Comparison of the epidemiology, drug resistance mechanisms, and virulence of and

Treatment of vaginitis caused by non-albicans Candida species

INTRODUCTION

In the face of increased frequency of non-albicans Candida vulvovaginitis (VVC) reported worldwide, there is a paucity of effective oral and topical antifungal drugs available. Drug selection is further handicapped by an absence of data of clinical efficacy of available antifungal drugs for these infections.

AREAS COVERED

In this review, attention is directed at the cause of drug shortage as well as increased frequency of non-albicans Candida (NAC) vulvovaginitis. There is widespread recognition of reduced in vitro azole drug susceptibility in NAC species. Moreover, antifungal susceptibility tests have not been standardized or validated for NAC isolates, hence clinicians rely on an element of empiricism especially given the absence of randomized controlled comparative studies targeting NAC species. Clinical spectrum of NAC species isolates is highly variable with ongoing difficulty in determining a causal role in symptomatic patients.

EXPERT OPINION

We have entered the era of demand for Candida species-specific therapy and although consensus treatment guidelines are emerging, new antifungal agents that target these multiple-azole resistant or relatively resistant vaginal NAC species are urgently needed.

Candida Non-albicans and Non-auris Causing Invasive Candidiasis in a Fourth-Level Hospital in Colombia: Epidemiology, Antifungal Susceptibility, and Genetic Diversity

Increasingly common and associated with healthcare settings, Candida infections are very important, since some species of this genus can develop antifungal resistance. We contribute data on the epidemiology, antifungal susceptibility, and genetic diversity of Candida non-albicans and non-auris affecting critically ill patients in a fourth-level hospital in Colombia. Ninety-seven isolates causing invasive infections, identified by conventional methods over 18 months, were studied. Data from patients affected by these yeasts, including sex, age, comorbidities, treatment, and outcome, were analysed. The antifungal susceptibility of the isolates was determined, and the ribosomal DNA was sequenced. Candida parapsilosis, Candida tropicalis, Candida glabrata, Candida dubliniensis, and Candida guilliermondii caused 48.5% of all cases of invasive candidiasis. The species were mainly recovered from blood (50%). Patients were mostly men (53.4%), between 18 days and 93 years old, hospitalized in the ICU (70.7%). Overall mortality was 46.6%, but patients in the ICU, using antibiotics, with diabetes mellitus, or with C. glabrata infections were more likely to die. Resistant isolates were identified in C. parapsilosis, C. tropicalis, and C. glabrata. This study provides epidemiological data for the surveillance of emerging Candida species, highlighting their clinical impact, as well as the emergence of antifungal resistance and clonal dispersal.

Septic arthritis caused by Candida dubliniensis following arthroscopic surgery

A 37-year-old immunocompetent man was admitted to the emergency department due to recurrent pain and oedema of his right knee. Two months earlier, he had undergone surgery to repair his meniscus. Arthroscopic joint lavage was performed and Candida dubliniensis was recovered in culture. The authors describe the first case of septic arthritis caused by Candida dubliniensis.

Questioning the 14-day dogma in candidemia treatment duration

The growing threat of antimicrobial resistance (AMR) is a global concern. With AMR directly causing 1.27 million deaths in 2019 and projections of up to 10 million annual deaths by 2050, optimising infectious disease treatments is imperative. Prudent antimicrobial use, including treatment duration, can mitigate AMR emergence. This is particularly critical in candidemia, a severe condition with a 45% crude mortality rate, as the 14-day minimum treatment period has not been challenged in randomised comparison. A comprehensive literature search was conducted in August 2023, revealing seven original articles and two case series discussing treatment durations of less than 14 days for candidemia. No interventional trials or prospective observational studies assessing shorter durations were found. Historical studies showed varying candidemia treatment durations, questioning the current 14-day minimum recommendation. Recent research observed no significant survival differences between patients receiving shorter or longer treatment, emphasising the need for evidence-based guidance. Treatment duration reduction post-blood culture clearance could decrease exposure to antifungal drugs, limiting selection pressure, especially in the context of emerging multiresistant Candida species. Candidemia's complexity, emerging resistance and potential for shorter in-hospital stays underscore the urgency of refining treatment strategies. Evidence-driven candidemia treatment durations are imperative to balance efficacy with resistance prevention and ensure the longevity of antifungal therapies. Further research and clinical trials are needed to establish evidence-based guidelines for candidemia treatment duration.

Spectrum and management of rare Candida/yeast infections in Kuwait in the Middle East

Invasive fungal infections (IFIs) are associated with high mortality rates and mostly affect patients with compromised immunity. The incidence of IFIs is increasing worldwide with the expanding population of susceptible patients. Candida and other yeast infections represent a major component of IFIs. Rare Candida/yeast infections have also increased in recent years and pose considerable diagnostic and management challenges as they are not easily recognized by routine phenotypic characteristic-based diagnostic methods and/or by the automated yeast identification systems. Rare Candida/yeasts also exhibit reduced susceptibility to antifungal drugs making proper management of invasive infections challenging. Here, we review the diagnosis and management of 60 cases of rare Candida/yeast IFIs described so far in Kuwait, an Arabian Gulf country in the Middle East. Interestingly, majority (34 of 60, 56.7%) of these rare Candida/yeast invasive infections occurred among neonates or premature, very-low-birth-weight neonates, usually following prior bacteremia episodes. The clinical details, treatment given, and outcome were available for 28 of 34 neonates. The crude mortality rate among these neonates was 32.2% as 19 of 28 (67.8%) survived the infection and were discharged in healthy condition, likely due to accurate diagnosis and frequent use of combination therapy. Physicians treating patients with extended stay under intensive care, on mechanical ventilation, receiving broad spectrum antibiotics and with gastrointestinal surgery/complications should proactively investigate IFIs. Timely diagnosis and early antifungal treatment are essential to decrease mortality. Understanding the epidemiology and spectrum of rare Candida/yeast invasive infections in different geographical regions, their susceptibility profiles and management will help to devise novel diagnostic and treatment approaches and formulate guidelines for improved patient outcome.

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

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

Prevalence of Closely Related Candida albicans Species among Patients with Vulvovaginal Candidiasis in Southern Poland Based on the hwp1 Gene Amplification

Candida albicans remains the most common species isolated from women with vulvovaginal candidiasis. However, closely related species such as Candida africana and Candida dubliniensis may also occur, although they are often misidentified. The aim of the study was to confirm the phenotypic identification of C. albicans and its closely related species isolated from women with genital tract infections by amplification of the hwp1 (hyphal wall protein 1) gene in a PCR assay. We report a detailed molecular identification of C. albicans and its closely related species among 326 patients in the Małopolska region, Poland. Initial phenotypic identifications were confirmed by amplification of the hwp1 gene. Based on molecular analysis, we revealed 307 strains (94.17%) as C. albicans and 17 as C. dubliniensis (5.22%). No strain of C. africana was detected. Two patients h ad co-infection with C. albicans and C. dubliniensis (0.61%). A PCR assay targeting the hwp1 gene was reliable for correctly identifying species among the C. albicans complex.

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

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

Controlling the Interaction between Fluorescent Gold Nanoclusters and Biointerfaces for Rapid Discrimination of Fungal Pathogens

Nondestructive detection and discrimination of fungal pathogens is essential for rapid and precise treatment, which further effectively prevents antifungal resistance from overused drugs. In this work, fluorescent gold nanoclusters served as the basis for discriminating Candida species. Varied on surface ligands, these gold nanoclusters demonstrated different optical properties as a result of the perturbation effects of ligands. The biointerface interaction between the surface ligands of gold nanoclusters and the cell walls of Candida species can be constructed, and their restriction on ligands perturbation effect produced enhanced fluorescence signals. Owing to the variation of the cell wall composition, cells of different Candida species demonstrated different degrees of association with the gold nanoclusters, leading to discriminable amounts of fluorescence enhancements. The reverse signal response from these gold nanoclusters gives rise to a synergistic and effective assay that allows identification of Candida species.

Antibiofilm Potential of Medicinal Plants against Candida spp. Oral Biofilms: A Review

The use of natural products to promote health is as old as human civilization. In recent years, the perception of natural products derived from plants as abundant sources of biologically active compounds has driven their exploitation towards the search for new chemical products that can lead to further pharmaceutical formulations. Candida fungi, being opportunistic pathogens, increase their virulence by acquiring resistance to conventional antimicrobials, triggering diseases, especially in immunosuppressed hosts. They are also pointed to as the main pathogens responsible for most fungal infections of the oral cavity. This increased resistance to conventional synthetic antimicrobials has driven the search for new molecules present in plant extracts, which have been widely explored as alternative agents in the prevention and treatment of infections. This review aims to provide a critical view and scope of the in vitro antimicrobial and antibiofilm activity of several medicinal plants, revealing species with inhibition/reduction effects on the biofilm formed by Candida spp. in the oral cavity. The most promising plant extracts in fighting oral biofilm, given their high capacity to reduce it to low concentrations were the essential oils extracted from Allium sativum L., Cinnamomum zeylanicum Blume. and Cymbopogon citratus (DC) Stapf.

Factors influencing the presence of Candida dubliniensis and other non-albicans species in patients with oral lichen planus: a retrospective observational study

Objectives

The epidemiologic distribution of non-albicans species in the oral cavity of oral lichen planus (OLP) patients remains uncertain. Therefore, the aim of this study was to identify factors associated with the presence of C. dubliniensis and other non-albicans species. Furthermore, independent risk factors for Candida superinfection in OLP should be identified.

Material and methods

Epidemiologic data and microbiological findings from 268 symptomatic OLP patients who underwent continuous oral swab culture over a 5-year period (2015–2019) were retrospectively reviewed. Candida species identification and semi-quantification were obtained by culture on CHROMagar Candida, followed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS).

Results

C. albicans was the most frequently isolated species (72.3%), followed by C. glabrata (7.3%), C. dubliniensis (5.8%), C. krusei and C. parapsilosis (both 2.6%). The presence of C. dubliniensis was significantly associated with tobacco smoking. Other non-albicans spp. were significantly more often detected in patients using removable dentures. Increasing age and the intake of psychotropic drugs were identified as independent risk factors of Candida superinfection in OLP.

Conclusion

In OLP patients, certain local and systemic factors increase the risk of carrying potentially drug-resistant Candida species and the development of Candida superinfection of OLP lesions.

Clinical relevance

Due to the frequent detection of non-albicans species in OLP, resistance or at least reduced sensitivity to azole antifungals should be expected, especially in smokers and patients using removable dentures. In the case of oral complaints, a superinfection with Candida should be considered, whereby older patients and patients taking psychotropic drugs have an increased risk for oral infection with Candida.

Inhibitors of DNA topoisomerases I and II applied to Candida dubliniensis reduce growth, viability, the generation of petite mutants and toxicity, while acting synergistically with fluconazole

The increasing resistance of Candida species to azoles emphasizes the urgent need for new antifungal agents with novel mechanisms of action. The aim of this study was to examine the effect of three DNA topoisomerase inhibitors of plant origin (camptothecin, etoposide and curcumin) on the growth of Candida dubliniensis. The phylogenetic analysis showed a close relationship between the topoisomerase enzymes of C. dubliniensis and Candida albicans. The alignment of the amino acid sequences of topoisomerase I and II of yeasts and humans evidenced conserved domains. The docking study revealed affinity of the test compounds for the active site of topoisomerase I and II in C. dubliniensis. Curcumin and camptothecin demonstrated a stronger in vitro antifungal effect than the reference drugs (fluconazole and itraconazole). Significant synergistic activity between the topoisomerase inhibitors and fluconazole at the highest concentration (750 µM) was observed. Fluconazole induced the petite phenotype to a greater degree than the topoisomerase inhibitors, indicating a tendency to generate resistance. Lower toxicity was found for such inhibitors versus reference drugs on Galleria mellonella larva. The topoisomerase inhibitors exhibited promising antifungal activity, and the DNA topoisomerase enzymes of C. dubliniensis proved to be an excellent model for evaluating new antifungal compounds.

Lineage-specific selection and the evolution of virulence in the Candida clade

Of the many microbial species on earth, only a small number are able to thrive in humans and cause disease. Comparison of closely related pathogenic and nonpathogenic species can therefore be useful in identifying key features that contribute to virulence. We created interspecies hybrids between Candida albicans, a prevalent fungal pathogen of humans, and Candida dubliniensis, a close, but much less pathogenic, relative. By comparing genome-wide expression differences between the two genomes in the same cell, we surmised that since the two species diverged from a common ancestor, natural selection has acted upon the expression level of an ancient metabolic pathway, illustrating that pathogenicity traits can arise over evolutionary timescales through small expression changes in deeply conserved proteins.

Candida albicans is the most common cause of systemic fungal infections in humans and is considerably more virulent than its closest known relative, Candida dubliniensis. To investigate this difference, we constructed interspecies hybrids and quantified mRNA levels produced from each genome in the hybrid. This approach systematically identified expression differences in orthologous genes arising from cis-regulatory sequence changes that accumulated since the two species last shared a common ancestor, some 10 million y ago. We documented many orthologous gene-expression differences between the two species, and we pursued one striking observation: All 15 genes coding for the enzymes of glycolysis showed higher expression from the C. albicans genome than the C. dubliniensis genome in the interspecies hybrid. This pattern requires evolutionary changes to have occurred at each gene; the fact that they all act in the same direction strongly indicates lineage-specific natural selection as the underlying cause. To test whether these expression differences contribute to virulence, we created a C. dubliniensis strain in which all 15 glycolysis genes were produced at modestly elevated levels and found that this strain had significantly increased virulence in the standard mouse model of systemic infection. These results indicate that small expression differences across a deeply conserved set of metabolism enzymes can play a significant role in the evolution of virulence in fungal pathogens.

Case Report: Candida dubliniensis as a Cause of Chronic Meningitis

Background: Candida dubliniensis is closely related to Candida albicans and rarely isolated in clinical specimens. C. dubliniensis is increasingly recognized as a pathogen in immunocompromised hosts. We present the third known case of Candida dubliniensis meningitis in a young immunocompetent host. Case Presentation: A 27-year-old female with a history of intravenous heroin use and chronic hepatitis C presented with a 10-month history of headaches and progressive bilateral vision loss. On physical examination, visual acuity was 20/20 in her right eye and grade II papilledema was noted. Examination of her left eye revealed complete loss of vision and grade IV papilledema. An MRI with and without contrast revealed increased leptomeningeal enhancement involving the posterior fossa and spinal cord. After multiple lumbar punctures, cerebrospinal fluid fungal cultures grew Candida dubliniensis. The patient was successfully treated with a combination of liposomal amphotericin and fluconazole for 6 weeks with complete resolution of her CNS symptoms, with the exception of irreversible vision loss. Conclusion: We report a case of chronic meningitis due to Candida dubliniensis in an immunocompetent woman with hepatitis C and a history of intravenous heroin use. Additional studies are needed to confirm risk factors for Candida dubliniensis colonization, which likely predisposes individuals to invasive candidiasis.

A Case of Bilateral Endogenous Candida dubliniensis Endophthalmitis Treated with Aggressive Local and Systemic Therapy

Candida dubliniensis is an emerging pathogen implicated in a variety of infections in immunocompromised hosts. A 79-year-old male with autoimmune pancytopenia on chronic oral steroid therapy was admitted for suspected sepsis and started on empirical antibiotics and micafungin. He developed floaters and decreased vision while on this regimen and was diagnosed with bilateral candida endophthalmitis. Blood cultures grew C. dubliniensis.Intravenous therapy was switched to voriconazole and amphotericin B. He also received aggressive intravitreal antifungal therapy consisting of 100 μg/0.1 mL voriconazole (4 OD, 3 OS) and 5 μg/0.1 mL amphotericin B (3 OD, 1 OS) over 2 weeks that resulted in local control of infection. The right eye developed a retinal detachment 1 month after initial presentation that was repaired by 25-gauge pars plana vitrectomy, scleral buckle, laser and silicone oil. At the 15-month follow-up exam, subsequent to silicone oil removal, membrane peel and cataract surgery, OD visual acuity had improved to 20/80. OS was phakic and 20/25. Aggressive intravitreal antifungal therapy combined with intravenous therapy may control endophthalmitis and avoid the risks associated with pars plana vitrectomy during acute infection.

Zinc at the Host-Fungus Interface: How to Uptake the Metal?

Zinc is an essential nutrient for all living organisms. However, firm regulation must be maintained since micronutrients also can be toxic in high concentrations. This notion is reinforced when we look at mechanisms deployed by our immune system, such as the use of chelators or membrane transporters that capture zinc, when threatened with pathogens, like fungi. Pathogenic fungi, on the other hand, also make use of a variety of transporters and specialized zinc captors to survive these changes. In this review, we sought to explain the mechanisms, grounded in experimental analysis and described to date, utilized by pathogenic fungi to maintain optimal zinc levels.

Activity of chitosan antifungal denture adhesive against common Candida species and Candida albicans adherence on denture base acrylic resin

STATEMENT OF PROBLEM

Candida adherence to the denture base is an important cause of denture stomatitis. In addition, infections with drug-resistant Candida have become more prevalent, especially among elderly and immunocompromised patients. Thus, alternative safe antifungal agents for oral applications are needed.

PURPOSE

The purpose of this in vitro study was to investigate the activity of chitosan, a natural biopolymer, against common oral Candida species and its efficacy in inhibiting C albicans adherence to denture-base acrylic resin.

MATERIAL AND METHODS

The minimum fungicidal concentrations (MFCs) of 5 types of chitosan against 6 species of Candida and 10 C albicans clinical isolates were determined by broth and agar dilution, respectively. N-succinyl chitosan (NSC), low- and high-molecular-weight water-soluble chitosan (LMWC and HMWC), and oligomer and polymer shrimp-chitosan were examined. NSC and HMWC, as pure gel and as a mixture with carboxymethylcellulose (CMC), were applied to acrylic resin disks, incubated with C albicans for 24 hours, and washed, and adherent cells were collected for colony count. The effects of HMWC on human gingival fibroblasts after 1 and 24 hours of treatment were measured by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. The retention force of HMWC gel was measured by using a universal testing machine. The Kruskal-Wallis and Mann-Whitney U tests were used to compare the antiadherence activity (α=.05).

RESULTS

HMWC had the highest antifungal activity against most Candida species tested and C albicans clinical isolates. HMWC gel completely inhibited C albicans adherence to denture base acrylic resin (P<.001). CMC denture adhesive significantly increased C albicans adherence (P<.001), but adding 2×MFC HMWC into CMC reduced the adherence, although this was not statistically significant (P=.06). HMWC at 1×MFC and 2×MFC showed no toxic effect on gingival fibroblast viability and proliferation. Moreover, the retention force provided by HMWC gel was sufficient for use as a denture adhesive (>5000 Pa).

CONCLUSIONS

High-molecular-weight, water-soluble chitosan is a biocompatible biopolymer that could inhibit C albicans adherence and that showed properties suitable for development into an antifungal denture adhesive.

Characterization of oral yeasts isolated from healthy individuals attended in different Colombian dental clinics

The aim of this study was to identify the most frequent yeasts in the oral cavity of adult individuals without immune disorders and to associate the presence of these oral yeasts with different characteristics of each individual. Oral rinse samples were obtained from 96 healthy adults and cultured in Sabouraud dextrose agar media and CHROMagar. Yeasts were identified by sequencing the D1/D2 region of the 28S rRNA gene. Probable association among the socio-demographic characteristics, body mass index, family and personal medical history, oral hygiene, tobacco and/or alcohol consumption habits and presence of oral fungi was analyzed. Contingency tables and logistic regression were employed to evaluate possible relationships between the presence of oral fungi and mixed colonization with these variables. 57.3% of the healthy individuals had oral yeasts and 21.8% had mixed colonization. The most prevalent yeasts were Candida albicans (52%), C. parapsilosis (17.9%), and C. dubliniensis (7.57%). Yeasts with most frequently mixed colonization were C. albicans and C. parapsilosis. No relationships were found among the variables analyzed. However, the presence of mixed colonization was related to the presence of dental prostheses (P<0.006), dental apparatuses (P=0.016) and O'Leary index (P=0.012). This is the first study that characterized oral yeasts in Colombian healthy individuals, determined the most prevalent oral yeasts C. albicans, C. parapsilosis and C. dublinensis and an association of mixed colonization with the use of dental prostheses and aparatology and poor hygiene.

Transcriptomic and Genomic Approaches for Unravelling Candida albicans Biofilm Formation and Drug Resistance-An Update

Candida albicans is an opportunistic fungal pathogen, which causes a plethora of superficial, as well as invasive, infections in humans. The ability of this fungus in switching from commensalism to active infection is attributed to its many virulence traits. Biofilm formation is a key process, which allows the fungus to adhere to and proliferate on medically implanted devices as well as host tissue and cause serious life-threatening infections. Biofilms are complex communities of filamentous and yeast cells surrounded by an extracellular matrix that confers an enhanced degree of resistance to antifungal drugs. Moreover, the extensive plasticity of the C. albicans genome has given this versatile fungus the added advantage of microevolution and adaptation to thrive within the unique environmental niches within the host. To combat these challenges in dealing with C. albicans infections, it is imperative that we target specifically the molecular pathways involved in biofilm formation as well as drug resistance. With the advent of the -omics era and whole genome sequencing platforms, novel pathways and genes involved in the pathogenesis of the fungus have been unraveled. Researchers have used a myriad of strategies including transcriptome analysis for C. albicans cells grown in different environments, whole genome sequencing of different strains, functional genomics approaches to identify critical regulatory genes, as well as comparative genomics analysis between C. albicans and its closely related, much less virulent relative, C. dubliniensis, in the quest to increase our understanding of the mechanisms underlying the success of C. albicans as a major fungal pathogen. This review attempts to summarize the most recent advancements in the field of biofilm and antifungal resistance research and offers suggestions for future directions in therapeutics development.

Anti-biofilm activity of antibody directed against surface antigen complement receptor 3-related protein-comparison of Candida albicans and Candida dubliniensis

Candida albicans and C. dubliniensis are related yeasts that differ in the expression of virulence-associated proteins involved in adherence and biofilm development. CR3-RP (complement receptor 3-related protein) is one of the surface antigens expressed by Candida species. The main objective of this research was to elucidate the effect of the polyclonal anti-CR3-RP antibody (Ab) on adherence and the biofilm formed by C. albicans SC5314 and C. dubliniensis CBS 7987 and two clinical isolates in vitro, ex vivo and in vivo. A comparison of species, and of treated vs. non-treated with the anti-CR3-RP Ab showed a reduction in adherence (22%-41%) that was dependent on the time point of evaluation (60, 90 or 120 min), but did not prove to be species-dependent. Confocal microscopy revealed a decreased thickness in biofilms formed by both species after pre-treatment with the anti-CR3-RP Ab. This observation was confirmed ex vivo by immunohistochemistry analysis of biofilms formed on mouse tongues. Moreover, anti-CR3-RP Ab administration, 1 h post-infection, has been shown to promote larval survival compared to the control group in a Galleria mellonella infection model. Our data suggest a potential activity of the anti-CR3-RP Ab relevant to immunotherapy or vaccine development against biofilm-associated Candida infections.

Candida dubliniensis: A novel cause of fungal keratitis

A 45-year-old female with history of contact lens wear presented with a persistent corneal ulcer that was unresponsive to topical moxifloxacin. The patient's exam was concerning for fungal keratitis. Cultures were obtained, and the patient was started on fortified amphotericin B drops and oral voriconazole. The cultures identified Candida dubliniensis as the causative organism. The patient's exam worsened despite treatment, and the decision was made for surgery. At the time of surgery, her cornea was found to have unexpectedly perforated. She underwent cryotherapy; tectonic penetrating keratoplasty; anterior chamber tap; intracameral voriconazole, amphotericin B, and cefuroxime; and a partial conjunctival flap. Pathology from the cornea showed GMS and PAS stains positive for fungal forms. C. dubliniensis is a yeast closely related to Candida albicans that was first described in 1995 as a cause of oral candidiasis in patients with AIDS. There are a few published cases of endophthalmitis due to C. dubliniensis in the ophthalmology literature, but to our knowledge, no cases of fungal keratitis due to this organism have been reported. C. dubliniensis is a novel cause of fungal keratitis that can be difficult to identify and treat but is felt to be less virulent than C. albicans and generally susceptible to available anti-fungal therapies.

White-to-opaque switching is involved in the phospholipase B production of Candida dubliniensis on Price's egg yolk agar

Measuring the production of Candida dubliniensis (C. dubliniensis) phospholipase B (PLase B) by the Price's method has long been considered to be unattainable because the levels of PLase produced are undetectable. In this study, C. dubliniensis, C. glabrata, C. guilliermondii, C. krusei, C. parapsilosis and C. tropicalis were shown to produce PLase B and form clear white zones around their colonies when peptone, a component of the original Price's egg yolk (OP) agar, is replaced with a yeast nitrogen base (YNB). This new medium is named modified Price's (MP) agar. Based on this finding, we propose a new modified Price's (NMP) agar containing 0.75% peptone and 0.25% YNB, which enabled measurement of PLase B production by C. dubliniensis and C. albicans with results consistent with those obtained for C. albicans grown on OP agar. We strongly believe that the MP and NMP agars are very useful for screening PLase B production by C. dubliniensis and non-albicans Candida spp. Moreover, the addition of several bioactive agents (the proteinase inhibitors pepstatin A and saquinavir, the calcineurin inhibitors cyclosporine A and tacrolimus, the cell-permeable cAMP analog dBcAMP, and the quorum-sensing molecule farnesol) to the OP agar enhanced PLase B production by C. dubliniensis. During the course of our study to clarify the reason why PLase B was not produced, we found that C. dubliniensis cells grown on OP agar undergo a white-to-opaque transition, which may explain why they showed minimal production of PLase B on this medium.

In Vitro Characterization of a Biaryl Amide Anti-virulence Compound Targeting Candida albicans Filamentation and Biofilm Formation

We have previously identified a small molecule compound, N-[3-(allyloxy)-phenyl]-4-methoxybenzamide (9029936), that exerts potent inhibitory activity against filamentation and biofilm formation by the Candida albicans SC5314 strain and represents a lead candidate for the development of anti-virulence approaches against C. albicans infections. Here we present data from a series of experiments to further characterize its in vitro activity and drug-like characteristics. We demonstrate the activity of this compound against a panel of C. albicans clinical isolates, including several displaying resistance to current antifungals; as well as against a set of C. albicans gain of function strains in key transcriptional regulators of antifungal drug resistance. The compound also inhibits filamentation and biofilm formation in the closely related species C. dubliniensis, but not C. glabrata or C. tropicalis. Combinatorial studies reveal the potential of compound 9029936 to be used together with currently available conventional antifungals. Results of serial passage experiments indicate that repeated exposure to this compound does not elicit resistance. Viability staining of C. albicans in the presence of high concentrations of compound 9029936 confirms that the compound is not toxic to fungal cells, and cytological staining using image flow cytometry analysis reveals that treatment with the lead compound affects hyphal length, with additional effects on cell wall and integrity of the membrane system. In vitro pharmacological profiling provides further evidence that the lead compound displays a safe profile, underscoring its excellent “drug-like” characteristics. Altogether these results confirm the potential of this compound to be further developed as a true anti-virulence agent for the treatment of C. albicans infections, including those refractory to treatment with conventional antifungal agents.

Candida dubliniensis abscess: A clinical case and a review of the literature

Candida dubliniensis infections are rare in the absence of prolonged immunocompromised status or intravenous drug abuse. We present a case of a C. dubliniensis soft tissue abscess in a patient with uncontrolled diabetes as his only immunocompromising risk factor, treated with surgical drainage and medical management.

In vitro inhibitory activities of magnolol against Candida spp

Candida spp. cause various infections involving the skin, mucosa, deep tissues, and even life-threatening candidemia. They are regarded as an important pathogen of nosocomial bloodstream infection, with a high mortality rate. As a result of prolonged exposure to azoles, the therapeutic failure associated with azoles resistance has become a serious challenge in clinical situations. Therefore, novel, alternative antifungals are required urgently. In the present study, the CLSI M-27A broth microdilution method and the 2,3-Bis-(2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide (XTT) reduction assay were used to evaluate the antifungal effects of magnolol against various standard Candida strains in planktonic mode and biofilm formation, respectively. The antifungal activity of magnolol was demonstrated in planktonic C. albicans and non-albicans Candida species, especially fluconazole-resistant Candida krusei, with the minimum inhibitory concentrations ranging from 10 to 40 μg/mL. The BMIC₉₀ (minimum concentration with 90% Candida biofilm inhibited) values of magnolol ranged from 20 to 160 μg/mL, whereas the BMIC₉₀ values of fluconazole were more than 128 μg/mL. As an alternative and broad-spectrum antifungal agent, magnolol might be of benefit to the treatment of refractory Candida infection.

Antimicrobial synergism and cytotoxic properties of Citrus limon L., Piper nigrum L. and Melaleuca alternifolia (Maiden and Betche) Cheel essential oils

OBJECTIVES

The chemical composition, antimicrobial and synergistic effect, and cytotoxic activity of Citrus limon (lemon), Piper nigrum (green pepper) and Melaleuca alternifoila (tea tree) essential oils (EOs) were investigated.

METHODS

Chemical analyses of essential oils were tested by GC-FID and GC-MS spectroscopy. The antimicrobial activity assay was conducted using microdilution method against several oral bacteria and Candida spp. originating from the humans with oral disorders. The synergistic antimicrobial activity was evaluated using checkerboard method. The cytotoxicity evaluation of EOs was assessed using MTT test.

KEY FINDINGS

Limonene (37.5%) and β-pinene (17.9%) were the major compounds in C. limon oil, β-pinene (34.4%), δ-3-carene (19.7%), limonene (18.7%) and α-pinene (10.4%) in P. nigrum oil and terpinen-4-ol (38.6%) and γ-terpinene (21.7%) in M. alternifolia oil. The broad-spectrum antimicrobial activity was achieved by tested three EOs, with C. limon oil being the strongest against bacteria and M. alternifolia oil strongest against fungi. The EOs demonstrated synergism; their combined application revealed an increase in antimicrobial activity. All tested essential oils showed lower cytotoxic activity in comparison with the positive control, and the obtained results confirmed a dose-dependent activity.

CONCLUSIONS

The results of this study encourage use of tested EOs in development of a novel agent intended for prevention or therapy of corresponding oral disorders.

Persistence of Candida dubliniensis and lung function in patients with cystic fibrosis

Objectives

Candida dubliniensis is an emerging yeast and demonstrated a high adherence property to cystic fibrosis respiratory tract. Therefore, it is important to determine the persistence of C. dubliniensis and to assess the possible relationship to the body mass index (BMI) and forced expiratory volume in 1st second (FEV1).

Results

Candida isolates were identified by MALDI-TOF MS to species level from 40/52 (76.9%) cystic fibrosis patients. C. dubliniensis was the most common organism isolated from 50/77 (65%) lower respiratory specimens of 29 patients. Patients with persistent C. dubliniensis isolates have higher mean BMI in comparison to intermittent C. dubliniensis group. However, this difference did not reach statistical significance (P = 0.539). In contrast, patients with persistent C. dubliniensis isolates have significantly lower FEV1% mean in comparison to intermittent C. dubliniensis group particularly at initial two visits (P < 0.05); however, at subsequent visit the difference observed was not statistically significant (P = 0.456). The persistence of C. dubliniensis is more frequent in adults having more advanced disease, co-infections with chronic P. aeruginosa, cystic fibrosis related diabetes, long-term nebulized tobramycin and oral Zithromax therapy than patients with intermittent C. dubliniensis. Patients with persistent C. dubliniensis have lower FEV1 percentage and higher BMI than the intermittent C. dubliniensis.

Exoenzyme activity and possibility identification of Candida dubliniensis among Candida albicans species isolated from vaginal candidiasis

OBJECTIVES

Vulvovaginal candidiasis (VVC) or vaginal candidiasis is a common fungal infection of the genitals causing inflammation, irritation, itching, and vaginal discharge. Common yeast infections are caused by the yeast species C. albicans. However, there are other species of Candida such as C. dubliniensis which are considered as the causative agents of this infection. Hydrolytic enzymes such as proteinase and coagulase are known as virulence factors. The aim of this study was the molecular confirmation and differentiation of C. dubliniensis among C. albicans strains isolated from women with vulvovaginal candidiasis by PCR-Restriction Fragment Length Polymorphism (PCR-RFLP) and the evaluation of proteinase and coagulase activities.

METHODS

A total of 100 C. albicans strains isolated from women with vulvovaginal candidiasis referred to Shiraz medical clinics were enrolled in the study. All the isolates were primarily identified by conventional methods. PCR-RFLP method was used for the confirmation and identification of C. albicans and C. dubliniensis. Moreover, in vitro proteinase and coagulase activities of these isolates were evaluated using bovine serum albumin media and classical rabbit plasma tube test.

RESULTS

As a result, PCR-RFLP identified 100% of the isolates as C. albicans, and no C. dubliniensis could be identified in this study. 84% of the isolates showed proteinase activity, whereas coagulase activity was only detected in 5% of the isolates.

CONCLUSIONS

This study reveals that C. dubliniensis plays no role in vaginal candidiasis in Iranian patients. Proteinase production could be an essential virulence factor in C. albicans pathogenicity, but coagulase activity has less potential in this matter.

Oral mycobiome in community-dwelling elderly and its relation to oral and general health conditions

OBJECTIVE

Oral fungal infection is generally associated with dysbiosis related to antibiotic use, immunodeficiency, or frailty. However, fungal colonization in a typical population without apparent symptoms and its associated conditions are poorly understood. In this study, oral fungal colonization in community-dwelling and independently living elderly populations was evaluated and factors affecting fungal colonization were analyzed.

SUBJECTS AND METHODS

The subjects (410; 181 males and 229 females) were 75-99 years of age; those under prior antibiotic use were excluded. Fungal populations in the saliva were evaluated by PCR-based molecular techniques. Body mass index (BMI), smoking habits, and oral health conditions were examined.

RESULTS

Salivary fungal amounts exceeded 10⁴  CFU/ml in 63 (15.4%) of 410 subjects. Candida albicans was most frequently detected (98.4%), followed by Candida glabrata (54.0%), and Candida dubliniensis (38.1%) in those subjects with fungi at 10⁴  CFU/ml or over. Fungi at 10⁴  CFU/ml or over in the presence of C. glabrata or C. dubliniensis was significantly associated with low BMI.

CONCLUSIONS

Candida albicans, C. glabrata, and C. dubliniensis dominated the oral mycobiome in Japanese community-dwelling elderly. Lower BMI might signify compromised health status and thus could result in susceptibility to specific candidiasis by C. glabrata and C. dubliniensis.

Population structure and molecular genetic characterization of 5-flucytosine-susceptible and -resistant clinical Candida dubliniensis isolates from Kuwait

Candida dubliniensis and Candida albicans are two closely related species. Although C. dubliniensis is less pathogenic, it has a higher propensity to develop resistance to fluconazole and some strains exhibit intrinsic resistance to 5-flucytosine (5-FC). All 5-FC-resistant isolates from Kuwait were previously shown to belong to one of seven internal transcribed spacer (ITS) region of rDNA-based haplotypes. This study performed fingerprinting of C. dubliniensis isolates by multilocus sequence typing (MLST) to determine population structure of 5-FC-resistant and -susceptible strains and compared the results with data from a global collection of isolates. Fifty-two C. dubliniensis isolates previously analyzed and 58 additional isolates mostly collected during 2010–2013 and characterized by phenotypic and molecular methods were used. ITS-based haplotypes were identified by haplotype-specific PCR and/or by PCR-DNA sequencing of rDNA. Population structure was determined by 8-loci-based MLST. E-test was used to determine susceptibility to 5-FC, fluconazole, voriconazole and amphotericin B. Five ITS haplotypes (ITSH) were detected among 110 C. dubliniensis isolates. The ITSH1 was most common (n = 80 isolates) followed by ITSH4 (n = 25 isolates). Two isolates each belonged to ITSH5 and ITSH8 while one isolate belonged to ITSH7. MLST identified 16 diploid sequence types (DSTs) including six new DSTs. DST11 (n = 52) and DST14 (n = 25) were dominant genotypes and were confined (together with DST21) to Middle-Eastern countries. Other DSTs (excluding some new DSTs) had a wider global distribution as they were identified from various other countries. Only ITSH4 isolates (n = 25) belonged to DST14, were resistant to 5-FC and contained S29L mutation in CdFCA1. ITSH5, ITSH7 and ITSH8 isolates belonged to different DSTs. Thus, clinical C. dubliniensis isolates in Kuwait exhibited limited genotypic heterogeneity and most isolates belonged to region-specific DSTs. All 5-FC-resistant C. dubliniensis isolates belonged to ITSH4 and MLST-based DST14 genotype. Placement of some isolates into additional ITS haplotypes is also supported by MLST data.

Prevalence of Candida albicans, Candida dubliniensis and Candida africana in pregnant women suffering from vulvovaginal candidiasis in Argentina

BACKGROUND

Vulvovaginal candidiasis (VVC) is a vulvovaginitis commonly diagnosed in gynecology care. In recent years, the taxonomy of the most important pathogenic Candida species, such as Candida albicans have undergone significant changes.

AIMS

This study examined the prevalence of C. albicans, Candida africana, and Candida dubliniensis in vaginal specimens from 210 pregnant women suffering from vulvovaginitis or having asymptomatic colonization.

METHODS

Phenotypic and molecular methods were used for the identification of the species.

RESULTS

During the studied period, 55 isolates of Candida or other yeasts were obtained from specimens collected from 52 patients suffering from vulvovaginitis (24.8%). C. albicans was the predominant Candida species in 42 isolates (80.7%), either alone or in combination with other species of the genus (5.7%, n=3). Additionally, nine isolates of C. albicans (50%) were obtained from asymptomatic patients (n=18). C. dubliniensis was the causative agent in 2 (3.8%) cases of VVC, and was also isolated in one asymptomatic patient. Molecular assays were carried out using specific PCR to amplify the ACT1-associated intron sequence of C. dubliniensis. The amplification of the HWP1 gene also correctly identified isolates of the species C. albicans and C. dubliniensis. No C. africana was isolated in this work. Some C. albicans isolates were either homozygous or heterozygous at the HWP1 locus. The distribution of heterozygous and homozygous C. albicans isolates at the HWP1 locus was very similar among patients suffering from VVC and asymptomatic patients (p=0.897).

CONCLUSIONS

The presence of C. albicans and C. dubliniensis, and the absence of C. africana in pregnant is noteworthy.

C. dubliniensis in an immunocompetent patient with metal lingual frenulum piercing

Candida spp. are opportunistic unicellular fungi, known to cause oral, vaginal, lung and occasionally systemic infections. Characteristically, they colonize the oral cavity, the mucosal surfaces of the cheek, palate, and tongue. Usually harmless, oral Candidas may become pathogenic under immunosuppressive conditions, dentures presence, or salivary flow impairment. Accurate species identification is important because C. dubliniensis can rapidly develop fluconazole resistance. We report C. dubliniensis in an immunocompetent patient with a metal lingual frenulum piercing.

Effect of dentin on the antimicrobial efficacy of 3% sodium hypochlorite, 2% chlorhexidine, 17% ethylenediaminetetraacetic acid, and 18% etidronic acid on Candida albicans: An in vitro study

AIM

The aim of this study was to evaluate the effect of dentin on the antimicrobial efficacy of 3% sodium hypochlorite, 2% chlorhexidine, 17% EDTA and 18% etidronic acid against C. albicans.

METHODOLOGY

Dentin powder was prepared from mandibular first premolar using electrical grinder and sterilized. 3% NaOCl, 2%CHX, 17% EDTA and 18% etidronic acid were tested against C. albicans in the presence and absence of dentin, in eppendorf tubes. Group 1 (presence of dentin):- 100ul dentin powder + 100ul C. albicans suspension + 100ul irrigating solution. Group 2 (absence of dentin):- 100ul C. albicans suspension+ 100ul irrigating solution.

CONTROL GROUP

- 100ul C. albicans suspension.+ 100ul sterile saline Suspension was thoroughly mixed, submitted for serial dilution upto10-5 after 1 min and colony forming units were counted.

RESULTS

In group 2 (without dentin powder), 3% NaOCl and 2% CHX showed the lowest bacterial count compared to group 1 (with dentin powder). Dentin had a significant inhibitory effect on 3% NaOCl (P < 0.001) and 2% CHX (P<0.001). 17% EDTA showed lowest bacterial count in group 1 (with dentin powder) compared to group 2 (without dentin powder). 18% Etidronic acid showed similar bacterial counts in the both the groups. No reduction was observed in the control group.

CONCLUSION

NaOCl & EDTA showed measurable antimicrobial effect even in the presence of dentin which can be promising in the reduction of C. albicans in root canal therapy.

Sensitivity of clinical isolates of Candida to essential oils from Burseraceae family

The aim of this study was to investigate the chemical composition and antifungal activity of four commercial essential oils from the Burseraceae family - two Boswellia carterii Flueck oils, Canarium luzonicum (Blume) A. Gray oil, and Commiphora myrrha (Nees) Engl oil, against most common Candida spp. recovered from the human oral cavity. The essential oil samples were analyzed by GC-FID and GC/MS. The analysis showed that major essential oils' components were α-pinene (23.04 % and 31.84 %), limonene (45.62 %) and curzerene (34.65 %), respectively. Minimum inhibitory (MIC) and minimum fungicidal (MFC) concentrations were determined using a microdilution standardized technique. All tested Candida spp. clinical isolates and ATCC strains showed susceptibility to tested essential oils in a dose dependent manner. The strongest antifungal activity was shown by essential oil of B. carterii, sample 2; the average MIC values ranged from 1.25 to 1.34 mg/ml, and MFC values ranged from 2.50 to 3.75 mg/ml, depending on the fungus. This study supports the possible use of essential oils from the Bursecaceae family in reduction and elimination of Candida spp. populations in patients with oral cavity fungal infections.

Survey and analysis of simple sequence repeats (SSRs) in three genomes of Candida species

Simple sequence repeats (SSRs) or microsatellites, which composed of tandem repeated short units of 1-6 bp, have been paying attention continuously. Here, the distribution, composition and polymorphism of microsatellites and compound microsatellites were analyzed in three available genomes of Candida species (Candida dubliniensis, Candida glabrata and Candida orthopsilosis). The results show that there were 118,047, 66,259 and 61,119 microsatellites in genomes of C. dubliniensis, C. glabrata and C. orthopsilosis, respectively. The SSRs covered more than 1/3 length of genomes in the three species. The microsatellites, which just consist of bases A and (or) T, such as (A)n, (T)n, (AT)n, (TA)n, (AAT)n, (TAA)n, (TTA)n, (ATA)n, (ATT)n and (TAT)n, were predominant in the three genomes. The length of microsatellites was focused on 6 bp and 9 bp either in the three genomes or in its coding sequences. What's more, the relative abundance (19.89/kbp) and relative density (167.87 bp/kbp) of SSRs in sequence of mitochondrion of C. glabrata were significantly great than that in any one of genomes or chromosomes of the three species. In addition, the distance between any two adjacent microsatellites was an important factor to influence the formation of compound microsatellites. The analysis may be helpful for further studying the roles of microsatellites in genomes' origination, organization and evolution of Candida species.

Novel strategies against Candida biofilms: interest of synthetic compounds

A biofilm is a consortium of microbial cells that are attached to a substratum or an interface. It should be considered a reservoir that may induce serious infections. Indeed, Candidaspp. biofilms may be involved in the persistence or worsening of some chronic inflammatory diseases as well as in systemic infections, which may lead to high morbidity and mortality rates. New strategies are currently being explored, utilizing several synthetic compounds to prevent or fight these Candida biofilms. This article focuses on active synthetic compounds classified with regards to their modes of action: inhibition of early adherence phase, inhibition or control of biofilm maturation and finally elimination of already formed biofilms. Some of them show promise in fighting biofilm.

Characterising atypical Candida albicans clinical isolates from six third-level hospitals in Bogotá, Colombia

BACKGROUND

Candida species are the most frequently found fungal pathogens causing nosocomial disease in a hospital setting. Such species must be correctly identified to ensure that appropriate control measures are taken and that suitable treatment is given for each species. Candida albicans is causing most fungal disease burden worldwide; the challenge lies in differentiating it from emerging atypical, minor and related species such as Candida dubliniensis and Candida africana. The purpose of this study was to compare identification based on MALDI-TOF MS to standard identification systems using a set of nosocomial isolates.

METHODS

Eleven nosocomial samples were collected from 6 third-level hospitals in Bogotá, Colombia. All the samples were identified by combining MALDI-TOF MS with morphological characters, carbohydrate assimilation and molecular markers (D1/D2 and HWP1).

RESULTS

The present work describes the first collection of atypical Colombian Candida clinical isolates; these were identified as Candida albicans/Candida africana by their MALDI-TOF MS profile. Phenotypical characteristics showed that they were unable to produce chlamydospores, assimilate trehalose, glucosamine, N- acetyl-glucosamine and barely grew at 42 °C, as would be expected for Candida africana. The molecular identification of the D1/D2 region of large subunit ribosomal RNA and HWP1 hyphal cell wall protein 1 sequences from these isolates was consistent with those for Candida albicans. The mass spectra obtained by MALDI-TOF MS were analysed by multi-dimensional scaling (MDS) and cluster analysis, differences being revealed between Candida albicans, Candida africana, Candida dubliniensis reference spectra and two clinical isolate groups which clustered according to the clinical setting, one of them being clearly related to C. albicans.

CONCLUSION

This study highlights the importance of using MALDI-TOF MS in combination with morphology, substrate assimilation and molecular markers for characterising Candida albicans-related and atypical C. albicans species, thereby overcoming conventional identification methods. This is the first report of hospital-obtained isolates of this type in Colombia; the approach followed might be useful for gathering knowledge regarding local epidemiology which could, in turn, have an impact on clinical management. The findings highlight the complexity of distinguishing between typical and atypical Candida albicans isolates in hospitals.

Comparison of Switching and Biofilm Formation between MTL-Homozygous Strains of Candida albicans and Candida dubliniensis

Candida albicans and Candida dubliniensis are highly related species that share the same main developmental programs. In C. albicans, it has been demonstrated that the biofilms formed by strains heterozygous and homozygous at the mating type locus (MTL) differ functionally, but studies rarely identify the MTL configuration. This becomes a particular problem in studies of C. dubliniensis, given that one-third of natural strains are MTL homozygous. For that reason, we have analyzed MTL-homozygous strains of C. dubliniensis for their capacity to switch from white to opaque, the stability of the opaque phenotype, CO2 induction of switching, pheromone induction of adhesion, the effects of minority opaque cells on biofilm thickness and dry weight, and biofilm architecture in comparison with C. albicans. Our results reveal that C. dubliniensis strains switch to opaque at lower average frequencies, exhibit a far lower level of opaque phase stability, are not stimulated to switch by high CO2, exhibit more variability in biofilm architecture, and most notably, form mature biofilms composed predominately of pseudohyphae rather than true hyphae. Therefore, while several traits of MTL-homozygous strains of C. dubliniensis appear to be degenerating or have been lost, others, most notably several related to biofilm formation, have been conserved. Within this context, the possibility is considered that C. dubliniensis is transitioning from a hypha-dominated to a pseudohypha-dominated biofilm and that aspects of C. dubliniensis colonization may provide insights into the selective pressures that are involved.

In Vitro Antimicrobial and Antiproliferative Activity of Amphipterygium adstringens

Amphipterygium adstringens is a plant widely used in Mexican traditional medicine for its known anti-inflammatory and antiulcer properties. In this work, we evaluated the in vitro antimicrobial and antiproliferative activities of the methanolic extract of A. adstringens against oral pathogens such as Streptococcus mutans, Porphyromonas gingivalis, Aggregatibacter actinomycetemcomitans, Candida albicans, and Candida dubliniensis, using microdilution (MIC) and agar diffusion methods (MBC), and the antiproliferative activity evaluating total growth inhibition (TGI) by staining the protein content with sulforhodamine B (SRB), using nine human cancer cell lines. Crude extract (CE) of A. adstringens showed some degree of activity against one or more of the strains with a MIC from 0.125 mg/mL to 63 mg/mL and MBC from 1.6 to 6.3 mg/mL and cytotoxic activity, particularly against NCI-ADR/RES, an ovarian cell line expressing multiple resistance drugs phenotype. The CE is a complex mixture of possible multitarget metabolites that could be responsible for both antimicrobial and antiproliferative activities, and further investigation is required to elucidate the identity of active compounds. Nevertheless the CE itself is useful in the development of new antimicrobial treatment based on natural products to prevent oral diseases and as alternative natural source for cancer treatment and prevention.

Candida albicans bloodstream isolates in a German university hospital are genetically heterogenous and susceptible to commonly used antifungals

From an eight-year-span, 99 Candida bloodstream isolates were collected at the University Hospital Wuerzburg, Germany. In this study, all strains were analyzed using molecular and phenotypic typing methods. Confirmatory species identification revealed three isolates that were initially diagnosed as C. albicans to be actually C. dubliniensis. Two isolates contained a mixed culture of C. albicans and C. glabrata, in one of the specimens both species could be separated while it was not possible to recover C. albicans in the other sample. The remaining 95 C. albicans isolates were profiled by multilocus sequence typing (MLST). Phylogenetic analyses showed a highly heterogenous collection of strains, associated with many different clades and constituting a set of new diploid sequence types (DST). For all strains with identical DST, patient data were reviewed for potential nosocomial transmission. In addition, all isolates were tested for their susceptibility to amphotericin B, caspofungin, fluconazole, itraconazole, posaconazole and voriconazole. No clinically relevant resistance could be detected. Furthermore, these data underline that correlation between minimal inhibitory concentrations for caspofungin and anidulafungin is low.

Csr1/Zap1 Maintains Zinc Homeostasis and Influences Virulence in Candida dubliniensis but Is Not Coupled to Morphogenesis

The supply and intracellular homeostasis of trace metals are essential for every living organism. Therefore, the struggle for micronutrients between a pathogen and its host is an important determinant in the infection process. In this work, we focus on the acquisition of zinc by Candida dubliniensis, an emerging pathogen closely related to Candida albicans. We show that the transcription factor Csr1 is essential for C. dubliniensis to regulate zinc uptake mechanisms under zinc limitation: it governs the expression of the zinc transporter genes ZRT1, ZRT2, and ZRT3 and of the zincophore gene PRA1. Exclusively, artificial overexpression of ZRT2 partially rescued the growth defect of a csr1Δ/Δ mutant in a zinc-restricted environment. Importantly, we found that, in contrast to what is seen in C. albicans, Csr1 (also called Zap1) is not a major regulator of dimorphism in C. dubliniensis. However, although a csr1Δ/Δ strain showed normal germ tube formation, we detected a clear attenuation in virulence using an embryonated chicken egg infection model. We conclude that, unlike in C. albicans, Csr1 seems to be a virulence factor of C. dubliniensis that is not coupled to filamentation but is strongly linked to zinc acquisition during pathogenesis.