Candida and its dual lifestyle as a commensal and a pathogen

Structure-Based Optimization of Novel Sterol 24-C-Methyltransferase Inhibitors for the Treatment of Candida albicans Infections

Interfering with sterol biosynthesis is an important strategy for developing safe and effective antifungal drugs. We previously identified compound H55 as an allosteric inhibitor of the fungal-specific C-24 sterol methyltransferase Erg6 for treating Candida albicans infections. Herein, 62 derivatives of H55 were designed and synthesized based on target-ligand interactions to identify more active candidates. Among them, d28 displayed the most potent antivirulence ability (MHIC50 = 0.25 μg/mL) by targeting Erg6, exhibiting an 8-fold increase in potency compared with H55. Moreover, d28 significantly outperformed H55 in inhibiting cell adhesion and biofilm formation, and exhibited minimal cytotoxicity and negligible potential to induce drug resistance. Of note, the coadministration of d28 and other sterol biosynthesis inhibitors, such as tridemorph or terbinafine, demonstrated a strong synergistic antifungal action in vitro and in vivo in a murine skin infection model. These results support the potential application of d28 in the treatment of C. albicans infections.

Limonene synergistically augments fluconazole susceptibility in clinical Candida isolates from cleft lip and palate patients

Background

Cleft lip and palate (CLP) patients are prone to Candida infections (oral thrush) mainly due to poor oral hygiene, repetitive surgeries, and orthodontic procedures.

Aim

This study was undertaken to evaluate the antifungal efficacy of limonene against clinical Candida isolates from CLP patients.

Materials and Methods

The antifungal efficacy of limonene was studied alone and in combination with fluconazole (FLC) against six standards, twenty nine FLC sensitive, and three FLC resistant clinical strains using broth dilution, checkerboard microdilution, agar disk diffusion, growth curves, and spot assays.

Results

This nontoxic monoterpene gave low minimum inhibitory concentration (MIC) values of 300-375 µg/mL and 500-520 µg/mL for FLC susceptible and FLC resistant strains, respectively. It showed synergistic interaction with FLC in all clinical and standard Candida strains (fractional inhibitory concentration (FIC) index ≤0.5).

Conclusion

Significant chemosensitization of FLC was observed even against resistant clinical isolates. Complete suppression of fungal growth was observed when using combinations. Negligible toxicity, easy availability, and potent antifungal properties suggest that limonene and FLC combinations in appropriate doses can make excellent antifungal mouthwashes during CLP treatment pre and post surgery. Impending in vivo studies are needed to validate the present data.

The Rfg1 and Bcr1 transcription factors regulate acidic pH-induced filamentous growth in Candida albicans

IMPORTANCE

Candida albicans is a human commensal and frequent pathogen that encounters a wide range of pH stresses. The ability of C. albicans to adapt to changes in extracellular pH is crucial for its success in colonization and pathogenesis. The Rim101 pH sensing pathway is well known to govern neutral-alkaline pH responses in this pathogen. Here, we report a novel Rfg1-Bcr1 regulatory pathway that governs acidic pH responses and regulates filamentous growth in C. albicans. In addition, the Rim101-Phr1 pathway, cAMP signaling pathway, transcription factors Efg1 and Flo8, and hyphal-specific G1 cyclin Hgc1 cooperate with this regulation. Our findings provide new insights into the regulatory mechanism of acidic pH response in C. albicans.

Efficacy of a medical grade honey formulation (L-Mesitran) in comparison with fluconazole in the treatment of women with recurrent vulvovaginal candidiasis: protocol for a randomised controlled trial (HONEY STUDY)

INTRODUCTION

Recurrent vulvovaginal candidiasis (RVVC) affects up to 9% of women worldwide. This amount is expected to increase due to lifestyle changes, increased fungal resistance and biofilm formation. Treatment options are limited and in 57% of the cases, relapses occur within 12 months after starting fluconazole therapy (golden standard). The pathogenesis of RVVC is multifactorial and includes fungal biology, the vaginal microenvironment and the immune system. Fluconazole is antimicrobial and effective in inducing short-term remission but a long-term cure is hard to achieve. Medical grade honey (MGH) has antimicrobial, protective, antioxidative and immunomodulatory activity and may therefore be a good alternative treatment. This study aims to investigate the clinical cure rate and long-term efficacy of MGH compared with fluconazole in patients with RVVC.

METHODS AND ANALYSIS

This study is a multicentre, randomised controlled trial (Maastricht University Medical Centre+ and Zuyderland Medical Centre). A total of 252 eligible women will be randomly assigned to the fluconazole group (control) or the MGH group (L-Mesitran, treatment). The primary objective is to investigate the mycological cure rate after 1 month assessed through a vaginal culture. Secondary objectives are the clinical cure rate regarding symptoms, the prophylactic activity after 6 months of maintenance therapy and the number of relapses within 12 months. Moreover, information about side effects, discomfort and quality of life will be collected with the use of questionnaires.

ETHICS AND DISSEMINATION

Ethical approval from the Medical Ethics Review Committee of the academic hospital Maastricht/University Maastricht has been obtained (NL 73974.068.21, V.7 on 8 February 2022). Additional approval was obtained from the Ethics Committee of the Zuyderland Medical Centre Heerlen (Z2021141 on 4 March 2022). The first patient was randomised on 22 August 2022. Results will be made available to researchers and healthcare professionals via conferences, meetings and peer-reviewed international publications.

TRIAL REGISTRATION NUMBER

NCT05367089.

3-Hydroxy coumarin demonstrates anti-biofilm and anti-hyphal efficacy against Candida albicans via inhibition of cell-adhesion, morphogenesis, and virulent genes regulation

Candida albicans, a common fungus of human flora, can become an opportunistic pathogen and causes invasive candidiasis in immunocompromised individuals. Biofilm formation is the prime cause of antibiotic resistance during C. albicans infections and treating biofilm-forming cells is challenging due to their intractable and persistent nature. The study intends to explore the therapeutic potential of naturally produced compounds by competitive marine bacteria residing in marine biofilms against C. albicans biofilm. To this end, 3-hydroxy coumarin (3HC), a compound identified from the cell-free culture supernatant of the marine bacterium Brevundimonas abyssalis, was found to exhibit anti-biofilm and anti-hyphal activity against both reference and clinical isolates of C. albicans. The compound demonstrated significant inhibitory effects on biofilms and impaired the yeast-to-hyphal transition, wrinkle, and filament morphology at the minimal biofilm inhibitory concentration (MBIC) of 250 µg mL^-1. Intriguingly, quantitative PCR analysis of 3HC-treated C. albicans biofilm revealed significant downregulation of virulence genes (hst7, ume6, efg1, cph1, ras1, als1) associated with adhesion and morphogenesis. Moreover, 3HC displayed non-fungicidal and non-toxic characteristics against human erythrocytes and buccal cells. In conclusion, this study showed that marine biofilms are a hidden source of diverse therapeutic drugs, and 3HC could be a potent drug to treat C. albicans infections.

Development of gut mycobiome in infants and young children: a prospective cohort study

BACKGROUND

The composition of the gut fungal microbiome, mycobiome, is likely associated with human health. Yet, the development of gut mycobiome is poorly understood in infants and children. Here we investigate how perinatal events influence the development of gut mycobiome.

METHODS

In this prospective cohort study of 140 infants, we used ITS gene sequencing of fecal samples from birth to the age of 18 months. We compared gut mycobiome composition according to delivery mode and exposure to intrapartum antibiotics during vaginal delivery.

RESULTS

At birth, gut mycobiome were dominated by the genus Candida, at 6-month stool samples by Malassezia and Cystofilobasidium, and the 18-month stool samples by Trichosporon and unidentified fungi. Perinatal factors altered mycobiome. At 18 months, gut mycobiome of infants born vaginally consisted mostly of Trichosporon (32%) and unidentified fungi (31%), while those born via Cesarean section delivery samples had mycobiome dominated by Saccharomyces (50%). At the age of 18 months, those exposed to intrapartum antibiotics had mycobiome dominated by Trichosporon (66%) not seen in those unexposed to antibiotics.

CONCLUSIONS

Delivery mode and exposure to intrapartum antibiotic prophylaxis were markedly associated with gut mycobiome composition from birth to 18 months of age.

IMPACT

The composition of the gut mycobiome is likely associated with human health. Yet, the development of gut mycobiome is poorly understood in infants and children. In this prospective cohort study, delivery mode and exposure to intrapartum antibiotic prophylaxis were markedly associated with gut mycobiome composition from birth to 18 months of age. The impact of intrapartum antibiotic prophylaxis on fungal microbiome in vaginally born infants, previously shown to influence gut bacteriome composition, may be explained by the interaction between bacteria and fungi. Gut mycobiome composition likely deserves further investigation in relation to gut microbiome and health in children.

Antifungal activity of vitamin D3 against Candida albicans in vitro and in vivo

The incidence of intra-abdominal candidiasis (IAC), characterized by high morbidity and mortality, has become a serious concern. The limitations of current antifungal drugs on the market underscores the importance of the development of novel antifungal agents. In the present study, the antifungal activity of vitamin D₃ (VD₃) against various Candida species was investigated. In vitro, the broth microdilution method and solid plate assay confirmed that VD₃ inhibited the growth of Candida spp. in a broad-spectrum, dose-dependent manner. VD₃ also had a significant antifungal effect on the initiation, development, and maturation phases of biofilm formation in Candida albicans. The mechanism of VD₃ action was explored by transcriptomics and reverse transcription quantitative PCR (RT-qPCR) analysis, and showed that VD₃ affects ribosome biogenesis, coenzyme metabolism, and carbon metabolism. These results suggested that VD₃ may have multitarget effects against C. albicans. In the murine IAC model, VD₃ reduced the fungal burden in the liver, kidneys, and small intestine. Further histopathological analysis and quantification of plasma cytokine levels confirmed that VD₃ treatment significantly decreased the infiltration of inflammatory cells and the levels of plasma interferon (IFN)-γ and tumor necrosis factor (TNF)-α. Taken together, these findings suggest a new antifungal mechanism for VD₃ and indicate that VD₃ could be an effective therapeutic agent for use in IAC treatment.

Experimental evolution of drug resistance in human fungal pathogens

Experimental evolution in vitro is a powerful tool to uncover the factors that contribute to resistance evolution and understand the genetic basis of adaptation. Here, we discuss recent experimental evolution studies from human fungal pathogens. We synthesize the results to highlight the common threads that influence resistance acquisition. The picture that emerges is that drug resistance consistently appears readily and rapidly. Mutations are often found in an overlapping set of genes and genetic pathways known to be involved in drug resistance, including whole or partial chromosomal aneuploidy. The likelihood of acquiring resistance and cross-resistance between drugs seems to be influenced by the specific drug (not just drug class), level of drug, and strain genetic background. We discuss open questions, such as the potential for increases in drug tolerance to evolve in static drugs. We highlight opportunities to use this framework to probe how different factors influence the rate and nature of adaptation to antifungal drugs in fungal microbes through a call for increased reporting on all replicates that were evolved, not just those that acquired resistance.

Exploring the global vaginal microbiome and its impact on human health

Around the world, more than 175,000,000 women are diagnosed every year with gynaecological disease, in many cases contributing to high morbidity and mortality. For this reason, knowledge of the composition of the vaginal microbiome and its variations represents a real health challenge, as this is key to improving therapeutic management. This review traces the history of the poorly known vaginal microbiome and focuses on the latest findings concerning this ecosystem. Studies in the past decade have targeted complex bacterial communities within the vagina. However, due to the development of technology and the emergence of next generation sequencing (NGS), the exact definition of the vaginal microbiome has changed and can no longer be linked solely to the presence of bacteria. In order to reach a global view of the vaginal microbiome, it is essential to take into account all microorganisms that the vagina harbours, including fungi, viruses, archaea, and candidate phyla radiation. Although these communities represent only a minimal percentage of the vaginal microbiome, they may act as modifiers of its basic physiology and may play a key role in the maintenance of microbial communities, as well as metabolic and immune functions. Studies of the complex interactions between these different microorganisms have recently begun and are not yet fully understood. Results to date indicate that these microbial communities together constitute the first line of defence against infections. On the other hand, the slightest disturbance in this microbiome may lead to disease. For this reason, enhanced knowledge of these associations is critical to better identify predispositions to certain illnesses, which may open new therapeutic avenues. Currently however, only the tip of the iceberg is understood and current research on this ecosystem is revolutionising our knowledge and understanding of human health and disease.

Fluorescent toys 'n' tools lighting the way in fungal research

Although largely overlooked compared to bacterial infections, fungal infections pose a significant threat to the health of humans and other organisms. Many pathogenic fungi, especially Candida species, are extremely versatile and flexible in adapting to various host niches and stressful situations. This leads to high pathogenicity and increasing resistance to existing drugs. Due to the high level of conservation between fungi and mammalian cells, it is hard to find fungus-specific drug targets for novel therapy development. In this respect, it is vital to understand how these fungi function on a molecular, cellular as well as organismal level. Fluorescence imaging allows for detailed analysis of molecular mechanisms, cellular structures and interactions on different levels. In this manuscript, we provide researchers with an elaborate and contemporary overview of fluorescence techniques that can be used to study fungal pathogens. We focus on the available fluorescent labelling techniques and guide our readers through the different relevant applications of fluorescent imaging, from subcellular events to multispecies interactions and diagnostics. As well as cautioning researchers for potential challenges and obstacles, we offer hands-on tips and tricks for efficient experimentation and share our expert-view on future developments and possible improvements.

Evaluation of overtime phenotypic variation of yeasts in chronic vulvovaginal candidosis cases

Chronic vulvovaginal candidosis results either from reinfection or from the ability of Candida spp. to persist in the vulva and/or vagina. Persistence is usually associated with increased antifungal (mainly azoles) resistance rates, which can explain treatment failure, and/or increased expression of virulence factors by Candida spp. The aim of this study was to assess the mechanisms leading to Candida spp persistence, by studying sequential isolates from women with chronic vulvovaginal candidosis, focusing on strains genotypes, azole resistance and ability to form biofilms along the period of clinical evaluation.The strains were identified at species level by automated analysis of biochemical profiles and molecular typing evaluated by polymorphic DNA analysis. The capacity to form biofilm was assessed with a microtiter plate assay. Fluconazole susceptibility was determined by the microdilution broth assay at both pH 7 (following the recommended guideline) and pH 4.5 (as representative of vaginal pH).We studied samples from 17 clinically recurrent cases. In 53% of the chronic cases there were two or more isolates that had a phylogenetic relationship while the remaining (47%) were caused by different species. In those cases where related strains were involved in recurrence, we verified an increase in MIC at pH 7 and also an increased capacity to form biofilms over time. Significant correlation between these two parameters was observed only in cases caused by C. glabrata, evidencing the importance of these two factors to enhance persistence in the vaginal mucosa for this particular species.

LAY ABSTRACT

Chronic vulvovaginal candidosis (VVC) affects millions of women worldwide. We found that persistence of the same Candida strain on the vaginal mucosa does not account for the great majority of VVC cases. Moreover, modulation of biofilm formation and azole resistance overtime was investigated.

Treating (Recurrent) Vulvovaginal Candidiasis with Medical-Grade Honey-Concepts and Practical Considerations

Recurrent vulvovaginal candidiasis (RVVC) is a relapsing vaginal fungal infection caused by Candida species. The prevalence varies among age populations and can be as high as 9%. Treatment options are limited, and in 57% of the cases, relapses occur within six months after fluconazole maintenance therapy, which is the current standard of care. The pathogenesis of RVVC is multifactorial, and recent studies have demonstrated that the vaginal microenvironment and activity of the immune system have a strong influence on the disease. Medical-grade honey (MGH) has protective, antimicrobial, and immunomodulatory activity and forms a putative alternative treatment. Clinical trials have demonstrated that honey can benefit the treatment of bacterial and Candida-mediated vaginal infections. We postulate that MGH will actively fight ongoing infections; eradicate biofilms; and modulate the vaginal microenvironment by its anti-inflammatory, antioxidative, and immunomodulatory properties, and subsequently may decrease the number of relapses when compared to fluconazole. The MGH formulation L-Mesitran Soft has stronger antimicrobial activity against various Candida species than its raw honey. In advance of a planned randomized controlled clinical trial, we present the setup of a study comparing L-Mesitran Soft with fluconazole and its practical considerations.

Anticandidal Activities by Lactobacillus Species: An Update on Mechanisms of Action

Lactobacilli are among the most studied bacteria in the microbiome of the orodigestive and genitourinary tracts. As probiotics, lactobacilli may provide various benefits to the host. These benefits include regulating the composition of the resident microbiota, preventing - or even potentially reverting- a dysbiotic state. Candida albicans is an opportunistic pathogen that can influence and be influenced by other members of the mucosal microbiota and, under immune-compromising conditions, can cause disease. Lactobacillus and Candida species can colonize the same mucosal sites; however, certain Lactobacillus species display antifungal activities that can contribute to low Candida burdens and prevent fungal infection. Lactobacilli can produce metabolites with direct anticandidal function or enhance the host defense mechanisms against fungi. Most of the Lactobacillus spp. anticandidal mechanisms of action remain underexplored. This work aims to comprehensively review and provide an update on the current knowledge regarding these anticandidal mechanisms.

Mycoplasma genitalium and Other Reproductive Tract Infections in Pregnant Women, Papua New Guinea, 2015-2017

Much about the range of pathogens, frequency of coinfection, and clinical effects of reproductive tract infections (RTIs) among pregnant women remains unknown. We report on RTIs (Mycoplasma genitalium, Chlamydia trachomatis, Neisseria gonorrhoeae, Trichomonas vaginalis, Treponema pallidum subspecies pallidum, bacterial vaginosis, and vulvovaginal candidiasis) and other reproductive health indicators in 699 pregnant women in Papua New Guinea during 2015–2017. We found M. genitalium, an emerging pathogen in Papua New Guinea, in 12.5% of participants. These infections showed no evidence of macrolide resistance. In total, 74.1% of pregnant women had >1 RTI; most of these infections were treatable. We detected sexually transmitted infections (excluding syphilis) in 37.7% of women. Our findings showed that syndromic management of infections is greatly inadequate. In total, 98.4% of women had never used barrier contraception. These findings will inform efforts to improve reproductive healthcare in Papua New Guinea.

The Vaginal Microbiota, Bacterial Biofilms and Polymeric Drug-Releasing Vaginal Rings

The diversity and dynamics of the microbial species populating the human vagina are increasingly understood to play a pivotal role in vaginal health. However, our knowledge about the potential interactions between the vaginal microbiota and vaginally administered drug delivery systems is still rather limited. Several drug-releasing vaginal ring products are currently marketed for hormonal contraception and estrogen replacement therapy, and many others are in preclinical and clinical development for these and other clinical indications. As with all implantable polymeric devices, drug-releasing vaginal rings are subject to surface bacterial adherence and biofilm formation, mostly associated with endogenous microorganisms present in the vagina. Despite more than 50 years since the vaginal ring concept was first described, there has been only limited study and reporting around bacterial adherence and biofilm formation on rings. With increasing interest in the vaginal microbiome and vaginal ring technology, this timely review article provides an overview of: (i) the vaginal microbiota, (ii) biofilm formation in the human vagina and its potential role in vaginal dysbiosis, (iii) mechanistic aspects of biofilm formation on polymeric surfaces, (iv) polymeric materials used in the manufacture of vaginal rings, (v) surface morphology characteristics of rings, (vi) biomass accumulation and biofilm formation on vaginal rings, and (vii) regulatory considerations.

New Insights into Vaginal Environment During Pregnancy

During pregnancy, the vaginal ecosystem undergoes marked changes, including a significant enrichment with Lactobacillus spp. and profound alterations in metabolic profiles. A deep comprehension of the vaginal environment may shed light on the physiology of pregnancy and may provide novel biomarkers to identify subjects at risk of complications (e.g., miscarriage, preterm birth). In this study, we characterized the vaginal ecosystem in Caucasian women with a normal pregnancy (n = 64) at three different gestational ages (i.e., first, second and third trimester) and in subjects (n = 10) suffering a spontaneous first trimester miscarriage. We assessed the vaginal bacterial composition (Nugent score), the vaginal metabolic profiles (¹H-NMR spectroscopy) and the vaginal levels of two cytokines (IL-6 and IL-8). Throughout pregnancy, the vaginal microbiota became less diverse, being mainly dominated by lactobacilli. This shift was clearly associated with marked changes in the vaginal metabolome: over the weeks, a progressive reduction in the levels of dysbiosis-associated metabolites (e.g., biogenic amines, alcohols, propionate, acetate) was observed. At the same time, several metabolites, typically found in healthy vaginal conditions, reached the highest concentrations at the end of pregnancy (e.g., lactate, glycine, phenylalanine, leucine, isoleucine). Lower levels of glucose were an additional fingerprint of a normal vaginal environment. The vaginal levels of IL-6 and IL-8 were significantly associated with the number of vaginal leukocytes, as well as with the presence of vaginal symptoms, but not with a condition of dysbiosis. Moreover, IL-8 concentration seemed to be a good predictor of the presence of vaginal Candida spp. Cytokine concentrations were negatively correlated to lactate, serine, and glycine concentrations, whereas the levels of 4-hydroxyphenyllactate, glucose, O-acetylcholine, and choline were positively correlated with Candida vaginal loads. Finally, we found that most cases of spontaneous abortion were associated with an abnormal vaginal microbiome, with higher levels of selected metabolites in the vaginal environment (e.g., inosine, fumarate, xanthine, benzoate, ascorbate). No association with higher pro-inflammatory cytokines was found. In conclusion, our analysis provides new insights into the pathophysiology of pregnancy and highlights potential biomarkers to enable the diagnosis of early pregnancy loss.

Species Distribution and Antifungal Susceptibility Profiles of Isolates from Women with Nonrecurrent and Recurrent Vulvovaginal Candidiasis

Recurrent vulvovaginal candidiasis (RVVC) is caused by Candida spp., a vaginal colonizer. Despite the clinical importance of RVVC, little is known regarding the characteristics of the disease in Portugal. Thirty-six clinical cases were analyzed, comprising 93 yeast vulvovaginal isolates obtained from women attending a gynecologic consultation at a private clinic. Of these, 18 women were diagnosed with RVVC, while other 18 women had a sporadic episode of infection (nonrecurrent vulvovaginal candidiasis [NR-VVC]). Species identification was performed with CHROMagar chromogenic medium and by analysis of biochemical profiles. In addition, antifungal susceptibility testing for two azole compounds was performed by broth microdilution. We found that Candida albicans was isolated from both NR-VVC and RVVC cases, being highly predominant; C. glabrata and C. tropicalis were also isolated. Resistance to at least one antifungal was detected in up to 65% of the isolates, and resistance to both antifungals reached a frequency of 25%. Moreover, azole-resistant isolates were distributed among all species identified. We conclude that in the studied group of patients, C. albicans is in fact the major player both in NR-VVC and in RVVC, C. glabrata being more frequently associated with recurrence (p < 0.05). In addition, we found a high proportion of azole-resistant strains.

Investigating natural antibiofilm components: a new therapeutic perspective against candidal vulvovaginitis

The rampant emergence of Candida albicans in the vagina and its ability to thrive as a biofilm has outstood the prevalence of candidal vulvovaginitis (CVV), a gender-based fungal infection approximately affecting 75% of the global female population. The biofilm represents a multidimensional microbial population, which often dictates prominent caveats of CVV such as increased fungal virulence, drug resistance and infection relapse/recurrence. Additionally, the conjugated issues of the ineffectiveness of conventional antifungals (azoles), prolonged treatment durations, compromised patient compliance, economic and social burden, exacerbates CVV complications as well. Henceforth, the current hypothesis narrates an investigational proposal for exploration and combination of naturally derived antibiofilm components with luliconazole (imidazole antifungal agent) as a new therapeutic paradigm against CVV. The purported hypothesis unravels a synergistic approach for fabricating Nanostructured Lipid Carriers, NLCs loaded transvaginal gel with dual APIs of natural (antibiofilm) as well as the synthetic (antifungal) origin to target high therapeutic efficacy, delivery, retention, controlled release and bioadhesion in a vaginal milieu. The multipronged effect of antibiofilm and antifungal agents will expectably enhance drug susceptibility thus, maintaining Minimum Inhibitory Concentration (MIC) against cells of C. albicans and targeting its biofilm in planktonic, adherent, and sessile phases. The effective disruption of a biofilm could further lower infection resistance and recurrence as well. In conclusion, the purported hypothesis could speed up the emergence of novel drug combinations and accelerates new product development with solid, synergistic, and complementary activities against C. albicans and its biofilm, making it amenable for generating pre-clinical and clinical results therebycreating a suitableroadmap for commercialization.

Candida Pathogenicity and Interplay with the Immune System

Candida species are opportunistic fungal pathogens that are part of the normal skin and mucosal microflora. Overgrowth of Candida can cause infections such as thrush or life-threatening invasive candidiasis in immunocompromised patients. Though Candida albicans is highly prevalent, several non-albicans species are also isolated from nosocomial infections. Candida sp. are over presented in the gut of people with Crohn's disease and certain types of neurological disorders, with hyphal form and biofilms being the most virulent states. In addition, Candida uses several secreted and cell surface molecules such as pH related antigen 1, High affinity glucose transporter, Phosphoglycerate mutase 1 and lipases to establish pathogenicity. A strong innate immune response is elicited against Candida via dendritic cells, neutrophils and macrophages. All three complement pathways are also activated. Production of proinflammatory cytokines IL-10 and IL-12 signal differentiation of CD4⁺ cells into Th1 and Th2 cells, whereas IL-6, IL-17 and IL-23 induce Th17 cells. Importance of T-lymphocytes is reflected in depleted T-cell count patients being more prone to Candidiasis. Anti- Candida antibodies also play a role against candidiasis using various mechanisms such as targeting virulent enzymes and exhibiting direct candidacidal activity. However, the significance of antibody response during infection remains controversial. Furthermore, some of the Candida strains have evolved molecular strategies to evade the sophisticated host attack by proteolysis of components of immune system and interfering with immune signalling pathways. Emergence of several non-albicans species that are resistant to current antifungal agents makes treatment more difficult. Therefore, deeper insight into interactions between Candida and the host immune system is required for discovery of novel therapeutic options.

Opportunist Coinfections by Nontuberculous Mycobacteria and Fungi in Immunocompromised Patients

Nontuberculous mycobacteria (NTM) and many fungal species (spp.) are commonly associated with opportunistic infections (OPIs) in immunocompromised individuals. Moreover, occurrence of concomitant infection by NTM (mainly spp. of Mycobacterium avium complex and Mycobacterium abscessus complex) and fungal spp. (mainly, Aspergillus fumigatus, Histoplasma capsulatum and Cryptococcus neoformans) is very challenging and is associated with poor patient prognosis. The most frequent clinical symptoms for coinfection and infection by single agents (fungi or NTM) are similar. For this reason, the accurate identification of the aetiological agent(s) is crucial to select the best treatment approach. Despite the significance of this topic it has not been sufficiently addressed in the literature. This review aims at summarizing case reports and studies on NTM and fungi coinfection during the last 20 years. In addition, it briefly characterizes OPIs and coinfection, describes key features of opportunistic pathogens (e.g., NTM and fungi) and human host predisposing conditions to OPIs onset and outcome. The review could interest a wide spectrum of audiences, including medical doctors and scientists, to improve awareness of these infections, leading to early identification in clinical settings and increasing research in the field. Improved diagnosis and availability of therapeutic options might contribute to improve the prognosis of patients' survival.

Anti-biofilm activity of chlorhexidine digluconate against Candida albicans vaginal isolates

OBJECTIVES

Recurrent vulvovaginal candidiasis (RVVC) causes significant morbidity. Candida albicans is the main pathogen associated with both sporadic and recurrent candidiasis. Due to unsatisfactory treatment effect, the impact of chlorhexidine digluconate and fluconazole alone or in combination on C. albicans and biofilm was investigated.

METHODS

Vaginal C. albicans isolates from 18 patients with recurrent candidiasis and commensals from 19 asymptomatic women were isolated by culture. Crystal violet, XTT and colony forming unit assay were used to analyze the effect of chlorhexidine digluconate and fluconazole on growth of C. albicans, formation of new and already established, mature, biofilm.

RESULTS

Fluconazole reduced the growth of planktonic C. albicans. However, in established biofilm, fluconazole had no effect on the candida cells and was not able to disperse and reduce the biofilm. By contrast, chlorhexidine digluconate had a direct killing effect on C. albicans grown both planktonically and in biofilm. Chlorhexidine digluconate also dispersed mature biofilm and inhibited formation of new biofilm. No major differences were observed between commensal isolates and candida causing recurrent vulvovaginitis with respect to biofilm or growth after chlorhexidine digluconate treatment.

CONCLUSION

Biofilm is a problem in patients with recurrent vulvovaginal candidiasis reducing the effect of antifungal treatment. Development of new treatment strategies are urgently needed to decrease the recurrences. In already established biofilm, chlorhexidine digluconate dispersed the biofilm and was more effective in eradicating candida compared to fluconazole. Future treatment strategy may thus be a combination of chlorhexidine digluconate and fluconazole and prophylactic use of chlorhexidine digluconate to prevent biofilm formation and restrict infections.

Recurrent Vulvovaginal Candidosis and Cluster Analysis of Clinical Signs and Symptoms: A Laboratory-Based Investigation

Recurrent vulvovaginal candidosis (RVVC) represents a major health problem that significantly affects a patient’s quality of life (QoL). This infection presents with a plethora of clinical manifestation, and this is the first study that carries out a cluster analysis of these signs and symptoms (SS). The goals are to evaluate the distribution of species causing RVVC, their in-vitro susceptibility to antifungals, and the patient’s QoL. Additionally, the clinical characteristics are analyzed using cluster analysis. Prospective analysis of data was performed for women diagnosed with RVVC in the period from January 2016 to December 2019 based on the analysis of data from a single-center’s records. The standard mycological methods and antifungal susceptibility testing were done. Clinical characteristics and QoL were examined by appropriate questions. The cluster analysis was used to identify clusters of SS. A total of 320 women were diagnosed. The dominant species was Candida (C.) albicans. Non-albicans Candida (NAC) yeast was found in 24.4%, and the most common was C. glabrata. Interestingly, Saccharomyces (S.) cerevisiae was detected in 2%. All of the isolated species, except C. parapsilosis and C. kefyr, demonstrated reduced susceptibility to antifungals. We confirmed the emergence of the NAC species and S. cerevisiae with reduced susceptibility to antifungals. Cluster analysis represented by a dendrogram revealed three SS clusters: irritation, uncommon, and discharge, but further studies are needed to examine the relationship between clusters, Candida strains, and outcomes.

Clinical significance of Candida isolation from dystrophic fingernails

BACKGROUND

Candida onychomycosis mostly involves fingernails. Yet, in contrast to dermatophytes, Candida isolation from dystrophic fingernails does not prove casualty, as sample contamination and non-pathogenic Candida growth occur. Characterising treatment outcome of Candida-positive dystrophic nails is crucial to avoid unnecessary treatment.

OBJECTIVE

To investigate predicators associated with treatment outcome among Candida-positive dystrophic fingernails.

PATIENTS AND METHODS

A retrospective cohort study was carried out among 108 adults with Candida-positive dystrophic fingernails not cured with adequate systemic anti-fungal course. Diagnosis was based on a single mycological culture. Patients with treatment failure (n = 85; 78.7% of the cases) were compared to patients with partial response (mild to almost cure; n = 23; 21.3% of the cases) at 9 to 12 months following treatment initiation.

RESULTS

Treatment failure was significantly associated with primary onycholysis (odds ratio [OR] 2.8; 95% confidence interval [CI] 1.1-7.4) and prolonged dystrophy (12.8 vs. 3.7 years in average), compared to partial treatment response. Non-responders had lower odds to present with distal lateral subungual onychomycosis, compared to partial responders (OR 0.3; 95% CI 0.1-0.7). Demographic and mycological characteristics, as well as number of nails affected, co-presence of paronychia, and treatment regime were not found to be associated with treatment response.

CONCLUSION

Candida-positive primary onycholysis was shown to be non-responsive to systemic anti-fungal treatment, suggesting that anti-fungal treatment is not indicated. For other clinical scenarios, high proportions of treatment non-response suggest that determining causality of Candida should not be based on a single positive mycological culture.

Unambiguous determination of farnesol and tyrosol in vaginal fluid using fast and sensitive UHPLC-MS/MS method

The new ultra-high performance liquid chromatography method with tandem mass spectrometry detection (UHPLC-MS/MS) has been optimized to allow fast, selective, and high-throughput analysis of two Candida albicans quorum sensing molecules (QSM), farnesol and tyrosol. The problem of the presence of the interference in the samples and system was successfully solved by careful optimization of chromatographic conditions. Charged hybrid stationary phase modified with pentafluorophenyl group and optimized gradient elution provided adequate separation selectivity and peak shapes. The impurity was identified as dibutyl phthalate and had the same m/z ions as farnesol leading to an important interference on selected reaction monitoring channel. Two different types of biological matrices originating from vaginal fluid, supernatant and sediment, were analysed. Micro-solid phase extraction in pipette tips was optimized for the selective isolation of QSM from the supernatant. The insufficient retention of farnesol on the extraction sorbent was improved when 1% of organic solvent was added prior to extraction, while the retention of tyrosol was only possible when using combined C8 and polymer sorbent type. Strong retention of farnesol had to be solved by increasing elution solvent strength and volume up to 600 μL. However, this approach did not allow the pretreatment of sediment samples due to the sorbent clogging. Therefore, our previously developed protein precipitation method was modified and validated to analyse the sediments. New developed UHPLC-MS/MS method provided suitable accuracy and precision for the determination of QSM in vaginal fluid while using only 50 μL sample volume and two different sample preparation methods.

Genomic evidence for a hybrid origin of the yeast opportunistic pathogen Candida albicans

Background

Opportunistic yeast pathogens of the genus Candida are an important medical problem. Candida albicans, the most prevalent Candida species, is a natural commensal of humans that can adopt a pathogenic behavior. This species is highly heterozygous and cannot undergo meiosis, adopting instead a parasexual cycle that increases genetic variability and potentially leads to advantages under stress conditions. However, the origin of C. albicans heterozygosity is unknown, and we hypothesize that it could result from ancestral hybridization. We tested this idea by analyzing available genomes of C. albicans isolates and comparing them to those of hybrid and non-hybrid strains of other Candida species.

Results

Our results show compelling evidence that C. albicans is an evolved hybrid. The genomic patterns observed in C. albicans are similar to those of other hybrids such as Candida orthopsilosis MCO456 and Candida inconspicua, suggesting that it also descends from a hybrid of two divergent lineages. Our analysis indicates that most of the divergence between haplotypes in C. albicans heterozygous blocks was already present in a putative heterozygous ancestor, with an estimated 2.8% divergence between homeologous chromosomes. The levels and patterns of ancestral heterozygosity found cannot be fully explained under the paradigm of vertical evolution and are not consistent with continuous gene flux arising from lineage-specific events of admixture.

Conclusions

Although the inferred level of sequence divergence between the putative parental lineages (2.8%) is not clearly beyond current species boundaries in Saccharomycotina, we show here that all analyzed C. albicans strains derive from a single hybrid ancestor and diverged by extensive loss of heterozygosity. This finding has important implications for our understanding of C. albicans evolution, including the loss of the sexual cycle, the origin of the association with humans, and the evolution of virulence traits.

Proposal for a microcosm biofilm model for the study of vulvovaginal candidiasis

This study proposes a microcosm biofilm (MiB) model for the study of vulvovaginal candidiasis (VVC). Different conditions that mimic the vaginal environment were tested for MiB formation. The best growth conditions were obtained with samples incubated in vaginal fluid simulator medium pH 4.5 at 35 °C under a microaerophilic atmosphere. MiBs were evaluated for growth kinetics, fluconazole susceptibility and morphology. Samples containing high numbers of bacteria were analyzed for metagenomics. At 48 h, MiBs presented a higher cell density (CFU ml^-1), a higher biomass and tolerance to fluconazole than their corresponding monospecies biofilms. Morphological analysis of MiBs revealed blastoconidia preferentially adhered to epithelial cells. Abundant Lactobacillus spp. were detected in two clinical samples; their MiBs showed a lower biomass and a higher fluconazole susceptibility. The proposed model proved to be a useful tool for the study of the complex microbial relationship in the vaginal environment, and may help to find new strategies for VVC control.

Adapting to survive: How Candida overcomes host-imposed constraints during human colonization

Successful human colonizers such as Candida pathogens have evolved distinct strategies to survive and proliferate within the human host. These include sophisticated mechanisms to evade immune surveillance and adapt to constantly changing host microenvironments where nutrient limitation, pH fluctuations, oxygen deprivation, changes in temperature, or exposure to oxidative, nitrosative, and cationic stresses may occur. Here, we review the current knowledge and recent findings highlighting the remarkable ability of medically important Candida species to overcome a broad range of host-imposed constraints and how this directly affects their physiology and pathogenicity. We also consider the impact of these adaptation mechanisms on immune recognition, biofilm formation, and antifungal drug resistance, as these pathogens often exploit specific host constraints to establish a successful infection. Recent studies of adaptive responses to physiological niches have improved our understanding of the mechanisms established by fungal pathogens to evade the immune system and colonize the host, which may facilitate the design of innovative diagnostic tests and therapeutic approaches for Candida infections.

Saccharomyces cerevisiae-Based Probiotics as Novel Antimicrobial Agents to Prevent and Treat Vaginal Infections

Vaginal infections affect 70% of women during their lifetimes and account for millions of annual doctors’ visits. These infections are predominantly represented by vulvovaginal candidiasis (VVC) and bacterial vaginosis (BV). Although standard antimicrobial agents remain the major strategy for the prevention and treatment of vaginal infections, both VVC and BV are difficult to treat due to high rates of resistance and recurrence, high probability of complications, and negative effects on the vaginal microbiota. This review focuses on a new approach of yeast-based probiotics for the prevention and/or treatment of these common vaginal infections.

Antifungal Activity of an Original Amino-Isocyanonaphthalene (ICAN) Compound Family: Promising Broad Spectrum Antifungals

: Multiple drug resistant fungi pose a serious threat to human health, therefore the development of completely new antimycotics is of paramount importance. The in vitro antifungal activity of the original, 1-amino-5-isocyanonaphthalenes (ICANs) was evaluated against reference strains of clinically important Candida species. Structure-activity studies revealed that the naphthalene core and the isocyano- together with the amino moieties are all necessary to exert antifungal activity. 1,1-N-dimethylamino-5-isocyanonaphthalene (DIMICAN), the most promising candidate, was tested further in vitro against clinical isolates of Candida species, yielding a minimum inhibitory concentration (MIC) of 0.04-1.25 µg/mL. DIMICAN was found to be effective against intrinsically fluconazole resistant Candida krusei isolates, too. In vivo experiments were performed in a severly neutropenic murine model inoculated with a clinical strain of Candida albicans. Daily administration of 5 mg/kg DIMICAN intraperitoneally resulted in 80% survival even at day 13, whereas 100% of the control group died within six days. Based on these results, ICANs may become an effective clinical lead compound family against fungal pathogens.

The Squeaky Yeast Gets Greased: The Roles of Host Lipids in the Clearance of Pathogenic Fungi

Fungal infections remain a global health threat with high morbidity and mortality. The human immune system must, therefore, perpetually defend against invasive fungal infections. Phagocytosis is critical for the clearance of fungal pathogens, as this cellular process allows select immune cells to internalize and destroy invading fungal cells. While much is known about the protein players that enable phagocytosis, the various roles that lipids play during this fundamental innate immune process are still being illuminated. In this review, we describe recent discoveries that shed new light on the mechanisms by which host lipids enable the phagocytic uptake and clearance of fungal pathogens.

Lactobacillus rhamnosus Lcr35 as an effective treatment for preventing Candida albicans infection in the invertebrate model Caenorhabditis elegans: First mechanistic insights

The increased recurrence of Candida albicans infections is associated with greater resistance to antifungal drugs. This involves the establishment of alternative therapeutic protocols, such as probiotic microorganisms whose antifungal potential has already been demonstrated using preclinical models (cell cultures, laboratory animals). Understanding the mechanisms of action of probiotic microorganisms has become a strategic need for the development of new therapeutics for humans. In this study, we investigated the prophylactic anti-C. albicans properties of Lactobacillus rhamnosus Lcr35® using the in vitro Caco-2 cell model and the in vivo Caenorhabditis elegans model. In Caco-2 cells, we showed that the strain Lcr35® significantly inhibited the growth (~2 log CFU.mL-1) and adhesion (150 to 6,300 times less) of the pathogen. Moreover, in addition to having a pro-longevity activity in the nematode (+42.9%, p = 3.56.10-6), Lcr35® protects the animal from the fungal infection (+267% of survival, p < 2.10-16) even if the yeast is still detectable in its intestine. At the mechanistic level, we noticed the repression of genes of the p38 MAPK signalling pathway and genes involved in the antifungal response induced by Lcr35®, suggesting that the pathogen no longer appears to be detected by the worm immune system. However, the DAF-16/FOXO transcription factor, implicated in the longevity and antipathogenic response of C. elegans, is activated by Lcr35®. These results suggest that the probiotic strain acts by stimulating its host via DAF-16 but also by suppressing the virulence of the pathogen.

Diversity of vaginal microbiome and metabolome during genital infections

We characterized the vaginal ecosystem during common infections of the female genital tract, as vulvovaginal candidiasis (VVC, n = 18) and Chlamydia trachomatis infection (CT, n = 20), recruiting healthy (HC, n = 21) and bacterial vaginosis-affected (BV, n = 20) women as references of eubiosis and dysbiosis. The profiles of the vaginal microbiome and metabolome were studied in 79 reproductive-aged women, by means of next generation sequencing and proton based-nuclear magnetic resonance spectroscopy. Lactobacillus genus was profoundly depleted in all the genital infections herein considered, and species-level analysis revealed that healthy vaginal microbiome was dominated by L. crispatus. In the shift from HC to CT, VVC, and BV, L. crispatus was progressively replaced by L. iners. CT infection and VVC, as well as BV condition, were mainly characterised by anaerobe genera, e.g. Gardnerella, Prevotella, Megasphaera, Roseburia and Atopobium. The changes in the bacterial communities occurring during the genital infections resulted in significant alterations in the vaginal metabolites composition, being the decrease of lactate a common marker of all the pathological conditions. In conclusion, according to the taxonomic and metabolomics analysis, we found that each of the four conditions is characterized by a peculiar vaginal microbiome/metabolome fingerprint.

Sweet Relief: Determining the Antimicrobial Activity of Medical Grade Honey Against Vaginal Isolates of Candida albicans

Recurrent vulvovaginal candidiasis (RVVC) is predicted to increase to almost 158 million cases annually by 2030. Extensive self-diagnosis and easily accessible over-the-counter (OTC) fungistatic drugs contribute to antifungal-resistance, illustrating the need for novel therapies. Honey possesses multiple antimicrobial mechanisms, and there is no antimicrobial resistance towards honey reported. We evaluated the susceptibility of five clinical isolates of Candida albicans and a control strain to regular honey and a medical grade honey (MGH) gel formulation (L-Mesitran, containing 40% honey and vitamins C and E) using an adapted version of the EUCAST protocol at pH 5.2, 4.6, and 4.0. 40% regular honey did not kill or inhibit C. albicans. In contrast, the minimal inhibitory concentration (MIC) of L-Mesitran was 25%-50%, while fungicidal effects occurred at a 50% concentration (MBC) of the MGH formulation, except for one strain which was not killed at pH 4.0. Overall, pH had little effect on antimicrobial activity. MGH formulation L-Mesitran has antimicrobial activity against C. albicans over a relevant pH range. The vitamin supplements or other components of L-Mesitran may enhance the antifungal activity of the honey. This study supports performing clinical trials for conditions, such as RVVC, to find an alternative to available OTC fungistatic drugs.

Chlamydia trachomatis and Chlamydia pneumoniae Interaction with the Host: Latest Advances and Future Prospective

Research in Chlamydia trachomatis and Chlamydia pneumoniae has gained new traction due to recent advances in molecular biology, namely the widespread use of the metagenomic analysis and the development of a stable genomic transformation system, resulting in a better understanding of Chlamydia pathogenesis. C. trachomatis, the leading cause of bacterial sexually transmitted diseases, is responsible of cervicitis and urethritis, and C. pneumoniae, a widespread respiratory pathogen, has long been associated with several chronic inflammatory diseases with great impact on public health. The present review summarizes the current evidence regarding the complex interplay between C. trachomatis and host defense factors in the genital micro-environment as well as the key findings in chronic inflammatory diseases associated to C. pneumoniae.

Candida albicans Interactions with Mucosal Surfaces during Health and Disease

Flexible adaptation to the host environment is a critical trait that underpins the success of numerous microbes. The polymorphic fungus Candida albicans has evolved to persist in the numerous challenging niches of the human body. The interaction of C. albicans with a mucosal surface is an essential prerequisite for fungal colonisation and epitomises the complex interface between microbe and host. C. albicans exhibits numerous adaptations to a healthy host that permit commensal colonisation of mucosal surfaces without provoking an overt immune response that may lead to clearance. Conversely, fungal adaptation to impaired immune fitness at mucosal surfaces enables pathogenic infiltration into underlying tissues, often with devastating consequences. This review will summarise our current understanding of the complex interactions that occur between C. albicans and the mucosal surfaces of the human body.

The Effects of Mentha × piperita Essential Oil on C. albicans Growth, Transition, Biofilm Formation, and the Expression of Secreted Aspartyl Proteinases Genes

The rise in resistance and changes in the spectrum of Candida infections have generated enormous interest in developing new antifungal drugs using natural molecules such as plant essential oils (EOs). Antimicrobial activity against foodborne pathogenic and spoilage microorganisms has been reported for EOs. The goal of this study was to assess the effect of Mentha × piperita essential oil (EO) on C. albicans growth, transition (change from blastospore to hyphae forms), and biofilm formation as well as on the expression of certain virulent genes. We show that whole EO and its vapor attenuated the yeast’s growth, compared to that in the control. The effect of the EO was comparable to that of amphotericin-B (AmB). The EO and its vapor significantly decreased the morphological changes of C. albicans, reduced biofilm formation, and disrupted mature C. albicans biofilms. The effect produced by whole EO on biofilm formation/disruption was notably comparable to that observed with AmB. Exposure of C. albicans to EO and its vapor downregulated the expression of various genes, such as secreted aspartyl proteinases (SAP 1, 2, 3, 9, 10) and hyphal wall protein 1 (HWP1). Altogether, these results provide new insight into the efficacy of Mentha × piperita EO against C. albicans and suggest the potential of Mentha × piperita EO for use as an antifungal therapy in multiple applications.

Biofilm in Genital Ecosystem: A Potential Risk Factor for Chlamydia trachomatis Infection

In healthy women, the cervicovaginal microbiota is mostly populated by Lactobacillus spp., the main host defense factor of the female genital tract. In addition to Lactobacilli, other microorganisms populate the cervicovaginal microbiota, like Candida spp. and Gardnerella vaginalis. The overgrowth of Candida spp. or G. vaginalis, known as biofilm-producing microorganisms in the genital ecosystem, may lead to microbial dysbiosis that increases the risk of acquiring sexually transmitted infections, like Chlamydia trachomatis. C. trachomatis, the leading cause of bacterial sexually transmitted diseases, is still considered an important public health problem worldwide because of the impact of asymptomatic infections on long-term reproductive sequelae, including pelvic inflammatory disease and infertility. The aim of our study was to investigate the interaction between C. trachomatis and the biofilm produced by Candida albicans or Gardnerella vaginalis, evaluating whether the biofilm can harbor C. trachomatis and influence its survival as well as its infectious properties. In order to do so, we developed an in vitro coculture transwell-based biofilm model. Our findings proved, for the first time, that C. trachomatis, an intracellular obligate pathogen, survived, for up to 72 hours after exposure, inside the biofilm produced by C. albicans or G. vaginalis, retaining its infectious properties, as evidenced by the typical chlamydial inclusions observed in the cell monolayer (chlamydial inclusion-forming units at 72 h: 9255 ± 1139 and 9873 ± 1015, respectively). In conclusion, our results suggest that the biofilm related to Candida or Gardnerella genital infections may act as a reservoir of C. trachomatis and, thus, contribute to the transmission of the infection in the population as well as to its dissemination into the upper genital tract, increasing the risk of developing severe reproductive sequelae.

Inherited CARD9 Deficiency: Invasive Disease Caused by Ascomycete Fungi in Previously Healthy Children and Adults

Autosomal recessive CARD9 deficiency underlies life-threatening, invasive fungal infections in otherwise healthy individuals normally resistant to other infectious agents. In less than 10 years, 58 patients from 39 kindreds have been reported in 14 countries from four continents. The patients are homozygous (n = 49; 31 kindreds) or compound heterozygous (n = 9; 8 kindreds) for 22 different CARD9 mutations. Six mutations are recurrent, probably due to founder effects. Paradoxically, none of the mutant alleles has been experimentally demonstrated to be loss-of-function. CARD9 is expressed principally in myeloid cells, downstream from C-type lectin receptors that can recognize fungal components. Patients with CARD9 deficiency present impaired cytokine and chemokine production by macrophages, dendritic cells, and peripheral blood mononuclear cells and defective killing of some fungi by neutrophils in vitro. Neutrophil recruitment to sites of infection is impaired in vivo. The proportion of Th17 cells is low in most, but not all, patients tested. Up to 52 patients suffering from invasive fungal diseases (IFD) have been reported, with ages at onset of 3.5 to 52 years. Twenty of these patients also displayed superficial fungal infections. Six patients had only mucocutaneous candidiasis or superficial dermatophytosis at their last follow-up visit, at the age of 19 to 50 years. Remarkably, for 50 of the 52 patients with IFD, a single fungus was involved; only two patients had IFDs due to two different fungi. IFD recurred in 44 of 45 patients who responded to treatment, and a different fungal infection occurred in the remaining patient. Ten patients died from IFD, between the ages of 12 and 39 years, whereas another patient died at the age of 91 years, from an unrelated cause. At the most recent scheduled follow-up visit, 81% of the patients were still alive and aged from 6.5 to 75 years. Strikingly, all the causal fungi belonged to the phylum Ascomycota: commensal Candida and saprophytic Trychophyton, Aspergillus, Phialophora, Exophiala, Corynesprora, Aureobasidium, and Ochroconis. Human CARD9 is essential for protective systemic immunity to a subset of fungi from this phylum but seems to be otherwise redundant. Previously healthy patients with unexplained invasive fungal infection, at any age, should be tested for inherited CARD9 deficiency.

KEY POINTS

• Inherited CARD9 deficiency (OMIM #212050) is an AR PID due to mutations that may be present in a homozygous or compound heterozygous state. • CARD9 is expressed principally in myeloid cells and transduces signals downstream from CLR activation by fungal ligands. • Endogenous mutant CARD9 levels differ between alleles (from full-length normal protein to an absence of normal protein). • The functional impacts of CARD9 mutations involve impaired cytokine production in response to fungal ligands, impaired neutrophil killing and/or recruitment to infection sites, and defects of Th17 immunity. • The key clinical manifestations in patients are fungal infections, including CMC, invasive (in the CNS in particular) Candida infections, extensive/deep dermatophytosis, subcutaneous and invasive phaeohyphomycosis, and extrapulmonary aspergillosis. • The clinical penetrance of CARD9 deficiency is complete, but penetrance is incomplete for each of the fungi concerned. • Age at onset is highly heterogeneous, ranging from childhood to adulthood for the same fungal disease. • All patients with unexplained IFD should be tested for CARD9 mutations. Familial screening and genetic counseling should be proposed. • The treatment of patients with CARD9 mutations is empirical and based on antifungal therapies and the surgical removal of fungal masses. Patients with persistent/relapsing Candida infections of the CNS could be considered for adjuvant GM-CSF/G-CSF therapy. The potential value of HSCT for CARD9-deficient patients remains unclear.

Psoriasin, a novel anti-Candida albicans adhesin

Abstract

Candida albicans belongs to the normal microbial flora on epithelial surfaces of humans. However, under certain, still not fully understood conditions, it can become pathogenic and cause a spectrum of diseases, from local infections to life-threatening septicemia. We investigated a panel of antimicrobial proteins and peptides (AMPs), potentially involved in mucosal immunity against this pathogen. Out of six studied AMPs, psoriasin was most up-regulated during a mucosal infection, an acute episode of recurrent Candida vulvovaginitis, although candidacidal activity has not been demonstrated. We here show that psoriasin binds to β-glucan, a basic component of the C. albicans cell wall, and thereby inhibits adhesion of the pathogen to surfaces and increases IL-8 production by mucosal epithelial cells. In conclusion, we show a novel mechanism of action of psoriasin. By inhibiting C. albicans adhesion and by enhancing cytokine production, psoriasin contributes to the immune response against C. albicans.

Key messages

The antimicrobial peptide psoriasin is highly up-regulated during a local mucosal infection, Candida albicans vulvovaginitis.

Psoriasin binds to β-glucan in the Candida albicans cell wall and thereby inhibits adhesion of the pathogen.

Binding of psoriasin to Candida albicans induces an immune response by mucosal epithelial cells.

Electronic supplementary material

The online version of this article (10.1007/s00109-018-1637-6) contains supplementary material, which is available to authorized users.

An Update on Candida tropicalis Based on Basic and Clinical Approaches

Candida tropicalis has emerged as one of the most important Candida species. It has been widely considered the second most virulent Candida species, only preceded by C. albicans. Besides, this species has been recognized as a very strong biofilm producer, surpassing C. albicans in most of the studies. In addition, it produces a wide range of other virulence factors, including: adhesion to buccal epithelial and endothelial cells; the secretion of lytic enzymes, such as proteinases, phospholipases, and hemolysins, bud-to-hyphae transition (also called morphogenesis) and the phenomenon called phenotypic switching. This is a species very closely related to C. albicans and has been easily identified with both phenotypic and molecular methods. In addition, no cryptic sibling species were yet described in the literature, what is contradictory to some other medically important Candida species. C. tropicalis is a clinically relevant species and may be the second or third etiological agent of candidemia, specifically in Latin American countries and Asia. Antifungal resistance to the azoles, polyenes, and echinocandins has already been described. Apart from all these characteristics, C. tropicalis has been considered an osmotolerant microorganism and this ability to survive to high salt concentration may be important for fungal persistence in saline environments. This physiological characteristic makes this species suitable for use in biotechnology processes. Here we describe an update of C. tropicalis, focusing on all these previously mentioned subjects.

Eve's garden: myths, legends and secrets unmasked

This special issue of Research in Microbiology aims to provide some insights in one of women's most fascinating interacting microbial communities: the vaginal microbiome. Even in the 21st century, with many advanced methods at hand, the definition of the healthy vaginal microbiome remains under debate. The interest in studying the dysbiosis of the vaginal microbiome is increasing and goes well beyond the study of bacterial vaginosis. The selection of contributions in this issue summarizes what is currently known in terms of inter- and intra-microorganisms interaction as well as the virulence factors that some of them may deploy.