Streptococcus Mutans Colonization Research Articles

Effects of glucose and lactate on Streptococcus mutans abundance in a novel multispecies oral biofilm model.

The oral microbiome plays an important role in protecting oral health. Here, we established a controlled mixed-species in vitro biofilm model and used it to assess the impact of glucose and lactate on the ability of Streptococcus mutans, an acidogenic and aciduric species, to compete with commensal oral bacteria. A chemically defined medium was developed that supported the growth of S. mutans and four common early colonizers of dental plaque: Streptococcus gordonii, Actinomyces oris, Neisseria subflava, and Veillonella parvula. Biofilms containing the early colonizers were developed in a continuous flow bioreactor, exposed to S. mutans, and incubated for up to 7 days. The abundance of bacteria was estimated by quantitative polymerase chain reaction (qPCR). At high glucose and high lactate, the pH in bulk fluid rapidly decreased to approximately 5.2, and S. mutans outgrew other species in biofilms. In low glucose and high lactate, the pH remained above 5.5, and V. parvula was the most abundant species in biofilms. By contrast, in low glucose and low lactate, the pH remained above 6.0 throughout the experiment, and the microbial community in biofilms was relatively balanced. Fluorescence in situ hybridization confirmed that all species were present in the biofilm and the majority of cells were viable using live/dead staining. These data demonstrate that carbon source concentration is critical for microbial homeostasis in model oral biofilms. Furthermore, we established an experimental system that can support the development of computational models to predict transitions to microbial dysbiosis based on metabolic interactions.IMPORTANCEWe developed a controlled (by removing host factor) dynamic system metabolically representative of early colonization of Streptococcus mutans not measurable in vivo. Hypotheses on factors influencing S. mutans colonization, such as community composition and inoculation sequence and the effect of metabolite concentrations, can be tested and used to predict the effect of interventions such as dietary modifications or the use of toothpaste or mouthwash on S. mutans colonization. The defined in vitro model (species and medium) can be simulated in an in silico model to explore more of the parameter space.

Evaluation of Mode of Delivery and Various Postnatal Factors on Acquisition of Oral Streptococcus mutans in Infants: A Prospective Study.

The objective of the current study is to assess and establish a relationship between the mode of delivery and postnatal factors in the early colonization of Streptococcus mutans (S. mutans) in infants' oral cavities. The primary goal of the investigation is to assess and compare the oral microflora of newborns immediately after birth and at 3, 6, 9, and 12 months of age in babies born by normal vaginal delivery and lower segment cesarean section and divided into (group III) and (group V), respectively. Around 50 mother-baby pairs in total had their swab samples collected for the identification of S. mutans and were monitored for a year. The role of other postnatal factors in the acquisition of S. mutans in infants was also evaluated. Data analysis showed that different postnatal factors like feeding patterns, oral hygiene practices, and socioeconomic factors affected the infant's oral cavity's initial colonization by S. mutans. Infants' first exposure to oral S. mutans depends on the delivery method and various postnatal factors. Sharma N, Bhargava N, Boruah B, et al. Evaluation of Mode of Delivery and Various Postnatal Factors on Acquisition of Oral Streptococcus mutans in Infants: A Prospective Study. Int J Clin Pediatr Dent 2023;16(5):663-666.

Evaluation of Streptococcus mutans Colonization and Oral Hygiene Status in Primary Molars Restored with Two Different Crowns: A Randomized Clinical Trial

Evaluation of Streptococcus mutans Colonization and Oral Hygiene Status in Primary Molars Restored with Two Different Crowns: A Randomized Clinical Trial

LiaSR two-component system modulates the oxidative stress response in Streptococcusmutans

Many commensal bacteria of the human oral microbiome can produce reactive oxygen species (ROS). ROS will inhibit the colonization of Streptococcusmutans (S.mutans), a major pathogenic bacteria in dental caries. The LiaSR two-component system in S.mutans can sense and respond to environmental oxidative stress. However, the molecular details of the LiaSR two-component system and oxidative stress response have been unclear. In this study, we aimed to elucidate the underlying mechanisms of the LiaSR two-component system and the mediated oxidative stress response in S.mutans. We performed the H2O2 killing assay, Confocal laser scanning microscopy, and 2,7-Dichlorofluoresce diacetate staining assay to evaluate the sensitivity of S.mutans to H2O2. The propidium iodide probe and TUNEL kit were used to detect the membrane permeability and DNA fragmentation. Quantitative real-time PCR was conducted to analyze the expression level of underlying regulated genes. The liaS and liaR deficient mutants were particularly sensitive to H2O2 compared to their wild strain S.mutans 593, which was previously isolated from a caries-active patient. The intracellular levels of ROS and membrane permeability increased in the mutants. The TUNEL assay showed that the rate of DNA fragmentation in the liaR mutant was higher compared to the wild strain and liaS mutant. Relative expression of the spxA2 gene in the mutants was lower than in the wild strain. The dpr and dinB genes were downregulated in the liaR mutant. These results indicated that the LiaSR two-component system mediated influence on spxA2 expression in S.mutans and contributed to membrane homeostasis, which was involved in the oxidative response process. S.mutans could also elevate the dpr and the dinB genes, which depend on the liaR component in the LiaSR system, may help reduce the DNA damage caused by ROS. This study provides valuable insights into the mechanisms of the LiaSR two-component system in the oxidative stress response of S.mutans.

The Antibacterial Effectiveness of Citrullus lanatus-Mediated Stannous Nanoparticles on Streptococcus mutans.

Introduction Dental caries is a prevalent oral health issue caused by the colonization of Streptococcus mutans in the oral cavity. Citrullus lanatus, commonly known as watermelon, is rich in bioactive compounds that possess antibacterial potential. In this study, we aimed to synthesize stannous chloride (SnCl2) nanoparticles (NPs) mediated by Citrullus lanatus extract and investigate their antibacterial effectiveness against Streptococcus mutans. Materials and method Stannous nanoparticles (SnNPs) synthesized by the green method were achieved by using the watermelon extract. Dilute stannous chloride solution was obtained by adding 0.45 gof stannous (Sn) chloride (Cl) powder to 60 mL of water, which was subjected to an orbital shaker with the watermelon extract. The nanoparticles obtained were subjected to characterization using antimicrobial testing, Fourier transform infrared (FTIR) spectroscopy, energy-dispersive X-ray (EDAX) analysis, and scanning electron microscopy (SEM). Agar well diffusion method was used against specific strains of S. aureus, S. mutans, and Escherichiacoli. Results The novel nanoparticles demonstrated promising antibacterial activity against S. mutans providing 10 mm of inhibitory action. Conclusion Due to its abundance of naturally occurring bioactive chemicals and improved efficacy against S. mutans, watermelon extract can be utilized to createstannous nanoparticles as opposed to the use of toxic chemicals. They can also be employed as oral administration systems.

A preliminarily Investigation on Oral Colonization and Counts of Streptococcus mutans and Streptococcus mitis in a Group of Predentate Infants in Relation to Some Maternal and Infant Factors (A Longitudinal Observational study).

Bacterial colonization of infants' oral cavities is a key factor for future caries risk. This study sought to longitudinally assess oral bacterial colonization in a group of predentate infants in relation to some mother and infant factors. A total of 50 mother-infant pairs were enrolled. When infants were 3-month-old, data were collected about some infant and mother factors; additionally, maternal Decayed, Missing, and Filled Teeth (DMFT) scores and salivary samples of mothers and infants were obtained. At 6 months of infant's age, another infants' salivary samples were obtained. Saliva was cultured to detect and quantify Streptococcus mutans (S. mutans) and Streptococcus mitis (S. mitis). Streptococcus mitis (S. mitis) was detected in all infants at 3 months. 74 and 96% of infants acquired S. mutans at 3 and 6 months, respectively. S. mutans detection was significantly higher with higher maternal DMFT scores, salivary S. mutans counts, and lower S. mitis counts, as well as when infants were given sugar-containing complementary foods/drinks. At 3-6 months, infants' S. mutans counts were significantly positively correlated with maternal S. mutans counts and DMFT scores and negatively correlated with maternal S. mitis counts. The opposite was evident for infants' S. mitis counts. Regression analysis showed that increased maternal DMFT scores and S. mutans counts, and Cesarean delivery were strong predictors for increased infant's S. mutans counts. While increased DMFT scores and maternal S. mutans counts were strong predictors for reduced infant's S. mitis counts. Poor maternal oral health, early introduction of sugars in the diet, and probably Cesarean delivery can negatively impact infants' oral bacterial colonization and possibly future caries risk. Understanding factors associated with oral colonization of both caries-producing and protective flora in infants of different populations is important for caries prevention. This, in turn, can aid tailoring oral health promotion programs for expectant mothers. Wassel MO, Salman NS, Metwalli NE. A preliminarily Investigation on Oral Colonization and Counts of Streptococcus mutans and Streptococcus mitis in a Group of Predentate Infants in Relation to some Maternal and Infant Factors (A Longitudinal Observational study). Int J Clin Pediatr Dent 2023;16(1):79-86.

Ecological influence by colonization of fluoride-resistant Streptococcus mutans in oral biofilm.

Dental caries is one of the oldest and most common infections in humans. Improved oral hygiene practices and the presence of fluoride in dentifrices and mouth rinses have greatly reduced the prevalence of dental caries. However, increased fluoride resistance in microbial communities is concerning. Here, we studied the effect of fluoride-resistant Streptococcus mutans (S. mutans) on oral microbial ecology and compare it with wild-type S. mutans in vitro. Biofilm was evaluated for its polysaccharide content, scanning electron microscopy (SEM) imaging, acid-producing ability, and related lactic dehydrogenase (LDH), arginine deiminase (ADS), and urease enzymatic activity determination. Fluorescence in situ hybridization (FISH) and quantitative real-time polymerase chain reaction (qRT-PCR) were used to evaluate the S. mutans ratio within the biofilm. It was followed by 16S rRNA sequencing to define the oral microbial community. Fluoride-resistant S. mutans produced increased polysaccharides in presence of NaF (P < 0.05). The enzymatic activities related to both acid and base generation were less affected by the fluoride. In presence of 275 ppm NaF, the pH in the fluoride-resistant strain sample was lower than the wild type. We observed that with the biofilm development and accumulative fluoride concentration, the fluoride-resistant strain had positive relationships with other bacteria within the oral microbial community, which enhanced its colonization and survival. Compared to the wild type, fluoride-resistant strain significantly increased the diversity and difference of oral microbial community at the initial stage of biofilm formation (4 and 24 h) and at a low fluoride environment (0 and 275 ppm NaF) (P < 0.05). Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis revealed that fluoride-resistant strain enhanced the metabolic pathways and glucose transfer. Fluoride-resistant S. mutans affected the microecological balance of oral biofilm and its cariogenic properties in vitro, indicating its negative impact on fluoride's caries prevention effect.

Antimicrobial effect of silver nanoparticles on polypropylene and acrylic resin denture bases.

The investigation of the antimicrobial action of Ag solutions in different surfaces has been performed, however, there is little data on the direct addition of those particles to the polypropylene denture base. The aim of this study was to evaluate the antimicrobial effect of silver nanoparticles in Candida albicans and Streptococcus mutans colonization in acrylic resin and polypropylene denture bases. Twenty test bodies (10×13×3 mm) were fabricated with (heat-polymerized) poly methyl methacrylate acrylic resin (group 1), (heat-polymerized) poly methyl methacrylate acrylic resin with silver nanoparticles (group 2), polypropylene (group 3) and polypropylene with silver nanoparticles (group 4). Candida albicans and Streptococcus mutans colonization were performed. A colony count was performed in Colony Forming Unit (CFU/ml) and registered to calculate the arithmetical mean of the duplicate values of each sample. Data was analyzed by Lilliefors test and since samples did not present a normal distribution, Kruskal-Wallis for variance analysis with the value of significance set at p<0.05. For Candida albicans colonies, when comparing nano-Ag in polypropylene, there were statistical difference between groups 3 and 4. For the same type of growth in heat-polymerized PMMA resin with and without nano-Ag, no statistical differences were found. The presence of nanoparticles did not affect Streptococcus mutans growth in the heat-polymerized PMMA resin. Value differences of S. mutans were not significant for comparisons between groups 1-2 and 3-4. Silver nanoparticles presented antifungal activity against C. albicans in polypropylene surfaces, but not in the heat-polymerized PMMA resin. Silver nanoparticles did not present antibacterial activity against S. mutans in any of the analyzed surfaces. Key words:Removable Partial Denture, Candida, Streptococcus mutans.

Early childhood caries prevalence among children with cleft lip and palate at padjadjaran university dental hospital

Background: Cleft lip and/or palate (CL/P) is a congenital abnormality that can be a risk factor for Early Childhood Caries (ECC). ECC is caries that occur in children aged 0-71 months. Poor oral hygiene often found in CL/P patients due to anatomic defects, treatment devices, and surgical scars that can facilitate the colonization of Streptococcus mutans and Lactobacilli as caries-causing bacteria. This study aims to determine the prevalence of ECC in children with CL/P aged 2-6 years at Padjadjaran Univeristy Dental Hospital from 2018 - June of 2021. Method: The study used a descriptive observational method with a cross-sectional approach. The data used is secondary data which is CL/P patients aged 2-6 years medical records at Padjadjaran University Dental Hospital from 2018 until June 2021. The sample obtained using total sampling is 102. Result: The prevalence of ECC in children with CL/P was 46.08%. Unilateral complete palatognatoschizis was the most found CL/P cases (49.02%), including patients with ECC (21.57%). Male is the most common gender in this study (62.75%) also the gender with the most ECC (28.43%). Most children aged 13-24 months (66,67%), while 25-60 months (22,55%) had the highest ECC cases. Most of the CL/P patients came from West Java (95.10%), including patients with ECC (43.14%) Conclusion: Children with CLP have a high risk of caries, regardless in this study, the prevalence was not that high. Although, there are still a hefty amount of children who experience ECC. Oral hygiene must be a concern of parents from an early age to prevent ECC.

A Prospective Longitudinal Study of Early Childhood Caries Onset in Initially Caries-Free Children.

Early childhood caries (ECC) is a complex oral disease that is prevalent in US children. The purpose of this 2-y prospective cohort study was to examine baseline and time-dependent risk factors for ECC onset in initially caries-free preschool children. A cohort of 189 initially caries-free children aged 1 to 3 y was recruited. At each 6-mo study visit, children were examined using the ICDAS index; salivary samples were collected to assess mutans streptococci (MS), lactobacilli, Candida species, salivary cortisol (prior and after a stressor), and salivary IgA. Diet and oral health behavior were assessed from parent report. Child and family stress exposure was assessed from measures of psychological symptoms, stressful life event exposure, family organization and violence exposure, and social support. Sociodemographic factors were also considered. A Kaplan-Meier estimator of survival function of time to ECC and a Cox proportional hazards model were used to identify predictors of ECC onset. Onset of ECC was associated with high salivary MS levels at baseline (log-rank test, P < 0.0001). Cox proportional hazards regression showed that the risk of dental caries significantly increased with salivary MS in log scale over the 6-mo period (hazard ratio, 1.08; P = 0.01). Other risk factors in the model did not reach statistical significance. Our results provide prospective evidence that an increase in salivary MS predicts ECC onset in young, initially caries-free children, confirming that a high salivary MS count likely plays a causal role in ECC onset, independent of covariates. These results suggest that we must focus on reducing salivary MS counts in young children and preventing or delaying MS colonization in infants and young children determined to be at risk for ECC.

THE EVALUATION OF Streptococcus Mutans COLONIZATION IN PRIVATE SCHOOL NURSERY-KINDERGARTEN CHILDREN's TOOTHBRUSH AT DIYARBAKIR REGION

AIM: Disinfection of the toothbrush is an essential parameter for oral hygiene. As a result, especially children can not clean their toothbrushes sufficiently after brushing their teeth. The purpose of this study was to evaluate the accumulation level of Streptococcus mutans colonization at private school nursery-kindergarten children's toothbrushes and evaluate the effectiveness of chlorhexidine solution in four weeks for disinfection. METHODS: This study was approved by the local ethics committee. Two hundred thirty-four private school nursery-kindergarten children were selected for this study, who's aged between 24-72 months. These selected children for this study did not have any dental, antibiotic, antimycotic treatment in the last three months. Before the study, a survey was conducted about parents' education, employment, the income. A pediatric dentist made an oral examination of these children, dental caries, fillings, and missing teeth were determined. Children were divided into two groups; toothbrushes, toothpaste, and practical solutions distilled water and %0,12 chlorhexidine gluconate solution was given in a bottle for four weeks. In addition, the toothbrushes of children were collected every week. After incubation, Streptococcus mutans colonization was evaluated under stereomicroscope. All the collected data were statistically evaluated. RESULTS: The DMF-T scores were statistically significant when evaluated with parents' education and income (p&amp;lt;0,05), but there was no statistical relationship between parents' employment and DMF-T scores (p0,05). Streptococcus mutans colony reduction at the Chlorhexidine group was statistically significant (p&amp;lt;0,05). CONCLUSION: From the first brushing, toothbrushes can be contaminated with bacteria. If the toothbrushes are not clean sufficiently, the bacteria taken from the oral environment have a chance to form a colony on the toothbrushes with the effect of moisture. In addition, Streptococcus Mutans is a bacteria that can stay on toothbrushes and cause re-infection. This study shows that toothbrush disinfection is essential to prevent bacteria from re-infection and contamination of oral flora.

Ca19Zn2(PO4)14 Nanoparticles: Synthesis, characterization and its effect on the colonization of Streptococcus mutans on tooth surface

The main cause of tooth decay is the biofilm formation of Streptococcus mutans. This study aimed to investigate the effect of the zinc oxide nanoparticles (ZnO NPs), hydroxyapatite nanoparticles (Ca10(PO4)6(OH)2) (HAP NPs), zinc oxide/hydroxyapatite nanocomposites (ZnO/HAP NCs), and Zn-substituted hydroxyapatite nanoparticles (Ca19Zn2(PO4)14 NPs) on the growth and biofilm formation, bacterial adherence, and the expression of ftf and gtf genes in Streptococcus mutans. The nanostructures were prepared via simple and fast co-precipitation route. Twelve isolates of Streptococcus mutans collected from children with dental caries referred to the dental clinic of Kashan University of Medical Sciences. All S. mutans isolates were susceptible to Ampicillin. The mean MIC for ZnO NPs, HAP NPs, Ca19Zn2(PO4)14, and ZnO/HAP NCs were 118, 260, 70.6, and 994 µg/mL, respectively. All prepared nanostructures significantly reduced biofilm formation at MIC and sub-MIC concentrations (p < 0.01). In biofilm and cell culture treated with nanoparticles, the expression of ftf and gtfC genes decreased. Results were shown that IC50 for the Ca19Zn2(PO4)14 was 8.5, and for non-toxic concentration, was 0.065 µg/mL. The attachment rate to the denture surface and HGF1 cell line treated with the Ca19Zn2(PO4)14 NPs has decreased. The results showed that the Ca19Zn2(PO4)14 NPs has a better effect than the ZnO/HAP NCs. It can therefore be used as a coating on dental surfaces. Investigation of Ca19Zn2(PO4)14 NPs form for covering dental teeth surface recommended in future study.

Changes in Color Stability and Surface Roughness of Teflon-Coated Arch Wires After Clinical Use.

Peeling of polytetrafluoroethylene (Teflon)-coated esthetic arch wires results in rough surfaces that may cause plaque accumulation, and the exposed core material may not meet the esthetic expectations of patients. The aim of this study was to evaluate the in-vivo surface roughness, Streptococcus mutans colonization, and color stability of Teflon-coated arch wires from 3 different manufacturers. Surface roughness and color data of 0.016-inch and 0.016 × 0.022-inch Teflon-coated arch wires from 3 different manufacturers were recorded as they were received (T0) and after 28 days of clinical exposure (retrieved) (T1) using an atomic force microscope and a spectrophotometer. The amount of S. mutans was assessed in terms of colony-forming units on the as-received and retrieved wires. The surface roughness increased significantly, and a clinically noticeable color change was observed in all groups after clinical use (P < .005). There was no statistically significant difference in the amount of S. mutans adhesion for most of the wires. No significant correlation was found between the amount of S. mutans adhesion and the surface roughness. All the arch wires showed increased surface roughness and clinically noticeable color change. The surface roughness values were not found to be correlated with the amount of S. mutans adhesion.

Contamination of Low Frictional Elastomeric Ligatures by Streptococcus mutans: A Prospective RT-PCR and AFM Study.

To compare Streptococcus mutans colonization between low-friction elastomeric ligatures and to correlate microbial colonization levels with the surface roughness status. The study included 160 premolars of 10 patients. During the study period, which consisted of 4 sessions each lasting 4 weeks, the ligature types Slide™ Low-Friction Ligature (Leone, Firenze, Italy), Tough-O Energy™ (Rocky Mountain Orthodontics, Denver, USA), and Sili Ties™ (Dentsply Sirona, Surrey KT13 0NY, UK), and steel ligatures (American Orthodontics, Sheboygan, USA) as a control, were fixed to the premolar teeth by clockwise rotation among the jaw quadrants. The plaque index (PI) and gingival index (GI) were obtained before bonding (T0), 6 weeks after bonding (T1), and subsequently every 4 weeks (T2, T3, T4). Presence of S. mutans was analyzed by real-time polymerase chain reaction at T1, T2, T3, T4. Surface roughness was evaluated with Atomic Force Microscopy (AFM) before ligation (Ra0) and after (Ra1) ligation. The paired t-test, ANOVA, repeated measures of ANOVA, and the Kruskal-Wallis test were used for the statistical analysis. S. mutans colonization was significantly higher on the Slide group (P < .05). The lowest Ra0 was seen in Slide and the highest was seen in the Tough-O Energy group. There was no correlation between S. mutans colonization and Ra1 parameters of elastomeric groups (P > .05). S. mutans colonization showed variations in low-friction elastomeric ligatures independent of surface roughness. Ringshaped low-friction elastomeric ligatures were not different from the steel ligature in terms of S. mutans colonization.

Oral colonization of Candida albicans and Streptococcus mutans in children with or without fixed orthodontic appliances: A pilot study

Background/purposeAdolescents undergoing fixed orthodontic therapy have an increased risk of oral diseases due to additional plaque accumulation sites. However, the effect of fixed orthodontics appliances (FOAs) on the colonization of Candida albicans (Ca) and Streptococcus mutans (Sm), two synergistic oral pathogens, is largely unknown and was, therefore, the primary objective of this pilot investigation. Material and methodsSixteen children aged 10–15 years were enrolled, nine in the FOA and seven in the control groups. Saliva and occlusal plaque were collected, and the Ca and Sm levels were quantified with a quantitative real-time polymerase chain reaction (qPCR) assay. ResultsA trend of higher Ca levels was observed in the saliva and occlusal plaque of the FOA group, while the control group contained higher levels of Sm. Furthermore, for Sm levels, a positive correlation between saliva and occlusal plaque was shown in both the FOA and control groups; in contrast, Ca levels were negatively correlated between these samples only in the FOA group. Between Ca and Sm, a positive correlation was observed in saliva and occlusal plaque in the control group; however, this relationship was disrupted in the FOA group. ConclusionOur preliminary study demonstrated that the presence of FOAs disturbs the colonization of Ca and Sm within the oral cavity. This perturbation might increase orthodontic patients’ risk for Ca- and Sm-related diseases.

Salivary counts of Streptococcus mutans and Lactobacillus in patients with and without cleft lip and/or palate undergoing orthodontic treatment: A meta-analysis.

To conduct a systematic review with meta-analysis to assess if cleft lip and palate (CLP) patients undergoing orthodontic treatment have a higher colonization of Streptococcus mutans and Lactobacillus than patients without this condition. Five electronic databases were searched systematically. The inclusion criteria were as follows: randomized clinical trials, non-randomized, or quasi-randomized controlled trials, prospective and retrospective studies published until March, 2021; articles that evaluated S.mutans and Lactobacillus profile in patients with and without cleft lip and palate undergoing orthodontic treatment. The random-effect model was used to perform the analysis of all the data collected. Statistic heterogeneity was evaluated with I2 test. In this systematic review, 2 cohort studies were included. The data analysis from 160 patients revealed that patients without cleft lip and palate had 4.5 times more predisposition to oral colonization with S.mutans than CLP patients. No statistical significant difference was found between these patients for colonization with Lactobacillus. Despite the limitations in the included studies, this systematic review suggested that CLP patients have a lower predisposition to oral colonization with S.mutans when compared to healthy patients.

In Vivo Colonization with Candidate Oral Probiotics Attenuates Colonization and Virulence of Streptococcus mutans.

A collection of 113 Streptococcus strains from supragingival dental plaque of caries-free individuals were recently tested in vitro for direct antagonism of the dental caries pathogen Streptococcus mutans, and for their capacity for arginine catabolism via the arginine deiminase system (ADS). To advance their evaluation as potential probiotics, twelve strains of commensal oral streptococci with various antagonistic and ADS potentials were assessed in a mouse model for oral (i.e., oral mucosal pellicles and saliva) and dental colonization under four diets (healthy or high-sucrose, with or without prebiotic arginine). Colonization by autochthonous bacteria was also monitored. One strain failed to colonize, whereas oral colonization by the other eleven strains varied by 3 log units. Dental colonization was high for five strains regardless of diet, six strains increased colonization with at least one high-sucrose diet, and added dietary arginine decreased dental colonization of two strains. Streptococcus sp. A12 (high in vitro ADS activity and antagonism) and two engineered mutants lacking the ADS (ΔarcADS) or pyruvate oxidase-mediated H2O2 production (ΔspxB) were tested for competition against S. mutans UA159. A12 wild type and ΔarcADS colonized only transiently, whereas ΔspxB persisted, but without altering oral or dental colonization by S. mutans In testing four additional candidates, S. sanguinis BCC23 markedly attenuated S. mutans' oral and dental colonization, enhanced colonization of autochthonous bacteria, and decreased severity of smooth surface caries under highly cariogenic conditions. Results demonstrate the utility of the mouse model to evaluate potential probiotics, revealing little correlation between in vitro antagonism and competitiveness against S. mutans in vivo IMPORTANCE Our results demonstrate in vivo testing of potential oral probiotics can be accomplished and can yield information to facilitate the ultimate design and optimization of novel anti-caries probiotics. We show human oral commensals associated with dental health are an important source of potential probiotics that may be used to colonize patients under dietary conditions of highly varying cariogenicity. Assessment of competitiveness against dental caries pathogen Streptococcus mutans and impact on caries identified strains or genetic elements for further study. Results also uncovered strains that enhanced oral and dental colonization by autochthonous bacteria when challenged with S. mutans, suggesting cooperative interactions for future elucidation. Distinguishing a rare strain that effectively compete with S. mutans under conditions that promote caries further validates our systematic approach to more critically evaluate probiotics for use in humans.

Degree of Streptococcus mutans Colonization on Common Restorative Materials Subjected to Wear Cycle.

To investigate and compare the degree of Streptococcus mutans (SM) colonization before and after in vitro wear simulation on monolithic zirconia (MZ), lithium disilicate (LD), ceramo-metal (CM), and composite resin (CR) specimens. Sixteen circular discs (10 × 3 mm) were fabricated for each group (MZ, LD, CR, CM). Half of the samples from each group (n = 8) were subjected to a wear cycle (n = 32 in total). The wild-type SM bacteria was incubated, diluted, and cultured for growth on the specimens with polished (n = 32) and worn surfaces (n = 32). The number of bacteria was calculated from colony-forming units (CFU). ANOVA followed by Tukey honest significant difference test (α < .05) was used for statistics. SM adhesion on the polished surfaces of all the tested materials exhibited similar values (P = .215), with the number of SM being lowest for LD (21.87 ± 28.14) and highest for CM (90.62 ± 76.69). After the wear cycle, ANOVA indicated significant differences (P = .000) for the number of bacteria between pre- and postwear conditions of all groups. MZ (21,028 ± 1,507.98) and CM (13,025 ± 2,690.85) showed the highest and lowest numbers of SM colonies, respectively. According to t test, postwear SM adhesion to all materials (P = .000) was significantly higher. SM colonization on the worn surfaces of all the materials showed significant differences (P < .05), except for between LD and CR (P = .973). Polished surfaces of evaluated materials showed similar SM colonization, which emphasizes the importance of following the minimum requirements of the polishing/glazing procedures. SM colonization on the material surfaces significantly increased after wear. MZ and CM possessed the highest and lowest SM colonizations, respectively.

Dietary Sugars, bacterial colonization and the behavior of fruit flies

Cavity remains prevalent in young children today. One major contributor is the modern diet, specifically the large amounts of dietary sugars consumed. Another key factor is bacteria in our mouth that eat these sugars. Streptococcus mutans among other acid producing bacteria is one of the leading microbes that initiate and promote cavity (tooth decay). It metabolizes sugars to produce plaque, which can build up over time and simultaneously increase acid production that causes cavity. So studying how quickly different sugars affect Streptococcus mutans colonization is important to understand the development of cavity and its impact on host behavior. My hypothesis was that S. mutans breaks down some sugars more efficiently and as a result, can colonize more quickly with some than others and produce more acid, thus impacting host behavior.To study bacterial colonization, I used a fruit fly model because fruit flies like sugars and Streptococcus mutans can readily colonize fruit flies when is mixed with sugars. Each sugar solution was mixed with green fluorescent protein (GFP) labeled S. mutans and fed fruit flies. We then waited for 6 days to let flies eat and grow at room temperature. After this incubation period, we took flies out every 2 days to image the green color under the fluorescent microscope, which indicates S. mutans colonization. On the final day, we took all of the remaining flies, ground them up, and performed appropriate dilutions to plate and count bacterial colonies, which represents bacterial colonization of flies. Colonization of flies fed with five different sugars by S. mutans was monitored by direct imaging and counting bacterial colony forming units. Flies fed with sucrose exhibited the best colonization, while flies fed with xylitol did not show any colonization. The pH values of S. mutans cultures (pH adjusted to 7.5) fed with different sugars were monitored using a pH meter. With all sugars, the pH dropped significantly after five minutes. The pH dropped below 4.5 with sucrose that supports the best colonization. The pH dropped at an average of 2.91 during the 30 minutes testing period, suggesting sugars and bacteria fuel acid production.Furthermore, flies colonized by S. mutans fed with sucrose were monitored for their behavior (locomotion) using beam breaks and analyzed by DAMsystems308 software. Sucrose fed flies exhibited more bacterial colonization and became hyperactive. Overall the data indicated that S. mutans utilizes some dietary sugars more efficiently and as a result, can colonize better, produce more acid and become more active. Our studies demonstrated that the interactions between bacteria and sugars are important for the development of cavity and impact host behavior.

Human Leucocyte Antigen Profile and Transmission of Mutans Streptococci in Mother-Child Pairs.

To investigate possible association between the transmission of mutans streptococci and sharing the immune system component Human Leucocyte Antigen (HLA) class II in mother-child pairs. Plaque samples from 43 mother-child pairs were cultivated and screened for mutans streptococci. In 14 pairs where both mother and child harboured the bacteria, the strains were genotyped by Random Amplified Polymorphic DNA and samples were run on PAGE gels. Analysis of genetic identity between mother and child strains was performed with help of software and Dice similarity index. The distribution of HLA of serogroup DR4 (HLA DR4) was studied in relation to maternal transmission and mutans streptococci colonisation in children. The study hypothesis was that in pairs where both mother and child were HLA DR4 positive, transmission of mutans streptococci was more likely. No correlation between the presence of HLA DR4 in mother and child and maternal transmission of mutans streptococci was established. However, the results showed no linkage between mutans streptococci colonisation and HLA DR 4. Of 15 children with mutans streptococci, 12 were HLA DR4 positive. The result suggests that presence of HLA DR4 could be a predisposing factor for colonisation with mutans streptococci in children.