Current classification of the oral streptococci

Limosilactobacillus reuteri inhibits the acid tolerance response in oral bacteria

Probiotic bacteria show promising results in prevention of the biofilm-mediated disease caries, but the mechanisms are not fully understood. The acid tolerance response (ATR) allows biofilm bacteria to survive and metabolize at low pH resulting from microbial carbohydrate fermentation. We have studied the effect of probiotic strains: Limosilactobacillus reuteri and Lacticaseibacillus rhamnosus on ATR induction in common oral bacteria. Communities of L. reuteri ATCC PTA5289 and Streptoccus gordonii, Streptococcus oralis, Streptococcus mutans or Actinomyces naeslundii in the initial stages of biofilm formation were exposed to pH 5.5 to allow ATR induction, followed by a low pH challenge. Acid tolerance was evaluated as viable cells after staining with LIVE/DEAD®BacLight™. The presence of L. reuteri ATCC PTA5289 caused a significant reduction in acid tolerance in all strains except S. oralis. When S. mutans was used as a model organism to study the effects of additional probiotic strains (L. reuteri SD2112, L. reuteri DSM17938 or L. rhamnosus GG) as well as L. reuteri ATCC PTA5289 supernatant on ATR development, neither the other probiotic strains nor supernatants showed any effect. The presence of L. reuteri ATCC PTA5289 during ATR induction led to down-regulation of three key genes involved in tolerance of acid stress (luxS, brpA and ldh) in Streptococci. These data suggest that live cells of probiotic L. reuteri ATCC PTA5289 can interfere with ATR development in common oral bacteria and specific strains of L. reuteri may thus have a role in caries prevention by inhibiting development of an acid-tolerant biofilm microbiota.

Dynamic interactions between Candida albicans and different streptococcal species in a multispecies oral biofilm

The oral cavity is colonized by a plethora of bacteria, fungi, and archaea, including streptococci of the mitis group (MSG) and the yeast Candida albicans. This study aims to investigate the role of streptococcal species in the development of oral biofilm and the cross-kingdom interactions between some of the members of the commensal MSG and the pathogen yeast C. albicans using a multispecies supragingival biofilm model. A total of nine different in vitro biofilms were grown, quantified with culture analyses, and visually examined with confocal laser scanning microscopy (CLSM). A four-species biofilm without any streptococcal species was used as a basic biofilm. In each subsequent inoculum, one species of MSG was added and afterward combined with Streptococcus mutans. The eight-species biofilm contained all eight strains used in this study. Culture analyses showed that the presence of S. mutans in a four-species biofilm with Streptococcus oralis or S. oralis subsp. tigurinus did not differ significantly in C. albicans colony-forming unit (CFU) counts compared to biofilms without S. mutans. However, compared to other mitis species, Streptococcus gordonii combined with S. mutans resulted in the lowest CFUs of C. albicans. Visual observation by CLSM showed that biofilms containing both S. mutans and one species of MSG seemed to induce the formation of filamentous form of C. albicans. However, when several species of MSG were combined with S. mutans, C. albicans was again found in its yeast form.

Human oral lectin ZG16B acts as a cell wall polysaccharide probe to decode host-microbe interactions with oral commensals

The oral microbiome is critical to human health and disease, yet the role that host salivary proteins play in maintaining oral health is unclear. A highly expressed gene in human salivary glands encodes the lectin zymogen granule protein 16 homolog B (ZG16B). Despite the abundance of this protein, its interaction partners in the oral microbiome are unknown. ZG16B possesses a lectin fold, but whether it binds carbohydrates is unclear. We postulated that ZG16B would bind microbial glycans to mediate recognition of oral microbes. To this end, we developed a microbial glycan analysis probe (mGAP) strategy based on conjugating the recombinant protein to fluorescent or biotin reporter functionality. Applying the ZG16B-mGAP to dental plaque isolates revealed that ZG16B predominantly binds to a limited set of oral microbes, including Streptococcus mitis, Gemella haemolysans, and, most prominently, Streptococcus vestibularis. S. vestibularis is a commensal bacterium widely distributed in healthy individuals. ZG16B binds to S. vestibularis through the cell wall polysaccharides attached to the peptidoglycan, indicating that the protein is a lectin. ZG16B slows the growth of S. vestibularis with no cytotoxicity, suggesting that it regulates S. vestibularis abundance. The mGAP probes also revealed that ZG16B interacts with the salivary mucin MUC7. Analysis of S. vestibularis and MUC7 with ZG16B using super-resolution microscopy supports ternary complex formation that can promote microbe clustering. Together, our data suggest that ZG16B influences the compositional balance of the oral microbiome by capturing commensal microbes and regulating their growth using a mucin-assisted clearance mechanism.

Microbial contamination and composition of oral samples subjected to clinical whole genome sequencing

Biological material from the oral cavity is an excellent source of samples for genetic diagnostics. This is because collection is quick, easy-to-access, and non-invasive. We have set-up clinical whole genome sequence testing for patients with suspected hereditary disease. Beside the excellent quality of human DNA that can be isolated from such samples, we observed the presence of non-human DNA sequences at varying percentages. We investigated the proportion of non-human mapped reads (NHMR) sequenced from buccal swabs and saliva, the type of microbial genomes from which they were derived, and impact on molecular classification. Read sequences that did not map to the human reference genome were aligned to complete reference microbial reference sequences from the National Center for Biotechnology Information's (NCBI) RefSeq database using Kraken2. Out of 765 analyzed samples over 80% demonstrated more than 5% NHMRs. The majority of NHMRs were from bacterial genomes (average 69%, buccal swabs and 54% saliva), while the proportion of viruses was low, averaging 0.32% (buccal swabs) and 0.07% (saliva). We identified more than 30 different bacterial families of which Streptococcus mitis and Rothia mucilaginosa were the most common species. Importantly, the level of contamination did not impact the diagnostic yield.

A Multifunctional Dental Resin Composite with Sr-N-Doped TiO2 and n-HA Fillers for Antibacterial and Mineralization Effects

Dental caries, particularly secondary caries, which is the main contributor to dental repair failure, has been the subject of extensive research due to its biofilm-mediated, sugar-driven, multifactorial, and dynamic characteristics. The clinical utility of restorations is improved by cleaning bacteria nearby and remineralizing marginal crevices. In this study, a novel multifunctional dental resin composite (DRC) composed of Sr-N-co-doped titanium dioxide (Sr-N-TiO2) nanoparticles and nano-hydroxyapatite (n-HA) reinforcing fillers with improved antibacterial and mineralization properties is proposed. The experimental results showed that the anatase-phase Sr-N-TiO2 nanoparticles were synthesized successfully. After this, the curing depth (CD) of the DRC was measured from 4.36 ± 0.18 mm to 5.10 ± 0.19 mm, which met the clinical treatment needs. The maximum antibacterial rate against Streptococcus mutans (S. mutans) was 98.96%, showing significant inhibition effects (p < 0.0001), which was experimentally verified to be derived from reactive oxygen species (ROS). Meanwhile, the resin exhibited excellent self-remineralization behavior in an SBF solution, and the molar ratio of Ca/P was close to that of HA. Moreover, the relative growth rate (RGR) of mouse fibroblast L929 indicated a high biocompatibility, with the cytotoxicity level being 0 or I. Therefore, our research provides a suitable approach for improving the antibacterial and mineralization properties of DRCs.

Transposon mutagenesis in oral streptococcus

Oral streptococci are gram-positive facultative anaerobic bacteria that are normal inhabitants of the human oral cavity and play an important role in maintaining oral microecological balance and pathogenesis. Transposon mutagenesis is an effective genetic manipulation strategy for studying the function of genomic features. In order to study cariogenic related genes and crucial biological element genes of oral Streptococcus, transposon mutagenesis was widely used to identify functional genes. With the advent of next-generation sequencing (NGS) technology and the development of transposon random mutation library construction methods, transposon insertion sequencing (TIS) came into being. Benefiting from high-throughput advances in NGS, TIS was able to evaluate the fitness contribution and essentiality of genetic features in the bacterial genome. The application of transposon mutagenesis, including TIS, to oral streptococci provided a massive amount of valuable detailed linkage data between genetic fitness and genetic backgrounds, further clarify the processes of colonization, virulence, and persistence and provides a more reliable basis for investigating relationships with host ecology and disease status. This review focuses on transposon mutagenesis, including TIS, and its applicability in oral streptococci.

Oral mitis group streptococci: A silent majority in our oral cavity

Members of the oral mitis group streptococci including Streptococcus oralis, Streptococcus sanguinis, and Streptococcus gordonii are the most abundant inhabitants of human oral cavity and dental plaque, and have been implicated in infectious complications such as bacteremia and infective endocarditis. Oral mitis group streptococci are genetically close to Streptococcus pneumoniae; however, they do not produce cytolysin (pneumolysin), which is a key virulence factor of S. pneumoniae. Similar to S. pneumoniae, oral mitis group streptococci possess several cell surface proteins that bind to the cell surface components of host mammalian cells. S. sanguinis expresses long filamentous pili that bind to the matrix proteins of host cells. The cell wall-anchored nuclease of S. sanguinis contributes to the evasion of the neutrophil extracellular trap by digesting its web-like extracellular DNA. Oral mitis group streptococci produce glucosyltransferases, which synthesize glucan (glucose polymer) from sucrose of dietary origin. Neuraminidase (NA) is a virulent factor in oral mitis group streptococci. Influenza type A virus (IAV) relies on viral NA activity to release progeny viruses from infected cells and spread the infection, and NA-producing oral streptococci elevate the risk of IAV infection. Moreover, oral mitis group streptococci produce hydrogen peroxide (H₂ O₂ ) as a by-product of sugar metabolism. Although the concentrations of streptococcal H₂ O₂ are low (1-2 mM), they play important roles in bacterial competition in the oral cavity and evasion of phagocytosis by host macrophages and neutrophils. In this review, we intended to describe the diverse pathogenicity of oral mitis group streptococci.

Antibiotic Resistance of Selected Bacteria after Treatment of the Supragingival Biofilm with Subinhibitory Chlorhexidine Concentrations

Due to increasing rates of antibiotic resistance and very few novel developments of antibiotics, it is crucial to understand the mechanisms of resistance development. The aim of the present study was to investigate the adaptation of oral bacteria to the frequently used oral antiseptic chlorhexidine digluconate (CHX) and potential cross-adaptation to antibiotics after repeated exposure of supragingival plaque samples to subinhibitory concentrations of CHX. Plaque samples from six healthy donors were passaged for 10 days in subinhibitory concentrations of CHX, while passaging of plaque samples without CHX served as control. The surviving bacteria were cultured on agar plates and identified with Matrix-assisted Laser Desorption/Ionization-Time of Flight-Mass spectrometry (MALDI-TOF). Subsequently, the minimum inhibitory concentrations (MIC) of these isolates toward CHX were determined using a broth-microdilution method, and phenotypic antibiotic resistance was evaluated using the epsilometertest. Furthermore, biofilm-forming capacities were determined. Repeated exposure of supragingival plaque samples to subinhibitory concentrations of CHX led to the selection of oral bacteria with 2-fold up to 4-fold increased MICs toward CHX. Furthermore, these isolates showed up to 12-fold increased MICs towards some antibiotics such as erythromycin and clindamycin. Conversely, biofilm-forming capacity was decreased. In summary, this study shows that oral bacteria are able to adapt to CHX, while also decreasing their susceptibility to antibiotics.

Extended biofilm formation time by Streptococcus sanguinis modifies its non-cariogenic behavior, in vitro

Although the commensal Streptococcus sanguinis [ S. sanguinis] is isolated from caries-free people, it can ferment carbohydrates producing acids. We aimed to characterize S. sanguinis cariogenic potential as a function of different enamel biofilm formation periods, in vitro. Saliva-coated enamel slabs were inoculated with S. sanguinis to form initial biofilms for 8, 12 or 16 h in presence of sucrose and followed by a period in medium with glucose for 16, 12 or 8 h, respectively, until completion of 24 h. To simulate cariogenic challenges, S. sanguinis biofilms were exposed to 10% sucrose for 5 minutes, 3x/day for 5 days. Biofilm biomass, viable cells, total proteins, intracellular and extracellular polysaccharides production, acidogenicity and enamel demineralization were determined. Biofilms of Streptococcus mutans [ S. mutans ] served as caries-positive control. Biofilms of S. sanguinis forming on enamel for 12 and 16 h showed higher demineralization than those formed during 8 h, but lower than S. mutans biofilms, regardless of the initial biofilm formation time. No differences were detected in the biofilm properties among the different biofilm formation times tested for S. sanguinis . Increased enamel initial biofilm formation time by S. sanguinis appears to induce a cariogenic potential, but lower than S. mutans .

Nitrogen doped titanium dioxide as an aesthetic antimicrobial filler in dental polymers

OBJECTIVE

To develop an aesthetic resin composite using a nitrogen-doped titanium dioxide (NTiO₂) filler that possesses antimicrobial properties against cariogenic bacteria.

METHODS

N-TiO₂ powder was manufactured by calcining commercial TiO₂ with urea. Free radical release from the N-TiO₂ powder under visible light irradiation was analysed using UV-Vis spectrophotometry. The N-TiO₂ powder was incorporated into a dental resin and the photocatalytic activity assessed using a dye under both visible light and dark conditions. Using XTT assay to measure the cellular metabolic activity, the antibacterial properties of the N-TiO₂ /resin composite discs were tested using Streptococcus mutans.

RESULTS

Doping nitrogen of TiO₂ resulted in a band gap shift towards the visible light spectrum, which enabled the powder to release reactive oxygen species when exposed to visible light. When incorporated into a dental resin, the N-TiO₂/resin composite still demonstrated sustained release of reactive oxygen species, maintaining its photocatalytic activity and showing an antibacterial effect towards Streptococcus mutans under visible light conditions.

SIGNIFICANCE

N-TiO₂ filled resin composite shows great promise as a potential aesthetic resin based adhesive for orthodontic bonding.

Problems with identifying and distinguishing salivary streptococci: a multi-instrumental approach

Aim: The purpose of this study was to create an alternative protocol for the DNA-based identification of salivary microbiota focused on the distinguishing of Streptococcus species. Materials & methods: Salivary bacteria were identified using 16S rDNA sequencing and proteins and lipids profiling using MALDI-TOF/MS as well as FTIR analysis. Results: Most of the isolates belonged to streptococci - mostly the salivarious group indistinguishable by the molecular technique. In turn, MALDI analysis allowed for their fast and reliable classification. Although FTIR spectroscopy demonstrated the correct species classification, the spectra interpretation was time consuming and complicated. Conclusion: MALDI-TOF/MS demonstrated the biggest effectiveness in the identification and discrimination between the salivary streptococci, which could be easily incorporated in the workflow of routine microbiological laboratories.

Antimicrobial and Anti-Inflammatory Effects of the Ethanol Extract of Polygonum cuspidatum as a Mouthwash Component

Polygonum cuspidatum (PC) has been used as traditional Korean medicine to treat various diseases including asthma, hypertension, cancer, and arteriosclerosis. In this study, we assessed the antibacterial and anti-inflammatory effects of PC ethanol extract. Persistent antibacterial activity against Streptococcus mutans for up to 23 days was observed when the extract was used at a concentration of 10 mg/mL. The minimum inhibitory concentration of PC against S. mutans was 0.2 mg/mL and the minimum bactericidal concentration was 10 mg/mL. We compared the antimicrobial activities of S. mutagens cultured with or without PC. Bacterial activity was observed only in the group where RE was not added. The anti-inflammatory effect of PC on RAW264.7 cells was assessed using the MTT assay; changes in nitric oxide (NO) production and inflammatory cytokine levels (tumor necrosis factor [TNF]-α and interleukin [IL]-6) were measured in the presence of PC. In lipopolysaccharide-induced RAW264.7 cells, PC inhibited NO production by 68.6% when used at a concentration of 50 µg/mL. The expression of TNF-α and IL-6 was reduced by PC in a concentration-dependent manner. These results suggest that the ethanol extract of PC could be used as a mouthwash component with antibacterial and anti-inflammatory effects.

Multiple biosurfactant production by Aureobasidium pullulans strain YTP6-14 in aqueous and heavy oil layers

Aureobasidium pullulans YTP6-14 was demonstrated to be an excellent multiple biosurfactant producer utilizing cheap carbon sources available in Thailand, including glycerol and cassava flour hydrolysate. A. pullulans YTP6-14 maximally produced 1.81 g/l biosurfactant in an aqueous layer (BS-AQ) in a medium containing glycerol, and 7.37 or 6.37 g/l biosurfactant in a heavy oil layer (BS-HO) in cassava flour hydrolysate or a glucose containing medium, respectively. Each BS-AQ and BS-HO had critical micelle concentration values of 41.32 mg/l and 13.51 mg/l, and both biosurfactants formed a stable food oil emulsion and reduced the amount of biofilms formed by Streptococcus sobrinus and Streptococcus mutans. BS-AQ and BS-HO were mainly composed of liamocins or exophilins and massoia lactone, respectively.

An Unusual Case of Streptococcus anginosus Endocarditis in a Healthy Host With Bicuspid Aortic Valve

Streptococcus anginosus group (SAG) is a subgroup of viridans streptococci and can be found ubiquitously in normal human flora. SAG is known to form invasive pyogenic infection when it becomes pathogenic. Yet, SAG is a very rare cause of endocarditis, and there is a dearth of case reports on this topic. We present a rare case of native bicuspid aortic valve endocarditis secondary to S. anginosus that caused aortic insufficiency and ascending aortic aneurysm. To our knowledge, this is the first well-documented case report of community-acquired S. anginosus endocarditis on a bicuspid aortic valve in an immunocompetent patient. The patient first presented with cough that was likely due to bronchus irritation from a 5.5 x 5.2 cm ascending aortic aneurysm. He underwent aortic valve replacement with bovine bioprosthesis and ascending aortic aneurysm repairment and was treated with a two-week regimen of IV ceftriaxone and gentamicin followed by another four weeks of IV ceftriaxone. He was eventually discharged to a rehabilitation facility. SAG is usually susceptible to beta-lactam antibiotics. The prognosis of SAG infection is usually good, but progression to bacteremia carries a poor outcome.

The Pathogenic Factors from Oral Streptococci for Systemic Diseases

The oral cavity is suggested as the reservoir of bacterial infection, and the oral and pharyngeal biofilms formed by oral bacterial flora, which is comprised of over 700 microbial species, have been found to be associated with systemic conditions. Almost all oral microorganisms are non-pathogenic opportunistic commensals to maintain oral health condition and defend against pathogenic microorganisms. However, oral Streptococci, the first microorganisms to colonize oral surfaces and the dominant microorganisms in the human mouth, has recently gained attention as the pathogens of various systemic diseases, such as infective endocarditis, purulent infections, brain hemorrhage, intestinal inflammation, and autoimmune diseases, as well as bacteremia. As pathogenic factors from oral Streptococci, extracellular polymeric substances, toxins, proteins and nucleic acids as well as vesicles, which secrete these components outside of bacterial cells in biofilm, have been reported. Therefore, it is necessary to consider that the relevance of these pathogenic factors to systemic diseases and also vaccine candidates to protect infectious diseases caused by Streptococci. This review article focuses on the mechanistic links among pathogenic factors from oral Streptococci, inflammation, and systemic diseases to provide the current understanding of oral biofilm infections based on biofilm and widespread systemic diseases.

Glucosidase activity in dental biofilms in adolescent patients with fixed orthodontic appliances - a putative marker for white spot lesions - a clinical exploratory trial

OBJECTIVES

Approximately 25% of the adolescents in the Scandinavian population are treated with a fixed orthodontic appliance (FOA). Adverse effects such as enamel decalcification (white spot lesions - WSL), seem to affect over 30% of patients. WSL have only a limited ability to improve, thus seriously jeopardising the treatment outcome. The aim of present study was to explore the biofilm phenotype by investigating plaque collected: 1) adjacent to brackets, and 2) in gingival margin of maxillary incisors in adolescents with FOA. Incidence of WSL after treatment was also assessed.

DESIGN

In eight adolescent patients treated with FOA, supra-gingival plaque formed on: 1) brackets, and 2) along the gingival margin of the maxillary incisors, was collected after 6-8 months of treatment. The patients were documented before and after treatment by intraoral photos. Plaque samples were tested for glycosidase- (fluorogenic substrates) and protease (FITC-labelled casein substrate) activities. The plaque samples were visualised by Live/Dead BacLight stain, following which cells were investigated by confocal scanning laser microscopy.

RESULTS

In the collected plaque samples, all enzymes tested displayed small variations in activity between the individuals, except glucosidases, which varied significantly. Four patients developed WSL. The patients displayed higher glucosidase activity in plaque of brackets compared to patients without WSL. In seven patients, plaque at the gingival margin displayed higher protease activity than plaque of brackets.

CONCLUSIONS

The current study shows two distinct environmentally induced biofilm phenotypes: 1) brackets with higher glucosidase activity, and 2) gingival margin with higher protease activity. Glucosidase activity might thus be used as a putative biomarker for risk of WSL.

An Update on the Evolution of Glucosyltransferase (Gtf) Genes in Streptococcus

In many caries-promoting Streptococcus species, glucosyltransferases (Gtfs) are recognized as key enzymes contributing to the modification of biofilm structures, disruption of homeostasis of healthy microbiota community and induction of caries development. It is therefore of great interest to investigate how Gtf genes have evolved in Streptococcus. In this study, we conducted a comprehensive survey of Gtf genes among 872 streptococci genomes of 37 species and identified Gtf genes from 364 genomes of 18 species. To clarify the relationships of these Gtf genes, 45 representative sequences were used for phylogenic analysis, which revealed two clear clades. Clade I included 12 Gtf genes from nine caries-promoting species of the Mutans and Downei groups, which produce enzymes known to synthesize sticky, water-insoluble glucans (WIG) that are critical for modifying biofilm structures. Clade II primarily contained Gtf genes responsible for synthesizing water-soluble glucans (WSG) from all 18 species, and this clade further diverged into three subclades (IIA, IIB, and IIC). An analysis of 16 pairs of duplicated Gtf genes revealed high divergence levels at the C-terminal repeat regions, with ratios of the non-synonymous substitution rate (dN) to synonymous substitution rate (dS) ranging from 0.60 to 1.03, indicating an overall relaxed constraint in this region. However, among the clade I Gtf genes, some individual repeat units possessed strong functional constraints by the same criterion. Structural variations in the repeat regions were also observed, with detection of deletions or recent duplications of individual repeat units. Overall, by establishing an updated phylogeny and further elucidating their evolutionary patterns, this work enabled us to gain a greater understanding of the origination and divergence of Gtf genes in Streptococcus.

Establishment and Development of Oral Microflora in 12-24 Month-Old Toddlers Monitored by High-Throughput Sequencing

A cohort study was conducted to evaluate oral microbial diversity among toddlers aged 12-24 months, and to describe the dynamic processes of colonization, development, and stabilization of the oral microflora during tooth eruption using high-throughput sequencing technology. A total of 20 healthy toddlers aged 12 months were included at baseline and followed up through 18-24 months. Clinical oral examinations of dental caries status and visible plaque index were carried out at three follow-up time points. Pooled supragingival plaque biofilm samples were also collected at ages 12, 18, and 24 months. Plaque biofilm DNA was extracted and analyzed by MiSeq sequencing. A total of 18 toddlers completed three follow-ups. At 12 months of age, all the toddlers only had eruption of the anterior teeth, without dental caries. At ages 18 and 24 months, one and two toddlers showed two and three teeth with carious white spots, respectively. Depth, Good's coverage, and sample size of sequencing were reasonable. The dominant bacterial genera in the oral cavity of 12-month-old toddlers were Capnocytophaga, Neisseria, Streptococcus, Kingella, and Leptotrichia; the oral microflora composition was relatively stable by 18 months of age and included unclassified Enterobacteriaceae, Selenomonas, Prevotella, Leptotrichia, and Veillonella as the dominant genera; unclassified Enterobacteriaceae, Streptococcus, Neisseria, Leptotrichia, and Selenomonas were the dominant genera by 24 months. There were significant differences among microbial compositions in the oral cavities of 12, 18, and 24-month-old toddlers, with relatively small differences observed between the 18 and 24 months samples. In conclusion, oral microbial community of toddlers showed a trend of dynamic development. Significant differences in oral microbial diversity among toddlers aged 12-24 months were observed, while the microbial diversity differences among toddlers aged 18-24 months tended to be more similar. The findings indicated that the oral microbial community gradually matures and tends to stabilize with the growth and development of toddlers.

Biology of Oral Streptococci

Bacteria belonging to the genus Streptococcus are the first inhabitants of the oral cavity, which can be acquired right after birth and thus play an important role in the assembly of the oral microbiota. In this article, we discuss the different oral environments inhabited by streptococci and the species that occupy each niche. Special attention is given to the taxonomy of Streptococcus, because this genus is now divided into eight distinct groups, and oral species are found in six of them. Oral streptococci produce an arsenal of adhesive molecules that allow them to efficiently colonize different tissues in the mouth. Also, they have a remarkable ability to metabolize carbohydrates via fermentation, thereby generating acids as byproducts. Excessive acidification of the oral environment by aciduric species such as Streptococcus mutans is directly associated with the development of dental caries. However, less acid-tolerant species such as Streptococcus salivarius and Streptococcus gordonii produce large amounts of alkali, displaying an important role in the acid-base physiology of the oral cavity. Another important characteristic of certain oral streptococci is their ability to generate hydrogen peroxide that can inhibit the growth of S. mutans. Thus, oral streptococci can also be beneficial to the host by producing molecules that are inhibitory to pathogenic species. Lastly, commensal and pathogenic streptococci residing in the oral cavity can eventually gain access to the bloodstream and cause systemic infections such as infective endocarditis.

A randomised controlled trial to evaluate the plaque removal efficacy of sodium bicarbonate dentifrices in a single brushing clinical model

OBJECTIVE

To evaluate plaque removal efficacy of dentifrices containing sodium bicarbonate (NaHCO3) compared with a non-NaHCO3 dentifrice after a single-timed brushing.

MATERIALS AND METHODS

A randomised, controlled, examiner-blinded, four-period, crossover study in 56 adults with a mean whole-mouth plaque index of ≥2.00 (six site modification of Turesky modification of Quigley-Hein Plaque Index [TPI]). Subjects brushed once for one timed minute with a 67% NaHCO3 dentifrice with herbs; a 67% NaHCO3 dentifrice without herbs; a 62% NaHCO3 dentifrice with herbs; or a non-NaHCO3 dentifrice without herbs. All contained 923 p.p.m. fluoride as sodium fluoride. Pre- and post-brushing plaque assessments were performed.

RESULTS

Mean TPI score decreased from pre- to post-brushing with all treatments. There were statistically significantly greater reductions in plaque for NaHCO3 dentifrices compared to non-NaHCO3 (p < 0.0001 for all) with no significant differences between NaHCO3-containing dentifrices. A post hoc analysis of plaque removal from different oral areas showed statistically significant differences in favour of the NaHCO3 dentifrices over the non-NaHCO3 dentifrice for almost all surfaces. No adverse events were reported.

DISCUSSION AND CONCLUSION

Plaque removal was significantly greater with NaHCO3-containing dentifrices compared with a non-NaHCO3 dentifrice after a single, timed brushing. There was no effect of herbal tinctures. This study was registered at ClincalTrials.org: NCT03285984.

Streptococcus oralis maintains homeostasis in oral biofilms by antagonizing the cariogenic pathogen Streptococcus mutans

Bacteria residing in oral biofilms live in a state of dynamic equilibrium with one another. The intricate synergistic or antagonistic interactions between them are crucial for determining this balance. Using the six-species Zürich "supragingival" biofilm model, this study aimed to investigate interactions regarding growth and localization of the constituent species. As control, an inoculum containing all six strains was used, whereas in each of the further five inocula one of the bacterial species was alternately absent, and in the last, both streptococci were absent. Biofilms were grown anaerobically on hydroxyapatite disks, and after 64 h they were harvested and quantified by culture analyses. For visualization, fluorescence in situ hybridization and confocal laser scanning microscopy were used. Compared with the control, no statistically significant difference of total colony-forming units was observed in the absence of any of the biofilm species, except for Fusobacterium nucleatum, whose absence caused a significant decrease in total bacterial numbers. Absence of Streptococcus oralis resulted in a significant decrease in Actinomyces oris, and increase in Streptococcus mutans (P < .001). Absence of A. oris, Veillonella dispar or S. mutans did not cause any changes. The structure of the biofilm with regards to the localization of the species did not result in observable changes. In summary, the most striking observation of the present study was that absence of S. oralis resulted in limited growth of commensal A. oris and overgrowth of S. mutans. These data establish highlight S. oralis as commensal keeper of homeostasis in the biofilm by antagonizing S. mutans, so preventing a caries-favoring dysbiotic state.

Antibacterial Effects of Natural Herbal Extracts on Streptococcus mutans: Can They Be Potential Additives in Dentifrices?

Background

Many plants or herbs exhibit potent antimicrobial activity against various microorganisms. They have no side effects and presumably act against and modulate the factors that are crucial for microbial survival or their activity. Streptococcus mutans is a pioneer bacteria implicated in dental caries. This study aims to evaluate the antimicrobial activity of garlic bulbs, pudina leaves, and mango and eucalyptus twig extracts on Streptococcus mutans by evaluating their zone of inhibition and determining their minimum inhibitory concentration (MIC).

Methods

Microbiological assay (well diffusion method) to determine zone of inhibition against pure forms of Streptococcus mutans was performed. The antibacterial effects of methanolic extracts of mango twigs, eucalyptus twigs, pudina leaves, and garlic bulbs were studied. Test compounds were further evaluated for their MIC.

Results

Extracts derived from mango and eucalyptus twigs showed significant antibacterial effects at test concentrations. Pudina and garlic extracts did not show any significant antibacterial effects at similar concentrations. Upon further evaluation of the 2 positive compounds for their MIC, mango twigs demonstrated more antimicrobial potential than eucalyptus twigs at a lower concentration.

Conclusion

Our observations indicated that the mango twig extracts possess higher antibacterial effects against Streptococcus mutans than other compounds at specific test concentration.

First Detection and Characterization of Streptococcus dentapri from Caries Active Subject

INTRODUCTION

Mutans streptococci (MS) are a group of oral bacteria generally regarded as the principal agents in the pathogenesis of dental caries.

AIM

The study aimed was characterize S. dentapri based on phylogenetic analysis and phenotypic methods from Caries Active Subject.

MATERIALS AND METHODS

While sequencing MS species which were isolated from 65 caries active subjects, one strain of S. dentapri was detected. Dental plaque samples were processed and cultured on mitis salivarius bacitracin agar. S. dentapri was characterized using phylogenetic analysis, colony morphology characterization and biotyping.

RESULTS

Among the study population, one strain designated as H14 was identified as S. dentapri by 16S rDNA sequencing. Morphologically, S. dentapri could not differentiate from other species of MS. S. dentapri H14 demonstrated biotype II biochemical characteristics of MS. The phylogenetic analysis showed S. dentapri is closely related to S. macacae.

CONCLUSION

The study concludes that S. dentapri can inhabit the human oral cavity and therefore further investigations are warranted to determine its role in caries.

Nicotine Upregulates Coaggregation of Candida albicans and Streptococcus mutans

PURPOSE

Denture stomatitis is a condition of painless inflammation of denture-bearing mucosa. Reports indicate that nicotine, the major psychoactive ingredient in tobacco, increases growth of Streptococcus mutans and Candida albicans in denture biofilm. The purpose of this study was to determine the in vitro effects of nicotine on coaggregation of C. albicans with S. mutans.

MATERIAL AND METHODS

C. albicans strain ATCC 10231, S. mutans strain UA159 (ATTC 700610), and nicotine dilutions (ranging from 0 to 32 mg/ml) were used for this study. Both microorganisms were grown for 24 hours in dilutions of nicotine (0 to 32 mg/ml) made in tryptic soy broth (TSB) or TSB supplemented with 1% sucrose (TSBS; S. mutans) or yeast peptone dextrose broth (YPD; C. albicans). Suspensions of the nicotine-treated cells were prepared, mixed together and incubated for up to 24 hours to determine if there was an increase in coaggregation of nicotine-treated cells compared to the no nicotine control cells. Qualitative analysis of coaggregation was performed using a visual aggregation assay and light microscopic observation. A spectrophotometric assay was used to provide a quantitative analysis of the coaggregation.

RESULTS

The visual aggregation assay indicated a significant increase in coaggregation between C. albicans and S. mutans with increasing incubation time (0 to 24 hours) and nicotine concentrations (0 to 4 mg/ml). Microbial growth in nicotine at 4 mg/ml demonstrated a significant increase in coaggregation after 24 hours of incubation. The numbers of coaggregated S. mutans/C. albicans cells exhibited a significant increase with incubation time and nicotine concentrations when the samples were examined microscopically. More coaggregation of S. mutans and C. albicans was observed with incubation time and increased nicotine compared to the 0 mg/ml nicotine group. There was a noticeable increase of coaggregation when cells were grown in TSBS compared to TSB. Absorbance of nicotine-treated cells (0.25 to 4 mg/ml) exhibited a decrease in values compared to 0 mg/ml at 0 hours of incubation, confirming increased coaggregation.

CONCLUSION

These results demonstrated the effect of nicotine in increasing the coaggregation of S. mutans with C. albicans. Coaggregation increased with incubation time and nicotine concentration. Coaggregation was increased with S. mutans grown in TSBS compared to TSB, suggesting that growth in sucrose media leads to an increase in receptors responsible for coaggregation.

Complete genome sequence of Streptococcus troglodytae TKU31 isolated from the oral cavity of a chimpanzee (Pan troglodytes)

Streptococcus troglodytae TKU31 was isolated from the oral cavity of a chimpanzee (Pan troglodytes) and was found to be the most closely related species of the mutans group streptococci to Streptococcus mutans. The complete sequence of TKU31 genome consists of a single circular chromosome that is 2,097,874 base pairs long and has a G + C content of 37.18%. It possesses 2082 coding sequences (CDSs), 65 tRNAs and five rRNA operons (15 rRNAs). Two clustered regularly interspaced short palindromic repeats, six insertion sequences and two predicted prophage elements were identified. The genome of TKU31 harbors some putative virulence associated genes, including gtfB, gtfC and gtfD genes encoding glucosyltransferase and gbpA, gbpB, gbpC and gbpD genes encoding glucan-binding cell wall-anchored protein. The deduced amino acid identity of the rhamnose-glucose polysaccharide F gene (rgpF), which is one of the serotype determinants, is 91% identical with that of S. mutans LJ23 (serotype k) strain. However, two other virulence-associated genes cnm and cbm, which encode the collagen-binding proteins, were not found in the TKU31 genome. The complete genome sequence of S. troglodytae TKU31 has been deposited at DDBJ/European Nucleotide Archive/GenBank under the accession no. AP014612.

Antibiotic Resistance of Non-pneumococcal Streptococci and Its Clinical Impact

The taxonomy of streptococci has undergone major changes during the last two decades. The present classification is based on both phenotypic and genotypic data. Phylogenetic classification of streptococci is based on 16S rRNA sequences [1], and it forms the backbone of the overall classification system of streptococci. Phenotypic properties are also important, especially for clinical microbiologists. The type of hemolysis on blood agar, reaction with Lancefield grouping antisera, resistance to optochin, and bile solubility remain important for grouping of clinical Streptococcus isolates and therefore treatment options [2]. In the following chapter, two phenotypic classification groups, viridans group streptococci (VGS) and beta-hemolytic streptococci, will be discussed.

Five-year longitudinal study of dental caries risk associated with Streptococcus mutans and Streptococcus sobrinus in individuals with intellectual disabilities

Streptococcus mutans (S. mutans) and Streptococcus sobrinus (S. sobrinus) are important etiologic agents in human dental caries. Using quantitative real-time polymerase chain reaction assays for the presence of those strains, we examined 145 outpatients with intellectual disability (ID), calculated the proportion of each of these strains to total bacteria, and compared dental caries incidence over 5 years. Plaque samples were collected from all erupted tooth sites, and dental examinations were performed annually to determine numbers of decayed, missing, and filled teeth (DMFT score; World Health Organization caries diagnostic criteria). Elevated DMFT scores were calculated as ∆DMFT, and sites of newly affected caries (∆SNAC) were identified. Sixty-six patients had both strains. The proportion of S. mutans to total bacteria was moderately correlated with DMFT in year 2, ∆DMFT in years 2 and 5, and ∆SNAC in years 2 and 5 (correlation coefficient = 0.470, P < 0.001), while the proportion of S. sobrinus to total bacteria was moderately correlated with DMFT in years 2 and 5, ∆DMFT in years 1, 2, and 5, and ∆SNAC in years 2 and 5 (correlation coefficient = 0.695, P < 0.001). Individuals with ID who harbored both bacterial strains had a higher risk of dental caries and a significantly higher proportion of S. sobrinus to total bacteria.

Proteome Analysis of Oral Pathogens

The oral environment contains diverse communities of micro-organisms including bacteria, fungi, protozoa, and viruses. Studies of oral ecology have led to an appreciation of the complexity of the interactions that oral micro-organisms have with the host in both health and disease. Despite this, diseases such as dental caries and periodontal diseases are still worldwide human ailments, resulting in a high level of morbidity and an economic burden to society. Proteomics offers a new approach to the understanding of holistic changes occurring as oral micro-organisms adapt to environmental change within their habitats in the mouth.

Streptococcuspantholopis sp. nov., isolated from faeces of the Tibetan antelope (Pantholops hodgsonii)

Two bacterial strains were isolated from faecal samples of Tibetan antelopes. The isolates were Gram-stain-positive, catalase-negative, coccus-shaped organisms that were tentatively identified as representing a novel streptococcal species based on their morphological features, biochemical test results and phylogenomic findings. Comparative 16S rRNA gene sequencing studies confirmed that the organisms were members of the genus Streptococcus, but they did not correspond to any recognized species of the genus. The nearest phylogenetic relative of the unknown coccus was Streptococcus ursoris NUM 1615T (93.4 % 16S rRNA gene sequence similarity). Analysis of groEL and rpoB gene sequences of the novel isolates showed interspecies divergence of 27.0 and 22.2 %, respectively, from the type strain of its closest 16S rRNA gene phylogenetic relative, S. ursoris. The complete genome of strain TA 26T has been sequenced. Digital DNA-DNA hybridization studies between strain TA 26T and other species of the genus Streptococcus deposited in the GenBank database showed less than 70 % DNA-DNA relatedness, supporting a novel species status of the strain. On the basis of their genotypic and phenotypic differences from recognized Streptococcus species, the two isolates represent a novel species of the genus Streptococcus, for which the nameStreptococcus pantholopis sp. nov. (type strain TA 26T=CGMCC 1.15667T=DSM 102135T) is proposed.

Activity of Synthetic Antimicrobial Peptide GH12 against Oral Streptococci

Controlling the growth of cariogenic microorganisms such as oral streptococci is an adjunct therapy for caries-active individuals to prevent and treat caries. Here we investigated the antimicrobial activity of the synthetic amphipathic α- helical antimicrobial peptide GH12 (GLLWHLLHHLLH-NH2) against oral streptococci in vitro. Circular dichroism studies showed that GH12 takes on an α-helical conformation in the presence of membrane-mimicking solvents, and reversed-phase high-performance liquid chromatography studies showed that GH12 remains stable in saliva. The peptide showed bactericidal activity against oral streptococci, with minimum inhibitory concentrations ranging from 6.7 to 32.0 μg/ml. GH12 concentrations 4-fold higher than the minimum bactericidal concentration completely killed oral streptococci within 20 min. Treating oral streptococci with GH12 caused noticeable changes in bacterial viability and morphology based on confocal laser scanning microscopy and scanning electron microscopy. Effects of GH12 on biofilm formation and on viability of mature biofilm were quantified by crystal violet staining and the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay. GH12 effectively inhibited biofilm formation and metabolic activity in biofilms of oral streptococci, especially S. mutans, S. sobrinus and S. salivarius. These results suggest that GH12 shows rapid and strong antimicrobial activity against oral streptococci in vitro, opening the door to preclinical and clinical studies to explore its potential for caries prevention and treatment.

Longitudinal study of dental caries incidence associated with Streptococcus mutans and Streptococcus sobrinus in patients with intellectual disabilities

Background

Mutans streptococci (Streptococcus mutans and S. sobrinus) are considered to be major etiologic agents of dental caries. Using a polymerase chain reaction method, we detected those bacteria from 145 outpatients (6–30 years old) with intellectual disabilities (ID) and their presence was compared with the incidence of dental caries.

Methods

Plaque samples were collected from all erupted tooth sites in subjects with a sterile toothbrush. A dental examination was performed to determine the number of decayed and filled teeth (DFT score) in permanent dentition using the WHO caries diagnostic criteria. A Mann–Whitney U-test was employed to compare the caries scores between combinations of the bacteria, and with a Wilcoxon rank test used to compare caries scores between the baseline and after 1 year.

Results

Among all subjects, S. mutans and S. sobrinus were possessed by 78.7 and 83.5 %, respectively, while 13.1 % were positive for S. mutans alone, 17.9 % for S. sobrinus alone, and 65.6 % for both organisms, with 3.4 % were negative for both. The mean DFT score of subjects positive for both S. mutans and S. sobrinus at after 1 year was significantly higher than that of those positive for S. mutans alone (P < 0.01). The increase in caries increment was also significantly greater in subjects with both bacteria detected (P < 0.001).

Conclusion

Our results indicate that patients with ID harboring both S. mutans and S. sobrinus have a significantly higher incidence of dental caries than those with S. mutans alone.

Association of oral streptococci community dynamics with severe early childhood caries as assessed by PCR-denaturing gradient gel electrophoresis targeting the rnpB gene

This study sought to investigate the possible association between the dynamics of oral streptococci community profiles and severe early childhood caries (S-ECC) development, compared with caries-free (CF) controls. Supragingival plaque samples were evaluated from 8-32-month-old children who had previously been assessed for overall profiles of their oral microbial community. Twelve children were in each group. Bacterial genomic DNA was extracted and amplified using rnpB-specific primers for streptococci; the products were then subjected to denaturing gradient gel electrophoresis (DGGE) and sequence analysis. We observed that the mean values for species richness (N) and diversity of oral streptococci (H') were significantly lower in the S-ECC group than in the CF group (N = 1.25 ± 4.14 vs 14.92 ± 2.84; H' = 1.41 ± 0.29 vs 1.64 ± 0.18) at 32  months of age (P < 0.05). Significantly higher detection rates of Streptococcus sanguinis and Streptococcus gordonii were found in the CF group compared with the S-ECC group at 32  months of age (P < 0.05). Cluster analysis of DGGE profiles showed that most of the clusters were constructed from one individual over time. These results suggested that the onset of S-ECC is accompanied by reduced diversity of oral streptococci, that the detection rates of S. sanguinis and S. gordonii have negative correlations with S-ECC; and that there are high levels of intra-individual similarity for the oral streptococci community over time.

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.

Streptococcus oriloxodontae sp. nov., isolated from the oral cavities of elephants

Two strains were isolated from oral cavity samples of healthy elephants. The isolates were Gram-positive, catalase-negative, coccus-shaped organisms that were tentatively identified as a streptococcal species based on the results of biochemical tests. Comparative 16S rRNA gene sequence analysis suggested classification of these organisms in the genus Streptococcus with Streptococcus criceti ATCC 19642T and Streptococcus orisuis NUM 1001T as their closest phylogenetic neighbours with 98.2 and 96.9 % gene sequence similarity, respectively. When multi-locus sequence analysis using four housekeeping genes, groEL, rpoB, gyrB and sodA, was carried out, similarity of concatenated sequences of the four housekeeping genes from the new isolates and Streptococcus mutans was 89.7 %. DNA–DNA hybridization experiments suggested that the new isolates were distinct from S. criceti and other species of the genus Streptococcus . On the basis of genotypic and phenotypic differences, it is proposed that the novel isolates are classified in the genus Streptococcus as representatives of Streptococcus oriloxodontae sp. nov. The type strain of S. oriloxodontae is NUM 2101T ( = JCM 19285T = DSM 27377T).

Draft Genome Sequence of an Atypical Strain of Streptococcus pneumoniae Isolated from a Respiratory Infection

Next-generation sequencing was used to investigate an unknown clinical respiratory infection. This new strain of Streptococcus pneumoniae, ASVL_JC_0001, was isolated from a clinical specimen from a patient with bronchitis and pulmonary inflammation. The draft genome sequence, obtained with an Illumina MiSeq sequencing system, consists of 83 large contigs, a total of 2,092,532 bp long, and has a GC content of 40.3%.

Monitoring caries risks before the window of infection and later caries increment: a caries prediction study on rapid detection of Streptococcus mutans using monoclonal antibodies

A new semi-quantitative enumeration system has been developed for the detection of Streptococcus mutans in saliva. Using two kinds of species-specific monoclonal antibodies, this system can quickly detect salivary S. mutans within 30 min and classify the results into three levels. The aim of this study was to evaluate the potential of this test kit in determining risk for the development of caries. Saliva samples collected during a compulsory dental examination from 56 children aged 18-months were tested. The children were classified into 3 groups according to the level of salivary S. mutans determined. After 18 months, 36 of the children underwent a second examination to investigate whether there was a correlation between salivary S. mutans level at the first examination and subsequent increment in caries. The results showed a good correlation between the two. This indicates that salivary S. mutans level before the window of infection is an indicator of caries risk and can be quickly detected using this test kit. This rapid test should be particularly useful in assessing risk of future caries in very young children.

Effective oral health in infective endocarditis: efficacy of high-street mouthwashes against the viridans group streptococci

AIM

Recent UK National Institute for Health and Clinical Excellence guidelines state that there is no longer a need for oral antibiotic prophylaxis in patients undergoing dental procedures who are at risk of infective endocarditis (IE), and advocate the importance of maintaining good oral health. As viridans group streptococci (VGS) are common etiological agents of IE and inhabitants of the mouth, the purpose of this study was to examine the efficacy of common high-street mouthwashes against four classes of VGS organisms (salivarius, mitis, anginosus, and mutans groupings).

METHODS

The survival of VGS, Streptococcus gordonii (National Collection of Type Cultures [NCTC] 7865), Streptococcus intermedius (NCTC 11324), Streptococcus mutans (NCTC 10449), Streptococcus oralis (NCTC 11427), Streptococcus pneumoniae (NCTC 7465, NCTC 7978, & American Type Culture Collection 49619) and Streptococcus salivarius (NCTC 8618) was assessed in vitro following treatment of approximately 10(7) c.f.u. in planktonic state with four mouthwashes.

RESULTS

No organisms were culturable following 1-min exposure, and were not recovered following non-selective enrichment following incubation in Brain Heart Infusion broth supplemented with 0.8% (w/v) yeast extract.

CONCLUSIONS

These data indicate that such mouthwashes are able to completely kill VGS organisms tested in planktonic solution, where their use would promote good oral hygiene in patients at risk of IE.

Community interactions of oral streptococci

It is now clear that the most common oral diseases, dental caries and periodontitis, are caused by mixed-species communities rather than by individual pathogens working in isolation. Oral streptococci are central to these disease processes since they are frequently the first microorganisms to colonize oral surfaces and they are numerically the dominant microorganisms in the human mouth. Numerous interactions between oral streptococci and other bacteria have been documented. These are thought to be critical for the development of mixed-species oral microbial communities and for the transition from oral health to disease. Recent metagenomic studies are beginning to shed light on the co-occurrence patterns of streptococci with other oral bacteria. Refinements in microscopy techniques and biofilm models are providing detailed insights into the spatial distribution of streptococci in oral biofilms. Targeted genetic manipulation is increasingly being applied for the analysis of specific genes and networks that modulate interspecies interactions. From this work, it is clear that streptococci produce a range of extracellular factors that promote their integration into mixed-species communities and enable them to form social networks with neighboring taxa. These "community integration factors" include coaggregation-mediating adhesins and receptors, small signaling molecules such as peptides or autoinducer-2, bacteriocins, by-products of metabolism including hydrogen peroxide and lactic acid, and a range of extracellular enzymes. Here, we provide an overview of various types of community interactions between oral streptococci and other microorganisms, and we consider the possibilities for the development of new technologies to interfere with these interactions to help control oral biofilms.

Distribution of Streptococcus troglodytae and Streptococcus dentirousetti in chimpanzee oral cavities

The aim of this study was to analyze the distribution and phenotypic properties of the indigenous streptococci in chimpanzee (Pan troglodytes) oral cavities. Eleven chimpanzees (aged from 9 to 44 years, mean ± SD, 26.9 ± 12.6 years) in the Primate Research Institute of Kyoto University were enrolled in this research and brushing bacterial samples collected from them. Streptococci were isolated from the oral cavities of all chimpanzees. The isolates (n = 46) were identified as thirteen species by 16S rRNA genes analysis. The predominant species was Streptococcus sanguinis of mitis streptococci from five chimpanzees (45%). Mutans streptococci were isolated from six chimpanzees (55%). The predominant species in the mutans streptococci were Streptococcus troglodytae from four chimpanzees (36%), this species having been proposed as a novel species by us, and Streptococcus dentirousetti from three chimpanzees (27%). Streptococcus mutans was isolated from one chimpanzee (9%). However, Streptococcus sobrinus, Streptococcus macacae and Streptococcus downei, which are indigenous to human and monkey (Macaca fasciclaris) oral habitats, were not isolated. Of the mutans streptococci, S. troglodytae, S. dentirousetti, and S. mutans possessed strong adherence activity to glass surface.