Candida-streptococcal interactions in biofilm-associated oral diseases

Association between pica practice, oral health, and cariogenic microorganisms of US pregnant women: A cross-sectional study

OBJECTIVE

To investigate the effects of pica practices during pregnancy on oral health risks and outcomes.

DESIGN

A cross-sectional study was conducted among pregnant women in New York. Demographic, medical history and oral hygiene practice data were collected using validated questionnaires. Comprehensive oral examinations included caries and periodontal status (plaque index and bleeding on probing). Clinical samples (saliva, plaque, and pica substances obtained from participants) were processed to assess the carriage of cariogenic microorganisms (Streptococcus mutans and Candida species) using culturing-dependent and -independent methods. We statistically compared oral clinical and microbial outcomes of pica and non-pica participants.

RESULTS

Among 20 women enrolled (8 (40 %) with pica and 12 (60 %) without pica), the mean gestational age was 25.55 ± 8.82 weeks. Candida species were detected in 25 % of pica samples (n = 2), predominantly from ice samples. The pica group exhibited poorer oral health conditions, showing more decayed-missing-filled teeth and surfaces than the non-pica counterparts (p = 0.016). Although not statistically significant, salivary carriage of C. albicans was 2.8 times higher in women with pica compared to those without (3.3 ± 5.7 × 103 CFU/ml versus 1.2 ± 3.8 × 103 CFU/ml in non-pica, p = 0.093). Women with pica reported markedly higher prevalence of anemia (50 %) compared to non-pica participants (8.3 %) (p = 0.035).

CONCLUSIONS

Pica practices were associated with maternal oral health risks, imploring that clinicians manage pica behaviors to mitigate oral diseases during pregnancy.

Commensalism and pathogenesis of Candida albicans at the mucosal interface

Fungi are important and often underestimated human pathogens. Infections with fungi mostly originate from the environment, from soil or airborne spores. By contrast, Candida albicans, one of the most common and clinically important fungal pathogens, permanently exists in the vast majority of healthy individuals as a member of the human mucosal microbiota. Only under certain circumstances will these commensals cause infections. However, although the pathogenic behaviour and disease manifestation of C. albicans have been at the centre of research for many years, its asymptomatic colonization of mucosal surfaces remains surprisingly understudied. In this Review, we discuss the interplay of the fungus, the host and the microbiome on the dualism of commensal and pathogenic life of C. albicans, and how commensal growth is controlled and permitted. We explore hypotheses that could explain how the mucosal environment shapes C. albicans adaptations to its commensal lifestyle, while still maintaining or even increasing its pathogenic potential.

Candida albicans impacts carbohydrate metabolism of Enterococcus faecalis in interkingdom biofilms

Objectives

This study investigated the transcriptional and physiological responses of Enterococcus faecalis, an opportunistic pathogen linked to endodontic infections, when cultivated in dual-species biofilms with Candida albicans, a yeast pathobiont found in the oral cavity.

Methods

Forty-eight-hour E. faecalis OG1RF biofilms were developed in BHI medium as mono- or dual-species with C. albicans SC5314. Biofilms were assessed for biomass, colony-forming units (CFUs), and architecture using confocal microscopy. RNA sequencing was performed on an Illumina platform. Mannose-PTS activity and glycerol quantification assays were conducted to investigate changes in carbohydrate metabolism.

Results

Transcriptomic analysis revealed 149 E. faecalis genes differentially expressed in dual-species biofilms. Genes linked to mannose-PTS and glycerol metabolism were notably upregulated. Mannose-PTS activity was significantly higher in dual-species biofilms. Mannose, as the sole carbohydrate source, increased E. faecalis CFUs and decreased C. albicans CFUs in co-culture, while glucose had no effect. As C. albicans is a glycerol net producer, glycerol levels were always higher when C. albicans was present, likely contributing to the upregulation of glycerol metabolism genes in E. faecalis when in co-cultures.

Conclusions

The presence of C. albicans alters E. faecalis gene expression and metabolism, suggesting metabolic crosstalk that may influence their pathogenicity and role in oral infections.

A Novel Sugar-Free Probiotic Oral Rinse Influences Oral Candida albicans in Children with Down Syndrome Post Complete Oral Rehabilitation: A Pilot Randomized Clinical Trial with 6-Month Follow-Up

Down syndrome (DS), caused by trisomy 21, affects 1 in 600-1000 live births and is associated with distinctive physical features, cognitive impairment, and oral health challenges such as increased susceptibility to dental caries, periodontal disease, and elevated prevalence of oral Candida spp. Barriers to dental care necessitate comprehensive strategies to address the unique oral health needs of children with DS. The aim of the study was to evaluate the effectiveness of a sugar-free probiotic oral rinse versus 0.2% chlorhexidine digluconate in reducing oral Candida albicans (OCA) counts and improving oral health outcomes in children with DS. A double-blind randomized controlled trial (CTRI/2022/10/046847) enrolled 30 children with DS (aged 6-14 years). Baseline evaluations included OCA quantification and oral health assessments (OHI-S and PHP). Following individualized oral rehabilitation, participants were randomized to either a probiotic rinse (Group 1) or chlorhexidine rinse (Group 2) for 2 weeks. OCA and oral health parameters were assessed at baseline (T0), 2 weeks post-rehabilitation (T1), 2 weeks post-rinse (T2), and 6 months post-rinse (T3). Both groups showed significant improvements in OHI-S and PHP scores (p < 0.05). The probiotic group demonstrated significantly lower OCA counts than the chlorhexidine group at T2 and T3 (p = 0.001). Hence, the probiotic oral rinse can be considered a safe, effective method for reducing OCA and improving oral health outcomes in children with DS, advocating its inclusion in oral health management strategies for this population.

Antibacterial Effects of Er:YAG Laser Irradiation on Candida-Streptococcal Biofilms

In contemporary dentistry, laser-based interventions have become one of the mainstays of care for patients with oral biofilm diseases, such as candidiasis, periodontal disease and peri-implantitis. The purpose of this study was to evaluate the effectiveness of Er:YAG laser (LightWalker, Ljubljana, Fotona, Slovenia) irradiation at varying irradiance levels (T1: 11.3 W/cm2 and T2: 120.54 W/cm2) on microbial viability in single- and dual-species biofilm models, focusing on Candida albicans, Candida glabrata and Streptococcus mutans, to address challenges in managing complex oral biofilms in clinically relevant settings. The results showed substantial microbial reduction, with C. albicans being the most susceptible microorganism (93-99.9%), while C. glabrata exhibited marked resistance at higher irradiance levels. Interestingly, S. mutans demonstrated varying reductions based on the biofilm composition, highlighting the influence of microbial interactions. This study concluded that the Er:YAG laser effectively reduced biofilm viability, with its efficacy depending on the microbial composition and irradiance settings. These findings highlight the need for tailored erbium laser parameters to optimize clinical outcomes, underscoring the need for individualized polymicrobial biofilm management, particularly in periodontal and peri-implant therapies.

Candida albicans Induces Oral Microbial Dysbiosis and Promotes Oral Diseases

Candida albicans are ubiquitous fungal organisms that colonize the oral cavity of healthy individuals without causing disease. C. albicans is an opportunistic microorganism with several virulent factors that influence the inflammatory process and allow it to invade tissues, evade host defense mechanisms, and release toxins, facilitating proliferation and degradation. At present, increasing emphasis is placed on polymicrobial interactions between C. albicans and various bacterial pathogens. Such interaction is mutually beneficial for both parties: it is competitive and antagonistic. Their complex interaction and colonization in the oral cavity serve as the basis for several oral diseases. The dispersion of C. albicans in saliva and the systemic circulation is noted in association with other bacterial populations, suggesting their virulence in causing disease. Hence, it is necessary to understand fungal-bacterial interactions for early detection and the development of novel therapeutic strategies to treat oral diseases. In this paper, we review the mutualistic interaction of C. albicans in oral biofilm formation and polymicrobial interactions in oral diseases. In addition, C. albicans virulence in causing biofilm-related oral diseases and its presence in saliva are discussed.

Association of oral fungal profiles with health status and bacterial composition in elderly adults receiving community support and home care service

Fungi compose a minority but a common component of normal oral microbiota and contribute to oral and systemic health by interacting with bacterial inhabitants. This study investigated the relationship of oral fungal profiles to health status and bacterial profiles of 159 elderly adults receiving community support and home care services. Fungal and bacterial densities and compositions were determined based on the fungal ribosomal internal transcribed spacer region and bacterial 16S rRNA gene amplicon analyses, respectively. The total fungal density of 87 individuals exceeded 5,000 copies, and their microbiota was characterized by significantly less dense bacterial populations and lower relative abundances of oral health-associated taxa, such as Neisseria perflava and Porphyromonas pasteri, compared with those with less than 5,000 copies of fungi. These individuals were significantly older, had fewer teeth, had lower physical function, and comprised more denture users and individuals with cognitive decline. Fungal compositions were classified into three profiles (Candida albicans-dominant, non-albicans Candida-dominant, and non-Candida-dominant), and individuals with a non-albicans Candida-dominant profile exhibited significantly lower physical and cognitive function than those with the Candida albicans-dominant profile. These results demonstrate that a high-density fungal population co-occurs with poor oral and systemic health status of the host and dysbiosis of the bacterial community, and particularly, the overgrowth of non-albicans Candida species may be implicated in worsening systemic conditions.

IMPORTANCE

The interaction between fungal and bacterial components involved in the virulence of oral microbiota has received attention. This study demonstrates that an increase in fungal components is associated with a dysbiotic bacterial community and poor health status in elderly adults. Among individuals with a high-density fungal population, particularly, those with a non-albicans Candida-dominant profile had lower physical and cognitive functions than those with a C. albicans-dominant profile. These findings indicate that the evaluation of fungal components, in addition to the bacterial components, is important to understand the involvement of oral microbiota in oral and systemic diseases in elderly adults.

Effect of hydroxyapatite nanoparticles coating of titanium surface on biofilm adhesion: An in vitro study

AIM

To evaluate the adhesion of mono and duospecies biofilm on a commercially available dental implant surface coated with hydroxyapatite nanoparticles (nanoHA).

MATERIAL AND METHODS

Titanium discs were divided into two groups: double acid-etched (AE) and AE coated with nanoHA (NanoHA). Surface characteristics evaluated were morphology, topography, and wettability. Mono and duospecies biofilms of Streptococcus sanguinis (S. sanguinis) and Candida albicans (C. albicans) were formed. Discs were exposed to fetal bovine serum (FBS) to form the pellicle. Biofilm was growth in RPMI1640 medium with 10% FBS and 10% BHI medium for 6 h. Microbial viability was evaluated using colony-forming unit and metabolic activity by a colorimetric assay of the tetrazolium salt XTT. Biofilm architecture and organization were evaluated by confocal laser scanning microscopy (CLSM) and scanning electron microscopy (SEM).

RESULTS

AE surface had more pores, while NanoHA had even nanoHA crystals distribution. Roughness was similar (AE: 0.59 ± 0.07 µm, NanoHA: 0.69 ± 0.18 µm), but wettability was different (AE: Θw= 81.79 ± 8.55°, NanoHA: Θw= 53.26 ± 11.86°; P = 0.01). NanoHA had lower S. sanguinis viability in monospecies biofilm (P = 0.007). Metabolic activity was similar among all biofilms. In SEM both surfaces on C. albicans biofilm show a similar distribution of hyphae in mono and duospecies biofilms. AE surface has more S. sanguinis than the NanoHA surface in the duospecies biofilm. CLSM showed a large proportion of live cells in all groups.

CONCLUSIONS

The nanoHA surface reduced the adhesion of S. sanguinis biofilm but did not alter the adhesion of C. albicans or the biofilm formed by both species.

Comparative analysis of microbiome in coronal and root caries

BACKGROUND

The global rise in the elderly population has increased the prevalence of root caries. Streptococcus mutans, Lactobacilli and Actinomyces are considered the primary pathogens of dental caries in culture-based studies. This study aimed to investigate bacterial profiles in coronal and root caries lesions and determine the association of specific bacterial genera at each site.

METHODS

Dentine samples from carious lesions were collected from 22 extracted teeth using an excavator. Microbial DNA was extracted from the samples using a protocol developed for this study. 16S rRNA gene amplicon sequencing was employed for microbial analysis. PCR amplification targeted the V3-V4 region of the bacterial 16S rRNA, and the amplicon sequencing used an Illumina MiSeq system (2 × 300 bp paired-end reads). Statistical analysis was performed by the Phyloseq and DESeq2 packages in R.

RESULTS

In coronal caries, Olsenella, Lactobacillus and Prevotella were the most prevalent genera, comprising approximately 70% of the microbiome community. In the root caries, however, although Olsenella, Prevotella and Lactobacillus remained the dominant genera, they accounted for only half of the microbiome community. This study identified significant differences in alpha diversity indices between the coronal and root caries. LEfSE analysis revealed several unique genera in each caries lesion.

CONCLUSION

The microbiome of root caries lesions was richer and more complex than the coronal caries microbiota. The results suggest that lesion-related variations in the oral microflora may be detected in carious dentine.

Surface-Charge Tuned Polymeric Nanoemulsions for Carvacrol Delivery in Interkingdom Biofilms

Biofilms, intricate microbial communities entrenched in extracellular polymeric substance (EPS) matrices, pose formidable challenges in infectious disease treatment, especially in the context of interkingdom biofilms prevalent in the oral environment. This study investigates the potential of carvacrol-loaded biodegradable nanoemulsions (NEs) with systematically varied surface charges─cationic guanidinium (GMT-NE) and anionic carboxylate (CMT-NE). Zeta potentials of +25 mV (GMT-NE) and -33 mV (CMT-NE) underscore successful nanoemulsion fabrication (∼250 nm). Fluorescent labeling and dynamic tracking across three dimensions expose GMT-NE's superior diffusion into oral biofilms, yielding a robust antimicrobial effect with 99.99% killing for both streptococcal and Candida species and marked reductions in bacterial cell viability compared to CMT-NE (∼4-log reduction). Oral mucosa tissue cultures affirm the biocompatibility of both NEs with no morphological or structural changes, showcasing their potential for combating intractable biofilm infections in oral environment. This study advances our understanding of NE surface charges and their interactions within interkingdom biofilms, providing insights crucial for addressing complex infections involving bacteria and fungi in the demanding oral context.

Anti-Infection of Oral Microorganisms from Herbal Medicine of Piper crocatum Ruiz & Pav

The WHO Global Status Report on Oral Health 2022 reveals that oral diseases caused by infection with oral pathogenic microorganisms affect nearly 3.5 billion people worldwide. Oral health problems are caused by the presence of S. mutans, S. sanguinis, E. faecalis and C. albicans in the oral cavity. Synthetic anti-infective drugs have been widely used to treat oral infections, but have been reported to cause side effects and resistance. Various strategies have been implemented to overcome this problem. Synthetic anti-infective drugs have been widely used to treat oral infections, but they have been reported to cause side effects and resistance. Therefore, it is important to look for safe anti-infective alternatives. Ethnobotanical and ethnopharmacological studies suggest that Red Betel leaf (Piper crocatum Ruiz & Pav) could be a potential source of oral anti-infectives. This review aims to discuss the pathogenesis mechanism of several microorganisms that play an important role in causing health problems, the mechanism of action of synthetic oral anti-infective drugs in inhibiting microbial growth in the oral cavity, and the potential of red betel leaf (Piper crocatum Ruiz & Pav) as an herbal oral anti-infective drug. This study emphasises the importance of researching natural components as an alternative treatment for oral infections that is more effective and can meet global needs.

In vitro biofilm formation of Gardnerella vaginalis and Escherichia coli associated with bacterial vaginosis and aerobic vaginitis

Objective

To determine the optimum biofilm formation ratio of Gardnerella vaginalis (G. vaginalis) in a mixed culture with Escherichia coli (E. coli).

Methods

G. vaginalis ATCC14018, E. coli ATCC25922, as well as five strains of G. vaginalis were selected from the vaginal sources of patients whose biofilm forming capacity was determined by the Crystal Violet method. The biofilm forming capacity of E. coli in anaerobic and non-anaerobic environments were compared using the identical assay. The Crystal Violet method was also used to determine the biofilm forming capacity of a co-culture of G. vaginalis and E. coli in different ratios. After Live/Dead staining, biofilm thickness was measured using confocal laser scanning microscopy, and biofilm morphology was observed by scanning electron microscopy.

Results

The biofilm forming capacity of E. coli under anaerobic environment was similar to that in a 5% CO2 environment. The biofilm forming capacity of G. vaginalis and E. coli was stronger at 106:105 CFU/mL than at other ratios (P<0.05). Their thicknesses were greater at 106:105 CFU/mL than at the other ratios, with the exception of 106:102 CFU/mL (P<0.05), under laser scanning microscopy. Scanning electron microscopy revealed increased biofilm formation at 106:105 CFU/mL and 106:102 CFU/mL, but no discernible E. coli was observed at 106:102 CFU/mL.

Conclusion

G. vaginalis and E. coli showed the greatest biofilm forming capacity at a concentration of 106:105 CFU/mL at 48 hours and could be used to simulate a mixed infection of bacterial vaginosis and aerobic vaginitis in vitro.

Unveiling the complexity of early childhood caries: Candida albicans and Streptococcus mutans cooperative strategies in carbohydrate metabolism and virulence

Objective

To explore the mechanisms underlying the virulence changes in early childhood caries (ECC) caused by Candida albicans (C. albicans) and Streptococcus mutans (S. mutans), with a focus on carbohydrate metabolism and environmental acidification.

Methods

A review of literature was conducted to understand the symbiotic relationship between C. albicans and S. mutans, and their role in the pathogenesis of ECC. The review also examined how their interactions influence carbohydrate metabolism and environmental acidification in the oral cavity.

Results

C. albicans and S. mutans play crucial roles in the onset and progression of ECC. C. albicans promotes the adhesion and accumulation of S. mutans, while S. mutans creates an environment favorable for the growth of C. albicans. Their interactions, especially through carbohydrate metabolism, strengthen their pathogenic potential. The review highlights the importance of understanding these mechanisms for the development of effective management and treatment protocols for ECC.

Conclusion

The symbiotic relationship between C. albicans and S. mutans, and their interactions through carbohydrate metabolism and environmental acidification, are key factors in the pathogenesis of ECC. A comprehensive understanding of these mechanisms is crucial for developing effective strategies to manage and treat ECC.

3Y-TZP/Ta Biocermet as a Dental Material: An Analysis of the In Vitro Adherence of Streptococcus Oralis Biofilm and an In Vivo Pilot Study in Dogs

The surface adhesion of bacterial cells and the in vivo biocompatibility of a new ceramic-metal composite made of zirconium dioxide and tantalum were evaluated. Within the framework of an in vitro study using the crystal violet staining and colony counting methods, a relatively similar adhesion of Streptococcus oralis to the 3Y-TZP/Ta biocermet (roughness Ra = 0.12 ± 0.04 µm) and Ti-Al6-V4 titanium alloy (Ra = 0.04 ± 0.01 µm) was found. In addition, in an in vivo preliminary study focused on the histological analysis of a series of rods implanted in the jaws of beagle dogs for a six-month period, the absence of any fibrous tissue or inflammatory reaction at the interface between the implanted 3Y-TZP/Ta biocermets and the new bone was found. Thus, it can be concluded that the developed ceramic-metal biocomposite may be a promising new material for use in dentistry.

Marine-derived κ-carrageenan-coated zinc oxide nanoparticles for targeted drug delivery and apoptosis induction in oral cancer

BACKGROUND

Kappaphycus alvarezii, a marine red algae species, has gained significant attention in recent years due to its versatile bioactive compounds. Among these, κ-carrageenan (CR), a sulfated polysaccharide, exhibits remarkable antimicrobial properties. This study emphasizes the synergism attained by functionalizing zinc oxide nanoparticles (ZnO NPs) with CR, thereby enhancing its antimicrobial efficacy and target specificity against dental pathogens.

METHODS

In this study, we synthesized ZnO-CR NPs and characterized them using SEM, FTIR, and XRD techniques to authenticate their composition and structural attributes. Moreover, our investigation revealed that ZnO-CR NPs possess better free radical scavenging capabilities, as evidenced by their effective activity in the DPPH and ABTS assay.

RESULTS

The antimicrobial properties of ZnO-CR NPs were systematically assessed using a zone of inhibition assay against dental pathogens of S. aureus, S. mutans, E. faecalis, and C. albicans, demonstrating their substantial inhibitory effects at a minimal concentration of 50 μg/mL. We elucidated the interaction between CR and the receptors of dental pathogens to further understand their mechanism of action. The ZnO-CR NPs demonstrated a dose-dependent anticancer effect at concentrations of 5 μg/mL, 25 μg/mL, 50 μg/mL, and 100 μg/mL on KB cells, a type of Human Oral Epidermal Carcinoma. The mechanism by which ZnO-CA NPs induced apoptosis in KB cells was determined by observing an increase in the expression of the BCL-2, BAX, and P53 genes.

CONCLUSION

Our findings unveil the promising potential of ZnO-CR NPs as a candidate with significant utility in dental applications. The demonstrated biocompatibility, potent antioxidant and antiapoptotic activity, along with impressive antimicrobial efficacy position these NPs as a valuable resource in the ongoing fight against dental pathogens and oral cancer.

Candida-bacterial cross-kingdom interactions

While the fungus Candida albicans is a common colonizer of healthy humans, it is also responsible for mucosal infections and severe invasive disease. Understanding the mechanisms that allow C. albicans to exist as both a benign commensal and as an invasive pathogen have been the focus of numerous studies, and recent findings indicate an important role for cross-kingdom interactions on C. albicans biology. This review highlights how C. albicans-bacteria interactions influence healthy polymicrobial community structure, host immune responses, microbial pathogenesis, and how dysbiosis may lead to C. albicans infection. Finally, we discuss how cross-kingdom interactions represent an opportunity to identify new antivirulence compounds that target fungal infections.

Surface adherence and vacuolar internalization of bacterial pathogens to the Candida spp. cells: Mechanism of persistence and propagation

BACKGROUND

The co-existence of Candida albicans with the bacteria in the host tissues and organs displays interactions at competitive, antagonistic, and synergistic levels. Several pathogenic bacteria take advantage of such types of interaction for their survival and proliferation. The chemical interaction involves the signaling molecules produced by the bacteria or Candida spp., whereas the physical attachment occurs by involving the surface proteins of the bacteria and Candida. In addition, bacterial pathogens have emerged to internalize inside the C. albicans vacuole, which is one of the inherent properties of the endosymbiotic relationship between the bacteria and the eukaryotic host.

AIM OF REVIEW

The interaction occurring by the involvement of surface protein from diverse bacterial species with Candida species has been discussed in detail in this paper. An in silico molecular docking study was performed between the surface proteins of different bacterial species and Als3P of C. albicans to explain the molecular mechanism involved in the Als3P-dependent interaction. Furthermore, in order to understand the specificity of C. albicans interaction with Als3P, the evolutionary relatedness of several bacterial surface proteins has been investigated. Furthermore, the environmental factors that influence bacterial pathogen internalization into the Candida vacuole have been addressed. Moreover, the review presented future perspectives for disrupting the cross-kingdom interaction and eradicating the endosymbiotic bacterial pathogens.

KEY SCIENTIFIC CONCEPTS OF REVIEW

With the involvement of cross-kingdom interactions and endosymbiotic relationships, the bacterial pathogens escape from the environmental stresses and the antimicrobial activity of the host immune system. Thus, the study of interactions between Candida and bacterial pathogens is of high clinical significance.

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.

Social networking at the microbiome-host interface

Microbial species colonizing host ecosystems in health or disease rarely do so alone. Organisms conglomerate into dynamic heterotypic communities or biofilms in which interspecies and interkingdom interactions drive functional specialization of constituent species and shape community properties, including nososymbiocity or pathogenic potential. Cell-to-cell binding, exchange of signaling molecules, and nutritional codependencies can all contribute to the emergent properties of these communities. Spatial constraints defined by community architecture also determine overall community function. Multilayered interactions thus occur between individual pairs of organisms, and the relative impact can be determined by contextual cues. Host responses to heterotypic communities and impact on host surfaces are also driven by the collective action of the community. Additionally, the range of interspecies interactions can be extended by bacteria utilizing host cells or host diet to indirectly or directly influence the properties of other organisms and the community microenvironment. In contexts where communities transition to a dysbiotic state, their quasi-organismal nature imparts adaptability to nutritional availability and facilitates resistance to immune effectors and, moreover, exploits inflammatory and acidic microenvironments for their persistence.

In vitro efficacy of synthetic lawsone derivative disinfectant solution on removing dual-species biofilms and effect on acrylic denture surface properties

Candida albicans (C. albicans) and Streptococcus mutans (S. mutans) biofilms involve in denture stomatitis. This study compared compound 1 to 2% chlorhexidine gluconate (CHX), Polident, and distilled water (DW) in biofilms reduction and effect on polymethylmethacrylate acrylic (PMMA) properties. The structure of lawsone (naphthoquinone derivative) was modified by the addition of an alkylnyloxy group to yield compound 1. Dual-species biofilms of C. albicans and S. mutans were developed on PMMA discs. The colony-forming unit count measured the number of residual biofilm cells after exposure to the test agents. PMMA discs were examined for color stability, surface roughness, hardness, and chemical structure after 28 days. At 3 min, compound 1 was less effective than CHX in reducing C. albicans (p = 0.004) and S. mutans (p = 0.034) but more effective than Polident in reducing C. albicans (p = 0.001). At 15 min, no viable cells were detectable for compound 1 and its effectiveness was comparable to CHX (p = 0.365). SEM showed fungal cell surface damages in CHX, compound 1 and Polident groups. Only color change was affected by time (p < 0.001) and type of test agent (p = 0.008), and only CHX reached a clinical perception level. Compound 1 is a promising agent for removing biofilm from the PMMA surface without substantially degrading surface properties.

In Vitro Evaluation of Candida albicans Adhesion on Heat-Cured Resin-Based Dental Composites

Microbial adhesion on dental restorative materials may jeopardize the restorative treatment long-term outcome. The goal of this in vitro study was to assess Candida albicans capability to adhere and form a biofilm on the surface of heat-cured dental composites having different formulations but subjected to identical surface treatments and polymerization protocols. Three commercially available composites were evaluated: GrandioSO (GR), Venus Diamond (VD) and Enamel Plus HRi Biofunction (BF). Cylindrical specimens were prepared for quantitative determination of C. albicans S5 planktonic CFU count, sessile cells CFU count and biomass optical density (OD570 nm). Qualitative Concanavalin-A assays (for extracellular polymeric substances of a biofilm matrix) and Scanning Electron Microscope (SEM) analyses (for the morphology of sessile colonies) were also performed. Focusing on planktonic CFU count, a slight but not significant reduction was observed with VD as compared to GR. Regarding sessile cells CFU count and biomass OD570 nm, a significant increase was observed for VD compared to GR and BF. Concanavalin-A assays and SEM analyses confirmed the quantitative results. Different formulations of commercially available resin composites may differently interact with C. albicans. The present results showed a relatively more pronounced antiadhesive effect for BF and GR, with a reduction in sessile cells CFU count and biomass quantification.

Perspective on receptor-associated immune response to Candida albicans single and mixed infections: Implications for therapeutics in oropharyngeal candidiasis

Oropharyngeal candidiasis (OPC), commonly known as 'thrush', is an oral infection that usually dismantles oral mucosal integrity and malfunctions local innate and adaptive immunities in compromised individuals. The major pathogen responsible for the occurrence and progression of OPC is the dimorphic opportunistic commensal Candida albicans. However, the incidence induced by non-albicans Candida species including C. glabrata, C. tropicalis, C. dubliniensis, C. parapsilosis, and C. krusei are increasing in company with several oral bacteria, such as Streptococcus mutans, S. gordonii, S. epidermidis, and S. aureus. In this review, the microbiological and infection features of C. albicans and its co-contributors in the pathogenesis of OPC are outlined. Since the invasion and concomitant immune response lie firstly on the recognition of oral pathogens through diverse cellular surface receptors, we subsequently emphasize the roles of epidermal growth factor receptor, ephrin-type receptor 2, human epidermal growth factor receptor 2, and aryl hydrocarbon receptor located on oral epithelial cells to delineate the underlying mechanism by which host immune recognition to oral pathogens is mediated. Based on these observations, the therapeutic approaches to OPC comprising conventional and non-conventional antifungal agents, fungal vaccines, cytokine and antibody therapies, and antimicrobial peptide therapy are finally overviewed. In the face of newly emerging life-threatening microbes (C. auris and SARS-CoV-2), risks (biofilm formation and interconnected translocation among diverse organs), and complicated clinical settings (HIV and oropharyngeal cancer), the research on OPC is still a challenging task.

Antifungal therapy: Novel drug delivery strategies driven by new targets

In patients with compromised immunity, invasive fungal infections represent a significant cause of mortality. Given the limited availability and drawbacks of existing first-line antifungal drugs, there is a growing interest in exploring novel targets that could facilitate the development of new antifungal agents or enhance the effectiveness of conventional ones. While previous studies have extensively summarized new antifungal targets inherent in fungi for drug development purposes, the exploration of potential targets for novel antifungal drug delivery strategies has received less attention. In this review, we provide an overview of recent advancements in new antifungal drug delivery strategies that leverage novel targets, including those located in the physio-pathological barrier at the site of infection, the infection microenvironment, fungal-host interactions, and the fungal pathogen itself. The objective is to enhance therapeutic efficacy and mitigate toxic effects in fungal infections, particularly in challenging cases such as refractory, recurrent, and drug-resistant invasive fungal infections. We also discuss the current challenges and future prospects associated with target-driven antifungal drug delivery strategies, offering important insights into the clinical implementation of these innovative approaches.

Effect of silver diamine fluoride upon the microbial community of carious lesions: A scoping review

OBJECTIVES

To explore the effects of silver diamine fluoride (SDF) on the microbial community of carious lesions.

DATA

Original studies evaluating the effect of SDF treatment on the microbial community of human carious lesions were included.

SOURCES

A systematic search of English-language publications was performed in PubMed, EMBASE, Scopus, and Web of Science. Gray literature was searched in ClinicalTrials.gov and Google Scholar.

STUDY SELECTION/RESULTS

This review included seven publications reporting the effects of SDF on microbial community of dental plaque or carious dentin, including the microbial biodiversity, relative abundance of microbial taxa, and predicted functional pathways of the microbial community. The studies on microbial community of dental plaque reported that SDF did not have a significant effect on both the within-community species diversity (alpha-diversity) and inter-community microbial compositional dissimilarity (beta-diversity) of the plaque microbial communities. However, SDF changed the relative abundance of 29 bacterial species of plaque community, inhibited carbohydrate transportation and interfered with the metabolic functions of the plaque microbial community. A study on the microbial community in dentin carious lesions reported that SDF affected its beta-diversity and changed the relative abundance of 14 bacterial species.

CONCLUSION

SDF showed no significant effects on the biodiversity of the plaque microbial community but changed the beta-diversity of the carious dentin microbial community. SDF could change the relative abundance of certain bacterial species in the dental plaque and the carious dentin. SDF could also affect the predicted functional pathways of the microbial community.

CLINICAL SIGNIFICANCE

This review provided comprehensive evidence on the potential effect of SDF treatment on the microbial community of carious lesions.

Combating polymicrobial biofilm: recent approaches

The polymicrobial biofilm (PMBF) is formed when microbes from multiple species co-aggregate into an envelope made of extra polymeric substances (EPS) that keep the microbes safe from external stresses. The formation of PMBF has been linked to a variety of human infections, including cystic fibrosis, dental caries, urinary tract infections, etc. Multiple microbial species co-aggregation during an infection results in a recalcitrant biofilm formation, which is a seriously threatening phenomenon. It is challenging to treat polymicrobial biofilms since they contain multiple microbes which show drug resistance to various antibiotics/antifungals. The present study discusses various approaches by which an antibiofilm compound works. Depending on their mode of action, antibiofilm compounds can block the adhesion of cells to one another, modify membranes/walls, or disrupt quorum-sensing systems.

Cross-kingdom Microbial Interactions Within the Oral Cavity and Their Implications for Oral Disease

Purpose of Review

This review serves to highlight the cross-kingdom interactions that can occur within the human oral cavity between fungus Candida albicans and oral bacteria, and their impact on the delicate balance between oral health and disease.

Recent Findings

A growing number of physical, chemical, and metabolic networks have been identified that underpin these cross-kingdom interactions. Moreover, these partnerships are often synergistic and can modulate microbial burden or virulence. This, in turn, can drive the onset or progression of oral diseases such as dental caries, periodontitis, denture-associated stomatitis, and oral cancer.

Summary

The impact of cross-kingdom interactions on the cellular, biochemical, and communal composition of oral microbial biofilms is increasingly clear. With growing insight into these processes at the molecular level, so this knowledge can be used to better inform the development of novel strategies to manipulate the oral microbiota to promote oral health and combat oral disease.

Characterization of the salivary microbiome before and after antibiotic therapy via separation technique

In the present research, the MALDI-TOF MS technique was applied as a tool to rapidly identify the salivary microbiome. In this fact, it has been monitored the changes occurred in molecular profiles under different antibiotic therapy. Significant changes in the composition of the salivary microbiota were noticed not only in relation to the non antibiotic (non-AT) and antibiotic treatment (AT) groups, but also to the used media, the antibiotic therapy and co-existed microbiota. Each antibiotic generates specific changes in molecular profiles. The highest number of bacterial species was isolated in the universal culture medium (72%) followed by the selective medium (48% and 38%). In the case of non-AT patients, the prevalence of Streptococcus salivarius (25%), Streptococcus vestibularis (19%), Streptococcus oralis (13%), and Staphylococcus aureus (6%) was identified while in the case of AT, Streptococcus salivarius (11%), Streptococcus parasanguinis (11%), Staphylococcus epidermidis (12%), Enterococcus faecalis (9%), Staphylococcus hominis (8%), and Candida albicans (6%) were identified. Notable to specified that the Candida albicans was noticed only in AT samples, indicating a negative impact on the antibiotic therapy. The accuracy of the MALDI-TOF MS technique was performed by the 16S rRNA gene sequencing analysis-as a reference method. Conclusively, such an approach highlighted in the present study can help in developing the methods enabling a faster diagnosis of disease changes at the cellular level before clinical changes occur. Once the MALDI tool allows for the distinguishing of the microbiota of non-AT and AT, it may enable to monitor the diseases treatment and develop a treatment regimen for individual patients in relation to each antibiotic. KEY POINTS: The salivary microbiota of antibiotic-treated patients was more bacteria variety MALDI-TOF MS is a promising tool for recording of reproducible molecular profiles Our data can allow to monitor the treatment of bacterial diseases for patients.

Effects of Nystatin oral rinse on oral Candida species and Streptococcus mutans among healthy adults

OBJECTIVES

To examine the effect of Nystatin oral rinse on oral Candida species and Streptococcus mutans carriage.

MATERIALS AND METHODS

Twenty healthy adults with oral candidiasis participated in the single-arm clinical trial and received Nystatin oral rinse for 7 days, 4 applications/day, and 600,000 International Units/application. Demographic-socioeconomic-oral-medical conditions were obtained. Salivary and plaque Candida species and Streptococcus mutans were assessed at baseline and 1-week and 3-month follow-ups. Twenty-four salivary cytokines were assessed. Candida albicans isolates underwent Nystatin susceptibility test.

RESULTS

Half of participants (10/20) were free of salivary C. albicans after using Nystatin rinse. Salivary S. mutans was significantly reduced at 3-month follow-up (p < 0.05). Periodontal status reflected by bleeding-on-probing was significantly improved at 1-week and 3-month follow-ups (p < 0.05). Plaque accumulation was significantly reduced at 1-week follow-up (p < 0.05). Interestingly, the responses to Nystatin oral rinse were not associated with race, gender, age, oral hygiene practice, adherence to Nystatin rinse, or sweet consumption (p > 0.05). No C. albicans isolates were resistant to Nystatin. Furthermore, salivary cytokine eotaxin and fractalkine were significantly reduced at 3-month follow-up among participants who responded to Nystatin rinse (p < 0.05).

CONCLUSIONS

The study results indicate that oral antifungal treatment had an effect on S. mutans salivary carriage. Future clinical trials are warranted to comprehensively assess the impact of antifungal treatment on the oral flora other than S. mutans and Candida.

CLINICAL RELEVANCE

Due to the potential cariogenic role of oral Candida species, antifungal approaches shed new light on the prevention and management of dental caries from a fungal perspective.

Impact of direct physical association and motility on fitness of a synthetic interkingdom microbial community

Mutualistic exchange of metabolites can play an important role in microbial communities. Under natural environmental conditions, such exchange may be compromised by the dispersal of metabolites and by the presence of non-cooperating microorganisms. Spatial proximity between members during sessile growth on solid surfaces has been shown to promote stabilization of cross-feeding communities against these challenges. Nonetheless, many natural cross-feeding communities are not sessile but rather pelagic and exist in turbulent aquatic environments, where partner proximity is often achieved via direct cell-cell adhesion, and cooperation occurs between physically associated cells. Partner association in aquatic environments could be further enhanced by motility of individual planktonic microorganisms. In this work, we establish a model bipartite cross-feeding community between bacteria and yeast auxotrophs to investigate the impact of direct adhesion between prokaryotic and eukaryotic partners and of bacterial motility in a stirred mutualistic co-culture. We demonstrate that adhesion can provide fitness benefit to the bacterial partner, likely by enabling local metabolite exchange within co-aggregates, and that it counteracts invasion of the community by a non-cooperating cheater strain. In a turbulent environment and at low cell densities, fitness of the bacterial partner and its competitiveness against a non-cooperating strain are further increased by motility that likely facilitates partner encounters and adhesion. These results suggest that, despite their potential fitness costs, direct adhesion between partners and its enhancement by motility may play key roles as stabilization factors for metabolic communities in turbulent aquatic environments.

Human Tooth as a Fungal Niche: Candida albicans Traits in Dental Plaque Isolates

Candida albicans, a fungus typically found in the mucosal niche, is frequently detected in biofilms formed on teeth (dental plaque) of toddlers with severe childhood caries, a global public health problem that causes rampant tooth decay. However, knowledge about fungal traits on the tooth surface remains limited. Here, we assess the phylogeny, phenotype, and interkingdom interactions of C. albicans isolated from plaque of diseased toddlers and compare their properties to reference strains, including 529L (mucosal isolate). C. albicans isolates exhibit broad phenotypic variations, but all display cariogenic traits, including high proteinase activity, acidogenicity, and acid tolerance. Unexpectedly, we find distinctive variations in filamentous growth, ranging from hyphal defective to hyperfilamentous. We then investigate the ability of tooth isolates to form interkingdom biofilms with Streptococcus mutans (cariogenic partner) and Streptococcus gordonii (mucosal partner). The hyphal-defective isolate lacks cobinding with S. gordonii, but all C. albicans isolates develop robust biofilms with S. mutans irrespective of their filamentation state. Moreover, either type of C. albicans (hyphae defective or hyperfilamentous) enhances sucrose metabolism and biofilm acidogenicity, creating highly acidic environmental pH (<5.5). Notably, C. albicans isolates show altered transcriptomes associated with pH, adhesion, and cell wall composition (versus reference strains), further supporting niche-associated traits. Our data reveal that C. albicans displays distinctive adaptive mechanisms on the tooth surface and develops interactions with pathogenic bacteria while creating an acidogenic state regardless of fungal morphology, contrasting with interkingdom partnerships in mucosal infections. Human tooth may provide new insights into fungal colonization/adaptation, interkingdom biofilms, and contributions to disease pathogenesis. IMPORTANCE Severe early childhood caries is a widespread global public health problem causing extensive tooth decay and systemic complications. Candida albicans, a fungus typically found in mucosal surfaces, is frequently detected in dental plaque formed on teeth of diseased toddlers. However, the clinical traits of C. albicans isolated from tooth remain underexplored. Here, we find that C. albicans tooth isolates exhibit unique biological and transcriptomic traits. Notably, interkingdom biofilms with S. mutans can be formed irrespective of their filamentation state. Furthermore, tooth isolates commonly share dental caries-promoting functions, including acidogenesis, proteolytic activity, and enhanced sugar metabolism, while displaying increased expression of pH-responsive and adhesion genes. Our findings reveal that C. albicans colonizing human teeth displays distinctive adaptive mechanisms to mediate interkingdom interactions associated with a disease-causing state on a mineralized surface, providing new insights into Candida pathobiology and its role in a costly pediatric disease.

Potential Use of Brazilian Green Propolis Extracts as New Photosensitizers for Antimicrobial Photodynamic Therapy against Cariogenic Microorganisms

The synergic effect of Streptococcus mutans and Candida albicans increases dental caries severity. Antimicrobial photodynamic therapy (aPDT) is a non-invasive treatment for antimicrobial aspects. However, the current photosensitizers (PS) have many downsides for dental applications. This study aimed to evaluate the efficiency of two different Brazilian green propolis (BGP-AF and BGP-AG) as PS for aPDT against these microorganisms. A single-species biofilm was irradiated with crude extracts and their fractions and controls. Such extracts showed the best results and were evaluated in dual-species biofilms. Photodegradation, reactive oxygen species (ROS), cytotoxicity, and color stability assays were also investigated. Reductions higher than 3 log₁₀ CFU/mL (p < 0.0001) occurred for crude BGP in single- and dual-species biofilms. Singlet oxygen was produced in BGP (p < 0.0001). BGP-mediated aPDT delayed S. mutans and C. albicans regrowth after 24 h of treatment (p < 0.0001). Both BGP did not change the color of dental materials (p > 0.05). BGP-AF-mediated aPDT showed 72.41% of oral keratinocyte viability (p < 0.0001). BGP extracts may be used in aPDT against S. mutans and C. albicans. Specifically, BGP-AF may represent a promising PS for dental applications.

Effect of Nystatin on Candida albicans - Streptococcus mutans duo-species biofilms

OBJECTIVE

To assess the effect of Nystatin on Candida albicans and Streptococcus mutans duo-species biofilms using an in vitro cariogenic biofilm model.

DESIGN

Biofilms were formed on saliva-coated hydroxyapatite discs under high sugar challenge (1 % sucrose and 1 % glucose), with inoculation of 105CFU/ml S. mutans and 103CFU/ml C. albicans. Between 20 and 68 h, biofilms were treated with 28,000 IU Nystatin solution, 5 min/application, 4 times/day, to mimic the clinical application. Biofilm's three-dimensional structure was assessed using multi-photon confocal microscopy. The expression of C. albicans and S. mutans virulence genes was assessed via real-time PCR. Duplicate discs were used in 3 independent repeats. t-test and Mann-Whitney U test were used to compare outcomes between treatment and control group.

RESULTS

Nystatin treatment eliminated C. albicans in biofilms at 44 h. Nystatin-treated group had a significant reduction of biofilm dry-weight and reduced S. mutans abundance by 0.5 log CFU/ml at 44 and 68 h (p < 0.05). Worth noting that biomass distribution across the vertical layout was altered by Nystatin treatment, resulting in less volume on the substrate layers in Nystatin-treated biofilms compared to the control. Reduction of microcolonies size and volume was also observed in Nystatin-treated biofilms (p < 0.05). Nystatin-treated biofilms formed unique halo-shaped microcolonies with reduced core EPS coverage. Furthermore, Nystatin-treated biofilms had significant down-regulations of S. mutans gtfD and atpD genes (p < 0.05).

CONCLUSIONS

Nystatin application altered the formation and characteristics of C. albicans and S. mutans duo-species biofilms. Therefore, developing clinical regimens for preventing or treating dental caries from an antifungal perspective is warranted.

Dual transcriptome of Streptococcus mutans and Candida albicans interplay in biofilms

Objective

To assess the interactions between Streptococcus mutans and Candida albicans during cariogenic biofilm formation.

Methods

The S. mutans and C. albicans duo-species biofilms were formed in 1% sucrose to mimic the high caries risk challenges. The biofilm structure was assessed using two-photon laser confocal microscopy. The transcriptome of 48h-biofilms was assessed by RNA-Seq. The expression of S. mutans and C. albicans virulence genes was examined via real-time reverse transcription-polymerase chain reaction.

Results

The morphogenesis of C. albicans-S. mutans duo-species biofilms was significantly altered when comparing to S. mutans or C. albicans single-species biofilm. Duo-species biofilms exhibited unique expression profile with a large number of differentially expressed genes (DEGs), including a higher expression of S. mutans atpD (acid-adaptive), C. albicans CHT2 (fungal cell wall chitin remodeling), and C. albicans SOD3 (cytotoxic oxygen radical destroying) (p < 0.05). KEGG pathway analyses further revealed that the majority of the up-regulated DEGs are related to microbial metabolism. Furthermore, the expressions of S. mutans and C. albicans key virulence genes (gtfB, gtfC, gtfD, ECE1, HWP1, ERG4, CHT2) were associated with sugar availability-related and time-related dynamics.

Conclusion

Cross-kingdom interactions impact S. mutans-C. albicans biofilm formations and dynamic expressions of virulence genes.

Biofilm ecology associated with dental caries: Understanding of microbial interactions in oral communities leads to development of therapeutic strategies targeting cariogenic biofilms

A biofilm is a sessile community characterized by cells attached to the surface and organized into a complex structural arrangement. Dental caries is a biofilm-dependent oral disease caused by infection with cariogenic pathogens, such as Streptococcus mutans, and associated with frequent exposure to a sugar-rich diet and poor oral hygiene. The virulence of cariogenic biofilms is often associated with the spatial organization of S. mutans enmeshed with exopolysaccharides on tooth surfaces. However, in the oral cavity, S. mutans does not act alone, and several other microbes contribute to cariogenic biofilm formation. Microbial communities in cariogenic biofilms are spatially organized into complex structural arrangements of various microbes and extracellular matrices. The balance of microbiota diversity with reduced diversity and a high proportion of acidogenic-aciduric microbiota within the biofilm is closely related to the disease state. Understanding the characteristics of polymicrobial biofilms and the association of microbial interactions within the biofilm (e.g., symbiosis, cooperation, and competition) in terms of their potential role in the pathogenesis of oral disease would help develop new strategies for interventions in virulent biofilm formation.

Drugs for the Quorum Sensing Inhibition of Oral Biofilm: New Frontiers and Insights in the Treatment of Periodontitis

Chemical molecules are used by microorganisms to communicate with each other. Quorum sensing is the mechanism through which microorganisms regulate their population density and activity with chemical signaling. The inhibition of quorum sensing, called quorum quenching, may disrupt oral biofilm formation, which is the main etiological factor of oral diseases, including periodontitis. Periodontitis is a chronic inflammatory disorder of infectious etiology involving the hard and soft periodontal tissues and which is related to various systemic disorders, including cardiovascular diseases, diabetes and obesity. The employment of adjuvant therapies to traditional scaling and root planing is currently being studied to further reduce the impact of periodontitis. In this sense, using antibiotics and antiseptics involves non-negligible risks, such as antibiotic resistance phenomena and hinders the re-establishment of eubiosis. Different quorum sensing signal molecules have been identified in periodontal pathogenic oral bacteria. In this regard, quorum sensing inhibitors are emerging as some interesting solutions for the management of periodontitis. Therefore, the aim of this review is to summarize the current state of knowledge on the mechanisms of quorum sensing signal molecules produced by oral biofilm and to analyze the potential of quorum sensing inhibitors for the management of periodontitis.

Cross-kingdom interaction between Candida albicans and oral bacteria

Candida albicans is a symbiotic fungus that commonly colonizes on oral mucosal surfaces and mainly affects immuno-compromised individuals. Polymicrobial interactions between C. albicans and oral microbes influence the cellular and biochemical composition of the biofilm, contributing to change clinically relevant outcomes of biofilm-related oral diseases, such as pathogenesis, virulence, and drug-resistance. Notably, the symbiotic relationships between C. albicans and oral bacteria have been well-documented in dental caries, oral mucositis, endodontic and periodontal diseases, implant-related infections, and oral cancer. C. albicans interacts with co-existing oral bacteria through physical attachment, extracellular signals, and metabolic cross-feeding. This review discusses the bacterial-fungal interactions between C. albicans and different oral bacteria, with a particular focus on the underlying mechanism and its relevance to the development and clinical management of oral diseases.

Interkingdom assemblages in human saliva display group-level surface mobility and disease-promoting emergent functions

Fungi and bacteria form multicellular biofilms causing many human infections. How such distinctive microbes act in concert spatiotemporally to coordinate disease-promoting functionality remains understudied. Using multiscale real-time microscopy and computational analysis, we investigate the dynamics of fungal and bacterial interactions in human saliva and their biofilm development on tooth surfaces. We discovered structured interkingdom assemblages displaying emergent functionalities to enhance collective surface colonization, survival, and growth. Further analyses revealed an unexpected group-level surface mobility with coordinated “leaping-like” and “walking-like” motions while continuously growing. These mobile groups of growing cells promote rapid spatial spreading of both species across surfaces, causing more extensive tooth decay. Our findings show multicellular interkingdom assemblages acting like supraorganisms with functionalities that cannot be achieved without coassembly.

Fungi and bacteria often engage in complex interactions, such as the formation of multicellular biofilms within the human body. Knowledge about how interkingdom biofilms initiate and coalesce into higher-level communities and which functions the different species carry out during biofilm formation remain limited. We found native-state assemblages of Candida albicans (fungi) and Streptococcus mutans (bacteria) with highly structured arrangement in saliva from diseased patients with childhood tooth decay. Further analyses revealed that bacterial clusters are attached within a network of fungal yeasts, hyphae, and exopolysaccharides, which bind to surfaces as a preassembled cell group. The interkingdom assemblages exhibit emergent functions, including enhanced surface colonization and growth rate, stronger tolerance to antimicrobials, and improved shear resistance, compared to either species alone. Notably, we discovered that the interkingdom assemblages display a unique form of migratory spatial mobility that enables fast spreading of biofilms across surfaces and causes enhanced, more extensive tooth decay. Using mutants, selective inactivation of species, and selective matrix removal, we demonstrate that the enhanced stress resistance and surface mobility arise from the exopolymeric matrix and require the presence of both species in the assemblage. The mobility is directed by fungal filamentation as hyphae extend and contact the surface, lifting the assemblage with a “forward-leaping motion.” Bacterial cell clusters can “hitchhike” on this mobile unit while continuously growing, to spread across the surface three-dimensionally and merge with other assemblages, promoting community expansion. Together, our results reveal an interkingdom assemblage in human saliva that behaves like a supraorganism, with disease-causing emergent functionalities that cannot be achieved without coassembly.

Entamoeba gingivalis is associated with periodontal conditions in Chinese young patients: A cross-sectional study

Background

This study investigated the prevalence and relative abundance of Entamoeba gingivalis (E. gingivalis) in Chinese young patients with different periodontal conditions, and its association with subgingival microbial composition, periodontal parameters, and cytokines in gingival crevicular fluid.

Methods

Participants (age: 18–45 years) diagnosed with stage II–IV periodontitis, gingivitis, or periodontal health underwent periodontal examination and sampling. Subgingival plaque was analyzed by 16S+18S sequencing for E. gingivalis detection and microbial analysis. The distribution of E. gingivalis in subgingival plaque was illustrated by fluorescence in situ hybridization. Interleukin-1β, interleukin-8, and tumor necrosis factor-α in gingival crevicular fluid were measured by multiplexed flow cytometric assay.

Results

This cross-sectional study included 120 sites from 60 participants. The prevalence and relative abundance of E. gingivalis were significantly increased in periodontitis (p<0.05). The sites were classified into three subgroups according to the relative abundance of E. gingivalis: negative group (Eg0, n=56); low-abundance group (Eg1, n=32); and high-abundance group (Eg2, n=32). The subgingival microflora in the subgroups showed stepwise changes at both the phylum and genus levels. The microflora compositions were significantly altered from Eg0 to Eg2 (p<0.001). Co-occurrence network analysis showed that Porphyromonas, Treponema, Tannerella, Filifactor, TG5, and Desulfobulbus were highly correlated with E. gingivalis (r>0.6, p<0.001). Correlation analysis showed that E. gingivalis was closely associated with important periodontal parameters and cytokines (p<0.01).

Conclusion

E. gingivalis was enriched in periodontitis and closely associated with subgingival microbial dysbiosis, periodontal parameters and cytokines in gingival crevicular fluid. Thus, it may be an important pathogen in periodontal disease.

Farnesol delivery via polymeric nanoparticle carriers inhibits cariogenic cross-kingdom biofilms and prevents enamel demineralization

Streptococcus mutans and Candida albicans are frequently detected together in the plaque from patients with early childhood caries (ECC) and synergistically interact to form a cariogenic cross-kingdom biofilm. However, this biofilm is difficult to control. Thus, to achieve maximal efficacy within the complex biofilm microenvironment, nanoparticle carriers have shown increased interest in treating oral biofilms in recent years. Here, we assessed the anti-biofilm efficacy of farnesol (Far), a hydrophobic antibacterial drug and repressor of Candida filamentous forms, against cross-kingdom biofilms employing drug delivery via polymeric nanoparticle carriers (NPCs). We also evaluated the effect of the strategy on teeth enamel demineralization. The farnesol-loaded NPCs (NPC+Far) resulted in a 2-log CFU/mL reduction of S. mutans and C. albicans (hydroxyapatite disc biofilm model). High-resolution confocal images further confirmed a significant reduction in exopolysaccharides, smaller microcolonies of S. mutans, and no hyphal form of C. albicans after treatment with NPC+Far on human tooth enamel (HT) slabs, altering the biofilm 3D structure. Furthermore, NPC+Far treatment was highly effective in preventing enamel demineralization on HT, reducing lesion depth (79% reduction) and mineral loss (85% reduction) versus vehicle PBS-treated HT, while NPC or Far alone had no differences with the PBS. The drug delivery via polymeric NPCs has the potential for targeting bacterial-fungal biofilms associated with a prevalent and costly pediatric oral disease, such as ECC.

Effects of a Novel, Intelligent, pH-Responsive Resin Adhesive on Cariogenic Biofilms In Vitro

Background: Secondary caries often result in a high failure rate of resin composite restoration. Herein, we studied the dodecylmethylaminoethyl methacrylate−modified resin adhesive (DMAEM@RA) to investigate its pH-responsive antimicrobial effect on Streptococcus mutans and Candida albicans dual-species biofilms and on secondary caries. Methods: Firstly, the pH-responsive antimicrobial experiments including colony-forming units, scanning electron microscopy and exopoly-saccharide staining were measured. Secondly, lactic acid measurement and transverse microradiography analysis were performed to determine the preventive effect of DMAEM@RA on secondary caries. Lastly, quantitative real-time PCR was applied to investigate the antimicrobial effect of DMAEM@RA on cariogenic virulence genes. Results: DMAEM@RA significantly inhibited the growth, EPS, and acid production of Streptococcus mutans and Candida albicans dual-species biofilms under acidic environments (p < 0.05). Moreover, at pH 5 and 5.5, DMAEM@RA remarkably decreased the mineral loss and lesion depth of tooth hard tissue (p < 0.05) and down-regulated the expression of cariogenic genes, virulence-associated genes, and pH-regulated genes of dual-species biofilms (p < 0.05). Conclusions: DMAEM@RA played an antibiofilm role on Streptococcus mutans and Candida albicans dual-species biofilms, prevented the demineralization process, and attenuated cariogenic virulence in a pH-dependent manner.

Streptococcus Mutans Membrane Vesicles Enhance Candida albicans Pathogenicity and Carbohydrate Metabolism

Streptococcus mutans and Candida albicans, as the most common bacterium and fungus in the oral cavity respectively, are considered microbiological risk markers of early childhood caries. S. mutans membrane vesicles (MVs) contain virulence proteins, which play roles in biofilm formation and disease progression. Our previous research found that S. mutans MVs harboring glucosyltransferases augment C. albicans biofilm formation by increasing exopolysaccharide production, but the specific impact of S. mutans MVs on C. albicans virulence and pathogenicity is still unknown. In the present study, we developed C. albicans biofilms on the surface of cover glass, hydroxyapatite discs and bovine dentin specimens. The results showed that C. albicans can better adhere to the tooth surface with the effect of S. mutans MVs. Meanwhile, we employed C. albicans biofilm-bovine dentin model to evaluate the influence of S. mutans MVs on C. albicans biofilm cariogenicity. In the S. mutans MV-treated group, the bovine dentin surface hardness loss was significantly increased and the surface morphology showed more dentin tubule exposure and broken dentin tubules. Subsequently, integrative proteomic and metabolomic approaches were used to identify the differentially expressed proteins and metabolites of C. albicans when cocultured with S. mutans MVs. The combination of proteomics and metabolomics analysis indicated that significantly regulated proteins and metabolites were involved in amino acid and carbohydrate metabolism. In summary, the results of the present study proved that S. mutans MVs increase bovine dentin demineralization provoked by C. albicans biofilms and enhance the protein and metabolite expression of C. albicans related to carbohydrate metabolism.

Dental Materials for Oral Microbiota Dysbiosis: An Update

The balance or dysbiosis of the microbial community is a major factor in maintaining human health or causing disease. The unique microenvironment of the oral cavity provides optimal conditions for colonization and proliferation of microbiota, regulated through complex biological signaling systems and interactions with the host. Once the oral microbiota is out of balance, microorganisms produce virulence factors and metabolites, which will cause dental caries, periodontal disease, etc. Microbial metabolism and host immune response change the local microenvironment in turn and further promote the excessive proliferation of dominant microbes in dysbiosis. As the product of interdisciplinary development of materials science, stomatology, and biomedical engineering, oral biomaterials are playing an increasingly important role in regulating the balance of the oral microbiome and treating oral diseases. In this perspective, we discuss the mechanisms underlying the pathogenesis of oral microbiota dysbiosis and introduce emerging materials focusing on oral microbiota dysbiosis in recent years, including inorganic materials, organic materials, and some biomolecules. In addition, the limitations of the current study and possible research trends are also summarized. It is hoped that this review can provide reference and enlightenment for subsequent research on effective treatment strategies for diseases related to oral microbiota dysbiosis.

The Role of Glycoside Hydrolases in S. gordonii and C. albicans Interactions

Candida albicans can coaggregate with Streptococcus gordonii and cocolonize in the oral cavity. Saliva provides a vital microenvironment for close interactions of oral microorganisms. However, the level of fermentable carbohydrates in saliva is not sufficient to support the growth of multiple species. Glycoside hydrolases (GHs) that hydrolyze glycoproteins are critical for S. gordonii growth in low-fermentable-carbohydrate environments such as saliva. However, whether GHs are involved in the cross-kingdom interactions between C. albicans and S. gordonii under such conditions remains unknown. In this study, C. albicans and S. gordonii were cocultured in heart infusion broth with a low level of fermentable carbohydrate. Planktonic growth, biofilm formation, cell aggregation, and GH activities of monocultures and cocultures were examined. The results revealed that the planktonic growth of cocultured S. gordonii in a low-carbohydrate environment was elevated, while that of cocultured C. albicans was reduced. The biomass of S. gordonii in dual-species biofilms was higher than that of monocultures, while that of cocultured C. albicans was decreased. GH activity was observed in S. gordonii, and elevated activity of GHs was detected in S. gordonii-C. albicans cocultures, with elevated expression of GH-related genes of S. gordonii. By screening a mutant library of C. albicans, we identified a tec1Δ/Δ mutant strain that showed reduced ability to promote the growth and GH activities of S. gordonii compared with the wild-type strain. Altogether, the findings of this study demonstrate the involvement of GHs in the cross-kingdom metabolic interactions between C. albicans and S. gordonii in an environment with low level of fermentable carbohydrates. IMPORTANCE Cross-kingdom interactions between Candida albicans and oral streptococci such as Streptococcus gordonii have been reported. However, their interactions in a low-fermentable-carbohydrate environment like saliva is not clear. The current study revealed glycoside hydrolase-related cross-kingdom communications between S. gordonii and C. albicans under the low-fermentable-carbohydrate condition. We demonstrate that C. albicans can promote the growth and metabolic activities of S. gordonii by elevating the activities of cell-wall-anchored glycoside hydrolases of S. gordonii. C. albicans gene TEC1 is critical for this cross-kingdom metabolic communication.

Enterococcus faecalis and Candida albicans dual-species biofilm: establishment of an in vitro protocol and characterization

Enterococcus faecalis is the most important agent of persistent apical periodontitis, and recently, Candida albicans has also been implicated in periapical infections. This study aimed to optimize an in vitro E. faecalis and C. albicans dual-species biofilm protocol for endodontic research. Different physicochemical conditions for biofilm formation were tested. Susceptibility assays to antimicrobials, biochemical composition and an ultra-morphological structure analyses were performed. Reproducible dual-species biofilms were established in BHI medium at 35 °C, for 48 h and in a microaerophilic atmosphere. An increase in biomass and chitin content was detected after vancomycin treatment. Structural analysis revealed that the dual-species biofilm was formed by both microorganisms adhered to the substrate. The proposed protocol could be useful for the study of interkingdom relationships and help to find new strategies against periapical infections.

In vitro effect of farnesol on planktonic cells and dual biofilm formed by Candida albicans and Escherichia coli

Many biofilm studies have focused on axial biofilms, however biofilms in nature and in vivo environment are multi-species. Farnesol is a sesquiterpene alcohol found in many essential oils. This study investigated the in vitro effects of farnesol on planktonic cells and biofilms of Candida albicans and Escherichia coli. The ultrastructural morphology of farnesol treated cells was evaluated by TEM. According to the XTT results, farnesol caused a significant decrease in metabolic activity and scanning electron microscope images confirmed a reduction in the preformed biofilm as a result of farnesol treatment for single species C. albicans and E. coli biofilms. Although farnesol has less effect on dual species biofilm compared to the single species biofilms, its effect on the dual biofilm was found to be stronger than amphotericin B or ampicillin. Further studies are needed to clarify the role of farnesol on fungal-bacterial biofilms.

Candida albicans and Early Childhood Caries

Early childhood caries (ECC) is a highly prevalent and costly chronic oral infectious disease in preschool children. Candida albicans has been frequently detected in children and has demonstrated cariogenic traits. However, since ECC is a multifactorial infectious disease with many predisposing non-microbial factors, it remains to be elucidated whether the presence and accumulation of C. albicans in ECC is merely a consequence of the adaptation of C. albicans to a cariogenic oral environment, or it plays an active role in the initiation and progression of dental caries. This review aims to summarize the current knowledge on C. albicans and the risk of ECC, with a focus on its synergistic relationship with the cariogenic pathogen Streptococcus mutans. We also highlight recent advances in the development of approaches to disrupt C. albicans-S. mutans cross-kingdom biofilms in ECC prevention and treatment. Longitudinal clinical studies, including interventional clinical trials targeting C. albicans, are necessary to ascertain if C. albicans indeed contributes in a significant manner to the initiation and progression of ECC. In addition, further work is needed to understand the influence of other bacteria and fungi of oral microbiota on C. albicans-S. mutans interactions in ECC.

Lactobacillus plantarum Disrupts S. mutans–C. albicans Cross-Kingdom Biofilms

Dental caries, an ecological dysbiosis of oral microflora, initiates from the virulent biofilms formed on tooth surfaces where cariogenic microorganisms metabolize dietary carbohydrates, producing acid that demineralizes tooth enamel. Forming cariogenic biofilms, Streptococcus mutans and Candida albicans are well-recognized and emerging pathogens for dental caries. Recently, probiotics have demonstrated their potential in treating biofilm-related diseases, including caries. However, limited studies have assessed their effect on cariogenic bacteria–fungi cross-kingdom biofilm formation and their underlying interactions. Here, we assessed the effect of four probiotic Lactobacillus strains (Lactobacillus rhamnosus ATCC 2836, Lactobacillus plantarum ATCC 8014, Lactobacillus plantarum ATCC 14917, and Lactobacillus salivarius ATCC 11741) on S. mutans and C. albicans using a comprehensive multispecies biofilm model that mimicked high caries risk clinical conditions. Among the tested probiotic species, L. plantarum demonstrated superior inhibition on the growth of C. albicans and S. mutans, disruption of virulent biofilm formation with reduced bacteria and exopolysaccharide (EPS) components, and formation of virulent microcolonies structures. Transcriptome analysis (RNA sequencing) further revealed disruption of S. mutans and C. albicans cross-kingdom interactions with added L. plantarum. Genes of S. mutans and C. albicans involved in metabolic pathways (e.g., EPS formation, carbohydrate metabolism, glycan biosynthesis, and metabolism) were significantly downregulated. More significantly, genes related to C. albicans resistance to antifungal medication (ERG4), fungal cell wall chitin remodeling (CHT2), and resistance to oxidative stress (CAT1) were also significantly downregulated. In contrast, Lactobacillus genes plnD, plnG, and plnN that contribute to antimicrobial peptide plantaricin production were significantly upregulated. Our novel study findings support further assessment of the potential role of probiotic L. plantarum for cariogenic biofilm control.

Select Streptococci Can Degrade Candida Mannan To Facilitate Growth

Multiple studies have found that streptococci have a synergistic relationship with Candida species, but the details of these interactions are still being discovered. Candida species are covered by mannan, a polymer of mannose, which could serve as a carbon source for certain microbes. We hypothesized that streptococci that possess mannan-degrading glycosyl hydrolases would be able to enzymatically cleave mannose residues, which could serve as a primary carbohydrate source to support growth. We analyzed 90 streptococcus genomes to predict the capability of streptococci to transport and utilize mannose and to degrade diverse mannose linkages found on mannan. The genome analysis revealed mannose transporters and downstream pathways in most streptococci, but only <50% of streptococci harbored the glycosyl hydrolases required for mannan degradation. To confirm the ability of streptococci to use mannose or mannan, we grew 6 representative streptococci in a chemically defined medium lacking glucose supplemented with mannose, yeast extract, or purified mannan isolated from Candida and Saccharomyces strains. Although all tested Streptococcus strains could use mannose, Streptococcus salivarius and Streptococcus agalactiae, which did not possess mannan-degrading glycosyl hydrolases, could not use yeast extract or mannan to enhance their growth. In contrast, we found that Streptococcus mitis, Streptococcus parasanguinis, Streptococcus sanguinis, and Streptococcus pyogenes possessed the necessary glycosyl hydrolases to use yeast extract and isolated mannan, which promoted robust growth. Our data indicate that several streptococci are capable of degrading fungal mannans and harvesting mannose for energy. IMPORTANCE This work highlights a previously undescribed aspect of streptococcal Candida interactions. Our work identifies that certain streptococci possess the enzymes required to degrade mannan, and through this mechanism, they can release mannose residues from the cell wall of fungal species and use them as a nutrient source. We speculate that streptococci that can degrade fungal mannan may have a competitive advantage for colonization. This finding has broad implications for human health, as streptococci and Candida are found at multiple body sites.

Metal Complexes—A Promising Approach to Target Biofilm Associated Infections

Microbial biofilms are represented by sessile microbial communities with modified gene expression and phenotype, adhered to a surface and embedded in a matrix of self-produced extracellular polymeric substances (EPS). Microbial biofilms can develop on both prosthetic devices and tissues, generating chronic and persistent infections that cannot be eradicated with classical organic-based antimicrobials, because of their increased tolerance to antimicrobials and the host immune system. Several complexes based mostly on 3D ions have shown promising potential for fighting biofilm-associated infections, due to their large spectrum antimicrobial and anti-biofilm activity. The literature usually reports species containing Mn(II), Ni(II), Co(II), Cu(II) or Zn(II) and a large variety of multidentate ligands with chelating properties such as antibiotics, Schiff bases, biguanides, N-based macrocyclic and fused rings derivatives. This review presents the progress in the development of such species and their anti-biofilm activity, as well as the contribution of biomaterials science to incorporate these complexes in composite platforms for reducing the negative impact of medical biofilms.

Candida albicans and Candida dubliniensis in Periodontitis in Adolescents and Young Adults

Aim

This study aims to evaluate the association of Candida albicans and Candida dubliniensis with periodontitis in adolescents and young adults in a Moroccan population.

Methods

426 subjects aged between 12 and 25 years were recruited for the study. A pool of plaque sample was taken. Samples were cultured on Sabouraud Chloramphenicol medium at 37°C for 24–48 hours and then identified by the Vitek 2 YST system. Clinical data and presence of Candida albicans and Candida dubliniensis were analyzed using Jamovi (Version 1.8).

Results

Candida albicans was observed in 25 subjects among 68 diseased patients (37%) and in 60 subjects among 358 healthy patients (17%). It can be reported that under normal yeast conditions, there is a statistically significant difference between these two groups (P < 0.001). Candida dubliniensis was more prevalent in periodontitis than in healthy subjects (P=0.026). Regarding clinical variables, subgroups of periodontitis subjects showed significant statistical differences for periodontal probing depth, clinical attachment loss, and number of decayed teeth in advanced periodontitis in comparison with initial or mild periodontitis. The results also indicate that the presence of the two species of Candida is not related to gender or age (P > 0.05) nor related to the severity of the periodontal disease in this population.

Conclusion

Within the limits of our study, Candida albicans is more frequently associated with periodontitis. The potential role of C. albicans in periodontitis pathogenesis is very complex. More studies on biofilm associated with different forms of periodontitis are necessary. It is also important to assess the coexistence of periodontitis and caries and the associated biofilms.