Filamentous Non-albicans Candida Species Adhere to Candida albicans and Benefit From Dual Biofilm Growth

Virulence-Related Genes Expression in Planktonic Mixed Cultures of Candida albicans and Non-Albicans Candida Species

INTRODUCTION

Candida albicans is the most common opportunistic pathogen causing fungal infections worldwide, especially in high-risk patients. Its pathogenicity is related to virulence factors gene expression, such as hyphal growth (HWP1), cell adhesion (ALS3), and protease secretion (SAP1) during infection spreading mechanisms. In recent years, an increase in non-albicans Candida infections has been reported, which may present coinfection or competitive interactions with C. albicans, potentially aggravating the patient's condition. This study aims to evaluate the expression of genes related to virulence factors of C. albicans and non-albicans Candida during planktonic stage.

METHODS

C. albicans (ATCC MYA-3573) as well as with three clinical strains (C. albicans DCA53, C. tropicalis DCT6, and C. parapsilosis DCP1) isolated from blood samples, were grown in 24-well plates at 37°C for 20 h, either in monocultures or mixed cultures. Quantitative real-time polymerase chain reaction was used to evaluate the expression levels of the genes HWP1, ALS3, and SAP1 in cells collected during the planktonic stage. In addition, hyphal filamentation was observed using a Scanning Electron Microscope.

RESULTS

The overexpression of HWP1 and ASL3 genes in mixed growth conditions between C. albicans and non-albicans Candida species suggests a synergistic relationship as well as an increased capacity for hyphal growth and adhesion. In contrast, C. parapsilosis versus C. tropicalis interaction shows an antagonistic relationship during mixed culture, suggesting a decreased virulence profile of C. parapsilosis during initial coinfection with C. tropicalis.

CONCLUSION

The expression of HWP1, ALS3, and SAP1 genes associated with virulence factors varies under competitive conditions among species of the genus Candida during planktonic stage.

Investigation of adhesion status of Candida species to the surface of resin materials produced at different angles with additive manufacturing

BACKGROUND

The aim of this study was to evaluate the adhesion of Candida glabrata, Candida albicans, Candida krusei, Candida parapsilosis and Candida tropicalis yeasts to disk-shaped resin materials produced from resin which used in the production of surgical guide with 0, 45 and 90-degrees printing orientations by Liquid Crystal Display additive manufacturing technology.

METHODS

Disk-shaped specimens were printed with surgical guide resin using the Liquid Crystal Display production technique in 3 printing orientations (0, 45 and 90-degrees). Surface roughness and contact angle values were evaluated. Real-Time PCR analysis was performed to evaluate Candida adhesion (C. glabrata, C. albicans, C. krusei, C. parapsilosis and C. tropicalis) Field emission scanning electron microscope (FESEM) images of the materials were obtained.

RESULTS

Specimens oriented at 45-degrees demonstrated higher surface roughness (P < .05) and lower contact angle values than other groups. No significant difference was found in the adhesion of C. glabrata, C. albicans, and C. parapsilosis among specimens printed at 0, 45, and 90-degrees orientations (P > .05). A higher proportion of C. krusei and C. tropicalis was found in the specimens printed at orientation degrees of 45 = 90 < 0 with statistical significance. Analyzing the adhesion of all Candida species reveals no statistical disparity among the printing orientations.

CONCLUSIONS

The surface roughness, contact angle, and adhesion of certain Candida species are affected by printing orientations. Hence, careful consideration of the printing orientation is crucial for fabricating products with desirable properties. In 45-degree production, roughness increases due to the layered production forming steps, whereas in 0-degree production, certain Candida species exhibit high adhesion due to the formation of porous structures. Consequently, considering these factors, it is advisable to opt for production at 90-degrees, while also considering other anticipated characteristics.

Prevalence of Oropharyngeal Candidiasis and distribution of Candida species among People Living with Human Immunodeficiency Virus in Africa: a systematic review and meta-analysis

Background

The incidence of oropharyngeal candidiasis among people living with human immunodeficiency virus in Africa is on the rise. Oropharyngeal candidiasis is mainly caused by C.albicans; however, a shift in the etiology towards non-Candida albicans species is increasing. In addition, there are variations in the epidemiological distribution of Candida species causing oropharyngeal candidiasis among people living with human immunodeficiency virus in Africa.

Objective

This review aimed to determine the prevalence of oropharyngeal candidiasis and the distribution of Candida species among people living with human immunodeficiency virus in Africa.

Materials and Methods

This systematic review protocol was registered in the base PROSPERO database prior to its conduct (CRD42021254473). The Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocol guidelines (PRISMA-P) were followed for this study. The PubMed, Scopus and EMBASE databases were searched to identify published studies published between 1st January 2000 and 8th October 2022. The eligible studies were included in the meta-analysis and analyzed using a random effects model. The risk of bias of the included studies was assessed using the Joanna Briggs Institute quality assessment tool for prevalence studies.

Results

The database search yielded 370 titles from PubMed (n=192), EMBASE (n=162) and SCOPUS (n=16). Fourteen studies with a total of 3,863 participants were included in the meta-analysis. The pooled prevalence of oropharyngeal candidiasis was 49.0% (95% CI: 37% - 62%). A total of 2,688 Candida isolates were reported; approximately 76.6% (n=2,060) were C. albicans, and 21.7% (n=582) were non-C. albicans. Among the non-Candida albicans species, C. glabrata was the most common isolate (29.6%), followed by C. tropicalis (27.7%), C. krusei (17.0%), C. parapsilosis (8.1%) and C. dubliniensis (5.2%). Out of 14 studies, 7 (50.0%) had a low risk of bias, 5 (35.7%) had a moderate risk of bias, and 2 (14.3%) had a high risk of bias.

Conclusion

Almost half of people living with HIV in Africa have oropharyngeal candidiasis, and C. albicans remains the most frequent cause of oropharyngeal candidiasis.

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.

In vitro evaluation of biofilm formation by Candida parapsilosis and Enterobacter cloacae. Scanning electron microscopy and efficacy of antimicrobial combinations study

Fungal-bacterial infections are being increasingly recognized in clinical settings, and the interaction between these species in polymicrobial biofilms often lead to infections that are highly resistant to treatment. In this in vitro study, we analyzed the formation of mixed biofilms using clinically isolated Candida parapsilosis and Enterobacter cloacae. Additionally, we assessed the potential of conventional antimicrobials, both alone and in combination, for treating polymicrobial biofilms built by these human pathogens. Our results demonstrate that C. parapsilosis and E. cloacae are capable of forming mixed biofilms, as confirmed by scanning electron microscopy. Interestingly, we found that colistin alone or in combination with antifungal drugs was highly effective reducing up to 80% of the total biomass of polymicrobial biofilms.

Case of Mixed Infection of Toenail Caused by Candida parapsilosis and Exophiala dermatitidis and In Vitro Effectiveness of Propolis Extract on Mixed Biofilm

Onychomycosis is a chronic fungal nail infection caused by several filamentous and yeast-like fungi, such as the genus Candida spp., of great clinical importance. Black yeasts, such as Exophiala dermatitidis, a closely related Candida spp. species, also act as opportunistic pathogens. Fungi infectious diseases are affected by organisms organized in biofilm in onychomycosis, making treatment even more difficult. This study aimed to evaluate the in vitro susceptibility profile to propolis extract and the ability to form a simple and mixed biofilm of two yeasts isolated from the same onychomycosis infection. The yeasts isolated from a patient with onychomycosis were identified as Candida parapsilosis sensu stricto and Exophiala dermatitidis. Both yeasts were able to form simple and mixed (in combination) biofilms. Notably, C. parapsilosis prevailed when presented in combination. The susceptibility profile of propolis extract showed action against E. dermatitidis and C. parapsilosis in planktonic form, but when the yeasts were in mixed biofilm, we only observed action against E. dermatitidis, until total eradication.

Biofilm: The invisible culprit in catheter-induced candidemia

Candidemia is the most common form of invasive fungal infection associated with several risk factors, and one of them is the use of medical devices, to which microbial biofilms can attach. Candidemia related to the use of peripheral intravascular and central venous catheters (CVC) is referred to as Candida catheter-related bloodstream infection, with more than 90% being related to CVC usage. The infection is associated with a higher morbidity and mortality rate than nosocomial bacterial infections. Candida spp. can protect themselves from the host immune system and antifungal drugs because of the biofilm structure, which is potentiated by the extracellular matrix (ECM). Candida albicans and Candida parapsilosis are the most pathogenic species often found to form biofilms associated with catheter usage. Biofilm formation of C. albicans includes four mechanisms: attachment, morphogenesis, maturation and dispersion. The biofilms formed between C. albicans and non-albicans spp. differ in ECM structure and composition and are associated with the persistence of colonization to infection for various catheter materials and antifungal resistance. Efforts to combat Candida spp. biofilm formation on catheters are still challenging because not all patients, especially those who are critically ill, can be recommended for catheter removal; also to be considered are the characteristics of the biofilm itself, which readily colonizes the permanent medical devices used. The limited choice and increasing systemic antifungal resistance also make treating it more difficult. Hence, alternative strategies have been developed to manage Candida biofilm. Current options for prevention or therapy in combination with systemic antifungal medications include lock therapy, catheter coating, natural peptide products and photodynamic inactivation.

Rapid Inactivation of mixed biofilms of Candida albicans and Candida tropicalis using antibacterial photodynamic therapy: Based on PAD™ Plus

Background

To investigate the sterilizing effect of antimicrobial photodynamic therapy (aPDT) based on PAD™ Plus on mixed biofilms of Candida albicans and Candida tropicalis.

Methods

A mature mixed biofilm model of C. albicans and C. tropicalis was constructed in vitro. FITC-concanavalin A staining was conducted to observe the formation of the extracellular matrix. MTT assay was performed to determine biofilm viability. The chromogenic medium was used to examine the Candida composition of the mixed biofilms. For aPDT treatment, based on PAD™ Plus, the biofilms were incubated with 1 mg/mL TBO for 1, 5, or 10 min, followed by 500 or 750 mW LED illumination for 1 or 2 min. The live/dead fungi were detected by SYTO9/propidium iodide staining. A multivariate factorial design was conducted to analyze the correlations of parameters with the inactivation effect of the mixed biofilms.

Results

Mature mixed biofilms formed at 24 h after seeding. Compared with untreated biofilms, following 1-min TBO incubation, 500 mW LED illumination for 1 min inactivated more than 90% of the fungi. Extending the incubation time did not significantly improve the inactivation effect. Application of 750 mW output power or 2 min LED illumination inactivated more than 99% of the fungi without increasing other parameters.

Conclusions

PAD™ Plus combined with 1 mg/mL TBO can rapidly inactivate the mature mixed biofilms of C. albicans and C. tropicalis, serving as a robust platform for the treatment of mixed infections of C. albicans and C. tropicalis.

Differential Susceptibility of Mixed Polymicrobial Biofilms Involving Ocular Coccoid Bacteria (Staphylococcus aureus and S. epidermidis) and a Filamentous Fungus (Fusarium solani) on Ex Vivo Human Corneas

Biofilms confer several advantages to the organisms associated with them, such as increased resistances to antibacterial and antifungal compounds compared to free living cells. Compared to monomicrobial biofilms involving a single microorganism, biofilms composed of microorganisms affiliated to bacterial and fungal kingdoms are predominant in nature. Despite the predominance of polymicrobial biofilms, and more so mixed polymicrobial biofilms, they are rarely studied. The objective of the current study is to evaluate the potential of ocular bacteria and a filamentous fungus to form monomicrobial and mixed polymicrobial biofilms on synthetic and natural substrates and to monitor their response to antibiotics. In this sense, we demonstrated that the ocular pathogens Staphylococcus aureus, S. epidermidis, and Fusarium solani form monomicrobial and mixed polymicrobial biofilms both on tissue culture polystyrene plates and on ex vivo human corneas from cadavers using confocal microscopy and scanning electron microscopy. Additionally, the mixed polymicrobial biofilms involving the above ocular bacteria and a filamentous fungus were less susceptible to different antibacterials and antifungals in relation to the corresponding control planktonic cells. Further, the MICs to the screened antibacterials and antifungals in polymicrobial biofilms involving a bacterium or a fungus was either increased, decreased, or unchanged compared to the corresponding individual bacterial or fungal biofilm. The results would be useful to the ophthalmologist to plan effective treatment regimens for the eye since these are common pathogens of the eye causing keratitis, endophthalmitis, conjunctivitis, etc.

Similarities and Differences among Species Closely Related to Candida albicans: C. tropicalis, C. dubliniensis, and C. auris

Although Candida species are widespread commensals of the microflora of healthy individuals, they are also among the most important human fungal pathogens that under certain conditions can cause diseases (candidiases) of varying severity ranging from mild superficial infections of the mucous membranes to life-threatening systemic infections. So far, the vast majority of research aimed at understanding the molecular basis of pathogenesis has been focused on the most common species—Candida albicans. Meanwhile, other closely related species belonging to the CTG clade, namely, Candida tropicalis and Candida dubliniensis, are becoming more important in clinical practice, as well as a relatively newly identified species, Candida auris. Despite the close relationship of these microorganisms, it seems that in the course of evolution, they have developed distinct biochemical, metabolic, and physiological adaptations, which they use to fit to commensal niches and achieve full virulence. Therefore, in this review, we describe the current knowledge on C. tropicalis, C. dubliniensis, and C. auris virulence factors, the formation of a mixed species biofilm and mutual communication, the environmental stress response and related changes in fungal cell metabolism, and the effect of pathogens on host defense response and susceptibility to antifungal agents used, highlighting differences with respect to C. albicans. Special attention is paid to common diagnostic problems resulting from similarities between these species and the emergence of drug resistance mechanisms. Understanding the different strategies to achieve virulence, used by important opportunistic pathogens of the genus Candida, is essential for proper diagnosis and treatment.

Candida lusitaniae: Biology, Pathogenicity, Virulence Factors, Diagnosis, and Treatment

The incidence of fungal infections is increasing at an alarming rate and has posed a great challenge for science in recent years. The rise in these infections has been related to the increase in immunocompromised patients and the resistance of different species to antifungal drugs. Infections caused by the different Candida species, especially Candida albicans, are one of the most common mycoses in humans, and the etiological agents are considered opportunistic pathogens associated with high mortality rates when disseminated infections occur. Candida lusitaniae is considered an emerging opportunistic pathogen that most frequently affects immunocompromised patients with some comorbidity. Although it is a low-frequency pathogen, and the mortality rate of C. lusitaniae-caused candidemia does not exceed 5%, some isolates are known to be resistant to antifungals such as amphotericin B, 5-fluorocytosine, and fluconazole. In this paper, a detailed review of the current literature on this organism and its different aspects, such as its biology, possible virulence factors, pathogen-host interaction, diagnosis, and treatment of infection, is provided. Of particular interest, through Blastp analysis we predicted possible virulence factors in this species.

Polymicrobial biofilms of ocular bacteria and fungi on ex vivo human corneas

Microbes residing in biofilms confer several fold higher antimicrobial resistances than their planktonic counterparts. Compared to monomicrobial biofilms, polymicrobial biofilms involving multiple bacteria, multiple fungi or both are more dominant in nature. Paradoxically, polymicrobial biofilms are less studied. In this study, ocular isolates of Staphylococcus aureus, S. epidermidis and Candida albicans, the etiological agents of several ocular infections, were used to demonstrate their potential to form mono- and polymicrobial biofilms both in vitro and on human cadaveric corneas. Quantitative (crystal violet and XTT methods) and qualitative (confocal and scanning electron microscopy) methods demonstrated that they form polymicrobial biofilms. The extent of biofilm formation was dependent on whether bacteria and fungi were incubated simultaneously or added to a preformed biofilm. Additionally, the polymicrobial biofilms exhibited increased resistance to different antimicrobials compared to planktonic cells. When the MBECs of different antibacterial and antifungal agents were monitored it was observed that the MBECs in the polymicrobial biofilms was either identical or decreased compared to the monomicrobial biofilms. The results are relevant in planning treatment strategies for the eye. This study demonstrates that ocular bacteria and fungi form polymicrobial biofilms and exhibit increase in antimicrobial resistance compared to the planktonic cells.

The Antibiofilm Role of Biotics Family in Vaginal Fungal Infections

“Unity in strength” is a notion that can be exploited to characterize biofilms as they bestow microbes with protection to live freely, escalate their virulence, confer high resistance to therapeutic agents, and provide active grounds for the production of biofilms after dispersal. Naturally, fungal biofilms are inherently resistant to many conventional antifungals, possibly owing to virulence factors as their ammunitions that persistently express amid planktonic transition to matured biofilm state. These ammunitions include the ability to form polymicrobial biofilms, emergence of persister cells post-antifungal treatment and acquisition of resistance genes. One of the major disorders affecting vaginal health is vulvovaginal candidiasis (VVC) and its reoccurrence is termed recurrent VVC (RVVC). It is caused by the Candida species which include Candida albicans and Candida glabrata. The aforementioned Candida species, notably C. albicans is a biofilm producing pathogen and habitually forms part of the vaginal microbiota of healthy women. Latest research has implicated the role of fungal biofilms in VVC, particularly in the setting of treatment failure and RVVC. Consequently, a plethora of studies have advocated the utilization of probiotics in addressing these infections. Specifically, the excreted or released compounds of probiotics which are also known as postbiotics are being actively researched with vast potential to be used as therapeutic options for the treatment and prevention of VVC and RVVC. These potential sources of postbiotics are harnessed due to their proven antifungal and antibiofilm. Hence, this review discusses the role of Candida biofilm formation in VVC and RVVC. In addition, we discuss the application of pro-, pre-, post-, and synbiotics either individually or in combined regimen to counteract the abovementioned problems. A clear understanding of the role of biofilms in VVC and RVVC will provide proper footing for further research in devising novel remedies for prevention and treatment of vaginal fungal infections.

A Denture Use Model Associated with Candida spp. in Immunocompetent Male and Female Rats

Denture stomatitis (DS) is a common infection in denture wearers, especially women. This study evaluated the induction of DS using acrylic devices attached to the palate of rats combined with inoculation of Candida spp. Immunocompetent male and female rats received a carbohydrate-rich diet. Impressions were taken from the rats’ palate to individually fabricate acrylic devices. Mono- and multispecies biofilms of C. albicans, C. glabrata, and C. tropicalis were grown on the devices, which were then cemented on posterior teeth and kept in the rats’ palate for four weeks. Microbial samples from the palate and the device were quantified. Oral microbiome of rats inoculated with C. albicans was analyzed by 16S rRNA gene sequencing. Log10(CFU/mL) were analyzed by mixed or two-way MANOVA (α = 0.05). Candida spp. and acrylic device did not induce palatal inflammation macroscopically nor microscopically. Although there was an increase (p < 0.001) of the total microbiota and female rats demonstrated higher (p = 0.007) recovery of Candida spp. from the palate, the gender differences were not biologically relevant. The microbiome results indicate an increase in inflammatory microbiota and reduction in health-associated micro-organisms. Although Candida spp. and acrylic device did not induce DS in immunocompetent rats, the shift in microbiota may precede manifestation of inflammation.

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.

Profuse diversity and acidogenicity of the candida-biome of deep carious lesions of Severe Early Childhood Caries (S-ECC)

Introduction: The retentive niches of deep caries lesions have a distinct biome. Methods: We evaluated the site-specific (occlusal and proximal) Candida-biome of Severe-Early Childhood Caries (S-ECC) in 66- children (132 lesions). Asymptomatic primary molars fitting the definition of the International Caries Detection and Assessment-(ICDAS)-caries-code 5/6 were analyzed. Deep-dentinal sampling and simultaneous assessment of pH were performed. Clinical isolates were speciated using multiplex-PCR and evaluated for their acidogenic and aciduric potential.Results: Surprisingly, a high prevalence of Candida species (72.7%), either singly or in combination, was noted from both the proximal and occlusal cavities. C. tropicalis was the most prevalent species (47%; 34/72), followed by C. krusei (43.1%; 31/72) and C. albicans (40.3%; 29/72), with C. glabrata being the least (9.7%; 7/72). Over 45% low-pH niches (pH <7) of both sites yielded either dual or triple species of Candida. Genotyping revealed three distinct C. albicans genotypes (A, B, and C) with (14/29; 48.3%) of strains belonging to Genotype A. All four evaluated Candida species exhibited acidogenic and aciduric potential, C. tropicalis being the most potent.Conclusion: This, the first report of the high-density, multispecies, yeast colonization of deep-dentinal lesions in S-ECC, suggests that the Candida-biome plays a significant etiologic role in the condition, possibly due to their profound acidogenicity in milieus rich in dietary carbohydrates.

Polymeric micelles with anti-virulence activity against Candida albicans in a single- and dual-species biofilm

Infections caused by fungal biofilms with rapidly evolving resistance against the available antifungal agents are difficult to manage. These difficulties demand new strategies for effective eradication of biofilms from both biological and inert surfaces. In this study, polymeric micelles comprised of di-block polymer, poly-(ethylene glycol) methyl ether methacrylate and poly 2-(N,N-diethylamino) ethyl methacrylate polymer, P(PEGMA-b-DEAEMA), were observed to exhibit remarkable inhibitory effects on hyphal growth of Candida albicans (C. albicans) and C. tropicalis, thus preventing biofilm formation and removing existing biofilms. P(PEGMA-b-DEAEMA) micelles showed biofilm removal efficacy of > 40% and a 1.4-log reduction in cell viability of C. albicans in its single-species biofilms. In addition, micelles alone promoted high removal percentage in a mixed biofilm of C. albicans and C. tropicalis (~ 70%) and remarkably reduced cell viability of both strains. Co-delivery of fluconazole (Flu) and amphotericin B (AmB) with micelles showed synergistic effects on C. albicans biofilms (3-log reduction for AmB and 2.2-log reduction for Flu). Similar effects were noted on C. albicans planktonic cells when treated with the micellar system combined with AmB but not with Flu. Moreover, micelle-drug combinations showed an enhancement in the antibiofilm activity of Flu and AmB against dual-species biofilms. Furthermore, in vivo studies using Caenorhabditis elegans nematodes revealed no obvious toxicity of the micelles. Targeting morphologic transitions provides a new strategy for defeating fungal biofilms of polymorphic resistance strains and can be potentially used in counteracting Candida virulence.

Synergistic antimicrobial combination of carvacrol and thymol impairs single and mixed-species biofilms of Candida albicans and Staphylococcus epidermidis

Candida albicans and Staphylococcus epidermidis are important opportunistic human pathogens, which form mixed-species biofilms and cause recalcitrant device associated infections in clinical settings. Further to many reports suggesting the therapeutic potential of plant-derived monoterpenoids, this study investigated the interaction of the monoterpenoids carvacrol (C) and thymol (T) against mono- and mixed-species growth of C. albicans and S. epidermidis. C and T exhibited synergistic antimicrobial activity. The time-kill study and post-antimicrobial effect results revealed the effective microbicidal action of the C + T combination. Filamentation, surface coating assays and live-dead staining of biofilms determined the anti-hyphal, antiadhesion, and anti-biofilm activities of the C + T combination, respectively. Notably, this combination killed highly tolerant persister cells of mono-species and mixed-species biofilms and demonstrated less risk of resistance development. The collective data suggest that the C + T combination could act as an effective therapeutic agent against biofilm associated mono-species and mixed-species infections of C. albicans and S. epidermidis.

Dynamics of Mono- and Dual-Species Biofilm Formation and Interactions Between Paracoccidioides brasiliensis and Candida albicans

The oral cavity is a highly diverse microbial environment in which microorganisms interact with each other, growing as biofilms on biotic and abiotic surfaces. Understanding the interaction among oral microbiota counterparts is pivotal for clarifying the pathogenesis of oral diseases. Candida spp. is one of the most abundant fungi in the oral mycobiome with the ability to cause severe soft tissue lesions under certain conditions. Paracoccidioides spp., the causative agent of paracoccidioidomycosis, may also colonize the oral cavity leading to soft tissue damage. It was hypothesized that both fungi can interact with each other, increasing the growth of the biofilm and its virulence, which in turn can lead to a more aggressive infectivity. Therefore, this study aimed to evaluate the dynamics of mono- and dual-species biofilm growth of Paracoccidioides brasiliensis and Candida albicans and their infectivity using the Galleria mellonella model. Biomass and fungi metabolic activity were determined by the crystal violet and the tetrazolium salt reduction tests (XTT), respectively, and the colony-forming unit (CFU) was obtained by plating. Biofilm structure was characterized by both scanning electronic- and confocal laser scanning- microscopy techniques. Survival analysis of G. mellonella was evaluated to assess infectivity. Our results showed that dual-species biofilm with P. brasiliensis plus C. albicans presented a higher biomass, higher metabolic activity and CFU than their mono-species biofilms. Furthermore, G. mellonella larvae infected with P. brasiliensis plus C. albicans presented a decrease in the survival rate compared to those infected with P. brasiliensis or C. albicans, mainly in the form of biofilms. Our data indicate that P. brasiliensis and C. albicans co-existence is likely to occur on oral mucosal biofilms, as per in vitro and in vivo analysis. These data further widen the knowledge associated with the dynamics of fungal biofilm growth that can potentially lead to the discovery of new therapeutic strategies for these infections.

How Biofilm Growth Affects Candida-Host Interactions

Candida spp. proliferate as surface-associated biofilms in a variety of clinical niches. These biofilms can be extremely difficult to eradicate in healthcare settings. Cells within biofilm communities grow as aggregates and produce a protective extracellular matrix, properties that impact the ability of the host to respond to infection. Cells that disperse from biofilms display a phenotype of enhanced pathogenicity. In this review, we highlight host-biofilm interactions for Candida, focusing on how biofilm formation influences innate immune responses.

Suppressive effects of 2-methacryloyloxyethyl phosphorylcholine (MPC)-polymer on the adherence of Candida species and MRSA to acrylic denture resin

Objectives

The effects of 2-methacryloyloxyethyl phosphorylcholine (MPC)-polymer on the adherence of microorganisms such as non-Candida albicans Candida (NCAC) and methicillin-resistant Staphylococcus aureus (MRSA), frequently detected in oral infections in immunocompromised and/or elderly people, to denture resin material, are still unclear. Here, we report the effects of MPC-polymer on the adherence of C. albicans, NCAC, and MRSA to acrylic denture resin.

Methods

Sixteen strains of C. albicans, seven strains of C. glabrata, two strains of C. tropicalis, one strain of C. parapsilosis, and six strains of MRSA were used. We cultured the fungal/bacterial strains and examined the cell growth and adherence of fungi/bacteria to mucin-coated acrylic denture resin plates (ADRP) with or without MPC-polymer coating, by scanning electron microscopy. The cell surface hydrophobicity of the fungal/bacterial strains was measured by the adsorption to hydrocarbons.

Results

MPC-polymer did not affect the growth of all strains of Candida species and MRSA, but significantly suppressed adherence to ADRP in most strains of C. albicans and all strains of NCAC and MRSA. A significant positive correlation was found between cell hydrophobicity and the reduction rates of microbial adherence to ADRP treated with 5% of MPC-polymer.

Conclusions

MPC-polymer treatment for acrylic resin material suppresses the adherence of C. albicans, NCAC and MRSA via their hydrophilicity interaction.

Clinical significance

The application of MPC-polymer for denture hygiene is potent to prevent oral candidiasis, denture stomatitis and opportunistic infection, caused by Candida species and MRSA, via suppressing the adherence of those fungus/bacteria.

Palmitic Acid Inhibits the Virulence Factors of Candida tropicalis: Biofilms, Cell Surface Hydrophobicity, Ergosterol Biosynthesis, and Enzymatic Activity

Biofilm is the fortitude of Candida species infections which eventually causes candidiasis in human. C. tropicalis is one of the predominant Candida species commonly found in systemic infections, next to C. albicans. In Candida species, biofilm maturity initiates irreversible surface attachment of cells and barricades the penetration of conventional antifungals. Hence, the current study investigated the antifungal and antivirulence potency of palmitic acid (PA) against C. tropicalis mature biofilm and its associated virulence factors. In vitro results revealed an effective inhibition of biofilm in PA-treated C. tropicalis, compared to C. albicans and C. glabrata. Also, PA reduced C. tropicalis mature biofilm at various time points. Further, PA treatment triggered apoptosis in C. tropicalis through ROS mediated mitochondrial dysfunction as demonstrated by confocal microscopic observation of PI, DAPI and DCFDA staining. PA regulated other virulence factors such as cell surface hydrophobicity, ergosterol biosynthesis, protease and lipase after 48 h of treatment. Downregulation of ERG11 (Lanosterol 14-alpha demethylase) was contributed to the reduction of ergosterol in PA-treated C. tropicalis. However, enhanced hyphal growth was observed in PA-treated C. tropicalis through upregulation HWP1 (Hyphal wall protein) and EFG1 (Enhanced filamentous growth). This study highlighted the antibiofilm and antivirulence potency of PA against C. tropicalis. Hence, PA could be applied synergistically with other antifungal agents to increase the efficacy for regulating NCAC infections.

Candida Biofilms: An Update on Developmental Mechanisms and Therapeutic Challenges

Fungi of the genus Candida are important etiological agents of superficial and life-threatening infections in individuals with a compromised immune system. One of the main characteristics of Candida is its ability to form highly drug tolerance biofilms in the human host. Biofilms are a dynamic community of multiple cell types whose formation over time is orchestrated by a network of transcription regulators. In this brief review, we provide an update of the processes involved in biofilm formation by Candida spp. (formation, treatment, and control), as well as the transcriptional circuitry that regulates its development and interactions with other microorganisms. Candida albicans is known to build mixed species biofilms with other Candida species and with various other bacterial species in different host niches. Taken together, these properties play a key role in Candida pathogenesis. In addition, this review gathers recent studies with new insights and perspectives for the treatment and control of Candida biofilms.

Candida spp./Bacteria Mixed Biofilms

The ability to form biofilms is a common feature of microorganisms, such as bacteria or fungi. These consortiums can colonize a variety of surfaces, such as host tissues, dentures, and catheters, resulting in infections highly resistant to drugs, when compared with their planktonic counterparts. This refractory effect is particularly critical in polymicrobial biofilms involving both fungi and bacteria. This review emphasizes Candida spp.-bacteria biofilms, the epidemiology of this community, the challenges in the eradication of such biofilms, and the most relevant treatments.