Acid tolerance mechanisms utilized by Streptococcus mutans.

Acid-tolerant bacteria such as Streptococcus mutans, Acidobacterium capsulatum, Escherichia coli, and Propionibacterium acidipropionici have developed several survival mechanisms to sustain themselves in various acid stress conditions. Some bacteria survive by minor changes in the environmental pH. In contrast, few others adapt different acid tolerance mechanisms, including amino acid decarboxylase acid resistance systems, mainly glutamate-dependent acid resistance (GDAR) and arginine-dependent acid resistance (ADAR) systems. The cellular mechanisms of acid tolerance include cell membrane alteration in Acidithiobacillus thioxidans, proton elimination by F1-F0-ATPase in Streptococcus pyogenes, biofilm formation in Pseudomonas aeruginosa, cytoplasmic urease activity in Streptococcus mutans, synthesis of the protective cloud of ammonia, and protection or repair of macromolecules in Bacillus caldontenax. Apart from cellular mechanisms, there are several acid-tolerant genes such as gadA, gadB, adiA, adiC, cadA, cadB, cadC, speF, and potE that help the bacteria to tolerate the acidic environment. This acid tolerance behavior provides new and broad prospects for different industrial applications and the bioremediation of environmental pollutants. The development of engineered strains with acid-tolerant genes may improve the efficiency of the transgenic bacteria in the treatment of acidic industrial effluents. KEY POINTS: • Bacteria tolerate the acidic stress by methylating unsaturated phospholipid tail • The activity of decarboxylase systems for acid tolerance depends on pH • Genetic manipulation of acid-tolerant genes improves acid tolerance by the bacteria.

Discrepancy in the dynamic metabolic progression of the dental biofilm leads to dental caries, which is a polymicrobial infection. The homeostasis of the biofilm is unaffected and is not apparent unless there is an imbalance in the mineralization pattern of the supragingival biofilm. Literature provides numerous facts on microorganisms related to dental caries. Pathologic colonizers in the early stages of tooth decay involve organisms like Streptococcus oralis, subsequent adherence of Streptococcus sobrinus, and Streptococcus mutans[1]. Reports suggest the association of highly complex, variable, and uncultivable microbial population with dental caries, even though prime organisms are commonly known to be allied with disease succession. Association of mutans group streptococci and lactobacilli with the initiation of caries and early caries development have been well documented [2]. Studies have shown transition of early caries causing gram-positive primary facultative bacteria to anaerobic gram-positive rods and cocci and gram-negative rods as the lesion progresses to deep carious lesion[3]. Mapping of bacterial taxa revealed up to 14 phyla along with 101 genera. This comprised around 706 diverse OTUs (Operational Taxonomic Units). Caries progression at various stages and bacterial profile of different species associated with several disease have been observed. Some of the observed species found abundantly in whitespot lesion and dentin lesion of both dentitions were S. Parasanguinis and S. salivarius[4]. Molecular methods for bacterial identification and enumeration are performed routinely to precisely study bacterial species associated with dental caries, including those that are not presently cultivable.

Streptococcus mutans naturally occurs in the human oral cavity, is a microorganism that plays an important role in the initiation of dental caries. One of the efforts to prevent dental caries is the use of natural ingredients that contain antibacterial substances that can interfere with the growth or kill bacteria. Nutmeg is a natural ingredient that has antibacterial properties. Bioactive compounds in nutmeg seeds have antibacterial properties. This research aimed to determine the formulation and concentration of nutmeg seed extract which has antibacterial activity against Streptococcus mutans. The type of research used is a laboratory experiment with a post test only group design. The treatment group used purified extract of nutmeg seeds with concentrations of 25%, 20%, 15%, 10%, 7.5%, 5.0%, 2.5%, 1.25%, the positive control group used mouthwash I, T and L. The test was carried out three repetitions at each concentration, then the inhibition zone was measured using the well diffusion method. Antibacterial activity testing was carried out using the well method, the data were analyzed using the Shapiro-Wilk test, the Levene test, the one way annova test and the PST hock test. Obtained the average inhibition of nutmeg seeds against Streptococcus mutans at a concentration of 25% (18.33 mm). 20% concentration (17.16 mm), 15% concentration (16.16 mm), 10% concentration (14.66 mm), 7.5% concentration (13.33 mm), 5% concentration (6.66 mm ), the concentration of 2.5% (2.6 mm) and the smallest concentration of 1.25% had no inhibition (0 mm), while in the control group I (4 mm), T (3 mm) and L (2 mm). The higher the concentration of purified extract of nutmeg seeds, the higher the antibacterial activity against Streptococcus mutans. further research on the concentration of nutmeg seed extract preparations was carried out in vivo tests on experimental animals in order to obtain purified extract preparations of nutmeg seeds that are safe and can be an alternative choice in maintaining oral health.

ObjectivesThere is a significant apprehension in medicine and dentistry concerning the emergence of antibiotic-resistant pathogens, as it composes a significant threat to global health, particularly oral health. The growing concern that oral pathogens may develop resistance against standard preventive measures raises the need for alternative measures to prevent these pathogens’ growth without inducing microbial resistance. Therefore, this study aims to assess the antibacterial properties of eucalyptus oil (EO) against two main oral disease pathogens, Streptococcus mutans, and Enterococci faecalis.MethodsS. mutans and E. faecalis biofilms were initiated using brain-heart infusion (BHI) broth supplemented with 2% sucrose with and without diluted EO. After 24 h of biofilm formation, total absorbance was measured via spectrophotometer; then, the biofilm was fixed, stained with crystal violet dye, and measured at 490 nm. An Independent t-test was used to compare the outcomes.ResultsDiluted EO revealed significant total absorbance reduction against S. mutans and E. faecalis compared to the control (p ≤ 0.001). For the biofilm measurement, S. mutans and E. faecalis biofilms were reduced by around 60- and 30-fold, respectively, compared to the group with no EO (p ≤ 0.001).ConclusionBased on this study’s results, using EO as an organic compound could be considered an adjunctive tool in preventing the growth of oral pathogens causing dental caries and endodontic infection.

To evaluate the emerging drug resistance among the caries pathogens isolated from carious dentine microbiologically. Specimens from dental caries were collected from 75 patients referred to Department of Conservative Dentistry and Endodontics, Vyas Dental College. Microbiological processing of all the samples was done within three hours to isolate the caries pathogens. The samples were inoculated on agar medium (Nutrient agar, Mac-conkey's agar) at 370C for 48 hours aerobically. The identification of strains was done by observing colony morphology and gram's staining. The predominant isolates were subjected to antimicrobial sensitivity test (Kirby Bauer's method). Statistical analysis of the isolates was done using paired t-test. Out of 75 patients more common isolates were Staphylococcus aureus, Klebsiella, Pseudomonas aeruginosa, Yeast. The predominant were Staphylococcus and Pseudomonas species. Newer antibiotics were proved to be effective against these predominant strains after evaluating antibiotic sensitivity tests. Although Streptococcus mutans (S.mutans) is the most prevalent microorganism seen in dental caries, the role of other microorganisms like Staphylococcus, Pseudomonas in initiation and progression of caries is evident from this study. Further extensive and large scale studies need to be conducted for better understanding the role of these microorganisms in dental caries.

IntroductionDental caries is a ubiquitous bacterial infection that has afflicted people for years. Streptococci mutans (S. mutans) are markers of dental caries and the population of S. mutans in the saliva is directly related to the number of surfaces colonized by them. Any intervention that can inhibit their growth and survival will negatively impact the initiation and progress of caries. Various antimicrobial agents have been tested against these microorganisms. The goal of this study was to assess the efficacy of cocoa bean husk, ginger, and chlorhexidine mouth rinse on S. mutans and Lactobacillus.Materials and methodsWe conducted a randomized controlled trial involving patients aged 18 to 25 years from July to September 2018. The study population was allocated into three groups. Each group received either cocoa bean, ginger, or chlorhexidine mouth rinses. The study followed a Latin square design. Study participants were instructed to use the assigned mouth rinse once daily for seven days. We collected saliva samples to measure S. mutans and Lactobacillus populations.ResultsCocoa bean husk and chlorhexidine rinses produced a significant reduction of S. mutans (p < 0.05). The ginger-based rinse significantly reduced the Lactobacillus population (p < 0.05).ConclusionOur findings indicate these natural mouth rinses offer promising anticariogenic and antiplaque efficacy as cost-effective alternatives to traditional mouth rinses.

Understanding the broader biological impact of carolacton, a macrolactone natural product, has been ongoing for the past decade. Multiple studies have shown connections to regulatory systems, acid tolerance mechanisms, biofilm formation, and recently folate dehydrogenase (FolD). Progress elucidating the cause of biofilm-specific activity in Streptococcus mutans has been limited due to low-throughput analyses of carolacton-treated cells. We disclose the discovery of a simplified carolacton-inspired analog that demonstrates inhibitory activity against S.mutans biofilm cells. This discovery permitted a proof of concept chemical genetic screen of S.mutans mutants identifying the carbon catabolite protein A signaling pathway as a putative target.

Crystal Structure of the V-region of Streptococcus mutans Antigen I/II at 2.4 Å Resolution Suggests a Sugar Preformed Binding Site

Effect of carbohydrate fatty acid esters on Streptococcus sobrinus and glucosyltransferase activity

Objective The main objective of the present study was to do the comparative study of clove oil and clove extract on the oral micro-biota causing dental caries and also to assess the antifungal activity. Materials and Methods The antimicrobial activity of clove oil and clove extract was assessed against Halobacterium sp., Lactobacillus sp., Pseudomonas sp., Micrococcus sp. and Streptococcus mutans (major causative bacteria of dental plaque) by the paper disc diffusion method. For each extract three replicate trials were conducted against each organism. The antifungal activity of clove oil and extract was also assessed against seven fungal species (Aspergillus niger, A. fumigatus, Aspergillus sp., Alternaria sp., Rhizomucor sp., Rhizopus sp. and Penicillium sp.) by agar disc diffusion method. Results Both clove oil and clove extract was found to exhibit broad spectrum of antibacterial activity inhibiting all the ten test bacterial species involved in dental caries. Clove oil produced maximum inhibition zone of diameter (IZD) against themajor causative bacteria of dental plaque as compared to clove extract, thereby, showing that clove oil possesses strong bactericidal activity against oral pathogens. The highest inhibition zone of diameter was observed by clove oil as compared to clove extract against the test fungal species Conclusion The clove oil has the potential to be used as a natural antibacterial agent for oral pathogens.

An extract of oolong tea (semifermented tea leaves of Camellia sinensis) and its chromatographically isolated polyphenolic compound was examined for in vitro inhibitory effects on glucosyltransferases (GTases) of mutans streptococci and on caries development in Sprague-Dawley rats infected with mutans streptococci. The samples showed no detectable effect on the growth of mutans streptococci. However, insoluble glucan synthesis from sucrose by the GTases of Streptococcus mutans MT8148R and Streptococcus sobrinus 6715 was markedly inhibited, as was sucrose-dependent cell adherence of these mutans streptococci. The administration of the oolong tea extract and the isolated polyphenol compound into diet 2000 and drinking water resulted in significant reductions in caries development and plaque accumulation in the rats infected with mutans streptococci. The active components in the oolong tea extract were presumptively identified as polymeric polyphenols which were specific for oolong tea leaves. These results indicate that the oolong tea polyphenolic compounds could be useful for controlling dental caries.

The study is based on the fact that common dental diseases affect a very significant part of the population. Even today with all the present literature, research and development against these diseases; dental caries and gingivitis affect all people in varying socioeconomic status. Through years of meticulous research the various causative organisms have been identified, however both dental caries as well as gingivitis are multibacterial and multifactorial diseases. Besides, the use of antibiotics is not a piece of cake due to the alarming rise in antibiotic resistance. This implies the need for newer, more natural sources of medicines at an affordable price to serve the society as a whole. Turbinaria conoides has antibacterial potential; however its scope against oral pathogens has never been scaled before. The study aims at achieving a sustainable cure with the use of natural resources and implies its development and use through incorporation into mouthwash and toothpaste; to extract antibacterial compounds from Turbinaria conoides, to determine the bactericidal property of Turbinaria conoides against Streptococcus mutans and Actinomycetes and to determine the minimal inhibitory concentration of the extract and to compare the effect of the extract between the two oral microorganism.

Recent RNA sequencing studies have given us a deeper insight into the cariogenic impact of carbohydrate sources in the bacterium Streptococcus mutans, the principal microbial agent in dental caries etiopathogenesis. The process of dental caries development is facilitated by the ability of this bacterium to ferment some carbohydrates into organic acids contributing to a pH decrease in the oral cavity and the demineralization of the hard tissues of the tooth. Furthermore, in dental caries progression, biofilm formation, which starts and ends with free planktonic cells, plays an important role and has several unique properties called virulence factors. The most cariogenic carbohydrate is sucrose, an easily metabolizable source of energy that induces the acidification and synthesis of glucans, forming typical bacterial cell clumps. We used multifaceted methodological approaches to compare the transcriptomic and metabolomic profiles of S. mutans growing in planktonic culture on preferred and nonpreferred carbohydrates and in fasting conditions. Streptococcus mutans in a planktonic culture with lactose produced the same pH drop as glucose and sucrose. By contrast, xylitol and lactose showed high effectiveness in regulating intracellular polysaccharide metabolism, cell wall structure, and overall virulence involved in the initial phase of biofilm formation and structure but with an opposite pattern compared with sucrose and glucose. Our results confirmed the recent findings that xylitol and lactose play a vital role in biofilm structure. However, they do not reduce its formation, which is related to the creation of a cariogenic environment.

Risk-specific caries prevention requires validated and simple parameters for a caries risk assessment. The aim of the study was to evaluate the validity of a site-specific chair-side mutans streptococci (MS) test for the prediction of caries incidence in fissures. In 230 6- to 7-yr-old children, occlusal plaque samples of teeth 16 and 36 were cultured with Dentocult SM tests at 37 degrees C for 24 hr. Caries (DMFS), initial caries, sealants, and a plaque index (QHI) were recorded and oral hygiene habits were assessed. Not erupted, carious, filled and sealed teeth were excluded from the analysis (n = 154). After 2 yr, the status of the fissures was re-examined, and a fluoride history was recorded with a questionnaire filled out by the children's parents. Sealed teeth were excluded again (n = 54). With a classification of MS score 0 or 1 as low and MS score 2 or 3 as high caries risk, 92% agreement was reached by two independently working examiners. The MS scores and caries incidence correlated significantly. Seventy-eight % of the caries progression in fissures was prognosed correctly. Sensitivity was 50%, specificity 82%, positive predictive value 29%, and negative predictive value 92%. Children with caries progression tended to have lower fluoride scores. Low MS scores were most likely to be associated with low caries incidence, while high mutans streptococci scores seem to be partially compensated by other parameters.

Background: Micro-organisms resistant to most of the commercial antibiotics are rapidly expanding and there is an urgent need for detection of novel antimicrobial compounds. Tooth decay is a dental infection with bacterial sources such as Streptococcus mutans and Streptococcus sanguis. Objectives: The present study aimed to evaluate the in vitro antibacterial effects of different concentrations of Citrus limon peel, pineapple fruit, and pineapple peel extracts on oral pathogens such as S. mutants and S. sanguis. Materials and Methods: In this experimental study, the hydroethanolic extracts of the selected plants were prepared by maceration method and their antibacterial effects were evaluated by agar well diffusion method. Results: Two-fold dilutions of plant extract solutions were tested to determine the minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against each selected microorganism. The results of the current study revealed that pineapple peel extracts had the highest antibacterial effect on S. sanguis (MIC: 1.56 mg/mL and MBC: 3.12 mg/mL). Pineapple fruit had the lowest antibacterial activity against S. mutans (MIC: 25 mg/mL and MBC: 100 mg/mL). C. limon peel had significant antibacterial activity against S. mutans and S. sanguis. Conclusion: The peel of C. limon and pineapple had significant antibacterial activity against cariogenic microorganisms such as S. mutans and S. sanguinis.