Candida Biofilms: Development, Architecture, and Resistance

Stimulus-responsive nanomaterials for ocular antimicrobial therapy

Nanomaterials exhibit a promising new avenue for treating infectious keratitis, having garnered considerable interest in the ophthalmic medical community due to their unique properties including higher target specificity, enhanced bioactivity of loaded agents, reduced drug dosage, and stimulus-responsive drug release. These stimulus-responsive nanomaterial-mediated therapeutic strategies offer innovative approaches for managing ocular antimicrobial diseases. In this review, we aim to summarize current applications of stimulus-responsive nanotherapeutics for ocular antimicrobial therapy. We briefly introduce the basic ocular structure, ocular barrier, infectious keratitis classification, and its microenvironment. Following this, we summarize the nanotherapeutic antimicrobial strategies employed in treating ocular infections including endogenous stimulus-responsive ocular nanodrugs, sonodynamic therapy, and wearable device-based therapy, focusing on their design principles, developmental progress, and advantages and limitations. Finally, we critically evaluate the biosafety profiles of responsive nanomaterials, specifically addressing cytotoxicity and immune interactions. To conclude, we discuss key challenges in this research field and future opportunities with explicit emphasis on clinical translation and practical medical applications.

Exploring quinazoline-derived copper(I) complex coated intravaginal ring against vulvovaginal candidiasis causing Candida species

Vulvovaginal candidiasis (VVC) is especially prevalent among intrauterine device (IUD) and intravaginal ring (IVR) users. Candida albicans is the leading causative agent of VVC followed by Candida glabrata. Ascribed to the increased drug resistance by Candida spp. to the currently available drugs, this study has focused on the novel quinazoline-derived copper(I) complexes as anti-candida agents. As a novel approach, a vaginal ring was coated with the best quinazoline-derived copper(I) complex, and biofilm disruption ability was evaluated. The coated vaginal ring eradicated 70% of preformed biofilms and also inhibited the hyphal transition of Candida albicans in a simulated vaginal fluid (SVF). The overall study validates the anti-biofilm and anti-virulent properties of the metal complex-coated vaginal ring using various microscopic studies.

Impact of citric acid and conventional denture cleansers on surface properties and antimicrobial performance of conventionally heat-processed acrylic resin: An in vitro study

STATEMENT OF PROBLEM

Effective decontamination of denture base acrylic resin is essential for biofilm removal but can compromise the integrity of the material. Citric acid has shown promise as a potent antimicrobial agent, though its effectiveness as a denture cleanser is unknown.

PURPOSE

The purpose of this in vitro study was to evaluate the effect of citric acid on the surface properties and efficacy of biofilm removal on denture base acrylic resin compared with commonly used denture cleansers.

MATERIAL AND METHODS

A total of 130 conventional, heat-processed denture base acrylic resin disks were randomly allocated into 1 of 5 groups based on the decontamination solution applied: control 0.9% sodium chloride (NaCl), 0.1% sodium hypochlorite (SH), Periogard (chlorhexidine digluconate), effervescent denture cleansing tablets (Corega Tabs), and 10% citric acid (CA). Surface properties (roughness, hydrophilicity, microhardness, and color stability) were assessed at 3 time points: baseline (T0), after 5 minutes of exposure (T1), and after 1 week of exposure (T2) to the respective solution. A microcosm biofilm was formed on specimen surfaces to evaluate antimicrobial efficacy of the decontamination solution groups, through assessment of microbial viability, metabolic activity, biofilm dry weight, and morphology. A 2-way repeated measures ANOVA was performed for surface properties evaluations and for microbiological analysis, 1-way ANOVA was used (α=.05).

RESULTS

No significant differences in average surface roughness (Ra) were observed between T0, T1, and T2 across all groups (P>.05). CA significantly increased surface hydrophilicity at T2 (P<.001) compared with the other groups. No significant differences in ΔE00 were seen among the groups: all values near the 50% perceptibility threshold. Compared with the control group, all denture cleansers significantly reduced the viability of total microorganisms and Candida species, with no viable colonies detected after treatment (P<.001). However, CA demonstrated a robust antimicrobial effect, with a significant reduction in biofilm dry weight and metabolic activity (P<.001), suggesting superior biofilm disruption compared with the other groups.

CONCLUSIONS

Citric acid effectively increased hydrophilicity of conventional, heat-processed acrylic resin without negatively impacting surface roughness, microhardness, or color stability.

Biofilm-Associated Candidiasis: Pathogenesis, Prevalence, Challenges and Therapeutic Options

The rising prevalence of fungal infections, especially those caused by Candida species, presents a major risk to global health. With approximately 1.5 million deaths annually, the urgency for effective treatment options has never been greater. Candida spp. are the leading cause of invasive infections, significantly impacting immunocompromised patients and those in healthcare settings. C. albicans, C. parapsilosis and the emerging species C. auris are categorized as highly dangerous species because of their pathogenic potential and increasing drug resistance. This review comparatively describes the formation of microbial biofilms of both bacterial and fungal origin, including major pathogens, thereby creating a novel focus. Biofilms can further complicate treatment, as these structures provide enhanced resistance to antifungal therapies. Traditional antifungal agents, including polyenes, azoles and echinocandins, have shown effectiveness, yet resistance development continues to rise, necessitating the exploration of novel therapeutic approaches. Antimicrobial peptides (AMPs) such as the anti-biofilm peptides Pom-1 and Cm-p5 originally isolated from snails represent promising candidates due to their unique mechanisms of action and neglectable cytotoxicity. This review article discusses the challenges posed by Candida infections, the characteristics of important species, the role of biofilms in virulence and the potential of new therapeutic options like AMPs.

Biofilm Formation in Clinical Isolates of Fusarium

Many microbial pathogens form biofilms, assemblages of polymeric compounds that play a crucial role in establishing infections. The biofilms of Fusarium species also contribute to high antifungal resistance. Using our collection of 29 clinical Fusarium isolates, we focused on characterizing differences in thermotolerance, anaerobic growth, and biofilm formation across four Fusarium species complexes commonly found in clinical settings. We investigated the role of carbon sources, temperature, and fungal morphology on biofilm development. Using fluorescence microscopy, we followed the stages of biofilm formation. Biofilms were screened for sensitivity/resistance to the antifungals voriconazole (VOR), amphotericin B (AmB), and 5-fluorocytosine (5-FC). Our findings revealed generally poor thermotolerance and growth under anaerobic conditions across all Fusarium species. VOR was more effective than AmB in controlling biofilm formation, but the combination of VOR, AmB, and 5-FC significantly reduced biofilm formation across all species. Additionally, Fusarium biofilm formation varied under non-glucose carbon sources, highlighting the species' adaptability to different nutrient environments. Notably, early stage biofilms were primarily composed of lipids, while polysaccharides became dominant in late-stage biofilms, suggesting a dynamic shift in biofilm composition over time.

Screening of the global health priority BoxⓇ reveals potential new disinfectants against the emerging multidrug-resistant pathogen Candida auris

BACKGROUND

Candida auris has been identified by the World Health Organization as a critical pathogen due to its invasive nature, resistance to multiple drugs, and high mortality rates in hospital outbreaks. This fungus can persist on surfaces and human skin for extended periods, complicating infection control efforts. The need for effective disinfection strategies is urgent, as current disinfectants are often ineffective against C. auris biofilms.

OBJECTIVE

The study aimed to identify potential disinfectants from a collection of 240 compounds in the Global Health Priority Box® that are effective against C. auris, particularly strains resistant to existing options.

METHODS

The research employed a screening protocol using a fluconazole-resistant strain of C. auris (149/23). Antifungal activity was assessed using the microdilution method to determine Minimum Inhibitory Concentrations (MICs) and Minimum Fungicidal Concentrations (MFCs). Additional assays were conducted to evaluate biofilm inhibition, biofilm eradication, cell membrane integrity, nucleotide leakage, sorbitol protection assay, efflux pump inhibition, and hemolysis assay.

RESULTS

Two compounds, Hydramethylnon (MMV1577471) and Flufenerim (MMV1794206), demonstrated significant inhibitory effects against C. auris. Hydramethylnon exhibited potent antifungal activity, inhibiting up to 93 % of fungal growth with an MFC of 16 μg/mL. Flufenerim inhibited up to 58 % of fungal growth, showing fungistatic action with an MFC greater than 4 μg/mL. Biofilm inhibition tests showed that both compounds significantly inhibited biofilm formation, with increased efficacy at higher concentrations. Both compounds showed eradication rates in both stages. Furthermore, Hydramethylnon and Flufenerim did not affect cell membrane integrity or nucleotide leakage, suggesting a mode of action not reliant on disrupting these cellular components. The sorbitol protection assay revealed that neither compound caused cell wall damage. In the efflux pump inhibition assay, Hydramethylnon did not activate efflux pumps, while Flufenerim activated efflux pumps, reducing its effectiveness. Hemocompatibility assay showed safety.

CONCLUSION

The study highlights Hydramethylnon and Flufenerim as promising candidates for further development as disinfectants, offering potential solutions to the urgent need for effective disinfection agents against C. auris. The findings underscore the value of screening compound collections to identify novel antifungal agents and understand their mechanisms of action, thereby contributing to the advancement of new disinfection strategies in healthcare settings.

Candida albicans skin infection in diabetic patients: An updated review of pathogenesis and management

Candida species, commensal residents of human skin, are recognized as the cause of cutaneous candidiasis across various body surfaces. Individuals with weakened immune systems, particularly those with immunosuppressive conditions, are significantly more susceptible to this infection. Diabetes mellitus, a major metabolic disorder, has emerged as a critical factor inducing immunosuppression, thereby facilitating Candida colonization and subsequent skin infections. This comprehensive review examines the prevalence of different types of Candida albicans-induced cutaneous candidiasis in diabetic patients. It explores the underlying mechanisms of pathogenicity and offers insights into recommended preventive measures and treatment strategies. Diabetes notably increases vulnerability to oral and oesophageal candidiasis. Additionally, it can precipitate vulvovaginal candidiasis in females, Candida balanitis in males, and diaper candidiasis in young children with diabetes. Diabetic individuals may also experience candidal infections on their nails, hands and feet. Notably, diabetes appears to be a risk factor for intertrigo syndrome in obese individuals and periodontal disorders in denture wearers. In conclusion, the intricate relationship between diabetes and cutaneous candidiasis necessitates a comprehensive understanding to strategize effective management planning. Further investigation and interdisciplinary collaborative efforts are crucial to address this multifaceted challenge and uncover novel approaches for the treatment, management and prevention of both health conditions, including the development of safer and more effective antifungal agents.

Procatechuic acid and protocatechuic aldehyde increase survival of Caenorhabditis elegans after fungal infection and inhibit fungal virulence

Protocatechuic acid (PCA) and protocatechuic aldehyde (PAL) are important phenolic compounds in plants. We here investigated their possible beneficial effect against fungal infection and the underlying mechanism. The model animal of Caenorhabditis elegans was used as host, and Candida albicans was used as fungal pathogen. The nematodes were first infected with C. albicans, and the PCA and PAL treatment were then performed. Post-treatment with 10-100 μM PCA and PAL suppressed toxicity of C. albicans infection in reducing lifespan. Accompanied with this beneficial effect, treatment with 10-100 μM PCA and PAL inhibited C. albicans accumulation in intestinal lumen. In addition, treatment with 10-100 μM PCA and PAL suppressed the increase in expressions of antimicrobial genes caused by C. albicans infection. The beneficial effect of PCA and PAL against C. albicans infection depended on p38 MAPK and insulin signals. Moreover, although treatment with 10-100 μM PCA and PAL could not exhibit noticeable antifungal activity, PCA and PAL treatment obviously suppressed biofilm formation, inhibited hyphal growth, and reduced expressions of virulence genes (ALS3, CaVps34, Vma7, Vac1, and/or HWP1) related to biofilm formation and hyphal growth in C. albicans. Therefore, our data demonstrated the potential of PCA and PAL post-treatment against fungal infection and fungal virulence.

Structure-activity relationship and biofilm formation-related gene targets of oleanolic acid-type saponins from Pulsatilla chinensis against Candida albicans

In the course of our investigations of antifungal natural products, the structure-activity relationship and antifungal activities of oleanolic acid-type saponins (1-28) from Pulsatilla chinensis against human and plant pathogenic fungi were elucidated. The analysis of structure-activity relationship of oleanolic acid-type saponins showed that the free carboxyl at C-28 was essential for their antifungal activities; the free hydroxyl group at the C-23 site of oleanolic acid-type saponins played a crucial role in their antifungal activities; the oligosaccharide chain at C-3 oleanolic acid-type saponins showed significant effects on antifungal efficacy and a disaccharide or trisaccharide moiety at position C-3 displayed optimal antifungal activity. The typical saponin pulchinenoside B3 (16, PB3) displayed satisfactory antifungal activity against human and plant pathogenic fungi, especially, C. albicans with an MIC value of 12.5 μg/mL. Furthermore, PB3 could inhibit the biofilm formation of C. albicans through downregulating the expression of the integrated network of biofilm formation-associated transcription factors (Bcr1 Efg1, Ndt80, Brg1, Rob1 and Tec1) and adhesion-related target genes (HWP1, ALS1, and ALS3). Meanwhile, we found that PB3 could effectively destroy the mature biofilm of C. albicans by the oxidative damage and inducing mitochondria-mediated apoptosis in cells.

Anti-Biofilm Activity of Assamsaponin A, Theasaponin E1, and Theasaponin E2 against Candida albicans

Biofilm formation plays a crucial role in the pathogenesis of Candida albicans and is significantly associated with resistance to antifungal agents. Tea seed saponins, a class of non-ionic triterpenes, have been proven to have fungicidal effects on planktonic C. albicans. However, their anti-biofilm activity and mechanism of action against C. albicans remain unclear. In this study, the effects of three Camellia sinensis seed saponin monomers, namely, theasaponin E1 (TE1), theasaponin E2 (TE2), and assamsaponin A (ASA), on the metabolism, biofilm development, and expression of the virulence genes of C. albicans were evaluated. The results of the XTT reduction assay and crystal violet (CV) staining assay demonstrated that tea seed saponin monomers concentration-dependently suppressed the adhesion and biofilm formation of C. albicans and were able to eradicate mature biofilms. The compounds were in the following order in terms of their inhibitory effects: ASA > TE1 > TE2. The mechanisms were associated with reductions in multiple crucial virulence factors, including cell surface hydrophobicity (CSH), adhesion ability, hyphal morphology conversion, and phospholipase activity. It was further demonstrated through qRT-PCR analysis that the anti-biofilm activity of ASA and TE1 against C. albicans was attributed to the inhibition of RAS1 activation, which consequently suppressed the cAMP-PKA and MAPK signaling pathways. Conversely, TE2 appeared to regulate the morphological turnover and hyphal growth of C. albicans via a pathway that was independent of RAS1. These findings suggest that tea seed saponin monomers are promising innovative agents against C. albicans.

Five-year cross-sectional study to determine the burden of Candida spp. infections of the urinary tract system among patients attending tertiary hospital in Northwestern Tanzania

OBJECTIVE

Urinary tract infections (UTIs) stand as a prominent global health concern. This study entails a 5-year retrospective analysis, using a cross-sectional study design to examine microbiology laboratory data of individuals clinically diagnosed with UTIs at Bugando Medical Centre to gain insights into the prevalence and factors linked to candiduria.

METHODOLOGY

Data extracted were meticulously cleaned and coded in an MS Excel sheet, subsequently transferred to STATA V.15 for analysis. Binary logistic regression analysis was used to identify factors associated with candiduria. A probability value below 0.05 at a 95% CI was considered statistically significant.

RESULTS

Urine samples for culture and sensitivity comprised 33.4% (20755) of the total biological samples (62335). The median age of the patients stood at 19 years. A slight majority were female, accounting for 52.8% (10051), and two-thirds sought treatment at outpatient departments (67.5%, 12843). Among patients with significant pathogenic growth, the prevalence of candiduria was 4.6% (221 out of 4772). Notably, inpatients exhibited a higher incidence of candiduria compared with outpatients, with rates of 9.4% (1882) versus 1.6% (2890), p value of 0.000. Non-albicans Candida spp. (NAC) remained the most prevalent pathogen. Factors significantly associated with candiduria included being female (OR=1.7, 95% CI 1.3 to 2.3) and hospital admission (OR=6.6, 95% CI 4.7 to 9.2). In conclusion, candiduria affect 5 out of every 100 UTI-diagnosed patients, predominantly among females and those admitted to the hospital. Clinicians at tertiary hospitals should consider urinary candidiasis as a potential diagnosis for patients at risk who present with UTI-like symptoms.

Occidiofungin inhibition of Candida biofilm formation on silicone elastomer surface

IMPORTANCE

Candida are opportunistic fungal pathogens with medical relevance given their association with superficial to life-threatening infections. An important component of Candida virulence is the ability to form a biofilm. These structures are highly resistant to antifungal therapies and are often the cause of treatment failure. In this work, we evaluated the efficacy of the antifungal compound, occidiofungin, against Candida biofilms developed on a silicone surface. We demonstrate that occidiofungin eliminated cells at all stages of biofilm formation in a dose-dependent manner. Consistent with our understanding of occidiofungin bioactivity, we noted alterations to actin organization and cell morphology following antifungal exposure. Given the challenges associated with the treatment of biofilm-associated infections, occidiofungin exhibits potential as a therapeutic antifungal agent in the future.

Exploring therapeutic avenues: mesenchymal stem/stromal cells and exosomes in confronting enigmatic biofilm-producing fungi

Fungal infections concomitant with biofilms can demonstrate an elevated capacity to withstand substantially higher concentrations of antifungal agents, contrasted with infectious diseases caused by planktonic cells. This inherent resilience intrinsic to biofilm-associated infections engenders a formidable impediment to effective therapeutic interventions. The different mechanisms that are associated with the intrinsic resistance of Candida species encompass drug sequestration by the matrix, drug efflux pumps, stress response cell density, and the presence of persister cells. These persisters, a subset of fungi capable of surviving hostile conditions, pose a remarkable challenge in clinical settings in virtue of their resistance to conventional antifungal therapies. Hence, an exigent imperative has arisen for the development of novel antifungal therapeutics with specific targeting capabilities focused on these pathogenic persisters. On a global scale, fungal persistence and their resistance within biofilms generate an urgent clinical need for investigating recently introduced therapeutic strategies. This review delves into the unique characteristics of Mesenchymal stem/stromal cells (MSCs) and their secreted exosomes, which notably exhibit immunomodulatory and regenerative properties. By comprehensively assessing the current literature and ongoing research in this field, this review sheds light on the plausible mechanisms by which MSCs and their exosomes can be harnessed to selectively target fungal persisters. Additionally, prospective approaches in the use of cell-based therapeutic modalities are examined, emphasizing the importance of further research to overcome the enigmatic fungal persistence.

Comparison of amphotericin B lipid complex, deoxycholate amphotericin B, fluconazole, and anidulafungin activity against Candida albicans biofilm isolated from breakthrough candidemia

INTRODUCTION

Biofilm formation causes virulence and resistance in Candida albicans. However, little is known about breakthrough candidemia isolates. We evaluated the antifungal activity of fluconazole, anidulafungin, deoxycholate amphotericin B (dAMB), and amphotericin B lipid complex (ABLC) against biofilms of C. albicans isolated from patients with breakthrough candidemia.

METHODS

The present study used strains of C. albicans isolated from breakthrough and non-breakthrough candidemia patients (control group). The susceptibility of planktonic cells to amphotericin B, anidulafungin, and fluconazole was determined by broth microdilution. Antifungal activity in sessile cells was evaluated using the minimum biofilm eradication concentration (MBEC), metabolic activity was estimated by reducing MTT, and biomass was estimated using crystal violet retention.

RESULTS

The planktonic strains were susceptible to amphotericin B, anidulafungin, and fluconazole, with minimum inhibitory concentrations of 1, ≤0.03, and 2mg/L, respectively. However, fluconazole and anidulafungin did not exert an antifungal effect on biofilms. Additionally, dAMB and ABCL reduced the metabolic activity and biomass. However, eradication was only achieved using 16mg/L dAMB. C. albicans isolates of breakthrough candidemia exhibited strong biofilm production, and the in vitro activity of available therapeutic options was poor.

CONCLUSION

In the present study, only dAMB and ABCL exhibited antibiofilm effects against sessile breakthrough candidemia isolates.

Anti-Biofilm Activity of Cocultimycin A against Candida albicans

Candida albicans (C. albicans), the most common fungal pathogen, has the ability to form a biofilm, leading to enhanced virulence and antibiotic resistance. Cocultimycin A, a novel antifungal antibiotic isolated from the co-culture of two marine fungi, exhibited a potent inhibitory effect on planktonic C. albicans cells. This study aimed to evaluate the anti-biofilm activity of cocultimycin A against C. albicans and explore its underlying mechanism. Crystal violet staining showed that cocultimycin A remarkably inhibited biofilm formation in a dose-dependent manner and disrupted mature biofilms at higher concentrations. However, the metabolic activity of mature biofilms treated with lower concentrations of cocultimycin A significantly decreased when using the XTT reduction method. Cocultimycin A could inhibit yeast-to-hypha transition and mycelium formation of C. albicans colonies, which was observed through the use of a light microscope. Scanning electron microscopy revealed that biofilms treated with cocultimycin A were disrupted, yeast cells increased, and hypha cells decreased and significantly shortened. The adhesive ability of C. albicans cells treated with cocultimycin A to the medium and HOEC cells significantly decreased. Through the use of a qRT-PCR assay, the expression of multiple genes related to adhesion, hyphal formation and cell membrane changes in relation to biofilm cells treated with cocultimycin A. All these results suggested that cocultimycin A may be considered a potential novel molecule for treating and preventing biofilm-related C. albicans infections.

In vitro activity of sanitizers against mono- and polymicrobial biofilms of C. parapsilosis and S. aureus

The emergence of disinfectant-resistant microorganisms poses a significant threat to public health. These resilient pathogens can survive and thrive in hospital settings despite routine disinfection practices, leading to persistent infections and the potential for outbreaks. In this study, we investigated the impact of 11 different commercial sanitizers at various concentrations and exposure times on biofilms consisting of clinical and nosocomial environmental isolates of Candida parapsilosis and Staphylococcus aureus. Among the sanitizers tested, 0.5% and 2.0% chlorhexidine (CLX), 10% polyvinyl pyrrolidone (PVP-I), a disinfectant based on quaternary ammonium compound (QAC), 2% glutaraldehyde, and 0.55% orthophthalaldehyde (OPA) demonstrated efficacy against both C. parapsilosis and S. aureus in monospecies and mixed biofilms. Analysis showed that 0.5% CLX and 10% PVP-I had fungicidal and bactericidal activity against all biofilms. However, the sanitizer based on QAC and 0.55% OPA proved to be bacteriostatic and fungicidal against both monospecies and mixed biofilms. In mixed biofilms, despite the last four sanitizers exerting fungicidal action, the reduction of fungal cells was approximately 4 log10 CFU/mL compared to monospecies biofilms, showing that the interaction provided more resistance of the yeast to the sanitizer. Formation of mixed biofilms in hospital settings can create an ecological niche that enhances the survival of pathogens against routine sanitization procedures. Therefore, effective sanitization practices, including regular cleaning with effective sanitizers, should be implemented to prevent C. parapsilosis/S. aureus biofilm formation in healthcare settings.

Biofilm Formation in Medically Important Candida Species

Worldwide, the number of infections caused by biofilm-forming fungal pathogens is very high. In human medicine, there is an increasing proportion of immunocompromised patients with prolonged hospitalization, and patients with long-term inserted drains, cannulas, catheters, tubes, or other artificial devices, that exhibit a predisposition for colonization by biofilm-forming yeasts. A high percentage of mortality is due to candidemia caused by medically important Candida species. Species of major clinical significance include C. albicans, C. glabrata, C. tropicalis, C. parapsilosis, C. krusei, and C. auris. The association of these pathogenic species in the biofilm structure is a serious therapeutic problem. Candida cells growing in the form of a biofilm are able to resist persistent therapy thanks to a combination of their protective mechanisms and their ability to disseminate to other parts of the body, thus representing a threat from the perspective of a permanent source of infection. The elucidation of the key mechanisms of biofilm formation is essential to progress in the understanding and treatment of invasive Candida infections.

Biofilm Formation and Aspartyl Proteinase Activity and Their Association with Azole Resistance Among Candida albicans Causing Vulvovaginal Candidiasis, Egypt

Background

Candida albicans (C. albicans) is a major cause of vulvovaginal candidiasis (VVC), a condition that is commonly treated with azole agents. Biofilm formation and aspartyl proteinase production are important virulence factors that could be linked to azole resistance in C. albicans impeding therapy.

Aim

To find out the association of both factors with azole resistance among C. albicans isolated from VVC cases in Egyptian nonpregnant women of childbearing age.

Patients and Methods

In a cross-sectional study, C. albicans was isolated from nonpregnant females diagnosed clinically as having VVC during a 1-year study period. Susceptibility to azole agents was tested using the disc diffusion method. Biofilm formation and aspartyl proteinase production were assessed phenotypically. Additionally, two biofilm-related genes (ALS1 and HWP1) and three proteinase genes (SAP2, SAP4, and SAP6) were screened for using polymerase chain reaction (PCR).

Results

Among 204 C. albicans isolates, azole resistance ratios were as follows: voriconazole (30.4%), itraconazole (17.6%), fluconazole (11.3%) and econazole (6.4%). Biofilm-producing capacity was detected in 63.2% of isolates, and 63.2% were proteinase producers. The frequencies of ALS1 and HWP1 were 69.6% and 74.5%, respectively, while SAP2, SAP4, and SAP6 were 69.2%, 88.7%, and 64.7%, respectively. Biofilm formation was significantly associated with azole resistance (P < 0.001 for each tested azole agent) as was proteinase production (P < 0.001 for fluconazole, voriconazole, and econazole resistance and P = 0.047 for itraconazole).

Conclusion

Among nonpregnant Egyptian women of childbearing age, azole resistance in C. albicans causing VVC is significantly associated with biofilm formation and proteinase production. The development of new therapeutic agents that can target these factors is warranted.

Inhibitory Effects of the Fungal Pigment Rubiginosin C on Hyphal and Biofilm Formation in Candida albicans and Candida auris

The two fungal human pathogens, Candida auris and Candida albicans, possess a variety of virulence mechanisms. Among them are the formation of biofilms to protect yeast against harsh conditions through the development of (pseudo)hyphae whilst also facilitating the invasion of host tissues. In recent years, increased rates of antifungal resistance have been associated with C. albicans and C. auris, posing a significant challenge for the effective treatment of fungal infections. In the course of our ongoing search for novel anti-infectives, six selected azaphilones were tested for their cytotoxicity and antimicrobial effects as well as for their inhibitory activity against biofilm and hyphal formation. This study revealed that rubiginosin C, derived from stromata of the ascomycete Hypoxylon rubiginosum, effectively inhibited the formation of biofilms, pseudohyphae, and hyphae in both C. auris and C. albicans without lethal effects. Crystal violet staining assays were utilized to assess the inhibition of biofilm formation, while complementary microscopic techniques, such as confocal laser scanning microscopy, scanning electron microscopy, and optical microscopy, were used to investigate the underlying mechanisms. Rubiginosin C is one of the few substances known to effectively target both biofilm formation and the yeast-to-hyphae transition of C. albicans and C. auris within a concentration range not affecting host cells, making it a promising candidate for therapeutic intervention in the future.

Nitric oxide-loaded nano- and microparticle platforms serving as potential new antifungal therapeutics

Fungal diseases are a leading threat to human health, especially in individuals with compromised immunity. Although there have been recent important advances in antifungal drug development, antifungal resistance, drug-drug interactions and difficulties in delivery remain major challenges. Among its pleiotropic actions, nitric oxide (NO) is a key molecule in host defense. We have developed a flexible nanoparticle platform that delivers sustained release of NO and have demonstrated the platform's efficacy against diverse bacteria as well as some fungal species. In this work, we investigate the effects of two NO-releasing particles against a panel of important human yeast. Our results demonstrate that the compounds are both effective against diverse yeast, including ascomycota and basidiomycota species, and that NO-releasing particles may be a potent addition to our armamentarium for the treatment of focal and disseminated mycoses.

Evaluation of the polyphenolic profile of native Ecuadorian stingless bee honeys (Tribe: Meliponini) and their antibiofilm activity on susceptible and multidrug-resistant pathogens: An exploratory analysis

Biofilms are associated with infections that are resistant to conventional therapies, contributing to the antimicrobial resistance crisis. The need for alternative approaches against biofilms is well-known. Although natural products like stingless bee honeys (tribe: Meliponini) constitute an alternative treatment, much is still unknown. Our main goal was to evaluate the antibiofilm activity of stingless bee honey samples against multidrug-resistant (MDR) pathogens through biomass assays, fluorescence (cell count and viability), and scanning electron (structural composition) microscopy. We analyzed thirty-five honey samples at 15% (v/v) produced by ten different stingless bee species (Cephalotrigona sp., Melipona sp., M. cramptoni, M. fuscopilosa, M. grandis, M. indecisa, M. mimetica, M. nigrifacies, Scaptotrigona problanca, and Tetragonisca angustula) from five provinces of Ecuador (Tungurahua, Pastaza, El Oro, Los Ríos, and Loja) against 24-h biofilms of Staphylococcus aureus, Klebsiella pneumoniae, Candida albicans, and Candida tropicalis. The present honey set belonged to our previous study, where the samples were collected in 2018-2019 and their physicochemical parameters, chemical composition, mineral elements, and minimal inhibitory concentration (MIC) were screened. However, the polyphenolic profile and their antibiofilm activity on susceptible and multidrug-resistant pathogens were still unknown. According to polyphenolic profile of the honey samples, significant differences were observed according to their geographical origin in terms of the qualitative profiles. The five best honey samples (OR24.1, LR34, LO40, LO48, and LO53) belonging to S. problanca, Melipona sp., and M. indecisa were selected for further analysis due to their high biomass reduction values, identification of the stingless bee specimens, and previously reported physicochemical parameters. This subset of honey samples showed a range of 63-80% biofilm inhibition through biomass assays. Fluorescence microscopy (FM) analysis evidenced statistical log reduction in the cell count of honey-treated samples in all pathogens (P <0.05), except for S. aureus ATCC 25923. Concerning cell viability, C. tropicalis, K. pneumoniae ATCC 33495, and K. pneumoniae KPC significantly decreased (P <0.01) by 21.67, 25.69, and 45.62%, respectively. Finally, scanning electron microscopy (SEM) analysis demonstrated structural biofilm disruption through cell morphological parameters (such as area, size, and form). In relation to their polyphenolic profile, medioresinol was only found in the honey of Loja, while scopoletin, kaempferol, and quercetin were only identified in honey of Los Rios, and dihydrocaffeic and dihydroxyphenylacetic acids were only detected in honey of El Oro. All the five honey samples showed dihydrocoumaroylhexose, luteolin, and kaempferol rutinoside. To the authors' best knowledge, this is the first study to analyze stingless bees honey-treated biofilms of susceptible and/or MDR strains of S. aureus, K. pneumoniae, and Candida species.

Candida Colonization on the Surface of Contact Lenses in Long-Term Wearers and Boston Type 1 Keratoprosthesis Patients Presenting as White Mulberry-Shaped Deposits

PURPOSE

To report Candida colonies on the surface of the contact lens in long-term contact lens wearers and patients with Boston type 1 keratoprosthesis (KPro I).

METHODS

A retrospective study was performed based on analyzing cultures from bandage contact lenses with small whitish mulberry-shaped deposits on their surface.

RESULTS

Eight samples (from seven patients) were positive for Candida. Seven of the eight were positive for Candida parapsilosis.

CONCLUSIONS

The whitish deposits on contact lenses are often Candida colonies that colonize the surface but do not cause an active infection in the eye. C. parapsilosis is well-known for colonizing prosthetic devices. We underline the importance of including Candida species in the differential diagnosis of lens deposits, especially in susceptible patients such as keratoprosthesis carriers.

Secreted aspartyl proteases family: a perspective review on the regulation of fungal pathogenesis

Secreted aspartyl proteases (SAPs) are important enzymes for fungal pathogenicity, playing a significant role in infection and survival. This article provides insight into how SAPs facilitate the transformation of yeast cells into hyphae and engage in biofilm formation, invasion and degradation of host cells and proteins. SAPs and their isoenzymes are prevalent during fungal infections, making them a potential target for antifungal and antibiofilm therapies. By targeting SAPs, critical stages of fungal pathogenesis such as adhesion, hyphal development, biofilm formation, host invasion and immune evasion can potentially be disrupted. Developing therapies that target SAPs could provide an effective treatment option for a wide range of fungal infections.

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.

Riboflavin Targets the Cellular Metabolic and Ribosomal Pathways of Candida albicans In Vitro and Exhibits Efficacy against Oropharyngeal Candidiasis

Oropharyngeal candidiasis (OPC), which has a high incidence in immunocompromised and denture stomatitis patients, is commonly caused by Candida albicans infection and in some cases develops into disseminated candidiasis throughout the throat and esophagus, resulting in high mortality. New drugs are needed to combat OPC because of the limited treatment options currently available and increasing resistance to existing drugs. Here, we confirmed that riboflavin (RF), a cofactor of flavin adenine mononucleotide and flavin adenine dinucleotide, has broad-spectrum anti-Candida activity. The formation of C. albicans hyphae and biofilm was inhibited by RF. Mechanistically, RF disrupted membrane and cell wall integrity, as well as promoting reactive oxygen species and pyruvate accumulation. Furthermore, RF targeted multiple essential pathways via functional disruption of thiamine and RF metabolic pathways, central carbon metabolism, and ribosome metabolism. Similar to the results in vitro, the inhibitory effect of RF on C. albicans hyphae was confirmed in a mouse model of OPC. Moreover, after 5 consecutive days of intraperitoneal injection, RF exhibited therapeutic efficacy, as demonstrated by phenotype investigation, the fungal burden, and histopathological analysis. These findings revealed that RF exerts a multifaceted anti-Candida effect and has potential benefits in the treatment of OPC. IMPORTANCE Candida species are common pathogens in fungal infections, causing mucosal infection and invasive infection in immunodeficient patients. Given the limited classes of drugs and resistance to these drugs, new antifungal agents need to be developed. Drug repurposing is a potential method for antifungal drug development. This study demonstrated that riboflavin (RF) exhibited broad-spectrum anti-Candida activity. RF affected multiple targets involving the membrane and cell wall integrity, the accumulation of reactive oxygen species and pyruvate, and the altered metabolic pathways in C. albicans. Moreover, RF exhibited efficacy in the treatment of C. albicans in an oropharyngeal candidiasis mouse model. Taken together, the antifungal activity and the promising clinical application of RF were highlighted.

Candida parapsilosis Virulence and Antifungal Resistance Mechanisms: A Comprehensive Review of Key Determinants

Candida parapsilosis is the second most common Candida species isolated in Asia, Southern Europe, and Latin America and is often involved in invasive infections that seriously impact human health. This pathogen is part of the psilosis complex, which also includes Candida orthopsilosis and Candida metapsilosis. C. parapsilosis infections are particularly prevalent among neonates with low birth weights, individuals who are immunocompromised, and patients who require prolonged use of a central venous catheter or other indwelling devices, whose surfaces C. parapsilosis exhibits an enhanced capacity to adhere to and form biofilms. Despite this well-acknowledged prevalence, the biology of C. parapsilosis has not been as extensively explored as that of Candida albicans. In this paper, we describe the molecular mechanistic pathways of virulence in C. parapsilosis and show how they differ from those of C. albicans. We also describe the mode of action of antifungal drugs used for the treatment of Candida infections, namely, polyenes, echinocandins, and azoles, as well as the resistance mechanisms developed by C. parapsilosis to overcome them. Finally, we stress the importance of the ongoing search for species-specific features that may aid the development of effective control strategies and thus reduce the burden on patients and healthcare costs.

Biofilm Lifestyle in Recurrent Urinary Tract Infections

Urinary tract infections (UTIs) represent one of the most common infections that are frequently encountered in health care facilities. One of the main mechanisms used by bacteria that allows them to survive hostile environments is biofilm formation. Biofilms are closed bacterial communities that offer protection and safe hiding, allowing bacteria to evade host defenses and hide from the reach of antibiotics. Inside biofilm communities, bacteria show an increased rate of horizontal gene transfer and exchange of resistance and virulence genes. Additionally, bacterial communication within the biofilm allows them to orchestrate the expression of virulence genes, which further cements the infestation and increases the invasiveness of the infection. These facts stress the necessity of continuously updating our information and understanding of the etiology, pathogenesis, and eradication methods of this growing public health concern. This review seeks to understand the role of biofilm formation in recurrent urinary tact infections by outlining the mechanisms underlying biofilm formation in different uropathogens, in addition to shedding light on some biofilm eradication strategies.

Inhibitory effects of vaginal Lactobacilli on Candida albicans growth, hyphal formation, biofilm development, and epithelial cell adhesion

Introduction

Antifungal agents are not always efficient in resolving vulvovaginal candidiasis (VVC), a common genital infection caused by the overgrowth of Candida spp., including Candida albicans, or in preventing recurrent infections. Although lactobacilli (which are dominant microorganisms constituting healthy human vaginal microbiota) are important barriers against VVC, the Lactobacillus metabolite concentration needed to suppress VVC is unknown.

Methods

We quantitatively evaluated Lactobacillus metabolite concentrations to determine their effect on Candida spp., including 27 vaginal strains of Lactobacillus crispatus, L. jensenii, L. gasseri, Lacticaseibacillus rhamnosus, and Limosilactobacillus vaginalis, with inhibitory abilities against biofilms of C. albicans clinical isolates.

Results

Lactobacillus culture supernatants suppressed viable fungi by approximately 24%-92% relative to preformed C. albicans biofilms; however, their suppression differed among strains and not species. A moderate negative correlation was found between Lactobacillus lactate production and biofilm formation, but no correlation was observed between hydrogen peroxide production and biofilm formation. Both lactate and hydrogen peroxide were required to suppress C. albicans planktonic cell growth. Lactobacillus strains that significantly inhibited biofilm formation in culture supernatant also inhibited C. albicans adhesion to epithelial cells in an actual live bacterial adhesion competition test.

Discussion

Healthy human microflora and their metabolites may play important roles in the development of new antifungal agent against C. albicans-induced VVC.

Biofilm Alterations on the Stepwise Acquisition of Fluconazole-resistant Candida Albicans Isolates

By assessing and comparing the phenotypic changes on the stepwise acquisition of fluconazole resistant Candida albicans isolates, we could find and describe the relationship between drug resistance and biofilm formation ability in a series of clonal strains.

The Antifungal and Antibiofilm Activities of Caffeine against Candida albicans on Polymethyl Methacrylate Denture Base Material

Background: In this study, the effect of pure caffeine was established against Candida albicans (C. albicans) using different microbiological techniques. Methods: Broth microdilution and colony forming units (CFUs) assays were used to detect the minimum inhibitory concentration (MIC) and minimum fungicidal concentration (MFC). The Live/Dead fluorescent dyes were implemented to determine the yeast viability. Polymethyl methacrylate acrylic resin (PMMA) discs were prepared to evaluate caffeine’s effects against adherent C. albicans using microplate reader, CFUs, and scanning electron microscope (SEM). Results: caffeine’s MIC was detected around 30 mg/mL, while the MFC was considered at 60 mg/mL. In an agar-well diffusion test, the inhibition zones were wider in caffeine groups. The Live/Dead viability test verified caffeine’s antifungal effects. The optical density of the adherent C. albicans on PMMA discs were lower at 620 nm or 410 nm in caffeine groups. CFU count was also reduced by caffeine treatments. SEM revealed the lower adherent C. albicans count in caffeine groups. The effect of caffeine was dose-dependent at which the 60 mg/mL dose demonstrated the most prominent effect. Conclusion: The study reinforced caffeine’s antifungal and antibiofilm properties and suggested it as an additive, or even an alternative, disinfectant solution for fungal biofilms on denture surfaces.

Evaluation of the biofilm life cycle between Candida albicans and Candida tropicalis

Candida tropicalis is an emergent pathogen with a high rate of mortality associated with its biofilm formation. Biofilm formation has important repercussions on the public health system. However, little is still known about its biofilm life cycle. The present study analyzed the biofilm life cycle of Candida albicans and C. tropicalis during various timepoints (24, 48, 72, and 96 h) through biomass assays, colony-forming unit (CFU) counting, and epifluorescence and scanning electron microscopies. Our results showed a significant difference between C. albicans and C. tropicalis biofilms in each biomass and viability assay. All-time samples in the biomass and viability assays confirmed statistical differences between the Candida species through pairwise Wilcoxon tests (p < 0.05). C. albicans demonstrated a lower biomass growth but reached nearly the same level of C. tropicalis biomass at 96 h, while the CFU counting assays exhibited a superior number of viable cells within the C. tropicalis biofilm. Statistical differences were also found between C. albicans and C. tropicalis biofilms from 48- and 72-h microscopies, demonstrating C. tropicalis with a higher number of total cells within biofilms and C. albicans cells with a superior cell area and higher matrix production. Therefore, the present study proved the higher biofilm production of C. tropicalis.

Rapid Synergistic Biofilm Production of Pseudomonas and Candida on the Pulmonary Cell Surface and in Mice, a Possible Cause of Chronic Mixed Organismal Lung Lesions

Due to the possible co-presence of Pseudomonas aeruginosa and Candida albicans (the most common nosocomial pathogens) in lungs, rapid interkingdom biofilm production is possible. As such, PA+CA produced more dominant biofilms on the pulmonary epithelial surface (NCI-H292) (confocal fluorescent extracellular matrix staining) with dominant psl upregulation, as demonstrated by polymerase chain reaction (PCR), after 8 h of experiments than PA alone. With a proteomic analysis, rhamnosyltransferase RhlB protein (Psl-associated quorum-sensing protein) was found to be among the high-abundance proteins in PA+CA than in PA biofilms, supporting psl-mediated biofilms in PA+CA on the cell surface. Additionally, PA+CA increased supernatant cytokines (IL-8 and IL-13, but not TNF-α, IL-6, and IL-10) with a similar upregulation of TLR-4, TLR-5, and TLR-9 (by PCR) compared with PA-stimulated cells. The intratracheal administration of PA+CA induced a greater severity of sepsis (serum creatinine, alanine transaminase, serum cytokines, and histology score) and prominent biofilms (fluorescent staining) with psl upregulation (PCR). In comparison with PA+CA biofilms on glass slides, PA+CA biofilms on biotic surfaces were more prominent (fluorescent staining). In conclusion, PA+CA induced Psl-predominant biofilms on the pulmonary cell surface and in mice with acute pneumonia, and these biofilms were more prominent than those induced by PA alone, highlighting the impact of Candida on rapid interkingdom biofilm production.

Molecular Mapping of Antifungal Mechanisms Accessing Biomaterials and New Agents to Target Oral Candidiasis

Oral candidiasis has a high rate of development, especially in immunocompromised patients. Immunosuppressive and cytotoxic therapies in hospitalized HIV and cancer patients are known to induce the poor management of adverse reactions, where local and systemic candidiasis become highly resistant to conventional antifungal therapy. The development of oral candidiasis is triggered by several mechanisms that determine oral epithelium imbalances, resulting in poor local defense and a delayed immune system response. As a result, pathogenic fungi colonies disseminate and form resistant biofilms, promoting serious challenges in initiating a proper therapeutic protocol. Hence, this study of the literature aimed to discuss possibilities and new trends through antifungal therapy for buccal drug administration. A large number of studies explored the antifungal activity of new agents or synergic components that may enhance the effect of classic drugs. It was of significant interest to find connections between smart biomaterials and their activity, to find molecular responses and mechanisms that can conquer the multidrug resistance of fungi strains, and to transpose them into a molecular map. Overall, attention is focused on the nanocolloids domain, nanoparticles, nanocomposite synthesis, and the design of polymeric platforms to satisfy sustained antifungal activity and high biocompatibility with the oral mucosa.

Characteristics of Biofilms Formed by C. parapsilosis Causing an Outbreak in a Neonatal Intensive Care Unit

Background: We dealt with the occurrence of an outbreak of Candida parapsilosis in a neonatal intensive care unit (NICU) in September 2020. There have been several reports of C. parapsilosis outbreaks in NICUs. In this study we describe our investigation into both the transmission route and the biofilm of C. parapsilosis. Methods: C. parapsilosis strains were detected in three inpatients and in two environmental cultures in our NICU. One environmental culture was isolated from the incubator used by a fungemia patient, and another was isolated from the humidifier of an incubator that had been used by a nonfungemia patient. To prove their identities, we tested them by micro satellite analysis. We used two methods, dry weight measurements and observation by electron microscopy, to confirm biofilm. Results: Microsatellite analysis showed the five C. parapsilosis cultures were of the same strain. Dry weight measurements and electron microscopy showed C. parapsilosis formed biofilms that amounted to clumps of fungal cells. Conclusions: We concluded that the outbreak happened due to horizontal transfer through the humidifier of the incubator and that the C. parapsilosis had produced biofilm, which promoted an invasive and infectious outbreak. Additionally, biofilm is closely associated with pathogenicity.

Epidemiology, Clinical Characteristics, Risk Factors, and Outcomes of Candidemia in a Large Tertiary Teaching Hospital in Western China: A Retrospective 5-Year Study from 2016 to 2020

The aim of this study was to investigate the current status of candidemia and evaluate the clinical characteristics, risk factors and outcomes among different species. We conducted a retrospective study by univariate and multivariate analysis between Candida albicans and non-albicans Candida (NAC) species in a Chinese national medical center from 2016 to 2020. Among the 259 episodes, C. albicans (38.6%) was the leading species, followed by C. tropicalis (24.3%), C. parapsilosis (20.5%), and C. glabrata (12.4%). Most C. albicans and C. parapsilosis were susceptible to nine tested antifungal agents, whereas C. tropicalis showed 30.2~65.9% resistance/non-wild-type to four azoles with great cross-resistance, indicating that fluconazole should not be used for empirical antifungal treatment. In multivariable models, the factor related to an increased risk of NAC was glucocorticoid exposure, whereas gastrointestinal hemorrhage and thoracoabdominal drainage catheters were associated with an increased risk in C. albicans. Subgroup analysis revealed leukemia and lymphoma, as well as glucocorticoid exposure, to be factors independently associated with C. tropicalis in comparison with C. albicans candidemia. No significant differences in 7-day mortality or 30-day mortality were observed between C. albicans and NAC. This study may provide useful information with respect to choosing empirical antifungal agents and exploring differences in molecular mechanisms.

Drug-loaded mesoporous carbon with sustained drug release capacity and enhanced antifungal activity to treat fungal keratitis

Fungal keratitis is a severe infectious corneal disease with a high rate of incidence and blindness. Since traditional treatments natamycin (NATA) eye drops, exhibit poor dissolution and bioavailability, and the efficacy of current therapeutic approaches remains limited. In this study, we innovatively utilized mesoporous carbon (Meso-C) and microporous carbon (Micro-C) as nanocarriers loaded with the antifungal drug NATA and silver nanoparticles (Ag-NPs). Porous carbon loaded with NATA and Ag-NPs has not previously been studied in fungal keratitis. Due to the mesoporous structure, high surface area and larger pore volume of Meso-C, it displayed greater superiority in sustained drug release and drug dispersity than Micro-C. Moreover, Meso-C could adsorb inflammatory cytokines during fungal infection. In vitro, Meso-C/NATA/Ag showed excellent antifungal effects. In vivo, compared with pure NATA treatment, Meso-C/NATA/Ag exhibited significantly improved therapeutic effects and reduced dosing frequency when treating fungal keratitis. Our study is the first to report the sustained drug release and improved drug dispersity of Meso-C/NATA and demonstrates that NATA and Ag-NPs-loaded Meso-C has therapeutic effects against fungal keratitis.

An intestinal Candida albicans model for monomicrobial and polymicrobial biofilms and effects of hydrolases and the Bgl2 ligand

Background and Aim: Candida albicans is the most prevalent human fungal pathogen. In biofilms, C. albicans becomes more resistant to antifungal agents because of the production of an extracellular matrix (ECM) that protects the yeast cells. This study aimed to determine the effects of hydrolase enzymes and the Bgl2 ligand on monomicrobial and polymicrobial biofilms. Materials and Methods: Biofilm induction in rats was carried out using streptomycin (25 mg/kg) and gentamicin (7.5 mg/kg) administered orally once per day for 5 days. Rats were injected subcutaneously with cortisone acetate (225 mg/kg) as an immunosuppressant on day 5. In addition, rats were orally administered C. albicans for the single microbial model and a combination of C. albicans with Escherichia coli for the polymicrobial model. Following the biofilm production, the groups were treated with glucosamine (8.57 mg/kg body weight) and Achatina fulica hydrolases (1.5 mL) orally for 2 weeks. The reduction of the biofilm was measured using confocal laser scanning microscopy (CLSM). Data were analyzed using a t-test, with a significance value of 95%. Results: CLSM images revealed a strong association between C. albicans and E. coli in the polymicrobial biofilm. On the contrary, the combination treatment using glucosamine and A. fulica hydrolases reduced the ECM of the single microbial biofilm (53.58%). However, treatment effectiveness against the matrix (19.17%) was reduced in the polymicrobial model. Conclusion: There is a strong association between C. albicans and E. coli in the formation of polymicrobial biofilms. The combination of glucosamine and the A. fulica enzyme can reduce the single microbial biofilm ECM; however, it is ineffective in the polymicrobial model.

Lack of Functional Trehalase Activity in Candida parapsilosis Increases Susceptibility to Itraconazole

Central metabolic pathways may play a major role in the virulence of pathogenic fungi. Here, we have investigated the susceptibility of a Candida parapsilosis mutant deficient in trehalase activity (atc1Δ/ntc1Δ strain) to the azolic compounds fluconazole and itraconazole. A time-course exposure to itraconazole but not fluconazole induced a significant degree of cell killing in mutant cells compared to the parental strain. Flow cytometry determinations indicated that itraconazole was able to induce a marked production of endogenous ROS together with a simultaneous increase in membrane potential, these effects being irrelevant after fluconazole addition. Furthermore, only itraconazole induced a significant synthesis of endogenous trehalose. The recorded impaired capacity of mutant cells to produce structured biofilms was further increased in the presence of both azoles, with itraconazole being more effective than fluconazole. Our results in the opportunistic pathogen yeast C. parapsilosis reinforce the study of trehalose metabolism as an attractive therapeutic target and allow extending the hypothesis that the generation of internal oxidative stress may be a component of the antifungal action exerted by the compounds currently available in medical practice.

Prevalence of biofilms in Candida spp. bloodstream infections: A meta-analysis

CONTEXT

Candida-related infections are nowadays a serious Public Health Problem emerging multidrug-resistant strains. Candida biofilm also leads bloodstream infections to invasive systemic infections.

OBJECTIVE

The present meta-analysis aimed to analyze Candida biofilm rate, type, and antifungal resistance among hospitalized patients between 1995 and 2020.

DATA SOURCES

Web of Science, Scopus, PubMed, and Google Scholar databases were searched for English papers using the following medical subject heading terms (MESH): "invasive candidiasis"; "bloodstream infections"; "biofilm formation"; "biofilm-related infections"; "mortality"; and "prevalence".

STUDY SELECTION

The major inclusion criteria included reporting the rate of biofilm formation and the prevalence of biofilm-related to Candida species, including observational studies (more exactly, cohort, retrospective, and case-control studies). Furthermore, data regarding the mortality rate, the geographical location of the study set, and the use of anti-fungal agents in clinical isolates were also extracted from the studies.

DATA EXTRACTION

Independent extraction of articles by 2 authors using predefined data fields, including study quality indicators.

DATA SYNTHESIS

A total of 31 studies from publicly available databases met our inclusion criteria. The biofilm formation in the data set varied greatly from 16 to 100% in blood samples. Most of the studies belonged to Europe (17/31) and Asia (9/31). Forest plot showed a pooled rate of biofilm formation of 80.0% (CI: 67-90), with high heterogeneity (Q = 2567.45, I2 = 98.83, τ2 = 0.150) in random effects model (p < 0.001). The funnel plot and Egger's linear regression test failed to find publication bias (p = 0.896). The mortality rate in Candida-related bloodstream infections was 37.9% of which 70.0% were from biofilm-associated infections. Furthermore, Candida isolates were also characterized in low, intermediate, or high biofilm formers through their level of biofilm mass (crystal violet staining or XTT assays) after a 24h growth. When comparing between countries, statistical differences were obtained (p = 0.0074), showing the lower and higher biofilm prevalence values in Italy and Spain, respectively. The prevalence of low, intermediate, and high biofilms were 36.2, 18.9, and 35.0% (p < 0.0001), respectively. C. tropicalis was the prevalent species in high biofilm formation (67.5%) showing statistically significant differences when compared to other Candida species, except for C. krusei and C. glabrata. Finally, the rates of antifungal resistance to fluconazole, voriconazole, and caspofungin related to biofilm were 70.5, 67.9 and 72.8% (p < 0.001), respectively.

CONCLUSIONS

Early detection of biofilms and a better characterization of Candida spp. bloodstream infections should be considered, which eventually will help preserve public health resources and ultimately diminish mortality among patients.

Hyposalivation and oral candidiasis-A short review

Oral candidiasis is an opportunistic fungal infection commonly encountered in immunocompromised individuals. The oral cavity harbours numerous microbes and along with immunity saliva also maintains oral health. The Candida species form biofilm over the tissue and prosthetic surfaces. The biofilm formation results in persistent colonisation and persistent infection. The saliva in the oral cavity maintains the integrity of the oral environment by washing away the microbes through its flow and with its antimicrobial agents. The significant role of salivary histatins as an antifungal agent diminishes with hyposalivation. The importance of saliva in preventing fungal colonisation and infection is discussed in this review.

Novel Antimicrobial 8-Hydroxyquinoline-Based Agents: Current Development, Structure-Activity Relationships, and Perspectives

The search for new antimicrobials is imperative due to the emergent resistance of new microorganism strains. In this context, revisiting known classes like 8-hydroxyquinolines could be an interesting strategy to discover new agents. The 8-hydroxyquinoline derivatives nitroxoline and clioquinol are used to treat microbial infections; however, these drugs are underused, being available in few countries or limited to topical use. After years of few advances, in the last two decades, the potent activity of clioquinol and nitroxoline against several targets and the privileged structure of 8-hydroxyquinoline nucleus have prompted an increased interest in the design of novel antimicrobial, anticancer, and anti-Alzheimer agents based on this class. Herein, we discuss the current development and antimicrobial structure-activity relationships of this class in the perspective of using the 8-hydroxyquinoline nucleus for the search for novel antimicrobial agents. Furthermore, the most investigated molecular targets concerning 8-hydroxyquinoline derivatives are explored in the final section.

The Flo Adhesin Family

The first step in the infection of fungal pathogens in humans is the adhesion of the pathogen to host tissue cells or abiotic surfaces such as catheters and implants. One of the main players involved in this are the expressed cell wall adhesins. Here, we review the Flo adhesin family and their involvement in the adhesion of these yeasts during human infections. Firstly, we redefined the Flo adhesin family based on the domain architectures that are present in the Flo adhesins and their functions, and set up a new classification of Flo adhesins. Next, the structure, function, and adhesion mechanisms of the Flo adhesins whose structure has been solved are discussed in detail. Finally, we identified from Pfam database datamining yeasts that could express Flo adhesins and are encountered in human infections and their adhesin architectures. These yeasts are discussed in relation to their adhesion characteristics and involvement in infections.

Synergic activity of oligostyrylbenzenes with amphotericin B against Candida tropicalis biofilms

Antimicrobial drug resistance is a serious challenge in clinical settings worldwide, with biofilm formation having been associated with this problem. In the present study, the synergism of oligostyrylbenzene (OSB) compounds in combination with amphotericin B (AmB) against Candida tropicalis biofilms was investigated. In addition, the toxicity in human blood cells was determined. Synergistic combinations of OSBs and AmB were evaluated to consider future effects of OSBs in vivo. The checkerboard microdilution method was used to study the interactions of one anionic (1) and two cationic (2 and 3) OSBs with AmB. We investigated the effects of OSBs on reactive oxygen species (ROS) and the levels of the reactive nitrogen intermediates (RNIs). The cellular stress affected biofilm growth through an accumulation of ROS and RNI, at synergistic concentrations of OSBs and AmB. Furthermore, significant surface topography differences were noted upon treatment with the OSB 2/AmB combination, using confocal laser scanning microscopy in conjunction with the image analysis software COMSTAT. The results revealed a low toxicity to leukocytes and red blood cells at synergistic combinations of cationic OSBs with AmB. These findings demonstrated the antibiofilm effects of OSBs and the synergism of AmB with cationic OSBs against biofilms of C. tropicalis for the first time.

First Study of Naturally Formed Fungal Biofilms on the Surface of Intragastric Balloons

BACKGROUND

Intragastric balloon (IGB) is a medical device used in the endoscopic treatment of pre-obesity and obesity. The involvement of IGB with biofilms has been previously reported; however, little is still known. We determine the frequency of biofilms naturally formed on the external surface of IGB, as well as some variables related to IGB types and patients features, species of fungi involved, and biofilm evidence.

METHODS

A retrospective study was conducted based on endoscopies and medical records of patients with explanted IGB between 2015 and 2018, which had masses strongly adhered to the surface of the balloon, suspecting the presence of a biofilm. From 2018, the samples of those masses were investigated seeking biofilm characterization based on mycological and structural aspects.

RESULTS

A total of 149 endoscopies were surveyed; 27 IGBs (18.12%) showed signs suggesting biofilm formation. There was no significant difference between biofilm involvement in IGB and the anthropometric and demographic profile of the patients. On the other hand, there was a significant difference regarding the IGB type, 24.05% of the adjustable IGB were compromised by biofilm, while in non-adjustable IGB, it was 11.43% (p = 0.04; OR 2.45; 95% CI, 0.98-6.12). Candida glabrata was the most isolated fungal species from the well-organized fungal biofilm.

CONCLUSIONS

The frequency of fungal biofilm naturally formed on the external surface of IGB was elevated. The risk of biofilm formation was increased for the adjustable IGB, but it did not relate to the demographic data and anthropometric patient profile.

Photodynamic Therapy Is Effective Against Candida auris Biofilms

Fungal infections are increasing in prevalence worldwide. The paucity of available antifungal drug classes, combined with the increased occurrence of multidrug resistance in fungi, has led to new clinical challenges in the treatment of fungal infections. Candida auris is a recently emerged multidrug resistant human fungal pathogen that has become a worldwide public health threat. C. auris clinical isolates are often resistant to one or more antifungal drug classes, and thus, there is a high unmet medical need for the development of new therapeutic strategies effective against C. auris. Additionally, C. auris possesses several virulence traits, including the ability to form biofilms, further contributing to its drug resistance, and complicating the treatment of C. auris infections. Here we assessed red, green, and blue visible lights alone and in combination with photosensitizing compounds for their efficacies against C. auris biofilms. We found that (1) blue light inhibited and disrupted C. auris biofilms on its own and that the addition of photosensitizing compounds improved its antibiofilm potential; (2) red light inhibited and disrupted C. auris biofilms, but only in combination with photosensitizing compounds; and (3) green light inhibited C. auris biofilms in combination with photosensitizing compounds, but had no effects on disrupting C. auris biofilms. Taken together, our findings suggest that photodynamic therapy could be an effective non-drug therapeutic strategy against multidrug resistant C. auris biofilm infections.

Fungal keratitis: Mechanisms of infection and management strategies

Fungal corneal ulcers are an uncommon, yet challenging, cause of vision loss. In the United States, geographic location appears to dictate not only the incidence of fungal ulcers, but also the fungal genera most encountered. These patterns of infection can be linked to environmental factors and individual characteristics of fungal organisms. Successful management of fungal ulcers is dependent on an early diagnosis. New diagnostic modalities like confocal microscopy and polymerase chain reaction are being increasingly used to detect and identify infectious organisms. Several novel therapies, including crosslinking and light therapy, are currently being tested as alternatives to conventional antifungal medications. We explore the biology of Candida, Fusarium, and Aspergillus, the three most common genera of fungi causing corneal ulcers in the United States and discuss current treatment regimens for the management of fungal keratitis.