Epidemiology and antifungal susceptibility of candidemia isolates of non-albicans Candida species from cancer patients

Carbon substrates promotes stress resistance and drug tolerance in clinical isolates of Candida tropicalis

Candida tropicalis is a human pathogen and one of the most prevalent non-Candida albicans Candida (NCAC) species causing invasive infections. Azole antifungal resistance in C. tropicalis is also gradually increasing with the increasing incidence of infections. The pathogenic success of C. tropicalis depends on its effective response in the host microenvironment. To become a successful pathogen, cellular metabolism, and physiological status determine the ability of the pathogen to counter diverse stresses inside the host. However, to date, limited knowledge is available on the impact of carbon substrate metabolism on stress adaptation and azole resistance in C. tropicalis. In this study, we determined the impact of glucose, fructose, and sucrose as the sole carbon source on the fluconazole resistance and osmotic (NaCl), oxidative (H2O2) stress adaptation in C. tropicalis clinical isolates. We confirmed that the abundance of carbon substrates influences or increases drug resistance and osmotic and oxidative stress tolerance in C. tropicalis. Additionally, both azole-resistant and susceptible isolates showed similar stress adaptation phenotypes, confirming the equal efficiency of becoming successful pathogens irrespective of drug susceptibility profile. To the best of our knowledge, our study is the first on C. tropicalis to demonstrate the direct relation between carbon substrate metabolism and stress tolerance or drug resistance.

Fruits are vehicles of drug-resistant pathogenic Candida tropicalis

IMPORTANCE

Of 123 identified isolates from the fruit surface, C. tropicalis was the most frequently found species, followed by Meyerozyma caribbica and Candida krusei. All three fluconazole-resistant C. tropicalis were non-susceptible to voriconazole and belonged to the same predominant genotype of azole-resistant C. tropicalis causing candidemia in patients in Taiwan. Our findings provide evidence that fruit should be washed before eaten not only to remove chemicals but also potential drug-resistant pathogenic microbes, especially for immunocompromised individuals. To keep precious treatment options in patients, we not only continuously implement antimicrobial stewardship in hospitals but also reducing/stopping the use of agricultural fungicide classes used in human medicine.

The impact of increasing non-albicans Candida trends on diagnostics in immunocompromised patients

Invasive candidiasis (IC) represents a growing concern worldwide, with a considerable increase in non-albicans Candida (NAC) species. The study's primary goal was to determine if species identification by semi-nested PCR (sn-PCR) with primers for the five most prevalent Candida species is sufficient to deal with the current trends of Candida infections in cancer patients. Over one year, Candida isolates were collected from samples of patients with hematological and solid organ tumors in a single center. Species of Candida were identified by chromagar and multiplex sn-PCR using specific primers for Candida albicans, Candida tropicalis, Candida glabrata, Candida krusei, and the Candida parapsilosis complex. Most Candida infection episodes are caused by NAC species (70.5% of 105 isolates). Rare species (14 isolates) accounted for 13.3% of isolates and were not identified by sn-PCR using the five most common Candida species primers. More than half of these rare species caused candidemia in cancer patients (57.1%; p = 0.011). The risk factor for candidiasis was recent surgeries (p = 0.020) in adults and chemotherapy in pediatric patients (p = 0.006). Prolonged hospitalization and genitourinary tract cancer were significantly associated with invasive infections (p = 0.005 and 0.049, respectively). Recent surgery was a significant risk factor associated with C. parapsilosis and C. glabrata infections (P = 0.038 and 0.003, respectively), while C. tropicalis was significantly more common in patients with hematological malignancies (P = 0.012). Techniques with a broader identification spectrum than the major five Candida species are crucial for the optimal management of cancer patients.

Analysis of CDR1 and MDR1 Gene Expression and ERG11 Substitutions in Clinical Candida tropicalis Isolates from Alexandria, Egypt

INTRODUCTION

Candida tropicalis is a common non-albicans Candida (NAC) species that causes numerous fungal infections. Increasing antifungal resistance to azoles in NAC is becoming a major health problem worldwide; however, in Egypt, almost no data is available regarding fluconazole resistance mechanisms in C. tropicalis. The current study aims to investigate two possible important molecular mechanisms involved in fluconazole resistance in C. tropicalis isolates.

MATERIALS

Fifty-four clinical C. tropicalis isolates were included. Identification and antifungal susceptibility profiles of the isolates were carried out using the VITEK 2 compact system. The molecular investigation of fluconazole resistance included the expression of the CDR1 and MDR1 genes by quantitative real-time RT-PCR as well as the sequence analysis of the ERG11 gene.

RESULTS

Antifungal susceptibility testing identified 30 fluconazole-non-susceptible isolates. Statistically, CDR1 gene expression in fluconazole-non-susceptible isolates was significantly higher than that in fluconazole-susceptible isolates, with MDR1 gene expression levels that were similar in both non-susceptible and susceptible isolates. Sequence analysis of the ERG11 gene of 26 fluconazole-resistant isolates identified two missense mutations: A395T (Y132F) and G1390A (G464S).

CONCLUSIONS

This study has highlighted the role of overexpression of the CDR1 gene and ERG11 gene mutations in fluconazole non-susceptibility. Further studies in Egypt are required to investigate other possible molecular mechanisms involved in azole resistance.

Port implantation-related bloodstream infection caused by Wickerhamomyces myanmarensis: A case report

Background and Purpose

Wickerhamomyces myanmarensis is a new opportunistic yeast previously named Pichai myanmarensis, which belongs to the order Saccharomycetales. Since its discovery, one environmental isolate of W. myanmarensis has been reported from Myanmar, and one clinical sample from Iran.

Case Report

We report a case of bloodstream infection related to an implantable venous access port. W. myanmarensis was isolated from patient's blood after chemotherapy, which was meant to control and heal T-cell lymphoblastic lymphoma. Broth dilution minimum inhibitory concentrations were performed according to the CLSI M27-A3 document. The patient recovered with intravenous voriconazole and was discharged with the recommended prescription of oral voriconazole as a maintenance drug.

Conclusion

So far, only one case of W. myanmarensis fungemia has been reported in the world in 2019. This is the second case of bloodstream infection with this yeast from a patient undergoing chemotherapy in Iran.

Multilocus sequence typing (MLST) analysis reveals many novel genotypes and a high level of genetic diversity in Candida tropicalis isolates from Italy and Africa

BACKGROUND

Candida tropicalis is a human pathogenic yeast frequently isolated in Latin America and Asian-Pacific regions, although recent studies showed that it is also becoming increasingly widespread throughout several African and south-European countries. Nevertheless, relatively little is known about its global patterns of genetic variation as most of existing multilocus sequence typing (MLST) data come from Asia and there are no genotyped African isolates.

OBJECTIVES

We report detailed genotyping data from a large set of C. tropicalis isolates recovered from different clinical sources in Italy, Egypt and Cameroon in order to expand the allele/genotype library of MLST database (https://pubmlst.org/ctropicalis), and to explore the genetic diversity in this species.

METHODS

A total of 103 C. tropicalis isolates were genotyped using the MLST scheme developed for this species. All isolates were also tested for in vitro susceptibility to various antifungals to assess whether certain genotypes were associated with drug-resistance.

RESULTS AND CONCLUSIONS

A total of 104 different alleles were detected across the MLST-loci investigated. The allelic diversity found at these loci resulted in 51 unique MLST genotypes of which 36 (70.6%) were novel. Global optimal eBURST analysis identified 18 clonal complexes (CCs) and confirm the existence of a specific Italian-cluster (CC36). Three CCs were also statistically associated with fluconazole resistance, which was elevated in Cameroon and Egypt. Our data show high genetic diversity in our isolates suggesting that the global population structure of C. tropicalis is still poorly understood. Moreover, its clinical impact in Italy, Egypt and Cameroon appears to be relevant and should be carefully considered.

Interactions between Candida albicans and the resident microbiota

Candida albicans is a prevalent, opportunistic human fungal pathogen. It usually dwells in the human body as a commensal, however, once in its pathogenic state, it causes diseases ranging from debilitating superficial to life-threatening systemic infections. The switch from harmless colonizer to virulent pathogen is, in most cases, due to perturbation of the fungus-host-microbiota interplay. In this review, we focused on the interactions between C. albicans and the host microbiota in the mouth, gut, blood, and vagina. We also highlighted important future research directions. We expect that the evaluation of these interplays will help better our understanding of the etiology of fungal infections and shed new light on the therapeutic approaches.

Systematic Characterization of Epidemiology, Antifungal Susceptibility, Risk Factors and Outcomes of Candidaemia: A Six-Year Chinese Study

Background

Candida bloodstream infection (BSI), the fourth most common nosocomial BSI, is an urgent global health challenge with the tremendous growth in antifungal resistance rate and mortality rate.

Purpose

To establish the epidemiology, species distribution, risk factors, and 30-day mortality of candidaemia among 115 patients in this 6-year surveillance study.

Materials and Methods

We retrospectively analyzed the clinical characteristics, epidemiology, antifungal susceptibility patterns, and risk factors for morbidity and mortality of 115 candidaemia cases diagnosed in one tertiary care hospital from January 2016 through December 2021.

Results

Of the 115 candidaemia cases, the most prevalent species were Candida tropicalis (33.0%), followed by Candida albicans (27.8%), Candida parapsilosis complex (19.1%), and others. The overall incidence was 0.21 cases/1000 admissions. The overall crude resistance rate of Candida spp. against azoles was 20.0% (23/115), while Candida tropicalis showed a significant increase in the resistance rate to azoles (from 1/6, 16.7% in 2017 to 6/10, 60.0% in 2021). Multivariate analyses demonstrated that hematological malignancy and neutropenia were significantly associated with Candida tropicalis BSI than Candida non-tropicalis BSI. Candida albicans BSI had a significantly higher rate of previous surgery than Candida non-albicans BSI. Candida parapsilosis BSI had a significantly higher rate of receiving total parenteral nutrition (TPN). The overall 30-day mortality rate was 27.0% (31/115). The presence of high age-adjusted Charlson comorbidity index (aCCI), neutropenia, and septic shock were factors independently associated with increased 30-day mortality.

Conclusion

Candida tropicalis are emerging as the predominant isolate in candidaemia. Of note, the unexpectedly increased resistance rate to azoles in Candida tropicalis BSI was observed. The aCCI scores, neutropenia, and septic shock were independently associated with 30-day mortality. Prompt, adequate antifungal treatment among high-risk patients may lead to a reduction in mortality.

Mechanisms of azole antifungal resistance in clinical isolates of Candida tropicalis

This study was designed to understand the molecular mechanisms of azole resistance in Candida tropicalis using genetic and bioinformatics approaches. Thirty-two azole-resistant and 10 azole-susceptible (S) clinical isolates of C. tropicalis were subjected to mutation analysis of the azole target genes including ERG11. Inducible expression analysis of 17 other genes potentially associated with azole resistance was also evaluated. Homology modeling and molecular docking analysis were performed to study the effect of amino acid alterations in mediating azole resistance. Of the 32 resistant isolates, 12 (37.5%) showed A395T and C461T mutations in the ERG11 gene. The mean overexpression of CDR1, CDR3, TAC1, ERG1, ERG2, ERG3, ERG11, UPC2, and MKC1 in resistant isolates without mutation (R-WTM) was significantly higher (p<0.05) than those with mutation (R-WM) and the sensitive isolates (3.2-11 vs. 0.2-2.5 and 0.3-2.2 folds, respectively). Although the R-WTM and R-WM had higher (p<0.05) CDR2 and MRR1 expression compared to S isolates, noticeable variation was not seen among the other genes. Protein homology modelling and molecular docking revealed that the mutations in the ERG11 gene were responsible for structural alteration and low binding efficiency between ERG11p and ligands. Isolates with ERG11 mutations also presented A220C in ERG1 and together T503C, G751A mutations in UPC2. Nonsynonymous mutations in the ERG11 gene and coordinated overexpression of various genes including different transporters, ergosterol biosynthesis pathway, transcription factors, and stress-responsive genes are associated with azole resistance in clinical isolates of C. tropicalis.

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

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

Advances in prophylaxis and treatment of invasive fungal infections: perspectives on hematologic diseases

Invasive fungal infections (IFIs) are common causes of mortality and morbidity in patients with hematologic diseases. Delayed initiation of antifungal treatment is related to mortality. Aspergillus sp. is the leading cause of IFI followed by Candida sp. Diagnosis is often challenging owing to variable conditions related to underlying diseases. Clinical suspect and prompt management is important. Imaging, biopsy, and non-culture-based tests must be considered together. New diagnostic procedures have been improved, including antigen-based assays and molecular detection of fungal DNA. Among hematologic diseases, patients with acute myeloid leukemia, myelodysplastic syndrome, recipients of hematopoietic stem cell transplantation are at high risk for IFIs. Antifungal prophylaxis is recommended for these high-risk patients. There are continuous attempts to achieve ideal management of IFIs. Scoring system for quality control has been developed with important recommendations of current guidelines. Higher adherence to guidelines is related to decreased mortality in IFIs.

Candidemia in patients with head and neck cancer: mortality and a novel risk factor

PURPOSE

Candidemia is a bloodstream infection (BSI) by Candida spp. and is associated with high mortality. However, there have been few reports about BSI in head and neck cancer (HNC). We aimed to evaluate the impact of candidemia in patients with HNC and compared it with bacteremia.

STUDY DESIGN

A multicenter retrospective study.

METHODS

We retrospectively analyzed 83 BSI episodes in HNC (2011 to 2020) and divided them into the candidemia and bacteremia groups. We then compared the survival rate and risk factors for candidemia between the groups.

RESULTS

The overall cumulative incidence (risk) of candidemia in BSI was 12 out of 83 episodes (14.5%). The 1-year mortality for the bacteremia and candidemia groups was 33.3% and 58.3%, respectively (log-rank p = 0.041). Broad-spectrum antibiotics (odds ratio [OR]: 29.5; 95% confidence interval [CI], 2.49-350), mucositis (OR 11.0; 95% CI, 1.52-80.1), and malignant wounds (OR 79.5; 95% CI 1.33-4737) were significant risk factors for candidemia in HNC.

CONCLUSIONS

Candidemia causes high mortality in patients with HNC. To our knowledge, malignant wounds have not been previously reported as a risk factor for candidemia. For early diagnosis and treatment of candidemia, risk factors should be considered, and antifungal therapy started earlier.

The influence of the chemical composition of essential oils of Clausena lansium seeds on the growth of Candida strains

Clausena lansium (Lour.) Skeels seeds have been shown to have diverse beneficial medical value due to their unique active components. This study analysed the composition of essential oils (EOs) of C. lansium seeds and investigated their potential antifungal effects against Candida strains. A total of forty-six components were identified in all samples by gas chromatography-mass spectrometry (GC–MS). The main components were sabinene, β-phellandrene and 4-terpineol. Thirteen EOs of C. lansium seeds were classified into three clusters based on their components. Cluster analysis showed that the difference between the tropics and subtropics was the greatest. These EOs and the three main chemicals showed different antifungal activities against five Candida species (C. albicans, C. tropicalis, C. glabrata, C. krusei and C. parapsilosis). The antifungal activity against C. glabrata and C. krusei was higher than that against other Candida strains. EOs of C. lansium seeds displayed noteworthy antifungal activity against both sensitive and fluconazole-resistant strains, with inhibition zone diameters in the range of 9.4–23.4 mm. Comprehensive analysis illustrated the importance of sabinene, β-phellandrene and 4-terpineol to antifungal activity, and there may be some synergistic effects with other components. These results represent the first report about the correlation between the chemical composition of EOs of C. lansium seeds and antifungal activity. Taken together, the results obtained provide scientific evidence for the traditional use of C. lansium seeds waste.

A Study on Prevalence and Characterization of Candida Species in Immunocompromised Patients

Candida spp. is one among the major causes of nosocomial infection, with candidemia gaining increasing prevalence worldwide in parallel with mortality rates ranging from 10-49%. Epidemiology and predisposing factors of candidemia have changed since the number of patients receiving transplants and immunosuppressive therapy, the use of broadspectrum antimicrobials, and the number of AIDS patients have increased. Candidemia is more common among patients with subcutaneous and cutaneous candida infections, through percutaneous inoculation. Major predisposing factors for invasive candidiasis includes neutropenia, haematological malignancies, bone marrow transplantation, total parenteral nutrition, chemotherapy, invasive procedures, and immune-suppressive agents. This study analyses the risk factors of immunocompromised patients with candidemia and antibiogram of Candida spp. isolated from ICU patients. To evaluate the prevalence, distribution and antibiogram of Candida spp., associated risk factors, and outcome in candidemia patients. Blood samples received from patients with clinically suspected fungal infections were subjected to gram staining, culture, sugar assimilation & fermentation, Candida Chrome agar (CCA) & Corn meal agar for identification and speciation. Antifungal susceptibility tests were performed by disk-diffusion tests. Among a total of 337 samples received, 22 (6.5%) samples were positive for candida infections, of which Candida tropicalis 9 (41%) was the predominant isolate followed by C. albicans 5 (23%), Candida glabrata 4 (18%), Candida parapsilosis 2 (9%) and Candida krusei 2 (9%). Male patients had a higher prevalence of candidemia 15 (68.2%). Among the age group of 51-70 years, uncontrolled DM(Diabetes mellitus) and CKD (chronic kidney disease) were found to be the predominant co-morbidities with candidemia.

Impact of Nutritional Assessment on the Clinical Outcomes of Patients with Non-albicans Candidemia: A Multicenter Study

Several studies have demonstrated that malnutrition is a negative prognostic factor for clinical outcomes. However, there is limited evidence for the effect of malnutrition on clinical outcomes in patients with candidemia. We investigated the relationship between malnutrition and all-cause 28-day mortality among patients with non-albicans candidemia. Between July 2011 and June 2014, all adult patients with non-albicans candidemia, including C. tropicalis, C. glabrata, C. parapsilosis and so on, were enrolled. The Malnutrition Universal Screening Tool (MUST) scores were used to determine the patients' nutritional status before the onset of candidemia. A total of 378 patients were enrolled; 43.4% developed septic shock and 57.1% had a high risk of malnutrition (MUST ≥ 2). The all-cause 28-day mortality rate was 40.7%. The Cox proportional hazards model revealed that C. tropicalis (HR, 2.01; 95% CI, 1.24-3.26; p = 0.005), Charlson comorbidity index (HR, 1.10; 95% CI, 1.03-1.18; p = 0.007), Foley catheter use (HR, 1.68; 95% CI, 1.21-1.35; p = 0.002), concomitant bacterial infections (HR, 1.55; 95% CI, 1.11-2.17; p = 0.010), low platelet count (HR, 3.81; 95% CI, 2.45-5.91; p < 0.001), not receiving antifungals initially (HR, 4.73; 95% CI, 3.07-7.29; p < 0.001), and MUST ≥ 2 (HR, 1.54; 95% CI, 1.09-2.17; p = 0.014) were independently associated with all-cause 28-day mortality. A simple screening tool for nutritional assessment should be used for patients with non-albicans candidemia to detect early clinical deterioration, and a tailored nutritional care plan should be established for malnourished individuals, to improve their clinical outcomes.

Virulence Factors and Azole-Resistant Mechanism of Candida Tropicalis Isolated from Candidemia

BACKGROUND

Limited knowledge exists on the virulence factors of Candida tropicalis and the mechanisms of azole resistance that lead to an intensified pathogenicity and treatment failure. We aimed to evaluate the virulence factors and molecular mechanisms of azole resistance among C. tropicalis isolated from patients with candidemia.

MATERIALS AND METHODS

Several virulence factors, including extracellular enzymatic activities, cell surface hydrophobicity (CSH), and biofilm formation, were evaluated. Antifungal susceptibility pattern and expression level of ERG11, UPC2, MDR1, and CDR1 genes of eight (4 fluconazole resistance and 4 fluconazole susceptible) clinical C. tropicalis isolates were assessed. The correlation between the virulence factors and antifungal susceptibility patterns was analyzed.

RESULTS

During a 4 year study, forty-five C. tropicalis isolates were recovered from candidemia patients. The isolates expressed different frequencies of virulence determinants as follows: coagulase 4 (8.9%), phospholipase 5 (11.1%), proteinase 31 (68.9%), esterase 43 (95.6%), hemolysin 44 (97.8%), biofilm formation 45 (100%) and CSH 45(100%). All the isolates were susceptible to amphotericin B and showed the highest resistance to voriconazole. There was a significant positive correlation between micafungin minimum inhibitory concentrations (MICs) and hemolysin production (r_s = 0.316). However, we found a negative correlation between fluconazole MICs and esterase production (r_s = -0.383). We observed the high expression of ERG11 and UPC2 genes in fluconazole-resistant C. tropicalis isolates.

CONCLUSION

C. tropicalis isolated from candidemia patients extensively displayed capacities for biofilm formation, hemolysis, esterase activity, and hydrophobicity. In addition, the overexpression of ERG11 and UPC2 genes was considered one of the possible mechanisms of azole resistance.

Candida auris: Epidemiology, Diagnosis, Pathogenesis, Antifungal Susceptibility, and Infection Control Measures to Combat the Spread of Infections in Healthcare Facilities

Candida auris, a recently recognized, often multidrug-resistant yeast, has become a significant fungal pathogen due to its ability to cause invasive infections and outbreaks in healthcare facilities which have been difficult to control and treat. The extraordinary abilities of C. auris to easily contaminate the environment around colonized patients and persist for long periods have recently resulted in major outbreaks in many countries. C. auris resists elimination by robust cleaning and other decontamination procedures, likely due to the formation of 'dry' biofilms. Susceptible hospitalized patients, particularly those with multiple comorbidities in intensive care settings, acquire C. auris rather easily from close contact with C. auris-infected patients, their environment, or the equipment used on colonized patients, often with fatal consequences. This review highlights the lessons learned from recent studies on the epidemiology, diagnosis, pathogenesis, susceptibility, and molecular basis of resistance to antifungal drugs and infection control measures to combat the spread of C. auris infections in healthcare facilities. Particular emphasis is given to interventions aiming to prevent new infections in healthcare facilities, including the screening of susceptible patients for colonization; the cleaning and decontamination of the environment, equipment, and colonized patients; and successful approaches to identify and treat infected patients, particularly during outbreaks.

Current and promising pharmacotherapeutic options for candidiasis

Introduction: Candida spp. are commensal yeasts capable of causing infections such as superficial, oral, vaginal, or systemic infections. Despite medical advances, the antifungal pharmacopeia remains limited and the development of alternative strategies is needed.Areas covered: We discuss available treatments for Candida spp. infections, highlighting advantages and limitations related to pharmacokinetics, cytotoxicity, and antimicrobial resistance. Moreover, we present new perspectives to improve the activity of the available antifungals, discussing their immunomodulatory potential and advances on drug delivery carriers. New therapeutic approaches are presented including recent synthesized antifungal compounds (Enchochleated-Amphotericin B, tetrazoles, rezafungin, enfumafungin, manogepix and arylamidine); drug repurposing using a diversity of antibacterial, antiviral and non-antimicrobial drugs; combination therapies with different compounds or photodynamic therapy; and innovations based on nano-particulate delivery systems.Expert opinion: With the lack of novel drugs, the available assets must be leveraged to their best advantage through modifications that enhance delivery, efficacy, and solubility. However, these efforts are met with continuous challenges presented by microbes in their infinite plight to resist and survive therapeutic drugs. The pharmacotherapeutic options in development need to focus on new antimicrobial targets. The success of each antimicrobial agent brings strategic insights to the next phased approach in treatingCandida spp. infections.

Reversal of azole resistance in Candida albicans by oridonin

OBJECTIVES

Candida albicans is a yeast that causes fungal infections with high mortality and is typically resistant to azole drugs. To overcome this resistance, we explored the combined use of oridonin (ORI) and three azole drugs, namely fluconazole (FLC), itraconazole (ITR) and voriconazole (VOR). Azole-resistant C. albicans strains were obtained from cancer patients and the reversal of drug resistance in these strains was investigated.

METHODS

The synergistic antifungal activity of ORI and azole drugs was measured by checkerboard microdilution and time-kill assays. The resistance reversal mechanisms, namely inhibition of drug efflux and induction of apoptosis, were investigated by flow cytometry. Expression levels of the efflux pump-related genesCDR1 and CDR2 were assessed by RT-qPCR.

RESULTS

The efflux pump inhibition assay with ORI showed that the minimum inhibitory concentrations (MICs) of FLC (128-fold), ITR (64-fold) and VOR (250-fold) decreased significantly. Upregulation of genes encodingCDR1 and CDR2 was confirmed in the resistant strain. The sensitising effect of ORI on FLC in the treatment of C. albicans also included the promotion of apoptosis.

CONCLUSION

We demonstrated that combining azoles with ORI exerted potent synergism and that ORI could promote sensitisation to azoles in azole-resistantC. albicans. The discovery that ORI can effectively inhibit drug efflux and promote apoptosis may provide new insights and therapeutic strategies to overcome increasing azole resistance in C. albicans.

Rapid detection of ERG11 polymorphism associated azole resistance in Candida tropicalis

Increasing reports of azole resistance in Candida tropicalis, highlight the development of rapid resistance detection techniques. Nonsynonymous mutations in the lanosterol C14 alpha-demethylase (ERG11) gene is one of the predominant mechanisms of azole resistance in C. tropicalis. We evaluated the tetra primer-amplification refractory mutation system-PCR (T-ARMS-PCR), restriction site mutation (RSM), and high-resolution melt (HRM) analysis methods for rapid resistance detection based on ERG11 polymorphism in C. tropicalis. Twelve azole-resistant and 19 susceptible isolates of C. tropicalis were included. DNA sequencing of the isolates was performed to check the ERG11 polymorphism status among resistant and susceptible isolates. Three approaches T-ARMS-PCR, RSM, and HRM were evaluated and validated for the rapid detection of ERG11 mutation. The fluconazole MICs for the 12 resistant and 19 susceptible isolates were 32–256 mg/L and 0.5–1 mg/L, respectively. The resistant isolates showed A339T and C461T mutations in the ERG11 gene. The T-ARMS-PCR and RSM approaches discriminated all the resistant and susceptible isolates, whereas HRM analysis differentiated all except one susceptible isolate. The sensitivity, specificity, analytical sensitivity, time, and cost of analysis suggests that these three methods can be utilized for the rapid detection of ERG11 mutations in C. tropicalis. Additionally, an excellent concordance with DNA sequencing was noted for all three methods. The rapid, sensitive, and inexpensive T-ARMS-PCR, RSM, and HRM approaches are suitable for the detection of azole resistance based on ERG11 polymorphism in C. tropicalis and can be implemented in clinical setups for batter patient management.

Drug-Resistant Fungi: An Emerging Challenge Threatening Our Limited Antifungal Armamentarium

The high clinical mortality and economic burden posed by invasive fungal infections (IFIs), along with significant agricultural crop loss caused by various fungal species, has resulted in the widespread use of antifungal agents. Selective drug pressure, fungal attributes, and host- and drug-related factors have counteracted the efficacy of the limited systemic antifungal drugs and changed the epidemiological landscape of IFIs. Species belonging to Candida, Aspergillus, Cryptococcus, and Pneumocystis are among the fungal pathogens showing notable rates of antifungal resistance. Drug-resistant fungi from the environment are increasingly identified in clinical settings. Furthermore, we have a limited understanding of drug class-specific resistance mechanisms in emerging Candida species. The establishment of antifungal stewardship programs in both clinical and agricultural fields and the inclusion of species identification, antifungal susceptibility testing, and therapeutic drug monitoring practices in the clinic can minimize the emergence of drug-resistant fungi. New antifungal drugs featuring promising therapeutic profiles have great promise to treat drug-resistant fungi in the clinical setting. Mitigating antifungal tolerance, a prelude to the emergence of resistance, also requires the development of effective and fungal-specific adjuvants to be used in combination with systemic antifungals.

Multilocus Sequence Typing Reveals Clonality of Fluconazole-Nonsusceptible Candida tropicalis: A Study From Wuhan to the Global

Candida tropicalis is a globally distributed human pathogenic yeast, and its increasing resistance to azoles makes clinical treatment difficult. In this study, we investigated the clinical features, azole resistance and genetic relatedness of 87 C. tropicalis isolates from central China and combined with the global database to explore the relationship between genetic information and fluconazole susceptibility. Of the 55 diploid sequence types (DSTs) identified by multilocus sequence typing (MLST), 27 DSTs were new to the C. tropicalis MLST database. Fluconazole-nonsusceptible (FNS) isolates were genetically closely related. goeBURST analysis showed that DST225, DST376, DST506, and DST546 formed a distinct and unique FNS clonal complex (CC) in Wuhan. The local FNS CC belongs to the large FNS CC (CC2) in China, in which the putative founder DST225 has been reported from the environment. The three most prevalent types (DST506, DST525, and DST546) in Wuhan had high minimum inhibitory concentrations (MICs) for antifungal azoles, and the six possible nosocomial transmissions we captured were all FNS strains, most of which were from CC2. Unique FNS CCs have been found in Singapore (CC8) and India (CC17) and are close to China's CC2 in the minimum spanning tree. There were no FNS CCs outside Asia. This study is the first to reveal a significant correlation between genetic information and fluconazole susceptibility worldwide and to trace geographical locations, which is of great value for molecular epidemiological surveillance and azole-resistance study of C. tropicalis globally.

Structural Insights into the Interactions of Candidal Enolase with Human Vitronectin, Fibronectin and Plasminogen

Significant amounts of enolase—a cytosolic enzyme involved in the glycolysis pathway—are exposed on the cell surface of Candida yeast. It has been hypothesized that this exposed enolase form contributes to infection-related phenomena such as fungal adhesion to human tissues, and the activation of fibrinolysis and extracellular matrix degradation. The aim of the present study was to characterize, in structural terms, the protein-protein interactions underlying these moonlighting functions of enolase. The tight binding of human vitronectin, fibronectin and plasminogen by purified C. albicans and C. tropicalis enolases was quantitatively analyzed by surface plasmon resonance measurements, and the dissociation constants of the formed complexes were determined to be in the 10⁻⁷–10⁻⁸ M range. In contrast, the binding of human proteins by the S.cerevisiae enzyme was much weaker. The chemical cross-linking method was used to map the sites on enolase molecules that come into direct contact with human proteins. An internal motif ₂₃₅DKAGYKGKVGIAMDVASSEFYKDGK₂₅₉ in C. albicans enolase was suggested to contribute to the binding of all three human proteins tested. Models for these interactions were developed and revealed the sites on the enolase molecule that bind human proteins, extensively overlap for these ligands, and are well-separated from the catalytic activity center.

Metabolic profiling of Candida clinical isolates of different species and infection sources

Candida species are the most common cause of opportunistic fungal infections. Rapid identification and novel approaches for the characterization of these fungi are of great interest to improve the diagnosis and the knowledge about their pathogenic properties. This study aimed to characterize clinical isolates of Candida spp. by proteomics (MALDI-TOF MS) and metabolomics (1H-NMR), and to correlate their metabolic profiles with Candida species, source of infection and different virulence associated parameters. In particular, 49 Candida strains from different sources (blood, n = 15; vagina, n = 18; respiratory tract, n = 16), belonging mainly to C. albicans complex (61%), C. glabrata (20%) and C. parapsilosis (12%) species were used. Several extracellular and intracellular metabolites showed significantly different concentrations among isolates recovered from different sources of infection, as well as among different Candida species. These metabolites were mainly related to the glycolysis or gluconeogenesis, tricarboxylic acid cycle, nucleic acid synthesis and amino acid and lipid metabolism. Moreover, we found specific metabolic fingerprints associated with the ability to form biofilm, the antifungal resistance (i.e. caspofungin and fluconazole) and the production of secreted aspartyl proteinase. In conclusion, 1H-NMR-based metabolomics can be useful to deepen Candida spp. virulence and pathogenicity properties.

Molecular epidemiology of Candida tropicalis isolated from urogenital tract infections

Candida tropicalis is a common human pathogenic yeast, and its molecular typing is important for studying the population structure and epidemiology of this opportunistic yeast, such as epidemic genotype, population dynamics, nosocomial infection, and drug resistance surveillance. In this study, the antifungal susceptibility test and multilocus sequence typing (MLST) analysis were carried out on C. tropicalis from central China. Among 64 urogenital isolates, 45 diploid sequence types (DST) were found, of which 20 DSTs (44.4%) were new to the central database. The goeBURST analysis showed that CC1 (clonal complex) was the only azole‐resistant (100%, 10/10) cluster in Wuhan, which was composed of DST546, DST225, DST376, and DST506, and most of the strains (90%, 9/10) were isolated from the urinary tract. Potential nosocomial infections were mainly caused by CC1 strains. The azole resistance rate of urinary isolates (50.0%, 21/42) was higher than that of vaginal isolates (27.3%, 6/22). The genotype diversity and novelty of vaginal isolates were higher than those of urinary isolates. C. tropicalis population in Wuhan was genetically diverse and divergent from that seen in other countries. In this study, there were significant differences in genotype and azole susceptibility between urine and vaginal strains. The azole‐resistant cluster (CC1) found in urine is of great significance for the clinical treatment and prevention of nosocomial infection. The newly discovered DSTs will contribute to further study the similarity, genetic relationship, and molecular epidemiology of C. tropicalis worldwide.

First Report of Candidemia Clonal Outbreak Caused by Emerging Fluconazole-Resistant Candida parapsilosis Isolates Harboring Y132F and/or Y132F+K143R in Turkey

Clonal outbreaks of fluconazole-resistant (FLZR) Candida parapsilosis isolates have been reported in several countries. Despite its being the second leading cause of candidemia, the azole resistance mechanisms and the clonal expansion of FLZR C. parapsilosis blood isolates have not been reported in Turkey. In this study, we consecutively collected C. parapsilosis blood isolates (n = 225) from the fifth largest hospital in Turkey (2007 to 2019), assessed their azole susceptibility pattern using CLSI M27-A3/S4, and sequenced ERG11 for all and MRR1, TAC1, and UPC2 for a selected number of C. parapsilosis isolates. The typing resolution of two widely used techniques, amplified fragment length polymorphism typing (AFLP) and microsatellite typing (MST), and the biofilm production of FLZR isolates with and without Y132F were compared. Approximately 27% of isolates were FLZR (60/225), among which 90% (54/60) harbored known mutations in Erg11, including Y132F (24/60) and Y132F+K143R (19/60). Several mutations specific to FLZR isolates were found in MRR1, TAC1, and UPC2 AFLP grouped isolates into two clusters, while MST revealed several clusters. The majority of Y132F/Y132F+K143R isolates grouped in clonal clusters, which significantly expanded throughout 2007 to 2019 in neonatal wards. Candida parapsilosis isolates carrying Y132F were associated with significantly higher mortality and less biofilm production than other FLZR isolates. Collectively, we documented the first outbreak of FLZR C. parapsilosis blood isolates in Turkey. The MRR1, TAC1, and UPC2 mutations exclusively found in FLZR isolates establishes a basis for future studies, which will potentially broaden our knowledge of FLZR mechanisms in C. parapsilosis MST should be a preferred method for clonal analysis of C. parapsilosis isolates in outbreak scenarios.

Quantification of Factor H Mediated Self vs. Non-self Discrimination by Mathematical Modeling

The complement system is part of the innate immune system and plays an important role in the host defense against infectious pathogens. One of the main effects is the opsonization of foreign invaders and subsequent uptake by phagocytosis. Due to the continuous default basal level of active complement molecules, a tight regulation is required to protect the body's own cells (self cells) from opsonization and from complement damage. A major complement regulator is Factor H, which is recruited from the fluid phase and attaches to cell surfaces where it effectively controls complement activation. Besides self cells, pathogens also have the ability to bind Factor H; they can thus escape opsonization and phagocytosis causing severe infections. In order to advance our understanding of the opsonization process at a quantitative level, we developed a mathematical model for the dynamics of the complement system-termed DynaCoSys model-that is based on ordinary differential equations for cell surface-bound molecules and on partial differential equations for concentration profiles of the fluid phase molecules in the environment of cells. This hybrid differential equation approach allows to model the complement cascade focusing on the role of active C3b in the fluid phase and on the cell surface as well as on its inactivation on the cell surface. The DynaCoSys model enables us to quantitatively predict the conditions under which Factor H mediated complement evasion occurs. Furthermore, investigating the quantitative impact of model parameters by a sensitivity analysis, we identify the driving processes of complement activation and regulation in both the self and non-self regime. The two regimes are defined by a critical Factor H concentration on the cell surface and we use the model to investigate the differential impact of complement model parameters on this threshold value. The dynamic modeling on the surface of pathogens are further relevant to understand pathophysiological situations where Factor H mutants and defective Factor H binding to target surfaces results in pathophysiology such as renal and retinal disease. In the future, this DynaCoSys model will be extended to also enable evaluating treatment strategies of complement-related diseases.

Epidemiology of candidemia in Shiraz, southern Iran: A prospective multicenter study (2016-2018)

Systematic candidemia studies, especially in southern Iran, are scarce. In the current prospective study, we investigated candidemia in three major healthcare centers of Shiraz, the largest city in southern Iran. Yeast isolates from blood and other sterile body fluids were identified by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and subjected to antifungal susceptibility testing (AFST) using the broth microdilution method. Clinical data were retrieved from patients' medical records. In total, 113 yeast isolates were recovered from 109 patients, over 60% of whom received fluconazole. Antifungal drugs were prescribed without considering species identification or AFST. The all-cause mortality rate was 28%. Almost 30% of the patients were from intensive care units (ICUs). Candida albicans (56/113; 49.5%) was the most prevalent species followed by C. glabrata (26/113; 23%), C. parapsilosis (13/113; 11.5%), C. tropicalis (7/113; 6.2%), and C. dubliniensis (5/113; 4.4%). Only five isolates showed antifungal resistance or decreased susceptibility to fluconazole: one C. orthopsilosis isolate from an azole-naïve patient and two C. glabrata, one C. albicans, and one C. dubliniensis isolates from patients treated with azoles, who developed therapeutic failure against azoles later. Our results revealed a low level of antifungal resistance but a notable rate of azole therapeutic failure among patients with candidemia due to non-albicans Candida species, which threaten the efficacy of fluconazole, the most widely used antifungal in southern regions of Iran. Candidemia studies should not be confined to ICUs and treatment should be administered based on species identification and AFST results.

Evaluation of Molecular Epidemiology, Clinical Characteristics, Antifungal Susceptibility Profiles, and Molecular Mechanisms of Antifungal Resistance of Iranian Candida parapsilosis Species Complex Blood Isolates

Clonal expansion of fluconazole resistant (FLZ-R) Candida parapsilosis isolates is increasingly being identified in many countries, while there is no study exploring the antifungal susceptibility pattern, genetic diversity, and clinical information for Iranian C. parapsilosis blood isolates. Candida parapsilosis species complex blood isolates (n = 98) were recovered from nine hospitals located in three major cities, identified by MALDI-TOF MS, and their genetic relatedness was examined by AFLP fingerprinting. Antifungal susceptibility testing followed CLSI-M27-A3 and ERG11, MRR1 and hotspots 1/2 (HS1/2) of FKS1 were sequenced to assess the azole and echinocandin resistance mechanisms, respectively. Ninety-four C. parapsilosis and four Candida orthopsilosis isolates were identified from 90 patients. Only 43 patients received systemic antifungal drugs with fluconazole as the main antifungal used. The overall mortality rate was 46.6% (42/90) and death mostly occurred for those receiving systemic antifungals (25/43) relative to those not treated (17/47). Although, antifungal-resistance was rare, one isolate was multidrug-resistant (FLZ = 16 μg/ml and micafungin = 8 μg/ml) and the infected patient showed therapeutic failure to FLZ prophylaxis. Mutations causing azole and echinocandin resistance were not found in the genes studied. AFLP revealed five genotypes (G) and G1 was the main one (59/94; 62.7%). Clinical outcome was significantly associated with city (P = 0.02, α <0.05) and Mashhad was significantly associated with mortality (P = 0.03, α <0.05). Overall, we found a low level of antifungal resistance for Iranian C. parapsilosis blood isolates, but the noted MDR strain can potentially become the source of future infections and challenge the antifungal therapy in antifungal-naïve patients. AFLP typing results warrants confirmation using other resolutive typing methods.

Inhibition of Candida auris Biofilm Formation on Medical and Environmental Surfaces by Silver Nanoparticles

Candida auris is an emerging pathogenic fungus implicated in healthcare-associated outbreaks and causes bloodstream infections associated with high mortality rates. Biofilm formation represents one of the major pathogenetic traits associated with this microorganism. Unlike most other Candida species, C. auris has the ability to survive for weeks on different surfaces. Therefore, there is an urgent need to develop new effective control strategies to combat the threat of C. auris. Advances in nanotechnologies have emerged that carry significant potential impact against Candida biofilms. We obtained pure round silver nanoparticles (AgNPs) (1 to 3 nm in diameter) using a microwave-assisted synthetic approach. When tested against C. auris, our results indicated a potent inhibitory activity both on biofilm formation (half maximal inhibitory concentration (IC₅₀) of 0.06 ppm) and against preformed biofilms (IC₅₀ of 0.48 ppm). Scanning electron microscopy images of AgNP-treated biofilms showed cell wall damage mostly by disruption and distortion of the outer surface of the fungal cell wall. In subsequent experiments AgNPs were used to functionalize medical and environmental surfaces. Silicone elastomers functionalized with AgNPs demonstrated biofilm inhibition (>50%) at relatively low concentrations (2.3 to 0.28 ppm). Bandage dressings loaded with AgNPs inhibited growth of C. auris biofilms by more than 80% (2.3 to 0.017 ppm). Also, to demonstrate long-lasting protection, dressings loaded with AgNPs (0.036 ppm) were washed thoroughly with phosphate-buffered saline, maintaining protection against the C. auris growth from cycles 1 to 3 (>80% inhibition) and from cycles 4 to 6 (>50% inhibition). Our results demonstrate the dose-dependent activity of AgNPs against biofilms formed by C. auris on both medical (silicone elastomer) and environmental (bandage fibers) surfaces. The AgNPs-functionalized fibers retain the fungicidal effect even after repeated thorough washes. Overall these results point to the utility of silver nanoparticles to prevent and control infections caused by this emerging pathogenic fungus.

Dynamics of in vitro development of azole resistance in Candida tropicalis

OBJECTIVES

Increasing incidence of azole resistance in Candida tropicalis, especially to fluconazole, has been seen in Asian countries including India. Limited knowledge is available on the molecular mechanisms associated with the development of azole resistance in C. tropicalis. The present study examined the dynamics of in vitro azole resistance in C. tropicalis after prolonged treatment with fluconazole.

METHODS

Nine fluconazole-susceptible isolates of C. tropicalis were used in this study. Fluconazole resistance was induced experimentally in C. tropicalis isolates. The stability of induced resistance and cross-resistance to other azoles was examined. The molecular mechanisms of azole resistance were assessed by measuring the expression and mutation analysis of different genes.

RESULTS

Varying degrees of resistance [five with minimum inhibitory concentrations (MICs) ≤32 mg/L and four with MICs ≥128 mg/L] were noticed, and the resistance was developed in 3 months. Of the nine resistant isolates, four induced resistant isolates with MICs ≥128 mg/L presented temporal resistance stability up to 10 subcultures. These four isolates presented cross-resistance to other azoles and also an inducible overexpression of transporters (CDR1, CDR2, CDR3 and MDR1), ergosterol biosynthesis pathway genes (ERG1, ERG2, ERG3 and ERG11), transcription factors (TAC1 and UPC2) and stress-responsive genes (HSP90 and MKC1) was noticed. No mutations were seen in any of the four genes (ERG1, ERG3, ERG11 and UPC2) tested.

CONCLUSIONS

Candida tropicalis isolates adapt themselves in the presence of continuous drug exposure and switch back to being susceptible in the absence of the drug. The acquisition of resistance in C. tropicalis is mediated by the overexpression of different resistance-related genes without any molecular alterations.

Mechanisms of Pathogenic Candida Species to Evade the Host Complement Attack

Candida species are common colonizers of the human skin, vagina, and the gut. As human commensals, Candida species do not cause any notable damage in healthy individuals; however, in certain conditions they can initiate a wide range of diseases such as chronic disseminated candidiasis, endocarditis, vaginitis, meningitis, and endophthalmitis. The incidence of Candida caused infections has increased worldwide, with mortality rates exceeding 70% in certain patient populations. C. albicans, C. glabrata, C. tropicalis, C. parapsilosis, and C. krusei are responsible for more than 90% of Candida-related infections. Interestingly, the host immune response against these closely related fungi varies. As part of the innate immune system, complement proteins play a crucial role in host defense, protecting the host by lysing pathogens or by increasing their phagocytosis by phagocytes through opsonization. This review summarizes interactions of host complement proteins with pathogenic Candida species, including C. albicans and non-albicans Candida species such as C. parapsilosis. We will also highlight the various ways of complement activation, describe the antifungal effects of complement cascades and explore the mechanisms adopted by members of pathogenic Candida species for evading complement attack.

Selection and evaluation of appropriate reference genes for RT-qPCR based expression analysis in Candida tropicalis following azole treatment

Candida tropicalis arises as one of the predominant non-Candida albicans Candida (NCAC) species causing invasive candidiasis in Asian countries. A rise in reports of C. tropicalis with a parallel increase in fluconazole resistance has also been observed. The genes and underlying pathways associated with azole antifungal resistance in C. tropicalis is still not properly understood. The RT-qPCR is the most promising approach for expression analysis of target genes to understand the mechanisms of resistance. The reliability and reproducibility of this technique depend on the selection of suitable reference genes for the normalization in expression study. The present study investigated the expression stability levels of ten genes including ACT1, EF1, GAPDH, PGK1, RDN5.8, RDN18, RDN28, SDHA, TUB1, and UBC13 for their suitability in fluconazole treated/untreated C. tropicalis. The stability levels of these genes were examined by the ∆∆CT, ΔCT, Pfaffl methods and five independent software including hkgFinder, geNorm, NormFinder, BestKeeper, and RefFinder software. We report, the EF1 and ACT1 were the most stable reference genes for normalization and can be used for the gene expression analysis in C. tropicalis. To the best of our knowledge, our study is the first to select and validate the reference genes in C. tropicalis for RT-qPCR based expression analysis.

Breakthrough Bloodstream Infections Caused by Echinocandin-Resistant Candida tropicalis: An Emerging Threat to Immunocompromised Patients with Hematological Malignancies

Background. Candida tropicalis is a virulent fungal pathogen for which echinocandins are the primary therapy. Emergence of resistance to echinocandins of C. tropicalis carries potentially ominous therapeutic implications. Methods. We describe herein two patients with breakthrough C. tropicalis fungemia during echinocandin therapy, characterize their molecular mechanism of resistance, and systematically review 13 previously reported cases of echinocandin-resistant C. tropicalis bloodstream infections (BSIs) and other diseases. Results. Among these 15 patients with echinocandin-resistant C. tropicalis infections, the median age was 61 years (ages 28–84 years) and 13 (86%) were immunocompromised. Thirteen (86%) of all patients had a history of pervious or concurrent exposure to echinocandins. Isolates of C. tropicalis from 11 cases, including the two index cases, underwent DNA sequencing of the FKS1 gene for mutations known to confer echinocandin resistance. The amino acid substitution Ser654Pro was shown in four cases, while other FKS1 mutations encoded Ser80S/Pro, Phe641Leu, Phe641Ser, Ser80S/Pro substitutions. These mutational events were not associated with collateral increases in minimum inhibitory concentrations to antifungal triazoles and amphotericin B. Overall mortality in patients with echinocandin-resistant C. tropicalis infections was 40%. Among those six patients who died, two received monotherapy with voriconazole, one was treated with fluconazole, one remained on caspofungin, and two were switched to liposomal amphotericin B. Nine patients (60%) survived after being treated with an antifungal agent other than an echinocandin. Conclusions. Emergence of resistance to echinocandins by C. tropicalis, occurs during antifungal therapy, is associated with high mortality, is mediated by a diverse range of FKS1 mutations, retains in vitro susceptibility to triazoles and amphotericin B, and constitutes an emerging threat to patients with hematological malignancies.

Clonality of Fluconazole-Nonsusceptible Candida tropicalis in Bloodstream Infections, Taiwan, 2011-2017

Candida tropicalis is the leading cause of non-C. albicans candidemia in tropical Asia and Latin America. We evaluated isolates from 344 patients with an initial episode of C. tropicalis candidemia. We found that 58 (16.9%) patients were infected by fluconazole-nonsusceptible (FNS) C. tropicalis with cross resistance to itraconazole, voriconazole, and posaconazole; 55.2% (32/58) of patients were azole-naive. Multilocus sequence typing analysis revealed FNS isolates were genetically closely related, but we did not see time- or place-clustering. Among the diploid sequence types (DSTs), we noted DST225, which has been reported from fruit in Taiwan and hospitals in Beijing, China, as well as DST376 and DST505-7, which also were reported from hospitals in Shanghai, China. Our findings suggest cross-boundary expansion of FNS C. tropicalis and highlight the importance of active surveillance of clinical isolates to detect dissemination of this pathogen and explore potential sources in the community.

Fungicidal and anti-biofilm activities of trimethylchitosan-stabilized silver nanoparticles against Candida species in zebrafish embryos

Herein, positively surface-charged silver nanoparticles (AgNPs) capped with trimethylchitosan nitrate (TMCN) were synthesized using an environmentally friendly method. Nano-sized TMCN-AgNPs (~80 nm) with high zeta potential (>30 mV) provide sufficient static repulsion to stabilize colloid AgNPs in aqueous solutions without aggregation for >3 months. In in vitro cell cycle assays, TMCN-AgNPs showed low cytotoxicity towards L929 cells. A microdilution inhibition assay demonstrated the antifungal potential of TMCN-AgNPs, with a minimum inhibitory concentration of 0.06 mM against Candida tropicalis ATCC 750, and 0.46 mM against both Candida albicans ATCC 76615 and Candida glabrata ATCC 15545. Moreover, the addition of TMCN-AgNPs at 0.23 mM significantly reduced biofilm formation in 96-well plates with C. albicans and C. tropicalis. Importantly, when zebrafish eggs were infected with Candida cells, 0.23 mM TMCN-AgNPs greatly diminished the amount of biofilm on eggs and rescued the survival of embryos by up to 70%.

Longitudinal Survey of Fungi in the Human Gut: ITS Profiling, Phenotyping, and Colonization

The fungal component of the intestinal microbiota of eight healthy subjects was studied over 12 months using metagenome survey and culture-based approaches. Aspergillus, Candida, Debaryomyces, Malassezia, Penicillium, Pichia, and Saccharomyces were the most recurrent and/or dominant fungal genera, according to metagenomic analysis. The biodiversity of fungal communities was lower and characterized by greater unevenness, when compared to bacterial microbiome. The dissimilarities both among subjects and over the time within the same subject suggested that most of the fungi passed through the gastro-intestinal tract (GIT) without becoming stable colonizers. Certain genera, such as Aspergillus and Penicillium, were isolated in a minority of cases, although they recurred abundantly and frequently in the metagenomics survey, likely being environmental or food-borne fungi that do not inhabit the GIT. Candida genus was recurrently detected. Candida albicans isolates dominated among the cultivable mycobiota and longitudinally persisted, likely as commensals inhabiting the intestine or regularly reaching it from Candida-colonized districts, such as the oral cavity. Other putative colonizers belonged to Candida zeylanoides, Geotrichum candidum, and Rhodotorula mucilaginosa, with persisting biotypes being identified. Phenotyping of fungal isolates indicated that C. albicans adhered to human epithelial cells more efficiently and produced greater amounts of biofilm in vitro than non-albicans Candida (NAC) and non-Candida fungi (NCF). The C. albicans isolates also induced the highest release of HBD-2 by human epithelial cells, further differing from NAC and NCF. Nine representative isolates were administered to mice to evaluate the ability to colonize the intestine. Only two out of three C. albicans strains persisted in stools of animals 2 weeks after the end of the oral administration, whereas NAC and NCF did not. These results confirm the allochthonous nature of most the intestinal fungi, while C. albicans appears to be commonly involved in stable colonization. A combination of specific genetic features in the microbe and in the host likely allow colonization from fungi normally present solely as passengers. It remains to be established if other species identified as potential colonizers, in addition to Candida, are true inhabitants of the GIT or rather reach the intestine spreading from other body districts.

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

Non-albicans Candida species (NACS) are often isolated along with Candida albicans in cases of oropharyngeal candidiasis. C. albicans readily forms biofilms in conjunction with other oral microbiota including both bacteria and yeast. Adhesion between species is important to the establishment of these mixed biofilms, but interactions between C. albicans and many NACS are not well-characterized. We adapted a real-time flow biofilm model to study adhesion interactions and biofilm establishment in C. albicans and NACS in mono- and co-culture. Out of five NACS studied, only the filamenting species C. tropicalis and C. dubliniensis were capable of adhesion with C. albicans, while C. parapsilosis, C. lusitaniae, and C. krusei were not. Over the early phase (0-4 h) of biofilm development, both mono- and co-culture followed similar kinetics of attachment and detachment events, indicating that initial biofilm formation is not influenced by inter-species interactions. However, the NACS showed a preference for inter-species cell-cell interactions with C. albicans, and at later time points (5-11 h) we found that dual-species interactions impacted biofilm surface coverage. Dual-species biofilms of C. tropicalis and C. albicans grew more slowly than C. albicans alone, but achieved higher surface coverage than C. tropicalis alone. Biofilms of C. dubliniensis with C. albicans increased surface coverage more rapidly than either species alone. We conclude that dual culture biofilm of C. albicans with C. tropicalis or C. dubliniensis offers a growth advantage for both NACS. Furthermore, the growth and maintenance, but not initial establishment, of dual-species biofilms is likely facilitated by interspecies cell-cell adherence.

Changing trends in epidemiology and antifungal susceptibility patterns of six bloodstream Candida species isolates over a 12-year period in Kuwait

Changing trends in incidence and antifungal susceptibility patterns of six Candida species causing candidemia in Kuwait between 2006–2017 are reported. A total of 2075 isolates obtained from 1448 patients were analyzed. Identity of Candida species isolates was determined by phenotypic methods and confirmed by PCR amplification/PCR-sequencing of rDNA and/or MALDI-TOF MS. Antifungal susceptibility was determined by Etest. C. albicans accounted for 539 (37.22%) cases followed by C. parapsilosis (n = 502, 34.67%), C. tropicalis (n = 210, 14.5%), C. glabrata (n = 148, 10.22%), C. krusei (n = 27, 1.81%) and C. dubliniensis (n = 22, 1.5%). The comparative percent distribution of Candida species causing candidemia between 2006–2011 and 2012–2017 was as follows: C. albicans 41.8% and 33.1%, C. parapsilosis complex 32.01% and 37.04%, C. tropicalis 13.59% and 15.31%, and C. glabrata 8.77% and 11.51%, C. krusei 2.0% and 1.7%, and C. dubliniensis 1.75 and 1.3%, respectively. Three of 371 C. albicans isolates during 2006–2011 and five of 363 during 2012–2017 were resistant to fluconazole. Among C. parapsilosis isolates, one of 310 during 2006–2011 and 21 of 446 during 2012–2017 were resistant to this drug. Furthermore, at an epidemiologic cutoff value (ECV) of ≤0.5 μg/ml, 70.1% C. albicans isolates were wild-type for fluconazole during 2006–2011 as compared to 58.1% during 2012–2017. Likewise, at an ECV of ≤2 μg/ml, 98.0% of C. parapsilosis isolates were wild-type during 2006–2011 as compared to 93.4% during 2012–2017. Clonal spread of fluconazole-resistant C. parapsilosis in one major hospital was documented. An 8.8% shift in favor of non-albicans Candida species with concomitant increase in MICs between the two periods preludes emergence of fluconazole-resistant candidemia cases in Kuwait.

Lactobacillus species increase the survival of Galleria mellonella infected with Candida albicans and non-albicans Candida clinical isolates

Investigation into new therapeutic strategies, such as the use of bacterial isolates with probiotic characteristics, has increased in importance due to the high incidence of Candida albicans and non-albicans Candida infections. This study evaluates Lactobacillus paracasei, Lactobacillus fermentum and Lactobacillus rhamnosus strains as prophylactic and therapeutic agents against infection caused by Candida albicans, Candida glabrata, Candida krusei, and Candida tropicalis in a Galleria mellonella model. Prophylactic treatment provided greater benefits during Candida spp. infection, increasing G. mellonella survival, compared to therapeutic treatment. This study demonstrated that the different Lactobacillus species are potent prophylactic agents of Candida species infection.

A prospective, multi-center study of Candida bloodstream infections in Chile

BACKGROUND

Active surveillance is necessary for improving the management and outcome of patients with candidemia. The aim of this study was to describe epidemiologic and clinical features of candidemia in children and adults in tertiary level hospitals in Chile.

METHODS

We conducted a prospective, multicenter, laboratory-based survey study of candidemia in 26 tertiary care hospitals in Chile, from January 2013 to October 2017.

RESULTS

A total of 780 episodes of candidemia were included, with a median incidence of 0.47/1,000 admissions. Demographic, clinical and microbiological information of 384 cases of candidemia, from 18 hospitals (7,416 beds), was included in this report. One hundred and thirty-four episodes (35%) occurred in pediatric patients and 250 (65%) in adult population. Candida albicans (39%), Candida parapsilosis (30%) and Candida glabrata (10%) were the leading species, with a significant difference in the distribution of species between ages. The use of central venous catheter and antibiotics were the most frequent risk factors in all age groups (> 70%). Three hundred and fifteen strains were studied for antifungal susceptibility; 21 strains (6.6%) were resistant to fluconazole, itraconazole, voriconazole, anidulafungin or micafungin. The most commonly used antifungal therapies were fluconazole (39%) and echinocandins (36%). The overall 30-day survival was 74.2%, significantly higher in infants (82%) and children (86%) compared with neonates (72%), adults (71%) and elderly (70%).

CONCLUSIONS

Our prospective, multicenter surveillance study showed a low incidence of candidemia in Chile, with high 30-day survival, a large proportion of elderly patients, C. glabrata as the third most commonly identified strain, a 6.6% resistance to antifungal agents and a frequent use of echinocandins.

Linking Cellular Morphogenesis with Antifungal Treatment and Susceptibility in Candida Pathogens

Fungal infections are a growing public health concern, and an increasingly important cause of human mortality, with Candida species being amongst the most frequently encountered of these opportunistic fungal pathogens. Several Candida species are polymorphic, and able to transition between distinct morphological states, including yeast, hyphal, and pseudohyphal forms. While not all Candida pathogens are polymorphic, the ability to undergo morphogenesis is linked with the virulence of many of these pathogens. There are also many connections between Candida morphogenesis and antifungal drug treatment and susceptibility. Here, we review how Candida morphogenesis-a key virulence trait-is linked with antifungal drugs and antifungal drug resistance. We highlight how antifungal therapeutics are able to modulate morphogenesis in both sensitive and drug-resistant Candida strains, the shared signaling pathways that mediate both morphogenesis and the cellular response to antifungal drugs and drug resistance, and the connection between Candida morphology, drug resistance, and biofilm growth. We further review the development of anti-virulence drugs, and targeting Candida morphogenesis as a novel therapeutic strategy to target fungal pathogens. Together, this review highlights important connections between fungal morphogenesis, virulence, and susceptibility to antifungals.

Differential Behavior of Non-albicans Candida Species in the Central Nervous System of Immunocompetent and Immunosuppressed Mice

The genus Candida includes commensal fungi that can cause local and systemic infections, frequently involving vital organs as the central nervous system (CNS). Candida spp. occupy the fourth place among infections that affect the CNS. Although the incidence of Candida albicans is decreasing among patients under immunosuppressive therapies, the incidence of non-albicans Candida is increasing. In this context, the objective of this work was to evaluate the ability of non-albicans Candida species to spread to the CNS of immunocompetent and immunosuppressed mice. Adult female C57BL/6 mice were treated with prednisolone, intravenously infected with Candida glabrata, Candida krusei and Candida parapsilosis yeasts and then evaluated at the 3rd and 14th days after infection. All Candida species disseminated to the brain from immunocompetent animals and induced local inflammation at the third day post-infection. The immunosuppression resulted in body weight loss, leukopenia and reduced IL-2 production by spleen cell cultures. Higher fungal loads were recovered from the CNS of immunosuppressed mice. Inflammatory infiltration associated to a Th1 subset profile was higher in brain samples from C. krusei immunosuppressed mice compared with immunocompetent ones. Additionally, C. krusei was able to transform into pseudohypha inside microglia in vitro infected cells and also to induce elevated nitric oxide production. Altogether, these results indicate that C. glabrata, C. krusei and C. parapsilosis are able to disseminate to the CNS and promote local inflammation in both immunocompetent and immunosuppressed mice. C. krusei displayed a distinct behavior at the CNS triggering a local Th1 profile. The possible contribution of these non-albicans Candida species to other CNS pathologies as multiple sclerosis, Parkinson’s and Alzheimer’s diseases deserves further attention.

Catheter-related candidemia and identification of causative Candida species in patients with cardiovascular disorder

Background and Purpose

Catheter-related blood circulation infection is the most dangerous and serious side-effects of vascular catheters, which leads to the enhancement of the costs, mortality, and hospital stay duration, especially in the Intensive Care Unit. Regarding this, the aim of the current study was to identify the prevalence of catheter-induced candidemia in the Tehran Heart Center, a heart hospital in Tehran, Iran.

Materials and Methods

This study was conducted on patients admitted to Tehran Heart Center for a minimum of 7 days during 18 months. To detect the fungal elements, blood culture and catheter culture were performed in the patients receiving central or peripheral venous catheter. Then, the polymerase chain reaction (PCR) was applied to determine the possible diagnosis.

Results

The investigation of 223 samples led to the identification of a total of 15 (6.7%) yeast isolates obtained from 9 (60%), 4 (26.6 %), and 2 (13.4%) catheter, blood, and skin (of the catheter insertion areas) cultures, respectively. Out of nine Candida isolates obtained from the catheter samples, 1 (11.1%), 1 (11.1%), 2 (22.2%), and 5 (55.6%) cases were identified as C. tropicalis, C. membranifaciens, C. glabrata, and C. albicans, respectively, using the internal transcribed spacer region sequencing. Furthermore, the four yeasts isolated from the blood culture included C. tropicalis, C. carpophila, C. membranifaciens, and Cryptococcus albidus. Additionally, one case of C. glabrata and one case of C. albicans were isolated from the skin culture of the catheter insertion areas in patients with positive catheter culture. We reported two cases of catheter-related candidemia caused by C. membranifaciens and C. tropicalis on the basis of the genetic similarity of the species isolated from the blood and catheter. These cases were treated successfully with intravenous fluconazole and catheter removal.

Conclusion

There is some evidence indicating the growing prevalence of non-albicans Candida infections. Many risk factors, including prior antibiotic therapy, use of a central venous catheter, surgery, and parenteral nutrition, are considered to be associated with candidemia in hospitalized heart failure patients. The identification of the route of infection in candidemia is difficult. In the current study, the positive blood and catheter cultures for Candida isolates and the similarity of the ITS region of ribosomal DNA sequence of Candida isolated from two patients confirmed the diagnosis of intravenous catheter-related candidemia.

Multilocus Sequence Typing (MLST) Genotypes of Candida glabrata Bloodstream Isolates in Korea: Association With Antifungal Resistance, Mutations in Mismatch Repair Gene (Msh2), and Clinical Outcomes

Candida glabrata bloodstream infection (BSI) isolates from a particular geographic area have been reported to comprise a relatively small number of the major sequence types (STs) by multilocus sequence typing (MLST) analysis. Yet little is known about the characteristics of major ST strains of C. glabrata. To address this question in Korea, we investigated antifungal resistance and non-synonymous mutations of the mismatch repair gene (msh2 mutations) in C. glabrata BSI isolates, as well as associated clinical characteristics, and compared the results according to MLST genotype. We assessed a total of 209 C. glabrata BSI isolates from seven hospitals in Korea for 2 years (2009 and 2014). Clinical features of candidemia and their outcomes were analyzed for 185 available cases. According to MLST, ST7 (47.8%) was the most common type, followed by ST3 (22.5%); the remainder represented 28 types of minor STs (29.7%). Fluconazole-resistance (FR) rates for ST7, ST3, and other strains were 9.0% (9/100), 8.5% (4/47), and 4.8% (3/62), respectively, and all were susceptible to amphotericin B and micafungin. All ST7 isolates harbored the V239L mutation in msh2, known to confer hypermutability, while 91.5% of ST3 isolates did not harbor the msh2 mutation. Overall, isolates of the same ST had identical msh2 mutations, with the exception of nine isolates. The msh2 mutations were identified in 68.8% (11/16) of the FR isolates and 67.4% (130/193) of the fluconazole susceptible-dose dependent isolates. There was no significant difference in all clinical characteristics between ST3 and ST7. However, the 30-day mortality of C. glabrata candidemia due to the two major ST (ST3 or ST7) strains was significantly higher than that of candidemia due to other minor ST strains (45.1 vs. 25.0%, p < 0.05). Multivariate logistic regression analysis also showed that two major STs (ST3 and ST7) were independent predictors of 30-day mortality. This study showed for the first time that two STs (ST7 and ST3) were predominant among BSI isolates in Korea, and that C. glabrata BSI isolates belonging to two major MLST genotypes are characterized by higher mortality. In addition, most msh2 mutations align with MLST genotype, irrespective of FR.

MDR1 overexpression combined with ERG11 mutations induce high-level fluconazole resistance in Candida tropicalis clinical isolates

Background

Marked increases in fluconazole resistance in Candida tropicalis have been recently reported. In this study, the molecular mechanisms behind fluconazole resistance were investigated.

Methods

Twenty-two C. tropicalis clinical isolates, including 12 fluconazole-resistant isolates and 10 fluconazole-susceptible isolates, were collected from a tertiary care teaching hospital in Beijing between 2013 and 2017. Antifungal susceptibility testing, multilocus sequence typing, ERG11 amplification and sequencing, quantitative real-time reverse transcription-polymerase chain reaction (ERG11, UPC2, MDR1, and CDR1), and clinical data collection were performed for all C. tropicalis isolates.

Results

Multilocus sequence typing revealed that the 10 fluconazole-susceptible isolates and 12 fluconazole-resistant isolates were divided into nine and seven diploid sequence types, respectively. Of the 12 patients with fluconazole-resistant isolates, six had been previously exposed to azole and four had a fatal outcome. Y132F and S154F amino acid substitutions in Erg11p were found in all fluconazole-resistant isolates except one. MDR1 gene overexpression was identified in fluconazole-resistant isolates. In particular, seven high-level fluconazole resistant isolates (minimum inhibitory concentration ≥ 128 mg/L) and three pan-azole resistant isolates were identified. CDR1, ERG11, and UPC2 gene expression levels in fluconazole-resistant isolates were not significantly different from the control isolates (P = 0.262, P = 0.598, P = 0.114, respectively).

Conclusions

This study provides evidence that the combination of MDR1 gene overexpression and ERG11 missense mutations is responsible for high-level fluconazole resistance and pan-azole resistance in C. tropicalis clinical isolates. To the best of our knowledge, this is the first study investigating the relationship between MDR1 gene overexpression and increased fluconazole resistance.