Mutacins of Streptococcus mutans

Streptococcus mutans supernatant affects the virulence of Candida albicans

Candida albicans causes a variety of clinical manifestations through multiple virulence factors that act simultaneously to overcome the immune system and invade the host tissues. Owing to the limited number of antifungal agents available, new candidiasis therapeutic strategies are required. Previous studies have demonstrated that the metabolites produced by Streptococcus mutans lead to a decrease in the number of Candida cells. Here, for the first time, we evaluated whether the C. albicans cells that survived the pretreatment with S. mutans supernatant can modify their virulence factors and their capability to infect Galleria mellonella larvae. Streptococcus mutans supernatant (SM-S) was obtained by filtering the culture supernatant of this bacterium. Then, C. albicans cells were pretreated with SM-S for 24 h, and the surviving cells were evaluated using in vitro and in vivo assays. The C. albicans pretreated with SM-S showed a significant inhibition of hyphal growth, an altered adhesion pattern, and an impaired capability to form biofilms; however, its proteolytic activity was not affected. In the in vivo assays, C. albicans cells previously exposed to SM-S exhibited a reduced ability to infect G. mellonella and a higher amount of circulating hemocytes. Thus, SM-S could inhibit important virulence factors of C. albicans, which may contribute to the development of new candidiasis therapeutic strategies.

Study on the role of nano antibacterial materials in orthodontics (a review)

Nanoparticles (NPs) are insoluble particles with a diameter of fewer than 100 nanometers. Two main methods have been utilized in orthodontic therapy to avoid microbial adherence or enamel demineralization. Certain NPs are included in orthodontic adhesives or acrylic resins (fluorohydroxyapatite, fluorapatite, hydroxyapatite, SiO2, TiO2, silver, nanofillers), and NPs (i.e., a thin layer of nitrogen-doped TiO2 on the bracket surfaces) are coated on the surfaces of orthodontic equipment. Although using NPs in orthodontics may open up modern facilities, prior research looked at antibacterial or physical characteristics for a limited period of time, ranging from one day to several weeks, and the limits of in vitro studies must be understood. The long-term effectiveness of nanotechnology-based orthodontic materials has not yet been conclusively confirmed and needs further study, as well as potential safety concerns (toxic effects) associated with NP size.

Elucidating the Role and Structure-Activity Relationships of the Streptococcus oligofermentans Competence-Stimulating Peptide

Streptococcus oligofermentans is an early colonizer of the oral microbiome with documented bactericidal activity against the oral pathogen Streptococcus mutans. S. oligofermentans has been observed to possess the typical comABCDE competence regulon found within most oral streptococci; however, the competence-stimulating peptide (CSP) responsible for QS activation and the regulatory role of the competence regulon is yet to be explored. Herein, we have both confirmed the identity of the S. oligofermentans CSP and utilized a wide range of phenotypic assays to characterize its regulatory role in competence, biofilm formation, and hydrogen peroxide formation. To determine the importance of each amino acid residue in CSP/ComD binding, we performed systematic replacement of amino acid residues within the S. oligofermentans CSP and developed a luciferase-based reporter system to assess the ability of these mutated analogues to modulate the competence regulon. Additionally, we performed CD analysis on mutated CSP analogues to determine the correlation between the peptide secondary structure and QS activation. To further explore S. oligofermentans' potential as a biotherapeutic against S. mutans infection, lead QS activators and inhibitors were used in interspecies competition assays to assess the effect of QS modulation on interactions between these two species. Lastly, we have documented a lack of S. oligofermentans-induced cytotoxicity, highlighting the potential of this native flora as a biotherapeutic with minimal health risks.

Antifungal effects of Streptococcus mutans extract on Candida strains susceptible and resistant to fluconazole: An in vivo study

Previous studies showed that the crude extract obtained from Streptococcus mutans inhibited the growth of Candida albicans reference strains. In this study, we evaluated whether the antifungal effects of S. mutans extract can be extended to clinical Candida isolates, including C. albicans and non-abicans strains with different susceptibilities to fluconazole. We verified that S. mutans extract increased the survival of Galleria mellonella larvae infected with C. albicans and C. glabrata and inhibited the fungal cells in hemolymph. These antifungal effects occurred for both fluconazole-susceptible and fluconazole-resistant strains. However, larvae infected by C. krusei were not affected by S. mutans extract.

LAY SUMMARY

Streptococcus mutans crude extract shows antifungal effects on clinical Candida strains susceptible and resistant to fluconazole in Galleria mellonella model.

Toward understanding the signals of bacteriocin production by Streptococcus spp. and their importance in current applications

Microorganisms have developed quorum sensing (QS) systems to detect small signaling molecules that help to control access to additional nutrients and space in highly competitive polymicrobial niches. Many bacterial processes are QS-regulated; two examples are the highly related traits of the natural genetic competence state and the production of antimicrobial peptides such as bacteriocins. The Streptococcus genus is widely studied for its competence and for its ability to produce bacteriocins, as these antimicrobial peptides have significant potential in the treatment of infections caused by multiple-resistant pathogens, a severe public health issue. The transduction of a two-component system controls competence in streptococci: (1) ComD/E, which controls the competence in the Mitis and Anginosus groups, and (2) ComR/S, which performs the same function in the Bovis, Mutans, Salivarius, and Pyogenic groups. The cell-to-cell communication required for bacteriocin production in the Streptococcus groups is controlled mainly by a paralog of the ComD/E system. The relationships between pheromone signals and induction pathways are related to the bacteriocin production systems. In this review, we discuss the recent advances in the understanding of signaling and the induction of bacteriocin biosynthesis by QS regulation in streptococci. This information could aid in the design of better methods for the development and production of these antimicrobial peptides. It could also contribute to the analysis and emerging applications of bacteriocins in terms of their safety, quality, and human health benefits.

Complete Genome Sequence of Streptococcus mutans Strain MD, Which Produces Highly Potent Mutacins

Here, we report the complete genome sequence of Streptococcus mutans strain MD, which produces potent mutacins capable of inhibiting streptococci. MD is a relatively uncharacterized strain whose genome information was unavailable. This study provides useful information for comparative genomic study and for understanding the repertoire of mutacins in S. mutans.

Here, we report the complete genome sequence of Streptococcus mutans strain MD, which produces potent mutacins capable of inhibiting streptococci. MD is a relatively uncharacterized strain whose genome information was unavailable. This study provides useful information for comparative genomic study and for understanding the repertoire of mutacins in S. mutans.

Early childhood caries prevention: non-dental health professionals' viewpoint

BACKGROUND

Dental caries can develop early in life and have harmful consequences. Objective: To examine non-dental practitioners' knowledge of early childhood caries (ECC).

METHODS

A questionnaire on oral health and caries knowledge was emailed to five types of health professional who work with young children: paediatricians, GPs, midwives, paediatric nurses and paediatric healthcare assistants. Questions concerned: when a child should first visit a dentist; at what age toothbrushing should start; aetiopathogenic factors; early diagnosis; and the effect of breastfeeding.

RESULTS

494 health professionals (79 paediatricians, 59 physicians, 217 midwives, 92 paediatric nurses and 47 paediatric healthcare assistants) participated. Although most (89.86%) discussed oral health with parents, responses on when a child should first see a dentist and when toothbrushing should start varied. Almost half of respondents said they could diagnose caries but not all were confident in this. Aetiological factors in ECC mentioned included oral hygiene, bottle feeding, sugar intake, genetics and a lack of fluoride.

CONCLUSION

Non-dental practitioners lack knowledge about ECC, so cannot help prevent it. Initiatives including interprofessional training would improve their knowledge of oral health in early childhood.

Complete Genome Sequences of Two Mutacin-Producing Streptococcus mutans Strains, T8 and UA140

Streptococcus mutans is known to produce various antimicrobial peptides called mutacins. Two clinical isolates, T8 and UA140, are well characterized regarding their mutacin production, but genome sequence information was previously unavailable. Complete genome sequences of these two mutacin-producing strains are reported here.

Streptococcus mutans is known to produce various antimicrobial peptides called mutacins. Two clinical isolates, T8 and UA140, are well characterized regarding their mutacin production, but genome sequence information was previously unavailable. Complete genome sequences of these two mutacin-producing strains are reported here.

Isolation and Bacteriocin-Related Typing of Streptococcus dentisani

Streptococcus oralis subspecies dentisani is explored as an anti-cariogenic probiotic. Here, subjecting freshly stimulated saliva samples of 35 healthy volunteers, six epidemiologically unrelated and two related strains were isolated (prevalence around 20%) applying a newly developed three-step procedure. Furthermore, the probiotic strain S. dentisani 7746 (AB-Dentisanium®) was tested under a variety of environmental conditions for its inhibitory effect on six S. mutans, two S. sobrinus, 15 other oral or intestinal streptococci, 15 S. dentisani strains, and six representatives of other species including periodontopathogens. All except one of the S. mutans strains were inhibited by 7746 colonies or culture supernatant concentrate but only if either the test cell number was low or the producer or its bacteriocin concentration, respectively, was high. S. sanguinis OMI 332, S. salivarius OMI 315, S. parasanguinis OMI 335, S. vestibularis OMI 238, and the intestinal S. dysgalactiae OMI 339 were not inhibited, while the other 10 streptococcal strains (especially S. oralis OMI 334 and intestinal S. gallolyticus OMI 326) showed a certain degree of inhibition. From the panel of other bacterial species only Aggregatibacter actinomycetemcomitans was slightly inhibited. With the exception of OMI 285 and OMI 291 that possessed a 7746 bacteriocin-like gene cluster, all S. dentisani strains and especially type strain 7747^T were strongly inhibited by 7746. In conclusion, probiotic strain 7746 might antagonize the initiation and progression of dental caries by reducing S. mutans if not too abundant. S. dentisani strains inhibit each other, but strains with similar bacteriocin-related gene clusters, including immunity genes, are able to co-exist due to cross-resistance. In addition, development of resistance and adaptation to 7746-bacteriocins was observed during our study and needs attention. Hence, mechanisms underlying such processes need to be further investigated using omics-approaches. On the manufacturing level, probiotic strains should be continuously tested for function. Further clinical studies investigating inhibition of S. mutans by AB-Dentisanium® are required that should also monitor the impact on the oral microbiome composition including resident S. dentisani strains.

The Biology of Streptococcus mutans

As a major etiological agent of human dental caries, Streptococcus mutans resides primarily in biofilms that form on the tooth surfaces, also known as dental plaque. In addition to caries, S. mutans is responsible for cases of infective endocarditis with a subset of strains being indirectly implicated with the onset of additional extraoral pathologies. During the past 4 decades, functional studies of S. mutans have focused on understanding the molecular mechanisms the organism employs to form robust biofilms on tooth surfaces, to rapidly metabolize a wide variety of carbohydrates obtained from the host diet, and to survive numerous (and frequent) environmental challenges encountered in oral biofilms. In these areas of research, S. mutans has served as a model organism for ground-breaking new discoveries that have, at times, challenged long-standing dogmas based on bacterial paradigms such as Escherichia coli and Bacillus subtilis. In addition to sections dedicated to carbohydrate metabolism, biofilm formation, and stress responses, this article discusses newer developments in S. mutans biology research, namely, how S. mutans interspecies and cross-kingdom interactions dictate the development and pathogenic potential of oral biofilms and how next-generation sequencing technologies have led to a much better understanding of the physiology and diversity of S. mutans as a species.

Contribution of Streptococcus Mutans Virulence Factors and Saliva Agglutinating Capacity to Caries Susceptibility in Children: A Preliminary Study

BACKGROUND

Many factors contribute to caries development in humans, such as diet, host factors - including different saliva components - and the presence of acidogenic bacteria in the dental biofilm, particularly Streptococcus mutans (S. mutans). Despite the influence of S. mutans in caries, this bacterium is also prevalent among healthy individuals, suggesting the contribution of genetic variation on the cariogenic potential. Based on this hypothesis, the present work investigated the influence of S. mutans virulence factors and saliva agglutinating capacity on caries susceptibility in children.

STUDY DESIGN

Saliva samples of 24 children from low income families (13 caries-free and 11 caries-active individuals) were collected and tested for their ability to agglutinate S. mutans. The bacteria were isolated from these samples and analyzed for the presence of the gene coding for mutacin IV (mut IV). Biofilm formation and acid tolerance were also investigated in both groups (caries-free and caries-active).

RESULTS

Saliva samples from caries-free children showed an increased capacity to agglutinate S. mutans (p=0.006). Also, bacteria isolated from the caries-free group formed less biofilm when compared to the caries-active group (p=0.04). The presence of mut IV gene did not differ between bacteria isolated from caries-free and caries-active individuals, nor did the ability to tolerate an acidic environment, which was the same for the two groups.

CONCLUSIONS

Altogether, the results suggest that the adhesive properties of S. mutans and the agglutinating capacity of the saliva samples correlated with the presence of caries lesions in children.

Mother-to-child transmission of mutans streptococci

Mutans streptococci (MS) are the major group of pathogens implicated in dental caries. Like other infectious diseases, transmission of the causative microorganisms is the initial and essential step that should be understood relative to disease control and prevention. This review summarizes current knowledge regarding MS transmission, especially from mothers to their children. Included are methods used to study transmission, sources of MS, initial acquisition, factors concerning transmission and prevention of transmission. Information accumulated over many decades showed the involvement of MS transmission in the pathogenesis of caries, hence several preventive measurements have been proposed. Nevertheless, some essential aspects remain to be elucidated for more benefits of practical application.