Biofilm growth and IL-8 & TNF-α-inducing properties of Candida albicans in the presence of oral gram-positive and gram-negative bacteria

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.

In Vitro Inhibitory Effect of Silver Diamine Fluoride Combined with Potassium Iodide against Mixed-Species Biofilm Formation on Human Root Dentin

Applying a saturated potassium iodide (KI) solution immediately after silver diamine fluoride (SDF) application may affect the inhibitory effects of SDF on biofilm formation. This study compared the efficacy of 38% SDF with and without KI on preventing mixed-species biofilm formation on human root dentin surfaces and assessed ion incorporation into root dentin. The biofilms, composed of Streptococcus mutans, Lactobacillus rhamnosus, and Actinomyces naeslundii, were grown on specimen surfaces treated with either SDF or SDF + KI. After 24 h, the biofilms were evaluated using scanning electron microscopy, live/dead staining, adenosine triphosphate (ATP) assays, colony-forming unit (CFU) counts, and quantitative polymerase chain reaction. A Mann-Whitney U test was used to compare the results between the groups. Ion incorporation was assessed using an electron probe microanalyzer. The relative ATP content in the SDF + KI group was significantly higher than that in the SDF group (p < 0.05). However, biofilm morphology and the logarithmic reduction in CFUs and bacterial DNA were comparable across the groups. The SDF + KI treatment resulted in less silver and fluoride ion incorporation than that yielded by SDF alone. The inhibitory effects of SDF and SDF + KI on mixed-species biofilm formation were almost equivalent, although KI application affected the ion incorporation.

Adhesion of Candida albicans on PTFE membranes used in guided bone regeneration

OBJECTIVES

Guided bone regeneration (GBR) is a core procedure used to regenerate bone defects. The aim of the study was to investigate the adherence of Candida albicans on six commercially available polytetrafluoroethylene (PTFE) membranes used in GBR procedures and the subsequent clinical consequences.

MATERIALS AND METHODS

Six commercially available PTFE membranes were tested. Two of the membranes had a textured surface and the other four a plane, nontextured one. C. albicans (ATCC 24433) was cultured for 24 h, and its cell surface hydrophobicity was assessed using a modified method. C. albicans adhesion to membrane discs was studied by scanning electron microscopy (SEM) and real-time polymerase chain reaction (PCR).

RESULTS

C. albicans was found to be hydrophobic (77.25%). SEM analysis showed that C. albicans adherence to all membranes examined was characterized by patchy, scattered, and small clustered patterns except for one nontextured membrane with a most rough surface in which a thick biofilm was observed. Real-time PCR quantification revealed significantly greater adhesion of C. albicans cells to PTFE membranes than the control membrane (p ≤ .001) with the membranes having a textured surface exhibiting the highest count of 2680 × 104 cells/ml compared to the count of 707 × 104 cells/mL on those with a nontextured one (p ≤ .001). One membrane with nontextured surface, but with most rough surface was found to exhibit the highest count of 3010 × 104 cells/ml (p ≤ .05).

CONCLUSION

The results of this study indicate that C. albicans adhesion on membranes' surfaces depends on the degree of surface roughness and/or on the presence of a texture. Textured PTFE membranes and/or membranes high roughness showed significantly more adhered C. albicans cells. These findings can impact the surgeon's choice of GBR membrane and postoperative maintenance.

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.

Microbial Interactions in Oral Biofilm: Evaluating Therapeutic Interventions and the Emergence of Resistance: A Narrative Review

The oral cavity comprises numerous anatomical surfaces that are inhabited by a diverse array of bacteria, collectively forming a bacterial biofilm. Within this complex microbial community, certain bacterial species are etiologically linked to the development of common oral pathologies, such as dental caries and periodontitis, which stand as prominent instances of bacterial infections frequently encountered in clinical settings. Most biofilms are believed to be multispecies consortia. While single-species biofilms have been well-researched, mixed-species biofilms and their interactions amongst themselves have not drawn interest. The aim of the current review was to assess the various interactions of dual-species microorganisms in oral biofilm formation. Farnesol given exogenously for the treatment of biofilm can enhance or inhibit the growth of certain organisms, as seen in Candida albicans. In the age of antibiotic resistance, it is imperative to develop and uncover drugs capable of simultaneously targeting multiple species in order to mitigate antimicrobial resistance.

In vitro activity of anti-rheumatic drugs on release of pro-inflammatory cytokines from oral cells in interaction with microorganisms

Periodontitis patients suffering concomitantly from rheumatoid arthritis (RA) often present with less inflamed periodontal tissues due to the ongoing anti-rheumatic therapy. This in vitro study was aimed to analyze whether anti-inflammatory drugs used in the therapy of RA can modulate the release of IL-8 and IL-1β by professional and non-professional immune cells stimulated with microorganisms. Periodontal ligament (PDL) fibroblasts, monocytic MONO-MAC-6-cells, and gingival keratinocytes were exposed to ibuprofen, prednisolone, and methotrexate with and without lysates of Fusobacterium nucleatum or Candida albicans. Supernatants were obtained and the levels of interleukin(IL)-8 and IL-1β (only MONO-MAC-6) were quantified. The addition of F. nucleatum lysate resulted in the strongest release of proinflammatory cytokines by PDL fibroblast and MONO-MAC-6 cells, while the modification by the tested anti-rheumatic drugs was only minor. After stimulation of the MONO-MAC-cells with F. nucleatum, prednisolone increased the release of IL-8, whereas methotrexate decreased the level. Anti-inflammatory drugs increased the adherence of C. albicans to epithelial cells. In patients with RA, the reduction of the microbial load in subgingival biofilm (biofilm removal) is of major importance; however, the intake of inflammatory drugs may interfere with the inflammatory response.

Recent Advances and Opportunities in the Study of Candida albicans Polymicrobial Biofilms

It is well known that the opportunistic pathogenic yeast, Candida albicans, can form polymicrobial biofilms with a variety of bacteria, both in vitro and in vivo, and that these polymicrobial biofilms can impact the course and management of disease. Although specific interactions are often described as either synergistic or antagonistic, this may be an oversimplification. Polymicrobial biofilms are complex two-way interacting communities, regulated by inter-domain (inter-kingdom) signaling and various molecular mechanisms. This review article will highlight advances over the last six years (2016-2021) regarding the unique biology of polymicrobial biofilms formed by C. albicans and bacteria, including regulation of their formation. In addition, some of the consequences of these interactions, such as the influence of co-existence on antimicrobial susceptibility and virulence, will be discussed. Since the aim of this knowledge is to inform possible alternative treatment options, recent studies on the discovery of novel anti-biofilm compounds will also be included. Throughout, an attempt will be made to identify ongoing challenges in this area.

The Role of Candida albicans Virulence Factors in the Formation of Multispecies Biofilms With Bacterial Periodontal Pathogens

Periodontal disease depends on the presence of different microorganisms in the oral cavity that during the colonization of periodontal tissues form a multispecies biofilm community, thus allowing them to survive under adverse conditions or facilitate further colonization of host tissues. Not only numerous bacterial species participate in the development of biofilm complex structure but also fungi, especially Candida albicans, that often commensally inhabits the oral cavity. C. albicans employs an extensive armory of various virulence factors supporting its coexistence with bacteria resulting in successful host colonization and propagation of infection. In this article, we highlight various aspects of individual fungal virulence factors that may facilitate the collaboration with the associated bacterial representatives of the early colonizers of the oral cavity, the bridging species, and the late colonizers directly involved in the development of periodontitis, including the “red complex” species. In particular, we discuss the involvement of candidal cell surface proteins—typical fungal adhesins as well as originally cytosolic “moonlighting” proteins that perform a new function on the cell surface and are also present within the biofilm structures. Another group of virulence factors considered includes secreted aspartic proteases (Sap) and other secreted hydrolytic enzymes. The specific structure of the candidal cell wall, dynamically changing during morphological transitions of the fungus that favor the biofilm formation, is equally important and discussed. The non-protein biofilm-composing factors also show dynamic variability upon the contact with bacteria, and their biosynthesis processes could be involved in the stability of mixed biofilms. Biofilm-associated changes in the microbe communication system using different quorum sensing molecules of both fungal and bacterial cells are also emphasized in this review. All discussed virulence factors involved in the formation of mixed biofilm pose new challenges and influence the successful design of new diagnostic methods and the application of appropriate therapies in periodontal diseases.

The Membranotropic Peptide gH625 to Combat Mixed Candida albicans/Klebsiella pneumoniae Biofilm: Correlation between In Vitro Anti-Biofilm Activity and In Vivo Antimicrobial Protection

The antibiofilm activity of a gH625 analogue was investigated to determine the in vitro inhibition and eradication of a dual-species biofilm of Candida albicans and Klebsiella pneumoniae, two leading opportunistic pathogens responsible for several resistant infections. The possibility of effectively exploiting this peptide as an alternative anti-biofilm strategy in vivo was assessed by the investigation of its efficacy on the Galleria mellonella larvae model. Results on larvae survival demonstrate a prophylactic efficacy of the peptide towards the infection of each single microorganism but mainly towards the co-infection. The expression of biofilm-related genes in vivo showed a possible synergy in virulence when these two species co-exist in the host, which was effectively prevented by the peptide. These findings provide novel insights into the treatment of medically relevant bacterial–fungal interaction.