOP was observed for TB+M group compared with TB group (TB+M group: from 32.2 to 14.93; TB group: from 34.00 to 26.0; p = .014). At T2, TB+M group had significant improvements (p < .05) in the PI, GI and BOP scores compared with TB group. There was no significant difference in the microbial counts of S. mutans and A. actinomycetemcomitans between the two groups at the end of the study period.

CONCLUSIONS

Oral hygiene and gingival health may be improved by complementing miswak chewing sticks with toothbrushing.

Phenotypic and Genotypic Characterization of Streptococcus mutans Strains Isolated from Endodontic Infections

Streptococcus mutans plays an important role in caries etiology and eventually in systemic infections. However, it is often found in infected root canals, but the pathophysiological characteristics of strains residing in this site are largely unknown. Here, we characterized strains of S. mutans isolated from root canals of primary (PI) and secondary/persistent (SI) endodontic infections in relation to serotype and genotype; presence of genes coding for collagen binding proteins (CBPs); collagen binding activity and biofilm formation capacity; ability to withstand environmental stresses; systemic virulence in Galleria mellonella; and invasion of human coronary artery endothelial cells and human dental pupal fibroblasts. Samples from 10 patients with PI and 10 patients with SI were collected, and a total of 14 S. mutans isolates, belonging to 3 genotypes, were obtained. Of these, 13 were serotype c, and 1 was serotype k. When compared with the reference strains, the clinical isolates were hypersensitive to hydrogen peroxide. Remarkably, all 14 strains harbored and expressed the CBP-encoding gene cbm, showing increased binding to collagen, enhanced systemic virulence in G. mellonella, and ability to invade human coronary artery endothelial cells and human dental pupal fibroblasts when compared with CBP-negative strains. Whole genome sequence analysis of PI and SI isolates revealed that these strains are phylogenetically related but genetically distinct from each other. Our findings highlight the importance of CBPs in facilitating colonization and persistence of S. mutans in collagenous substrates such as root canals and their potential role in the pathogenesis of endodontic infections.

Species-specific genomic sequences for classification of bacteria

Modern bacterial classification relies on genomic relatedness. Genetic variation in bacterial populations present a big challenge for taxonomic classification and recently several bacterial species have been reclassified based on the intra-species genome comparison. These were facilitated by next generation sequencing technologies and advances in genome comparison approaches which led to the rearrangement of diverse bacterial species and revolution in the microbial classification system. One of the outcome of these studies is the development of suitable DNA barcodes as reliable and cost-effective method for identifying various bacterial genera. Towards refining this further, we have applied a genome comparison approach in 1104 bacterial genome assemblies (excluding plasmids) to identify unique genomic segments among intra-species genome assemblies. Using extensive bioinformatics analysis, we have identified species-specific genomic regions and designed unique primers for 100 different species (belonging to 62 genera) which includes 62 pathogenic and 13 opportunistic pathogenic bacterial species and built a database (http://slsdb.manipal.edu/bact/). These species-specific genomic regions will have a major impact on in silico and molecular methods aimed at bacterial classification and identification. These may also serve as better DNA barcodes than the markers currently used for delineation of bacteria and may also find application in various translational research programs.

Biofilm growth and IL-8 & TNF-α-inducing properties of Candida albicans in the presence of oral gram-positive and gram-negative bacteria

Background

Interaction of C. albicans with oral bacteria is crucial for its persistence, but also plays a potential role in the infection process. In the oral cavity, it grows as part of dental plaque biofilms. Even though growth and interaction of C. albicans with certain bacterial species has been studied, little is known about its biofilm growth in vitro in the simultaneous presence of Gram-negative and Gram-positive bacteria. The aim was to evaluate the growth of C. albicans in polymicrobial biofilms comprising oral Gram-negative and Gram-positive bacteria. Further, we also aimed to assess the potential of C. albicans in the Candida-bacteria polymicrobial biofilm to elicit cytokine gene expression and cytokine production from human blood cells.

Results

C. albicans cell counts increased significantly up to 48 h in polymicrobial biofilms (p < 0.05), while the bacterial counts in the same biofilms increased only marginally as revealed by qPCR absolute quantification. However, the presence of bacteria in the biofilm did not seem to affect the growth of C. albicans. Expression of IL-8 gene was significantly (p < 0.05) higher upon stimulation from biofilm-supernatants than from biofilms in polymicrobial setting. On the contrary, TNF-α expression was significantly higher in biofilms than in supernatants but was very low (1–4 folds) in the monospecies biofilm of C. albicans. ELISA cytokine quantification data was in agreement with mRNA expression results.

Conclusion

Persistence and enhanced growth of C. albicans in polymicrobial biofilms may imply that previously reported antagonistic effect of A. actinomycetemcomitans was negated. Increased cytokine gene expression and cytokine production induced by Candida-bacteria polymicrobial biofilms and biofilm supernatants suggest that together they possibly exert an enhanced stimulatory effect on IL-8 and TNF-α production from the host.

Solidago virgaurea L. Plant Extract Targeted Against Candida albicans to Reduce Oral Microbial Biomass: a Double Blind Randomized Trial on Healthy Adults

Oral microbiome plays an important part on oral health and endogenous bacteria and fungi should not be eradicated. However, their proliferation must be controlled by oral hygiene care. In vitro, Solidago virgaurea ssp. virgaurea L. (SV) plant extract inhibits the adherence and hyphal formation of a fungus, Candida albicans. It reduces the biomass of Candida-bacterial biofilms but not fungal or bacterial growth. Unlike chemical antiseptics, like triclosan and chlorhexidine for instance, SV is a plant extract easily biodegradable. The purpose of this study was to assess the in vivo effectiveness of SV extract in reducing oral biomass. A randomized, double-blind clinical study, with dental plaque evaluation designed to assess the effectiveness of a fluorinated toothpaste containing SV (Bucovia™, Givaudan, Vernier, Switzerland) was conducted. Sixty-six subjects (SV group n = 33 vs. control n = 33) brushed their teeth twice a day for a 4-week period. Supragingival dental plaque was sampled. Total bacterial load (broad spectral bacterial quantitative Polymerase Chain Reaction (qPCR)), C. albicans and seven bacterial species were quantified by qPCR. In the Intervention group, there was a decrease of Total bacterial load (ΔD0D28 p = 0.005 and ΔD14D28 p = 0.026), Streptococcus mutans (ΔD0D14 p = 0.024) and C. albicans (ΔD0D28 p = 0.022). In the Control group Total bacterial load tended to decrease from baseline to day 28 (ΔD0D28 p = 0.062 and ΔD14D28 p = 0.009). Plaque Index and Gingival Index improved in both groups.

Real-time polymerase chain reaction quantification of the salivary levels of cariogenic bacteria in patients with orthodontic fixed appliances

Aim

The aim was to investigate the salivary detection frequencies and quantities of caries‐associated bacteria from patients with orthodontic brackets.

Methods

Patients wearing orthodontic brackets (n = 40, mean age = 26 years) and healthy controls without brackets (n = 40, mean age = 17 years) were enrolled in the study. Saliva samples from each patient was collected. After DNA purification, target species comprising streptococci and a Lactobacillus species were detected and quantified from the samples using polymerase chain reaction (PCR) and real‐time quantitative PCR.

Results

Detection frequencies did not differ between the orthodontic patients and the control subjects for any target species except for Streptococcus sobrinus, which showed significantly lower detection rates in orthodontic patients (p < .05). Lactobacillus casei and Streptococcus gordonii were found at the highest detection frequencies with both species being detected in 38 (95%) of the saliva samples of orthodontic patients. Similarly, L. casei and Streptococcus salivarius were the species with highest detection frequencies (35, 87.5%) in the control subjects. Real‐time PCR revealed that Streptococcus mutans and S. salivarius quantities were significantly higher in orthodontic patients than in the control subjects (p < .05).

Conclusions

Application of orthodontic brackets for 12 months leads to increased salivary levels of cariogenic bacteria and may serve as a potential risk factor for caries initiation.

Identification of Non- Streptococcus mutans Bacteria from Predente Infant Saliva Grown on Mitis-Salivarius-Bacitracin Agar

Objective: Although mitis-salivarius-bacitracin (MSB) agar is a commonly used selective medium for detecting Streptococcus mutans in clinical studies, non-S. mutans microorganisms are cultivatable on MSB agar. Since few studies have identified non-S. mutans bacteria grown on MSB, this study aimed to identify and differentiate MSB-grown non-S. mutans bacteria from predente infants' oral cavity. Study design: The saliva from 51 predente infants were plated on MSB agars. Bacteria colonies were characterized based on their morphology under direct visualization and light microscopic observation. Colony PCR targeting S. mutans htrA locus and 16S rRNA DNA sequencing were used for further bacteria identification. Results: Overall, 80% of the predente infants had oral bacteria grown on the MSB agar. Nine bacteria were identified, including S. mutans, Staphylococcus epidermidis, Klebsiella quasi-pneumoniae, Klebsiella pneumoniae, Enterobacter kobei, Enterococcus faecalis, Staphylococcus hominis, Streptococcus anginosus and Phytobacter. The most frequently detected bacteria were S. epidermidis (41.5%), followed by E. kobei (24.4%), K. pneumoniae (17.1%) and S. mutans (9.8%.) Conclusions: Multiple non-S. mutans bacteria from infants' oral cavity could grow on MSB agar. Caution should be exercised in counting the colony forming units of S. mutans from oral samples on MSB agar to avoid overestimation by assuming that all colonies on the MSB agar are S. mutans. Using the colony morphological guide we summarized, these non-S. mutans bacteria could be distinguished from S. mutans. Our study provides a key reference to pediatric cariology clinical-epidemiological studies that commonly use MSB to identify/quantify S. mutans in infants and young children.

Salivary Microbiological and Gingival Health Status Evaluation of Adolescents With Overweight and Obesity: A Cluster Analysis

Given the high prevalence of obesity in children and adolescents, the investigation of early markers is of clinical importance to better manage this condition. Thus, the aim was to evaluate the cross-sectional relationship between salivary microbiota, gingival health status, and excess weight in adolescents. A total of 248 students (14-17 y; 119 girls) were included, free of caries lesions and periodontal pockets. Physical examination included measures of height, weight, and body fat percentage (%BF). Oral examination was performed to gather information on dental (DMFT index) and gingival health status. Unstimulated saliva was submitted to qPCR reactions to quantify Streptococcus mutans, Porphyromonas gingivalis, Bifidobacteria, and Streptococcus pneumoniae percentages and the NFKappaB expression. Two-way ANOVA was applied considering group (normal-weight/overweight/obesity) and sex factors, in addition to cluster analysis. Group effect was significant for %S. mutans (partial eta² = 0.20; p < 0.001) and %Bifidobacteria (partial eta² = 0.19; p < 0.001), with overweight and obesity groups showing the highest levels compared to normal-weight ones, with no significant sex effect. There was no difference in the frequency of gingivitis, P. gingivalis, and S. pneumoniae percentages or NFKappaB expression between groups. Cluster analysis generated three clusters according to body fat accumulation: "Higher %BF," "Moderate %BF," and "Lower %BF." "Higher %BF" cluster was characterized by higher body fat percentage and higher salivary %Bifidobacteria, while cluster "Lower %BF" was characterized by lower body fat percentage and lower frequency of gingivitis ("Moderate %BF" cluster was the contrast). According to nutritional status, a difference in salivary S. mutans and Bifidobacteria percentages was found, with overweight or obesity adolescents showing the highest percentages than normal-weight ones. Besides, a positive relationship between body fat accumulation and Bifidobacteria count was observed, indicating a possible interaction between oral bacteria communities and weight gain.

Oral health and Candida carriage in socioeconomically disadvantaged US pregnant women

Background

Despite the well-documented associations between poor maternal oral health and increased risk for adverse birth outcomes and dental caries in children after birth, prenatal oral health care is under-utilized, especially among the underserved population. In addition, oral Candida has recently been suggested as a potential culprit for children’s dental caries, with evident maternal contributions. Therefore, this study aimed to obtain epidemiological data on the oral health and oral Candida carriage in a cohort of underserved US pregnant women, and reveal factors associated with their oral Candida carriage.

Methods

Demographic-medical-oral hygiene practice data were collected. Comprehensive oral examination was conducted. Caries status and plaque index were recorded. Oral samples (saliva, plaque and swab) were processed to identify Candida species and Streptococcus mutans by culturing-dependent and -independent methods. Multiple logistic regression analyses were used to identify factors associated with oral Candida carriage and caries severity.

Results

Eighty-two socioeconomically disadvantaged women (48 pregnant and 34 non-pregnant) were enrolled. More pregnant women (79.1%) had > = 1 untreated decayed tooth when compared to their non-pregnant counterparts (47.1%) (p = 0.01). The average number of decayed teeth in pregnant and non-pregnant women was 3.9 and 3.1 (p > 0.05). Caries severity was positively associated with race (African American vs. white), plaque index and salivary Candida albicans level. C. albicans was the most predominant/abundant Candida strain, with cheek and tonsil as the most common colonized sites. The detection of C. albicans was 56%/56% in saliva and 40%/47% in plaque of the pregnant and non-pregnant groups, respectively. Study women’s oral Candida carriage is positively associated with hypertension [p = 0.03, odds ratio = 14.47(1.28, 163.51)], decayed teeth number [p = 0.04, odds ratio = 1.31 (1.01,1.69)] and salivary S. mutans level [p = 0.03, odds ratio = 4.80 (1.18–19.43)].

Conclusions

Socioeconomically disadvantaged US women are in need of improved prenatal oral health, a large proportion of them have untreated decayed teeth and high carriage of oral Candida. Due to the observed significant association between the decayed teeth number and oral Candida carriage, providing oral health care during pregnancy (including limiting decayed teeth) will not only improve women’s oral health, but also present as a promising approach to reduce oral Candida carriage in women.

Streptococcus mutans isolated from children with severe-early childhood caries form higher levels of persisters

OBJECTIVES

Dental caries is the most common chronic infectious disease in children. Streptococcus mutans, the main cariogenic bacterial species, produces persisters, nongrowing dormant variants of regular cells associated with chronicity of diseases. We hypothesized that the recurrent nature of caries, particularly within populations with high-caries risk, is due partly to specific phenotypic features of S. mutans such as its ability to form persisters. We aimed to investigate the genotypic and phenotypic differences between the S. mutans from children with severe early-childhood caries (S-ECC) and those without caries.

METHODS

S. mutans from plaque samples of caries-free (CF) and S-ECC children were tested for their ability to adapt to a lethal pH in an acid tolerance response assay. The persister levels of S. mutans isolates was quantified in both groups.

RESULTS

S. mutanswas identified in all 23 S-ECC but only 6 of the 21 CF subjects. In most subjects, only one dominant S. mutans genotype was detected. No statistically significant differences in the mean survival percentage of S. mutans were observed between the two groups at a lethal pH of 3.5. However, the dominant genotype within a particular S-ECC subject exhibited a higher percentage of cell survival compared to those in the CF group. In S-ECC patients, S. mutans isolates displayed a ∼15-fold higher persistence phenotype than S. mutans isolates from CF patients.

CONCLUSIONS

The ability of S. mutans to produce high levels of persisters may contribute to part of an individual's ability to control caries disease activity and recurrent lesions.

Factors governing extracellular DNA degradation dynamics in soil

We examined the impacts of soil moisture, temperature, agricultural management and habitat type on the degradation dynamics of eDNA in soils. Synthetic eDNA was added to soil microcosms, and its disappearance over time was measured using both high-throughput sequencing and qPCR. The synthetic eDNA was degraded rapidly, but a small fraction remained detectable throughout the experiments (39-80 days). The eDNA degradation rate was positively correlated with moisture and temperature, but negatively correlated with soil organic carbon content. End-point stabilization of eDNA was highest at low moisture and temperature, but exhibited no relationship with soil organic carbon. Tilled soils had higher rates of degradation and less stabilization than no-till soils. Among different habitats we observed that forest soils had the slowest degradation rate, and meadow soils had the greatest stabilization of eDNA. While eDNA was detectable by qPCR in all treatments across all time-points, it became inconsistently detectable with high-throughput gene sequencing in less than 1 week. We conclude that eDNA degradation and stabilization dynamics vary with moisture, temperature and habitat characteristics, that small amounts of eDNA may persist in soils indefinitely, and that the ability of persistent eDNA to impact microbial community estimates depends on method sensitivity and experimental objectives.

Streptococcus mutans detection in saliva and colostrum samples

Objective

To detect Streptococcus mutans in colostrum and saliva of neonates and compare with its detection in saliva of mothers.

Methods

Forty-three healthy women, full-term gestations with no complications, submitted to elective Cesarean section, and their newborns were included in the study. Samples were investigated by polymerase chain reaction to detect S. mutans in genetic material from the samples.

Results

Approximately 16% of colostrum samples showed S. mutans , but not correlated with the presence of the bacteria in both samples of saliva. S. mutans was detected in 49 and 30% of saliva samples of mothers and neonates, respectively. There was a positive correlation in S. mutans detection between types of saliva. The number of maternal samples of saliva with detectable S. mutans was smaller in women receiving dental treatment during pregnancy. Tooth brushing, three times a day, influenced the detection of S. mutans in both the saliva and the colostrum.

Conclusion

Although maternal saliva may present S. mutans , few samples of colostrum present the bacteria. The presence of bacteria in neonate saliva may be related to contact before birth. Dental treatment and hygiene habits seem to influence the detection of S. mutans in samples of maternal saliva and colostrum.

Complete Genome Sequence of Streptococcus mutans Strain LAB761, Which Harbors Several Bacteriocin Loci, Isolated from a Caries-Active Child in Canada

Streptococcus mutans LAB761 has been isolated from dental plaque collected from a child with severe caries. We report here the complete genome sequence of S. mutans strain LAB761, which has a chromosome of 2.0 Mb.

Streptococcus mutans LAB761 has been isolated from dental plaque collected from a child with severe caries. We report here the complete genome sequence of S. mutans strain LAB761, which has a chromosome of 2.0 Mb. The genome sequence reported herein contains several loci encoding double-glycine-motif peptides and lantibiotic and nonlantibiotic bacteriocins.

Streptococcus mutans in Umbilical Cord Blood, Peripheral Blood, and Saliva from Healthy Mothers

The aims of this study were to analyze the presence of Streptococcus mutans (SM)-DNA in cord blood (CB), maternal peripheral blood (PB), and maternal saliva (SA) and compare with data collected in health surveys. Sixty-four healthy women with pregnancies to term and without complications attending for elective cesarean section in the Clinical Hospital of Ribeirao Preto, Sao Paulo were included. Samples of PB and unstimulated SA were obtained on the day of hospitalization and samples of CB were collected after the delivery section. Samples were investigated using polymerase chain reaction for the presence of SM-DNA using specific primers. The results show over 50% of the sample of PB and CB showed SM-DNA detectable. There was a positive correlation between the SM detection in PB/CB and SA (P < 0.05). Pregnant women, who reported tooth brushing more than three times a day, often showed detectable SM-DNA in PB and CB (P < 0.05). In conclusion, the majority of children can have contact with SM-DNA during the intrauterine life by the CB. SM probably transferred from salivary habitat to PB and CB. The tooth brushing can be associated to S. mutans detection in blood samples.

Whole genome sequence and phenotypic characterization of a Cbm+ serotype e strain of Streptococcus mutans

We report the whole genome sequence of the serotype e Cbm+ strain LAR01 of Streptococcus mutans, a dental pathogen frequently associated with extra-oral infections. The LAR01 genome is a single circular chromosome of 2.1 Mb with a GC content of 36.96%. The genome contains 15 phosphotransferase system gene clusters, seven cell wall-anchored (LPxTG) proteins, all genes required for the development of natural competence and genes coding for mutacins VI and K8. Interestingly, the cbm gene is genetically linked to a putative type VII secretion system that has been found in Mycobacteria and few other Gram-positive bacteria. When compared with the UA159 type strain, phenotypic characterization of LAR01 revealed increased biofilm formation in the presence of either glucose or sucrose but similar abilities to withstand acid and oxidative stresses. LAR01 was unable to inhibit the growth of Strpetococcus gordonii, which is consistent with the genomic data that indicate absence of mutacins that can kill mitis streptococci. On the other hand, LAR01 effectively inhibited growth of other S. mutans strains, suggesting that it may be specialized to outcompete strains from its own species. In vitro and in vivo studies using mutational and heterologous expression approaches revealed that Cbm is a virulence factor of S. mutans by mediating binding to extracellular matrix proteins and intracellular invasion. Collectively, the whole genome sequence analysis and phenotypic characterization of LAR01 provides new insights on the virulence properties of S. mutans and grants further opportunities to understand the genomic fluidity of this important human pathogen.

Effect of preparation method and storage period on the stability of saliva DNA

Saliva is an attractive source for oral microbial detection and quantification since sampling is non-invasive and rapid.

OBJECTIVES

To determine whether different saliva preparation methods or preservation time periods affect DNA stability.

METHODS

Saliva samples from 4 healthy adult volunteers were processed to obtain 3 different preparations: whole saliva, and after centrifugation pellet and supernatant. Purified DNA (MasterPure™) from each sample was divided into 4 aliquots, one for immediate analysis and 3 (stored at -80°C) for later analyses after 1 week and 2 and 6 months. DNA concentrations and qPCR based quantities of Porphyromonas gingivalis, Prevotella intermedia, Parvimonas micra, Fusobacterium nucleatum, Filifactor alocis and Streptococcus mutans were determined.

RESULTS

DNA concentration did not decrease (P>0.05) during the 6-month period in any sample. Mean (SE) DNA concentrations (ng/μl) in whole saliva were 152.2 (51.2) and 147.8 (50) at day 0 and 6 months, respectively. Similarly, the values for pellet were 134.9 (42.5) and 133.6 (42.9), and for supernatant, 11 (1.9) and 8.9 (2.3), the difference being significant (P<0.001) between supernatant and whole saliva or pellet. The quantities of most bacterial species found at day 0 remained stable over the 6-month period in all saliva preparations. In supernatant, species quantities were lower (P<0.05) than in whole saliva or pellet.

CONCLUSIONS

DNA concentrations were comparable between whole saliva and pellet, suggesting that either of them can be used for DNA-based analyses. Our results also demonstrated that DNA extracted from saliva can be preserved at -80°C for at least 6 months without decrease in DNA concentration.

Identification of ssDNA aptamers specific to clinical isolates of Streptococcus mutans strains with different cariogenicity

Streptococcus mutans, a Gram-positive facultative anaerobic bacterium, is considered to be a major etiological factor for dental caries. In this study, plaques from dental enamel surfaces of caries-active and caries-free individuals were obtained and cultivated for S. mutans isolation. Morphology examination, biochemical characterization, and polymerase chain reaction were performed to identify S. mutans The cariogenicity of S. mutans strains isolated from clinical specimens was evaluated by testing the acidogenicity, aciduricity, extracellular polysaccharide production, and adhesion ability of the bacteria. Finally, subtractive SELEX (systematic evolution of ligands by exponential enrichment) technology targeting whole intact cells was used to screen for ssDNA aptamers specific to the strains with high cariogenicity. After nine rounds of subtractive SELEX, sufficient pool enrichment was achieved as shown by radioactive isotope analysis. The enriched pool was cloned and sequenced randomly, followed by MEME online and RNA structure software analysis of the sequences. Results from the flow cytometry indicated that aptamers H1, H16, H4, L1, L10, and H19 could discriminate highly cariogenic S. mutans strains from poorly cariogenic strains. Among these, Aptamer H19 had the strongest binding capacity with cariogenic S. mutans strains with a dissociation constant of 69.45 ± 38.53 nM. In conclusion, ssDNA aptamers specific to highly cariogenic clinical S. mutans strains were successfully obtained. These ssDNA aptamers might be used for the early diagnosis and treatment of dental caries.

Accuracy of commercial kits and published primer pairs for the detection of periodontopathogens

OBJECTIVES

Despite the input of microbiome research, a group of 20 bacteria continues to be the focus of periodontal diagnostics and therapy. The aim of this study was to compare three commercial kits and laboratory-developed primer pairs for effectiveness in detecting such periodontopathogens.

MATERIALS AND METHODS

Fourteen bacterial mock communities, consisting of 16 randomly assembled bacterial strains, were used as reference standard for testing kits and primers. Extracted DNA from mock communities was analyzed by PCR in-house with specific primers and forwarded for analysis to the manufacturer's laboratory of each of the following kits: ParoCheck®Kit 20, micro-IDent®plus11, and Carpegen® Perio Diagnostik.

RESULTS

The kits accurately detected Fusobacterium nucleatum, Prevotella intermedia/Prevotella nigrescens, Parvimonas micra, Aggregatibacter actinomycetemcomitans, Campylobacter rectus/showae, Streptococcus mitis, Streptococcus mutans, and Veillonella parvula. The in-house primers for F.nucleatum were highly specific to subtypes of the respective periopathogen. Other primers repeatedly detected oral pathogens not present in the mock communities, indicating reduced specificity.

CONCLUSIONS

The commercial kits used in this study are reliable tools to support periodontal diagnostics. Whereas the detection profile of the kits is fixed at a general specificity level, the design of primers can be adjusted to differentiate between highly specific strains. In-house primers are more error-prone. Bacterial mock communities can be established as a reference standard for any similar testing.

CLINICAL RELEVANCE

The tested kits render good results with selected bacterial species. Primers appear to be less useful for routine clinical diagnostics and of limited applicability in research. Basic information about the periodontopathogens identified in this study supports clinical decision-making.

Regulation of oxidative response and extracellular polysaccharide synthesis by a diadenylate cyclase in Streptococcus mutans

Cyclic diadenosine monophosphate (c-di-AMP) has been implicated in the control of many important bacterial activities. However, the function of this molecule in Streptococcus mutans, the primary aetiological agent of human dental caries, is unknown. In this study, we identified and characterized a diadenylate cyclase, named CdaA, in S. mutans. Furthermore, we showed that in-frame deletion of the cdaA gene in S. mutans causes decreased c-di-AMP levels, increased sensitivity to hydrogen peroxide and increased production of extracellular polysaccharides. Global gene expression profiling revealed that more than 200 genes were significantly upregulated or downregulated (> 2.0-fold) in the cdaA mutant. Interestingly, genes with increased or decreased expression were clustered in cellular polysaccharide biosynthetic processes and oxidoreductase activity respectively. Notably, the expression of several genomic islands, such as GTF-B/C, TnSmu, CRISPR1-Cas and CRISPR2-Cas, was found to be altered in the cdaA mutant, indicating a possible link between these genomic islands and c-di-AMP signalling. Collectively, the results reported here show that CdaA is an important global modulator in S. mutans and is required for optimal growth and environmental adaption. This report also paves the way to unveil further the roles of c-di-AMP signalling networks in the biology and pathogenicity of S. mutans.

FT-Raman Spectroscopy Study of the Remineralization of Microwave-Exposed Artificial Caries

Dental caries is a microbially mediated disease that can result in significant tooth structure degradation. Although the preponderance of lesions is treated by surgical intervention, various strategies have been developed for its noninvasive management. Here, we use a novel approach for noninvasive treatment based on killing Streptococcus mutans with high-frequency microwave energy (ME). The rationale for this approach is based on modulating the pH of caries to a physiological state to enable spontaneous tooth remineralization from exogenous sources. In the present study, after demonstrating that ME kills >99% of S. mutans in planktonic cultures, 8 enamel slabs were harvested from a single tooth. Baseline mineral concentration at each of 12 points per slab was obtained using Fourier transform (FT)-Raman spectroscopy. Surface demineralization was subsequently promoted by subjecting all samples to an S. mutans acidic biofilm for 6 d. Half of the samples were then exposed to high-frequency ME, and the other half were used as controls. All samples were next subjected to a remineralization protocol consisting of two 45-min exposures per 24-h period in tryptic soy broth followed by immersion in a remineralizing solution for the remaining period. After 10 d, samples were removed and cleaned. FT-Raman spectra were again obtained at the same 12 points per sample, and the mineral concentration was determined. The effect of the remineralization protocol on the demineralized slabs was expressed as a percentage of mineral loss or gain relative to baseline. The mineral concentration of the microwave-exposed group collectively approached 100% of baseline values, while that of the control group was in the order of 40%. Differences between groups were significant (P = 0.001, Mann-Whitney U test). We concluded that killing of S. mutans by ME promotes effective remineralization of S. mutans-demineralized enamel compared with controls.

Molecular analysis of biofilms on the surface of neonatal endotracheal tubes based on 16S rRNA PCR-DGGE and species-specific PCR

Ventilator-associated pneumonia (VAP) results in considerable morbidity and mortality in neonatal intensive care units. VAP is associated with polymicrobial biofilms that form on endotracheal tubes (ETTs). We aimed to evaluate the diversity and the bacterial community in biofilms on ETTs extubated from mechanically ventilated newborns. ETTs (N = 29) and aerobic sputum cultures were obtained from 20 mechanically ventilated newborns. Denaturing gradient gel electrophoresis (DGGE) was used to characterize the bacterial species in the biofilms on the ETTs. Species-specific PCR was used to detect common oropharyngeal Streptococcus species and known ETT-associated pathogens. DGGE profiling of ETT biofilms showed multiple banding patterns indicating a diverse bacterial community. The dominant bacterial species were Klebsiella spp. (29/29), Streptococcus spp. (27/29), and Pseudomonas spp. (24/29). The most frequently occurring Streptococcus species was Streptococcus mitis (N = 18). Oropharyngeal bacteria were present in 25 of 29 ETT specimens. Streptococcus spp. often co-existed with K. pneumoniae and/or P. aeruginosa. In contrast, only one bacterial species was isolated from each sputum culture, K. pneumoniae or Acinetobacter baumannii. Our results demonstrated that Klebsiella spp., Streptococcus spp., and Pseudomonas spp. were the most frequent microbes on the surface of neonatal ETTs. The co-existence of oral commensals and pathogenic bacteria on the same tubes may play a crucial role for biofilm formation.

Streptococcus mutans and Streptococcus sobrinus colonization and caries experience in 3- and 5-year-old Thai children

OBJECTIVES

The aim of this study was to examine the colonization of Streptococcus mutans and Streptococcus sobrinus in supra-gingival plaque samples and to determine their correlation with the prevalence of early childhood caries (ECC) in Thai children.

MATERIALS AND METHODS

A total of 344 Thai children, ages 3 and 5 years, were invited to participate in this study. Caries status of the children was examined. Supra-gingival plaque samples were collected. Quantitative real-time PCR was performed to evaluate DNA levels of S. mutans and S. sobrinus.

RESULTS

Eighty-five percent of the children were colonized by S. mutans and 50.9% of them were colonized by S. sobrinus. The prevalence of ECC was 43.8% and 56.2% among 3- and 5-year-old children, respectively, and was significantly associated with the presence of S. mutans and S. sobrinus. The severity of ECC was significantly correlated with increased DNA levels of the two bacteria. Children who were positive for S. mutans and S. sobrinus (Sm+/Sb+) were 8 times or 44 times more likely to experience ECC than children who were Sm-/Sb + or were Sm-/Sb-.

CONCLUSIONS

The study evidence further suggest that children colonized by both S. mutans and S. sobrinus are at the higher risk for ECC.

CLINICAL RELEVANCE

Molecular-based qPCR can be used to detect and quantify S. mutans and S. sobrinus colonization for epidemiological and clinical studies for ECC risk assessment.

PCR applications in identification of saliva samples exposed to different conditions (streptococci detection based)

Oral streptococci represent about 20% of the total oral bacteria, so if it is possible to detect the presence of oral specific bacteria from a forensic specimen by Polymerase chain reaction, this could be used to verify the presence of saliva. Aim of this study is detection of Streptococcus salivarius which is one of the most common streptococci in oral bacteria and Streptococcus mutans which is common in cases of dental caries in various body fluids and skin swabs and assessment of which one of both organisms is more reliable in saliva identification, cross sectional study on Egypt population. Negative control samples (15 samples) were taken from various body fluids (urine, semen) and skin swabs. Mock forensic samples (85 samples) included fresh saliva, saliva, cotton fabrics contaminated with saliva, cigarette butts, bitten apple and semen mixed with saliva samples). DNA extraction was done using DNeasy blood and tissue kit (Qiagen, Tokyo, Japan). Polymerase chain reaction was done for DNA amplification using Polymerase chain reaction master mix then gel electrophoresis was done for samples qualification. Control bacteria were S. salivarius and Streptococcus mutans. Streptococcus salivarius was detected in 83.5% of all saliva contained samples and S. mutans was detected in 67% of saliva contained samples. Both bacteria were not detected in other body fluids and skin swabs, so S. salivarius is more reliable in saliva identification as well as differentiating it from other body fluids. Polymerase chain reaction is valuable in detection of saliva by detecting S. salivarius.

DNA from oral bacteria by sodium hydroxide-paper method suitable for polymerase chain reaction

In the oral cavity, we can find a complex mixture of microorganisms, commensals, and pathogens. The studies of normal oral microbiota, as well as the studies of much oral pathology (e.g., caries, periodontitis), involve the isolation and cultivation of these microorganisms and their molecular analysis. The aim of this study was to validate a quick, easy, efficient, and inexpensive DNA extraction method for the recovery of genomic DNA from gram-positive and gram-negative oral bacteria to be used in polymerase chain reaction amplification. This method worked great with all samples analyzed, providing an approach to extract DNA for different microorganisms.

Mutans streptococci genetic strains in children with severe early childhood caries: follow-up study at one-year post-dental rehabilitation therapy

Background

Genotypic strains of cariogenic mutans streptococci (MS) may vary in important virulence properties. In previous published studies, we identified 39 MS strains from pediatric patients undergoing full-mouth dental rehabilitation, including the removal and/or repair of carious lesions and application of antimicrobial rinse and fluoride varnish.

Objectives

The objectives of this current 1-year follow-up study are to assess the variability of MS strains that occur at 1-year post-rehabilitation and characterize the xylitol-resistance properties of MS strains that predominate.

Methods

Plaque from five children with severe early childhood caries was collected 1-year post-rehabilitation. MS isolates were subjected to arbitrarily primed-polymerase chain reaction (AP-PCR) for identification of genetic strains and in vitro xylitol-inhibition experiments. To more precisely define strain distributions within each patient, we isolated large numbers of isolates per patient.

Results

MS strains diminished from several strains pre-rehabilitation, to one dominant strain at 1-year post-rehabilitation, with several new emergent strains. The majority of the clinical MS strains, as well as the Streptococcus mutans laboratory strains ATCC 25175 and 35668, were predicted to undergo 50% inhibition with 2.48–5.58% xylitol, with some clinical MS strains being significantly more resistant in vitro.

Conclusions

Our follow-up study using patients from the original cohort demonstrates that specific MS strains are dominant at 1-year post-dental rehabilitation. Most of the clinical MS strains are similar in xylitol resistance to the attenuated S. mutans ATCC control strains, with some strains being more resistant to xylitol in vitro.

Shifts in the microbial population in relation to in situ caries progression

The shift in microbial diversity from young to mature plaque, related to caries activity on sound and restored surfaces, was studied using denaturing gradient gel electrophoresis. During a 20-week in situ study on caries progression 8 subjects wearing restored and unrestored dentin and enamel sections, biofilm was sampled after 1 and 20 weeks (young or mature plaque). A higher microbial diversity (mature plaque) was seen in caries-active compared to caries-free subjects. Rothia dentocariosa and Scardovia inopinata were absent from all caries-free sites, but appeared in 50% of the caries-active sites.

Real-time quantitative polymerase chain reaction for enumeration of Streptococcus mutans from oral samples

This study compared SYBR Green real-time quantitative PCR (qPCR) with standard plate counting for the enumeration of Streptococcus mutans in oral samples. Oral samples (n = 710) were collected from high-caries-risk children for quantification of S. mutans by qPCR using primer pairs. The S. mutans copy number was calculated with reference to a qPCR quantification cycle (Cq) standard curve and compared with the absorbance value at 600 nm of a standard suspension of S. mutans UA159. The S. mutans copy number results were evaluated in relation to standard plate count (SPC) results obtained from each sample following culture on Petri plates containing S. mutans selective media and reported as colony-forming units (CFUs). The mean S. mutans copy number calculated from qPCR was higher than the SPC CFUs (1.3 × 10(6) and 1.5 × 10(5) CFUs, respectively). The qPCR values were usually higher in individual samples and qPCR detected the presence of S. mutans 84% (231/276) of the time that the SPC did not, compared with 33% (4/12) of the time when qPCR failed to detect S. mutans and the SPC did. The qPCR technique was found to be more sensitive for detection of S. mutans from oral samples, a method that is not dependent on the viability of the sample taken and therefore is proposed as a more reliable and efficient means of quantification of S. mutans.

Children with severe early childhood caries: pilot study examining mutans streptococci genotypic strains after full-mouth caries restorative therapy

PURPOSE

Genotypic strains of mutans streptococci (MS) may vary in important virulence properties and be differentially affected by specific components of full-mouth caries restorative therapy. The purpose of this pilot study was to identify mutans streptococci strains that predominate following caries restorative therapy.

METHODS

Plaque from 7 children with severe early childhood caries was collected before and following therapy. MS isolates (N=828) were subjected to polymerase chain reaction (PCR) and arbitrarily primed-PCR (AP-PCR) for assignment within MS strains. Determining the longitudinal changes in MS strain distribution over time within each patient required the isolation of larger numbers of isolates per patient, but from fewer patients.

RESULTS

Up to 39 genotypic strains of Streptococcus mutans and Streptococcus sobrinus, and 7 genotypic strains of non-MS streptococci were identified by AP-PCR and 16S ribosomal rRNA gene sequencing. The number of MS strains isolated from each patient were 3 to 7 prior to treatment, diminishing to 1 to 2 dominant MS strains in most patients 6 months following therapy.

CONCLUSIONS

Caries restorative therapy resulted in shifts of specific mutans streptococcus and non-mutans streptococcus strains. The implications are that caries restorative therapy affects the distribution of MS strains, and that well-accepted practices for caries prevention should be more closely examined for efficacy.

Molecular analysis of microbial communities in endotracheal tube biofilms

Background

Ventilator-associated pneumonia is the most prevalent acquired infection of patients on intensive care units and is associated with considerable morbidity and mortality. Evidence suggests that an improved understanding of the composition of the biofilm communities that form on endotracheal tubes may result in the development of improved preventative strategies for ventilator-associated pneumonia.

Methodology/Principal Findings

The aim of this study was to characterise microbial biofilms on the inner luminal surface of extubated endotracheal tubes from ICU patients using PCR and molecular profiling. Twenty-four endotracheal tubes were obtained from twenty mechanically ventilated patients. Denaturing gradient gel electrophoresis (DGGE) profiling of 16S rRNA gene amplicons was used to assess the diversity of the bacterial population, together with species specific PCR of key marker oral microorganisms and a quantitative assessment of culturable aerobic bacteria. Analysis of culturable aerobic bacteria revealed a range of colonisation from no growth to 2.1×10⁸ colony forming units (cfu)/cm² of endotracheal tube (mean 1.4×10⁷ cfu/cm²). PCR targeting of specific bacterial species detected the oral bacteria Streptococcus mutans (n = 5) and Porphyromonas gingivalis (n = 5). DGGE profiling of the endotracheal biofilms revealed complex banding patterns containing between 3 and 22 (mean 6) bands per tube, thus demonstrating the marked complexity of the constituent biofilms. Significant inter-patient diversity was evident. The number of DGGE bands detected was not related to total viable microbial counts or the duration of intubation.

Conclusions/Significance

Molecular profiling using DGGE demonstrated considerable biofilm compositional complexity and inter-patient diversity and provides a rapid method for the further study of biofilm composition in longitudinal and interventional studies. The presence of oral microorganisms in endotracheal tube biofilms suggests that these may be important in biofilm development and may provide a therapeutic target for the prevention of ventilator-associated pneumonia.

Distribution of putative virulence genes in Streptococcus mutans strains does not correlate with caries experience

Streptococcus mutans, a member of the human oral flora, is a widely recognized etiological agent of dental caries. The cariogenic potential of S. mutans is related to its ability to metabolize a wide variety of sugars, form a robust biofilm, produce copious amounts of lactic acid, and thrive in the acid environment that it generates. The remarkable genetic variability present within the species is reflected at the phenotypic level, notably in the differences in the cariogenic potential between strains. However, the genetic basis of these differences is yet to be elucidated. In this study, we surveyed by PCR and DNA hybridization the distribution of putative virulence genes, genomic islands, and insertion sequences across a collection of 33 strains isolated from either children with severe early childhood caries (S-ECC) or those who were caries free (CF). We found this genetically diverse group of isolates to be remarkably homogeneous with regard to the distribution of the putative virulence genes and genetic elements analyzed. Our findings point to the role of other factors in the pathogenesis of S-ECC, such as uncharacterized virulence genes, differences in gene expression and/or enzymatic activity, cooperation between S. mutans strains or with other members of the oral biota, and host factors.

PCR detection of Streptococcus mutans and Aggregatibacter actinomycetemcomitans in dental plaque samples from Haitian adolescents

Streptococcus mutans and Aggregatibacter actinomycetemcomitans are oral pathogens associated with dental caries and periodontitis, respectively. The aim of this study was to determine the colonization of these two microorganisms in the dental plaque of a group of Haitian adolescents using two different polymerase chain reaction (PCR) methods, standard PCR, and quantitative real-time PCR (qPCR) assays. Fifty-four pooled supra-gingival plaque samples and 98 pooled sub-gingival plaque samples were obtained from 104 12- to19-year-old rural-dwelling Haitians. The total genomic DNA of bacteria was isolated from these samples, and all participants also received caries and periodontal examinations. Caries prevalence was 42.2%, and the mean decayed, missing, and filled surface (DMFS) was 2.67 ± 5.3. More than half of the adolescents (53.3%) experienced periodontal pockets (Community Periodontal Index score ≥3). S. mutans was detected in 67.3% by qPCR and 38.8% by PCR of the supra-gingival plaque samples (p < 0.01), and 36.6% by qPCR and 8.1% by PCR of the sub-gingival samples (p < 0.01). A. actinomycetemcomitans was detected in 85.1% by qPCR and 44.0% by PCR of the sub-gingival samples (p < 0.01), but the prevalence was similar, 67.3% by qPCR and 59.2% by PCR, in the supra-gingival plaque samples. Neither age nor gender was significantly correlated to the bacterial colonization. The results demonstrated a moderate-to-high prevalence of S. mutans and A. actinomycetemcomitans in the Haitian adolescent population, and qPCR is more sensitive than standard PCR in field conditions. These findings suggest that qPCR should be considered for field oral epidemiologic studies and may be necessary in investigations having major logistic challenges.

Inhibitory activity by barley coffee components towards Streptococcus mutans biofilm

It was shown that barley coffee (BC) interferes with Streptococcus mutans adsorption to hydroxyapatite. After BC component fractionation by dialysis and gel filtration chromatography (GFC), it was found that the low molecular mass (<1,000 Da) fraction (LMM fraction) containing polyphenols, zinc and fluoride ions and, above all, a high molecular mass (HMM > 1,000 kDa) melanoidin fraction display strong anti-adhesive properties towards S. mutans. In this study, we have further examined the potential of BC, BC LMM fraction and BC HMM melanoidin fraction as caries controlling agents by evaluating their anti-biofilm activity.The effects of BC and BC fractions on biofilm formation by S. mutans ATCC 25175 and its detachment from pre-developed biofilms were evaluated by microtiter plate assay. It was found that BC and its fractions, at concentrations ranging from 60 to 15 mg ml(-1) that are devoid of antimicrobial activity, inhibited S. mutans biofilm formation. An increase of S. mutans ATCC 25175 detachment from 24 h developed biofilm was observed at the highest tested concentrations. Interestingly, BC and BC fractions also showed anti-biofilm activity towards a variety of S. mutans clinical strains isolated from saliva, plaque and caries lesions of adult donors. In general, the HMM melanoidin fraction was more active than the LMM fraction. These findings, classifying BC LMM fraction and BC HMM melanoidin fractions as natural anti-biofilm agents, represent the basis for studying their possible use as anti-caries agents.

Development of species-specific primers for detection of Streptococcus pyogenes from throat swabs

A species-specific molecular marker has been developed to detect the human pathogen Streptococcus pyogenes from throat swabs. Streptococcus pyogenes is an important pathogen among Gram-positive organisms. A rapid and simple diagnostic tool is of utmost importance for the identification of this pathogen. The random amplified polymorphic DNA (RAPD) technique was used to differentiate the S. pyogenes strains. A differentially amplified fragment obtained from RAPD profiles was sequenced and characterized, which was developed into a sequence characterized amplified region (SCAR) marker to evaluate the specificity of S. pyogenes from other species of Streptococcus. The sensitivity of the SCAR primers was studied by qualitative PCR and the detection limit was found to be 10(-1) ng of genomic DNA or one to two cells of S. pyogenes. The specificity of the primers was assayed in 270 clinical throat swabs wherein 23 samples turned to be positive, which was highly significant over culture-based methods. This species-specific primer enables accurate detection of S. pyogenes from clinical samples and will be a useful tool in epidemiological studies.

Generation of diversity in Streptococcus mutans genes demonstrated by MLST

Streptococcus mutans, consisting of serotypes c, e, f and k, is an oral aciduric organism associated with the initiation and progression of dental caries. A total of 135 independent Streptococcus mutans strains from caries-free and caries-active subjects isolated from various geographical locations were examined in two versions of an MLST scheme consisting of either 6 housekeeping genes [accC (acetyl-CoA carboxylase biotin carboxylase subunit), gki (glucokinase), lepA (GTP-binding protein), recP (transketolase), sodA (superoxide dismutase), and tyrS (tyrosyl-tRNA synthetase)] or the housekeeping genes supplemented with 2 extracellular putative virulence genes [gtfB (glucosyltransferase B) and spaP (surface protein antigen I/II)] to increase sequence type diversity. The number of alleles found varied between 20 (lepA) and 37 (spaP). Overall, 121 sequence types (STs) were defined using the housekeeping genes alone and 122 with all genes. However pi, nucleotide diversity per site, was low for all loci being in the range 0.019-0.007. The virulence genes exhibited the greatest nucleotide diversity and the recombination/mutation ratio was 0.67 [95% confidence interval 0.3-1.15] compared to 8.3 [95% confidence interval 5.0-14.5] for the 6 concatenated housekeeping genes alone. The ML trees generated for individual MLST loci were significantly incongruent and not significantly different from random trees. Analysis using ClonalFrame indicated that the majority of isolates were singletons and no evidence for a clonal structure or evidence to support serotype c strains as the ancestral S. mutans strain was apparent. There was also no evidence of a geographical distribution of individual isolates or that particular isolate clusters were associated with caries. The overall low sequence diversity suggests that S. mutans is a newly emerged species which has not accumulated large numbers of mutations but those that have occurred have been shuffled as a consequence of intra-species recombination generating genotypes which can be readily distinguished by sequence analysis.

Maternal transmission of mutans Streptococci in severe-early childhood caries

PURPOSE

This study utilized multiple genetic analyses to detect evidence of maternal MS acquisition in children with S-ECC.

METHODS

Twenty-seven mother/child pairs were selected from children with 5-ECC preceding dental rehabilitation under general anesthesia. Plaque samples were collected from the mother, child, and the child's carious lesion. Arbitrarily primed-polymerase chain reaction (AP-PCR) genotyped 6-8 MS isolates from each plaque sample, and unique genotypes were identified. Representative MS isolates with unique genotypes were characterized by pulsed-field gel electrophoresis (PFGE). Cluster analysis using the Dice band-based similarity coefficient was used to generate dendrograms from gel bonding patterns. A Dice coefficient >70% indicated similarity or match among PFGE genotypes.

RESULTS

In 26% (7/27) of mother/child pairs, all of the child's isolates matched the mother. In 15% (4/27), some of the child's genotypes matched the mother, and in 59% (16/27), no isolates matched the mother. Maternal transmission was a mode of MS acquisition in 41% (11/27) of mother/child pairs, while acquisition from non-maternal sources occurred in 74% (20/27).

CONCLUSIONS

MS genotypes that did not match maternal strains were identified in the majority of children (74%) within this S-ECC population. Evidence of maternal transmission was detected in 41% of mother/child pairs.