Twenty Years of the SENTRY Antifungal Surveillance Program: Results for Candida Species From 1997-2016

Genomic analyses reveal high diversity and rapid evolution of Pichia kudriavzevii within a neonatal intensive care unit in Delhi, India

Pichia kudriavzevii causes life-threatening infections in immunocompromised hosts, including hospitalized neonates. This pathogen is intrinsically resistant to fluconazole, while uncommon P. kudriavzevii strains resistant to multiple antifungal drugs, including voriconazole, amphotericin B, and echinocandins, have also been reported from healthcare environments. Thus, understanding how P. kudriavzevii spread, persist, and adapt to healthcare settings could help us develop better infection management strategies. In this study, whole genome sequencing identifies multiple outbreaks of bloodstream infections in a single neonatal intensive care unit (NICU) over 5 years caused by genetically diverse strains of P. kudriavzevii. Interestingly, two genetically distinct clusters of P. kudriavzevii strains showed frequent loss of heterozygosity (LOH) events between two temporal samples. The first outbreak cluster (2015-2016) showed LOH at chromosomes 1, 4, and 5, and the other outbreak cluster (2020) exhibited LOH at chromosome 2. The circulation of two separate strain clusters of P. kudriavzevii suggests nosocomial transmission in the NICU in different time periods. Furthermore, we compared the transcriptomic profiles of three isolates of clusters I and II that exhibited distinct fluconazole and itraconazole MICs. While no significant difference in gene expression was found at the azole-target gene ERG11 or the ATP-binding cassette (ABC) transporter genes, such differences were found in genes involved in cell division and filamentation, such as SIR2 (sirtuin deacetylase) and RFA1 (replication factor A). Interestingly, increased filamentation was observed in clade I isolate exhibiting high fluconazole MICs. Together, our study indicates significant diversity, persistence, and rapid evolution of P. kudriavzevii within a single NICU.

Structure-guided optimization of small molecules targeting Yck2 as a strategy to combat Candida albicans

Candida albicans is the most common cause of life-threatening fungal infection in the developed world but remains a therapeutic challenge. Protein kinases have been rewarding drug targets across diverse indications but remain untapped for antifungal development. Previously, screening kinase inhibitors against C. albicans revealed a 2,3-aryl-pyrazolopyridine, GW461484A (GW), which targets casein kinase 1 (CK1) family member Yck2. Here, we report optimization of GW via two complementary approaches, synthesis of bioisosteres possessing an imidazo[1,2-a]pyridine core, and R-group substitution of GW's pyrazolo[1,5-a]pyridine core. Characterization of compounds reveals two 6-cyano derivatives with improved pharmacological properties that retain whole-cell bioactivity and selectivity for fungal Yck2 compared to human CK1α. Efficacy studies in mice indicate both analogs possess single-agent activity against C. albicans resistant to first-line echinocandin antifungals and potentiate non-curative echinocandin treatment. Results validate Yck2 as an antifungal target and encourage further development of inhibitors acting by this previously unexploited mode of action.

Invasive Candidiasis

Invasive candidiasis (IC) is a term that refers to a group of infectious syndromes caused by a variety of Candida species, 6 of which cause the vast majority of cases globally. Candidemia is probably the most commonly recognized syndrome associated with IC; however, Candida species can cause invasive infection of any organ, especially visceral organs, vasculature, bones and joints, eyes, and central nervous system. The optimal use of these newer diagnostics coupled with a thoughtful clinical assessment of at-risk patients and the judicious use of effective antifungal therapy is a key to achieving good antifungal stewardship and improved patient outcomes.

Candida krusei (Pichia kudriavzevii) multilocus sequence typing and antifungal susceptibility profile in Cameroon

Among the Candida species commonly involved in superficial and more significant life-threatening infections, C. krusei exhibits the most worrisome resistance profile to antifungals. This study aimed to analyse the population structure using multilocus sequence typing (MLST), and to evaluate the antifungal susceptibility profile of C. krusei isolated from patients living with human immunodeficiency virus (HIV) in Cameroon. C. krusei isolated from stool, urine, mouth and vaginal samples were identified using routine laboratory techniques and matrix-assisted laser desorption ionization-time-of-flight mass spectrometry (MALDI-TOF MS). The C. krusei isolates were further analysed by MLST. In vitro antifungal susceptibility testing was performed using the Sensititre Yeast One™ microdilution technique. Forty three (43) C. krusei isolates were included in the study. The MLST identified 32 Diploid sequence type (DST), of which 31 were new that were not included in the current database. New alleles were not observed. Different DSTs were observed in isolates from the same geographical area, from different anatomical sites in the same patient. An eBURST analysis clustered all identified DSTs of former isolates in clonal complex 1. Heterogeneous antifungal MICs were observed in isolates of the same DST and/or from the same geographical area. 32.6% of the isolates displayed a resistant or non-wild-type phenotype to at least 3 distinct antifungal agent classes. The achieved results support the setting up of molecular epidemiology and antifungal resistance surveillance of C. krusei.

Distribution and Antibiotic Resistance Analysis of 13,048 Clinically Common Isolates

Objective

This study investigated the distribution and antibiotic resistance profiles of common bacteria isolated from clinical specimens at a hospital's microbiology laboratory between 2020 and 2022.

Methods

A retrospective analysis was conducted on microbial culture results from clinical specimens collected over three years, including sample types, departmental distribution, pathogen species, and resistance profiles.

Results

A total of 13,048 unique pathogenic strains were isolated, predominantly from respiratory and urine specimens. Secretion specimens exhibited the highest positive detection rate (73.6%), while blood specimens showed a lower rate (9.7%). The five most frequently isolated pathogens were: Klebsiella pneumoniae (K. pneumoniae) (19.6%), Pseudomonas aeruginosa (P. aeruginosa) (14.7%), Escherichia coli (E. coli) (9.2%), Acinetobacter baumannii (A. baumannii) (8.0%), and Candida albicans (C. albicans) (7.0%). Gram-negative bacteria constituted 53.7% of all isolates (7009/13,048). A total of 7590 multidrug-resistant organisms (MDRO) were identified, corresponding to a detection rate of 21.3% (7590/35,613). The detection rates of carbapenem-resistant Enterobacteriaceae (CRE) increased annually: 7.2% (2020), 8.6% (2021), and 14.4% (2022).

Conclusion

The annual detection rate of CRE increased during the study period, while the rate of methicillin-resistant Staphylococcus aureus (MRSA) declined. Timely and effective interventions targeting pathogenic bacteria are essential for controlling and mitigating nosocomial infection risks.

Antifungal Natural Products Originating from Endophytic and Rhizospheric Microbes Isolated from Coastal Vegetation

Candida infections severely impact patients who are immunocompromised. Currently, there are limited options to treat fungal infections, especially drug-resistant-fungal infections. Therefore, investigating alternative or repurposed antifungals is paramount. Endophytic microbes (EMs) and rhizospheric microbes (RMs) emerge as promising reservoirs of bioactive natural compounds. Interestingly, plants that have adapted to various environmental conditions harbour a plethora of microbes producing a variety of bioactive natural products that can be assessed for potential antifungal activity. To date, EMs and RMs residing in coastal plants and their associated antifungals have not been extensively studied or reviewed. Therefore, this comprehensive review will focus on antifungal natural products, extracted from coastal-vegetation-associated microbiota to draw the attention of research in this field. A comprehensive literature search was conducted by examining both Scopus and Google Scholar databases during the period of 2013-2024 related to the following coastal vegetation: mangroves, sand dune plants, salt marsh plants, and seagrasses. To date, 65 novel antifungal compounds derived from coastal-plant EMs and RMs have been identified. Mangroves were found to be the most prominent host harbouring antifungal-producing EMs and RMs compared with other coastal plants. Coastal-plant-associated fungal partners were the most prominent producers of antifungals compared to their bacterial counterparts. Fifty-four fungal-EM/RM derived antifungals have been reported to demonstrate activities against plant pathogenic fungi as well as human fungal pathogens. Most of the bacterial-derived antifungals (11 antifungals) have previously been reported to have antifungal activity against Candida albicans.

Gastrointestinal anaerobes and Enterococcus faecalis promote Candida glabrata gastrointestinal colonization and organ dissemination

BACKGROUND

Candida glabrata is a common causative pathogen of endogenous candidiasis. It is assumed that the gastrointestinal flora affects C. glabrata gastrointestinal colonization and organ dissemination in the gastrointestinal tract (GIT). However, no reports have yet described the relationships between C. glabrata and bacteria in the GIT. This study aimed to clarify these relationships using a mouse endogenous candidiasis model with cortisone acetate immunosuppression.

METHODS

Dysbiosis was induced in the GIT by several antibiotic combinations, and then C. glabrata gastrointestinal colonization and organ dissemination were evaluated. Next, metagenomic sequencing analysis of the gastrointestinal flora was performed to identify bacteria associated with C. glabrata organ dissemination. Finally, coinfection experiments were performed using bacteria isolated from the mouse GIT.

RESULTS

C. glabrata organ dissemination was significantly promoted using specific antibiotics regardless of the amount of colonization in the GIT. Metagenomic sequencing analysis of the gastrointestinal flora showed that Enterococcus species and anaerobes were significantly associated with enhanced organ dissemination, whereas Enterobacterales, such as Escherichia species and Klebsiella species, were associated with the suppression of organ dissemination. In coinfection experiments, Enterococcus faecalis and Faecalibaculum rodentium inoculation, but not either of them, increased C. glabrata organ dissemination without affecting gastrointestinal colonization.

CONCLUSIONS

Coinfection with gastrointestinal bacteria promoted C. glabrata organ dissemination, which would indicate that gastrointestinal flora could affect C. glabrata dissemination. Therefore, the gastrointestinal flora could be a target for intervention or treatment in clinical settings. Insights from this study would lead to better control of endogenous candidiasis focusing on the gastrointestinal flora.

Heterogeneity of Candida bloodstream isolates in an academic medical center and affiliated hospitals

Invasive Candida bloodstream infections (candidemia) are a deadly global health threat. Rare Candida species are increasingly important causes of candidemia and phenotypic data, including patterns of antifungal drug resistance, is limited. There is geographic variation in the distribution of Candida species and frequency of antifungal drug resistance, which means that collecting and reporting regional data can have significant clinical value. Here, we report the first survey of species distribution, frequency of antifungal drug resistance, and phenotypic variability of Candida bloodstream isolates from an academic medical center and 5 affiliated hospitals in the Minneapolis-Saint Paul region of Minnesota, collected during an 18-month period from 2019 to 2021. We collected 288 isolates spanning 11 species from 119 patients. C. albicans was the most frequently recovered species, followed by C. glabrata and C. parapsilosis, with 10% of cases representing additional, rare species. We performed antifungal drug susceptibility for the three major drug classes and, concerningly, we identified fluconazole, micafungin and multidrug resistance rates in C. glabrata that were ~ 2 times higher than that reported in other regions of the United States. We report some of the first phenotypic data in rare non-albicans Candida species. Through analysis of serial isolates from individual patients, we identified clinically relevant within-patient differences of MIC values in multiple drug classes. Our results provide valuable clinical data relevant to antifungal stewardship efforts and highlight important areas of future research, including within-patient dynamics of infection and the mechanisms of drug resistance in rare Candida species.

An update on newer antifungals

INTRODUCTION

Fungal infections constitute a significant global health threat, with an estimated incidence of 6.5 million invasive fungal infections and 2.5 million associated deaths each year. New antifungal agents are being developed to address the challenges of fungal infections management, driven by the evolving fungal epidemiology, the emergence of antifungal resistance, and the limitations of existing treatments.

AREA COVERED

This review provides a thorough overview of the latest developments in novel antifungal agents, highlighting pivotal evidence obtained from clinical trials.

EXPERT OPINION

New antifungal agents hold promising future for difficult-to-treat fungal infections, providing for improved bioavailability, pharmacokinetic properties, adverse events and drug interactions, as well as, spectrum of activity. However, further data is needed before incorporating these agents in everyday clinical practice for the management of invasive fungal infections.

Multi-locus sequence typing of Candida tropicalis among Candiduria shows an outbreak in azole-susceptible isolates and clonal cluster enriched in azole-resistant isolates

BACKGROUND

The increasing detection rate of C. tropicalis and its azole resistance have made clinical treatment difficult. The presence of candiduria seems to correlate with invasive candida infection, especially for patients admitted to ICUs. However, the prevalence and antifungal resistance of C. tropicalis isolates in urine samples has not been well studied.

AIM

To retrospectively investigate the clinical features, antifungal resistance, and genetic relatedness of C. tropicalis isolates from urine samples.

METHODS

A total of 107 clinical C. tropicalis isolates were retrospectively studied, including phenotypes of isolates and characteristics of patients. The genetic profiles of 107 isolates were genotyped using multi-locus sequence typing (MLST). Phylogenetic analysis was inferred using unweighted pair group method with arithmetic averages. MLST clonal clusters (CCs) were analysed by goeBURST.

FINDINGS

Of the 107 isolates, 27.1% were resistant to fluconazole, and there was a notable increasing trend of fluconazole resistance from 16.1% in 2019 to 40.0% in 2021. Forty-seven diploid sequence types (DSTs) were assigned to ten major CCs. CC1 was the predominant fluconazole-susceptible group; 24 isolates from CC1 belonged to DST333, an outbreak clone in NICU ward. The azole-resistant CC4 contained 19 isolates, accounting for 65.5% of the azole-resistant isolates in this study. CC4 belongs to a prevalent FNS CC1 globally, of which the putative founder genotype was DST225.

CONCLUSION

This study revealed an outbreak of azole-susceptible C. tropicalis isolates in urine specimens and a high azole resistance rate of C. tropicalis in candiduria, and the MLST type showed clonal aggregation in azole-resistant isolates from urine samples.

Diagnosis and Prevention of Invasive Fungal Infections in the Immunocompromised Host

TOPIC IMPORTANCE

The prevalence of invasive fungal infections (IFIs) has risen in the past 3 decades, attributed to advancements in immune-modulatory therapies used in transplantation, rheumatology, and oncology.

REVIEW FINDINGS

Organisms that cause IFI evade the host's natural defenses or at opportunities of immunologic weakness. Infections occur from inhalation of potentially pathogenic organisms, translocation of commensal organisms, or reactivation of latent infection. Organisms that cause IFI in immunocompromised populations include Candida species, Cryptococcus species, environmental molds, and endemic fungi. Diagnosis of these infections is challenging due to slow organism growth and fastidious culture requirements. Moreover, fungal biomarkers tend to be nonspecific and can be negatively impacted by prophylactic antifungals. Antibody-based tests are not sensitive in immunocompromised hosts making antigen-based testing necessary. Prevention of IFI is guided by pathogen avoidance, removal or minimization of immune-suppressing factors, and pharmacologic prophylaxis in select hosts.

SUMMARY

Understanding the complex interplay between the immune system and opportunistic fungal pathogens plays a key role in early diagnosis and prevention.

Fluconazole step-down therapy versus echinocandins for the treatment of Candida glabrata invasive candidiasis with candidaemia

OBJECTIVES

Candida glabrata is the second most common species responsible for invasive candidiasis, including candidaemia. Echinocandins are typically the first-line therapy for C. glabrata candidaemia, with the option to transition to oral fluconazole. Studies are needed to evaluate clinical outcomes in patients initially treated with echinocandins then transitioned to fluconazole.

METHODS

This was a retrospective, single-centre cohort study of patients with C. glabrata candidaemia from November 2011 to August 2023. Inpatients aged 18-89 years who received an echinocandin within 24 h of the initial positive blood culture were included. Patients were excluded if they received antifungal treatment less than 48 h, combination therapy, or fluconazole as initial therapy. The primary composite outcome was 30-day clinical failure.

RESULTS

A total of 186 patients were included (n = 153 echinocandin only; n = 33 fluconazole step-down). The most common source of candidaemia was line-associated in both groups with the majority having source control (43% echinocandin versus 58% fluconazole; P = 0.32). Compared to fluconazole, patients in the echinocandin group had a higher rate of concomitant bacteraemia (45% versus 24%; P = 0.03) and endovascular complications (11% versus 0%; P = 0.05). There was no significant difference in treatment duration between echinocandin and fluconazole (16 versus 19 days; P = 0.46), incidence of persistent candidaemia (22% versus 24%; P = 0.7), or 30-day clinical failure (15% versus 9%; P = 0.58).

CONCLUSIONS

Fluconazole appears to be a safe and reasonable step-down therapy in the management of C. glabrata candidaemia.

Comparative evaluation of antifungal susceptibility testing methods of invasive Candida species and detection of FKS genes mutations in caspofungin intermediate and resistant isolates

BACKGROUND

Fungal invasive infections caused by Candida species pose a substantial public health risk with limited therapeutic options. Antifungal susceptibility testing (AFST) is necessary to optimize the therapy. The study aimed to compare different AFST methods of Candida spp. and detect FKS gene mutations among caspofungin-intermediate and resistant isolates.

METHODS

A total of 60 non-replicative invasive Candida isolates recovered from various clinical samples were included. In-vitro AFST was carried out using the ATB FUNGUS 3, Vitek-2 AST-YS08, and E-test. Hotspot (HS) regions of FKS genes were sequenced for caspofungin-intermediate and resistant isolates.

RESULTS

Candida albicans (58.3%) was the most predominant spp., followed by C. glabrata (28.3%). Based on the clinical breakpoints (CBPs), fluconazole resistance was found in C. albicans (45.7%), C. tropicalis (25%), and the C. parapsilosis isolate, while 35.3% of C. glabrata were susceptible dose-dependent (SDD). None of C. albicans, C. tropicalis, or C. parapsilosis isolates were resistant to voriconazole. Using the epidemiological cut-off values (ECVs) for amphotericin B, 6.7% of isolates were non-wild type (non-WT), including C. guilliermondii (50%), C. tropicalis (25%), and C. glabrata (11.8%), while all C. albicans, C. parapsilosis, and C. kefyr isolates were classified as wild-type (WT). ATB FUNGUS 3 and Vitek-2 had the highest categorical agreement (CA) (83.1%) for amphotericin B, while a lower concordance was detected with voriconazole (23.2%) and fluconazole (52.2%). For caspofungin, Vitek-2 and E-test had a CA of 89.8%. Eleven isolates (10 C. glabrata and one C. parapsilosis) exhibited resistance or intermediate susceptibility to caspofungin (MICs: 0.25‒>32 µg/ml). Molecular characterization of the FKS gene demonstrated that FKS1 mutations V47I, V52K, V56T, D57S, L62F, I71Y, I71Q in the HS1 region, and G7S, P11H mutations in the HS2 region were associated with increased caspofungin MIC values (16 µg/ml). Mutations at the HS1 of the FKS2 gene; K33V, W35K, and W35V; were associated with the highest caspofungin MICs of > 32 µg/ml.

CONCLUSIONS

ATB FUNGUS 3 demonstrated acceptable performance for AFST, however, azole activity against Candida spp. should be interpreted carefully. Novel mutations within HS regions of FKS genes elucidated different levels of caspofungin resistance in C. glabrata and C. parapsilosis isolates.

Impact of Fluconazole Resistance on the Outcomes of Patients With Candida parapsilosis Bloodstream Infections: A Retrospective Multicenter Study

BACKGROUND

This study assesses the impact of fluconazole resistance on 30-day all-cause mortality and 1-year recurrence in patients with Candida parapsilosis bloodstream infections (BSI).

METHODS

A multicenter retrospective study was performed at 3 hospitals in Italy and Spain between 2018 and 2022. Adult patients with positive blood cultures for C. parapsilosis who received appropriate targeted therapy with either echinocandins or fluconazole were included.

RESULTS

Among 457 patients, 196 (42.9%) had fluconazole-resistant C. parapsilosis (FLZR-CP) BSI and 261 (57.1%) had fluconazole-susceptible C. parapsilosis (FLZS-CP) BSI. All FLZR-CP patients received targeted echinocandins, while FLZS-CP patients received either echinocandins (60.5%) or fluconazole (39.5%). Unadjusted 30-day all-cause mortality rates were 28.6% for FLZR-CP and 28.4% for FLZS-CP (log-rank test, P = .998). In multivariable analysis, increased mortality was associated with age (adjusted hazard ratio [aHR] 1.03 per year; 95% confidence interval [CI], 1.01-1.05; P = .0005), solid tumor (aHR 1.91; 95% CI, 1.06-3.46; P = .0302), previous antifungal treatment (aHR 1.84; 95% CI, 1.12-3.10; P = .0192), and septic shock (aHR 2.39; 95% CI, 1.42-4.06; P = .0010), but not fluconazole resistance (aHR 1.00; 95% CI, .62-1.63; P = .9864) nor the type of initial antifungal therapy (aHR 1.46; 95% CI, .69-3.06; P = .3202). Propensity score-matched analysis showed no 30-day all-cause mortality difference between echinocandin-treated FLZR-CP and fluconazole-treated FLZS-CP patients (HR 0.81; 95% CI, .37-1.75; P = .5915). However, a higher 1-year recurrence risk was observed in FLZR-CP patients (odds ratio, 7.37; 95% CI, 2.11-25.80; P = .0018).

CONCLUSIONS

Our results suggest that fluconazole resistance is not associated with a higher mortality risk in patients with C. parapsilosis BSI, though 1-year recurrence rates were higher in the FLZR-CP group.

Candida glabrata: A Tale of Stealth and Endurance

Candida (Nakaseomyces) glabrata, an opportunistic human fungal pathogen, causes mucosal and deep-seated infections in immunocompromised individuals. Recently designated as a high-priority fungal pathogen by the World Health Organization (WHO), C. glabrata exhibits low inherent susceptibility to azole antifungals. In addition, about 10% clinical isolates of C. glabrata display co-resistance to both azole and echinocandin drugs. Molecular mechanisms of antifungal resistance and virulence in C. glabrata are currently being delineated in-depth. This Review provides an overview of the epidemiology, biology, drug resistance, tools and host model systems for C. glabrata. Additionally, we discuss the immune evasion strategies that aid C. glabrata in establishing infections in the host. Overall, this Review aims to contribute to ongoing efforts to raise awareness of human pathogenic fungi, the growing threat of antifungal drug resistance and the unmet need for novel antifungal therapies, with an ultimate goal of improving clinical outcomes of affected individuals.

Chemoproteomic Profiling of C. albicans for Characterization of Anti-fungal Kinase Inhibitors

Candida albicans is a growing health concern as the leading causal agent of systemic candidiasis, a life-threatening fungal infection with a mortality rate of ~40% despite best available therapy. Yck2, a fungal casein kinase 1 (CK1) family member, is the cellular target of inhibitors YK-I-02 (YK) and MN-I-157 (MN). Here, multiplexed inhibitor beads paired with mass spectrometry (MIB/MS) employing ATP-competitive kinase inhibitors were used to define the selectivity of these Yck2 inhibitors across the global C. albicans proteome. The MIB matrix captured 89% of the known and predicted C. albicans protein kinases present in cell lysate. In MIB/MS competition assays, YK and MN demonstrated exquisite selectivity across the C. albicans fungal kinome with target engagement of only three CK1 homologs (Yck2, Yck22, and Hrr25) and a homolog of human p38α (Hog1). Additional chemoproteomics using a custom MN-kinobead identified only one additional C. albicans protein, confirming its remarkable fungal proteome-wide selectivity. To identify new Yck2 inhibitors with selectivity over Hog1, thirteen human CK1 kinase inhibitors were profiled for fungal kinase-binding activity using MIB/MS competition assays and in-cell NanoBRET target engagement assays. A new chemotype of family-selective Yck2 inhibitors with antifungal activity was identified. Together, these findings expand the application of MIB/MS proteomic profiling for non-human kinomes and demonstrate its utility in the discovery and development of selective inhibitors of fungal kinases with potential antimicrobial activity.

Structure-guided optimization of small molecules targeting the yeast casein kinase, Yck2, as a therapeutic strategy to combat Candida albicans

Candida albicans is the most common cause of life-threatening fungal infection in the developed world but remains a therapeutic challenge. Protein kinases have been rewarding drug targets across diverse indications but remain untapped for antifungal development. Previously, screening kinase inhibitors against C. albicans revealed a 2,3-aryl-pyrazolopyridine, GW461484A (GW), which targets casein kinase 1 (CK1) family member Yck2. Here, we report optimization of GW via two complementary approaches, synthesis of bioisosteres possessing an imidazo[1,2-a]pyridine core, and R-group substitution of GW's pyrazolo[1,5-a]pyridine core. Characterization of compounds synthesized revealed two 6-cyano derivatives with improved pharmacological properties that retained whole-cell bioactivity and selectivity for fungal Yck2 compared to human CK1α. Efficacy studies in mice indicated both analogs possess single-agent activity against C. albicans resistant to first-line echinocandin antifungals and potentiate non-curative echinocandin treatment. Results validate Yck2 as an antifungal target and encourage further development of inhibitors acting by this previously unexploited mode of action.

A MALDI-TOF MS-based multiple detection panel of drug resistance-associated multiple single-nucleotide polymorphisms in Candida tropicalis

Candida tropicalis is one of the main causes of invasive candidiasis. Rapid identification of antifungal resistance is crucial for selection of an appropriate antifungal to improve patient outcomes. Mutations at specific loci are strongly correlated with resistance to antifungal agents. In this study, we developed a multi-single-nucleotide polymorphism (SNP) panel to accurately identify 36 mutation sites across seven genes of C. tropicalis that are associated with resistance to azoles and/or echinocandins. Ten isolates were selected to test repeatability, and another 20 isolates of C. tropicalis were selected to validate consistency. Intra-assay and inter-assay repeatability of the panel was 100%, with the loci accuracy being 99.44% (716 of 720). Furthermore, 109 isolates were examined for clinical research, and the most commonly detected mutations were G751A and A866T of UPC2, A491T of TAC1, and A395T and C461T of ERG11. The G751A and A866T mutations of UPC2 as well as the A395T and C461T mutations of ERG11 co-existed. The SNP panel enables identification of specific mutations at critical sites of drug-resistant strains to facilitate the rapid selection of appropriate antifungal agents and efficient monitoring of the regional epidemiological trends of resistance of C. tropicalis.IMPORTANCEC. tropicalis infections pose a growing global public health challenge, with mortality rates approaching 40%. C. tropicalis is one of the top four Candida spp. responsible for candidiasis, particularly in the Asia-Pacific region and Latin America, notably affecting patients with neutropenia and malignancies. The azole resistance rate of C. tropicalis ranges from 0% to 30%. Between 2009 and 2018, the China Hospital Invasive Fungal Surveillance Network reported an increase in fluconazole and voriconazole resistance from 5.7% to ~30%. Although resistance to echinocandins and amphotericin B remains low, multi-resistance to echinocandins and azoles has been observed. Current methods for detecting drug resistance are limited by the long turnaround time of antifungal susceptibility testing, low throughput of Sanger sequence to target resistance mutations, complex data analysis, and high costs of second-generation sequencing. We developed and validated a rapid, high-throughput, and cost-effective panel to detect and monitor drug-resistance mutations of C. tropicalis.

Rapid Identification of Clinically Relevant Candida spp. by I-dOne Software Using Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) Spectroscopy

Attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy is a spectrum-based technique that quantifies the absorption of infrared light by molecules present in the microbial cell. The aim of the present study was to evaluate the performance of the ATR-FTIR spectroscopic technique via I-dOne software (Version 2.0) compared with the MALDI-TOF MS in identifying Candida spp. Each infrared spectrum was compared with spectra stored in the software database. The updated version of the I-dOne software was used to analyze ATR-FTIR spectra. All Candida isolates 284/284 (100%) were classified correctly according to the genus. Overall species identification yielded 272/284 (95.8%) concordant identification results with MALDI-TOF MS. Additionally, all 79 isolates belonging to the Candida parapsilosis species complex were identified correctly to the species level with the updated version of the I-dOne software. Only 12 (4.2%) isolates were misidentified at the species level. The present study highlights the potential diagnostic performance of the I-dOne software with ATR-FTIR spectroscopic technique referral spectral database as a real alternative for routine identification of the most frequently isolated Candida spp.

The distinctive pharmacokinetic profile of rezafungin, a long-acting echinocandin developed in the era of modern pharmacometrics

Echinocandin drugs are the current first-line therapy for fungal infections caused by Candida spp. Most patients require once-daily intravenous (IV) administration in a hospital or outpatient setting for treatment, which may negatively impact their quality of life and stress healthcare resources. Similar to other echinocandins, the novel FDA-, EMA-, and Medical and Healthcare Products Regulatory Agency-approved echinocandin, rezafungin (CD101), exhibited strong antifungal activity against several fungal pathogens and a low drug-drug interaction liability, which are important for medically complex patients. A pharmacometric-based approach has been adopted throughout the development of rezafungin, which contrasts with older echinocandins where dosing regimens were largely derived empirically, and only recently based on pharmacometric guidance. This state-of-the-art approach used model-based simulations incorporating pre-clinical and clinical data as it became available to optimize the dosing regimen for rezafungin. The enhanced stability of the molecular structure and the safety profile of rezafungin allow for the administration of once-weekly IV doses, compared to the daily dosing requirement for other echinocandin drugs, with this distinctive pharmacokinetic profile of rezafungin resulting in a front-loaded dosing regimen with high exposures early in therapy for enhanced fungal killing. The long shelf-life of rezafungin makes this echinocandin more flexible in terms of storage and manufacturing. Demonstrated across clinical development, rezafungin may provide patients with next-generation first-line antifungal treatment for the treatment of candidaemia and invasive candidiasis.

Inter-Institutional Dynamics and Impact of Fluconazole-Resistant Candida parapsilosis

BACKGROUND

Infections with fluconazole-resistant Candida parapsilosis have been increasing in Israeli hospitals with unclear implications for patient outcomes.

OBJECTIVES

To determine the frequency, mechanisms, molecular epidemiology, and outcomes of azole-resistant C. parapsilosis bloodstream infections in four hospitals in Israel.

PATIENTS/METHODS

C. parapsilosis bloodstream isolates were collected at four hospitals in central Israel during varying periods from 2005 to 2022. Antifungal susceptibility testing was done using CLSI broth microdilution. Risk factors for fluconazole resistance were investigated using logistic regression. ERG11 gene sequencing was performed on all isolates. Genetic relatedness was determined using multilocus microsatellite genotyping. Clinical cure, microbiological eradication, and mortality rates were compared between fluconazole-susceptible and resistant isolates.

RESULTS

A total of 192 patient-specific C. parapsilosis isolates were analysed. Resistance to fluconazole and voriconazole was detected in 80 (41%) and 14 (7.2%) isolates, respectively. The ERG11 Y132F substitution was found in 91% of fluconazole-resistant and 1% of fluconazole-susceptible isolates. Increasing age, intensive care hospitalisation, haemodialysis, and recent exposure to antibiotics were risk factors for fluconazole-resistant C. parapsilosis. Distinct but related genotypes predominated at each centre, indicating extensive dissemination within hospitals and limited transmission among them. Fluconazole resistance was associated with increased likelihood of microbiological failure but no significant difference in clinical cure and mortality.

CONCLUSIONS

We found high rates of fluconazole resistance in C. parapsilosis, attributable to nosocomial spread of hospital-specific clones bearing the Y132F substitution. Fluconazole resistance was associated with a higher risk of microbiological but not clinical failure. Strategies to limit nosocomial transmission of C. parapsilosis are needed.

Rezafungin acetate for the treatment of candidemia and invasive candidiasis: a pharmacokinetic evaluation

INTRODUCTION

Rezafungin, formerly SP3025 and CD101, is a next-generation echinocandin, chemically related to anidulafungin, with differentiated pharmacokinetic characteristics, including a prolonged half-life allowing extended-interval dosing.

AREAS COVERED

Herein, we discuss the role of rezafungin in the treatment of candidemia and invasive candidiasis, with a specific focus on pharmacokinetics considerations.

EXPERT OPINION

Rezafungin exhibits potent in vitro activity against most wild-type and azole-resistant Candida species, including Candida auris. The differentiated PK characteristics of rezafungin which enables once weekly dosing could reduce catheter overuse and provide a rapid transition to outpatient treatment for Candida infections in which azoles cannot be used, due to resistance or drug-drug interactions. Besides weekly dosing, other potential pharmacokinetic/pharmacodynamic advantages of rezafungin are its good penetration into anatomically challenging sites and a potentially reduced probability of local resistance promotion, making it an attractive option also for deep-seated infections that could warrant dedicated clinical investigation.

Risk factors associated with short-term mortality in patients with candidemia and the predictive value of serum cytokine level

BACKGROUND

Some pro-inflammatory and anti-inflammatory cytokines were significantly elevated in patients with candidemia patients, but no studies have included these cytokines in the analysis of risk factors for mortality of candidemia. This study aims to analyze the risk factors of short-term mortality of candidemia and the predictive value of serum cytokines.

METHODS

We retrospectively analyzed and compared the clinical features, risk factors and cytokine interleukin (IL)-6, interferon-γ (IFN-γ), IL-10 and IL-17 between survival group and death group in 53 patients with candidemia. Receiver operating of the characteristic curve (ROC) analysis was performed and figured up area under the curve (AUC), sensitivity and specificity values to assess the predictive power of independent factors associated with mortality.

RESULTS

The overall in-hospital mortality rate of candidemia was 62.3 % (33/53), and the 30-day mortality rate was 52.8 % (28/53). The C. albicans accounting for 17.0 % (9/53), and the non-albicans Candida was 83.0 % (44/53). Serum IL-6 (p = 0.041, HR = 1.009), IFN-γ (p = 0.013, HR = 1.007, 95 %), procalcitonin (PCT) (p = 0.010, HR = 0.899) and Candida score (p = 0.033, HR = 1.659) were independent risk factors, while Initiation of targeted antifungal therapy within 48 h of positive blood cultures (BC) (P = 0.015, HR = 0.266) was a protective factor. The AUC of ROC for Candida score, serum IL-6, PCT, IFN-γ, and Initiation of targeted antifungal therapy within 48 h of positive BC showed 0.933, 0.841, 0.801, 0.732, 0.714, respectively. IL-6 and IFN-γ comprised good performing model for predicting 30-day and 90-day mortality, while IL-6 and IL-10 were the best combinations for predicting 90-day mortality.

CONCLUSIONS

Serum IL-6, IFN-γ, PCT, and Candida score can predict short-term mortality risk in patients with candidemia, while prompt and targeted antifungal treatment may reduce mortality. IL-6 could serve as a possible biomarker for predicting short-term mortality of candidemia and its combination with IL-10 or IFN-γ may further improve the predictive value.

Invasive Candidiasis in Pediatric Hematologic Malignancy: Increased Risk of Dissemination With Candida tropicalis

BACKGROUND

Candida species are the most common cause of invasive fungal disease, and children with hematologic malignancy are at increased risk. Non- albicans Candida (NAC) now account for more than half of all invasive candidiasis (IC) and carry a worse prognosis. We aimed to compare the epidemiology, risk factors, organ dissemination, biomarkers and outcomes in IC based on the species implicated and evaluate trends in antifungal resistance over time.

METHODS

Patients 0-18 years of age with hematologic malignancy and IC at 2 centers were included. Fifty-three patients from 2011 to 2022 were identified. Information related to demographics, host and risk factors, Candida species and antifungal susceptibilities, treatment and outcomes was collected via retrospective chart review. Data were analyzed at the species level.

RESULTS

The incidence rate of IC was 29 per 1000 patients with leukemia and lymphoma. The median time to infection from diagnosis of malignancy was 38 days. Candida tropicalis (n = 17; 30%) was the most identified species followed by Candida albicans (n = 14; 25%). Patients with C. tropicalis infection were more likely to have dissemination to the eyes ( P = 0.035), spleen ( P = 0.001) and skin ( P = 0.003) than patients with C. albicans or other NAC. Of the 34 patients who underwent dilated retinal examination, 24% (n = 8) had evidence of intraocular candidiasis. Seven of the 8 patients with intraocular disease had prolonged candidemia (3 or more days; P = 0.003). The 12-week crude mortality rate was 16.9%.

CONCLUSIONS

NAC, specifically C. tropicalis , accounted for most of the IC in children with hematological malignancies. Screening for intraocular candidiasis continues to play an important role in patients with IC, and future studies are needed to determine if screening can be limited to patients with select risk factors.

Efficacy of two novel antifungal lipopeptides, AF4 and AF5 of bacillomycin D family in murine models of invasive candidiasis, cryptococcosis, and aspergillosis

Invasive fungal diseases are an important public health concern due to an increase in the at-risk population and high mortality associated with these infections. Managing invasive fungal infections poses a significant challenge given the limited antifungal options and the emergence of resistance in key fungal pathogens. Through a comprehensive approach, we evaluated the in vitro antifungal activity and the in vivo efficacy of two novel lipopeptides, AF4 and AF5 in murine models of disseminated candidiasis, cryptococcosis, and aspergillosis. Flow cytometry analysis with propidium iodide showed a dose-dependent increase in the permeability and disruption of fungal cell membranes, underscoring the membrane perturbing effects of AF4 and AF5. These observations were further substantiated by SEM analyses that showed yeast cell and hyphal deformation and leakage of cellular contents. Our in vivo investigations utilizing two doses (5 and 10 mg/kg bodyweight) of each lipopeptide and its comparison with standard antifungal therapies showed lipopeptides significantly improved the odds of mice survival in invasive candidiasis and cryptococcosis models, with a reduction in organ fungal burden by 2 to 3-log10 order. Additionally, in the disseminated aspergillosis model, treatment with 10 mg/kg of AF4 significantly improved median survival from 4 to 10 days while achieving a notable 1-log10 order reduction in organ fungal burden. Overall, our study underscores the potent and broad-spectrum antifungal activity of lipopeptides in mouse infection models, hinting at their promising therapeutic potential in invasive fungal disease.

Candidemia chronicles: Retrospective analysis of candidemia epidemiology, species distribution, and antifungal susceptibility patterns in Bahrain

BACKGROUND

Invasive fungal infections, particularly candidemia, pose significant clinical challenges globally. Understanding local epidemiology, species distribution, and antifungal susceptibility patterns is crucial for effective management despite regional variations.

AIM

To investigate the epidemiology, species distribution, antifungal susceptibility patterns, and associated risk factors of candidemia among patients in Bahrain from 2021 to 2023.

METHODS

This retrospective study analyzed demographic data, Candida species distribution, antifungal susceptibility profiles, and risk factors among candidemia patients treated at a tertiary care hospital in Bahrain over three years. Data was collected from medical records and analyzed using descriptive statistics.

RESULTS

A total of 430 candidemia cases were identified. The mean age of patients was 65.7 years, with a mortality rate of 85.5%. Candida albicans (C. albicans) was the most common species, followed by Candida parapsilosis, Candida tropicalis (C. tropicalis), and emerging multidrug-resistant Candida auris (C. auris). Antifungal susceptibility varied across species, with declining susceptibility to azoles observed, particularly among C. albicans and C. tropicalis. Major risk factors included central venous catheters, broad-spectrum antibiotics, and surgical procedures.

CONCLUSION

This study highlights the substantial burden of candidemia among older adults in Bahrain, characterized by diverse Candida species. It also concerns levels of antifungal resistance, notably in C. auris. The findings underscore the importance of local epidemiological surveillance and tailored treatment strategies to improve outcomes and mitigate the spread of multidrug-resistant Candida species. Future research should focus on molecular resistance mechanisms and optimizing therapeutic approaches to address this growing public health concern.

Ellagic Acid Potentiates the Inhibitory Effects of Fluconazole Against Candida albicans

Background/Objectives: Antifungal resistance to azoles, coupled with the increasing prevalence of Candida albicans infections, represents a significant public health challenge and has driven the search for new natural compounds that can act as alternatives or adjuvants to the current antifungals. Ellagic acid (EA) has demonstrated antifungal activity; however, its effects are not fully understood. In this study, we investigated the in vitro anti-Candida activity of EA and its ability to potentiate the effects of fluconazole (FLZ) on C. albicans.Methods: The Minimum Inhibitory Concentration (MIC) of EA was determined by broth microdilution and its interaction with FLZ was assessed using a checkerboard assay. Additionally, we examined the effects of EA on yeast-to-hypha transition, inhibition of biofilm formation, time-kill kinetics, hemolytic activity, and cytotoxicity in HeLa ATCC® CCL-2™ cells. Results: EA exhibited MIC values ranging from 250 to 2000 µg/mL and showed synergistic and additive interactions with FLZ, resulting in a marked reduction in the MIC values of FLZ (up to 32-fold) and EA (up to 16-fold). In the time-kill assay, the most effective combinations were 4× EA MIC, 2× EA MIC, and FIC EA + FLZ, which showed fungicidal activity. Furthermore, EA did not show hemolytic activity and demonstrated low and dose-dependent cytotoxicity in HeLa cells, with no cytotoxic effects observed in combination with FLZ. EA and the synergistic combination of EA and FLZ interfered with both the yeast-to-hypha transition process in C. albicans cells and biofilm formation. In addition to its antifungal efficacy, EA demonstrated a favorable safety profile at the concentrations used. Conclusions: This study presents promising results regarding the potential use of EA in combination with FLZ for the treatment of C. albicans infections.

Anticandidal Efficacy of Green Synthesized Silver Nanoparticles Using Trans-Himalayan Plant Extracts Against Drug Resistant Clinical Isolates of Candida auris

Candida auris is the most common, globally detected nosocomial fungal pathogen with multi-drug resistance. The high prevalence of C. auris infections has raised concern about drug resistance and adverse effects, compounded by a lack of effective alternative drugs. Bioengineered nanomaterials play a significant role in combating nosocomial infections. Silver nanoparticles (AgNPs) have emerged as an extensively used nanomaterial due to their prominent antimicrobial properties. One of the most promising approaches is to incorporate herbal extracts that contain a range of phytoconstituents, being used for curing various chronic illnesses. This study aimed to produce eco-friendly, cost-effective green synthesized AgNPs with trans-Himalayan medicinal plant extracts (Trillium govanianum & Bergenia ligulata) and assess their anticandidal and antibiofilm potential. The green-synthesized AgNPs formation and crystalline nature were confirmed by UV-visible spectroscopy, dynamic light scattering and X-ray diffraction analysis. The UV-Vis spectra of the AgNPs revealed bands in the range of 415-430 nm. Phytoconstituents as reducing agents were involved in the stabilization of AgNPs as identified by FTIR spectra. HR-TEM of AgNPs' displayed a spherical shape with size in the range of 10-100 nm. Results of activity tests performed using various C. auris clinical strains showed half maximum growth inhibition (IC50) at 8.02 µg/mL, which inhibited 65% of biofilm for T. govanianum extract. The free radical scavenging activity evaluated for green synthesized AgNPs using DPPH showed more than 90% antioxidant activity. Green synthesized AgNPs displayed potent growth inhibition (IC50) at 4.01 µg/mL with 87.0% biofilm inhibition. Green synthesized AgNPs coated bandages and catheters inhibited the growth of C. auris. This study concluded that green synthesized AgNPs formulation in conjunction with antifungal agents exhibits potential biomedical application and also could be used as alternative therapeutics.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12088-024-01277-8.

Susceptibility patterns of Candida species collected from intensive care units in Portugal: a prospective study in 2020-2022

Background

For Candida infections antifungal therapy is often empirical and mainly depends on locally antifungal surveillance data, which differs between geographic regions.

Aims

To monitor the epidemiology and antifungal susceptibility of Candida spp. from combined axillar-groin samples in intensive care unit (ICU) patients on admission (day1, D1), day 5 (D5) and day 8 (D8).

Methods

From 2020 to 2022, 675 patients from three ICUs were enrolled. Candida isolates were identified by MALDI-TOF MS and PCR. In vitro antifungals susceptibility tests (AFST) were performed for fluconazole, voriconazole, amphotericin B and anidulafungin, by concentration gradient Etest® strip technique.

Results

Out of 988 swabs, 355 isolates were identified as Candida species from 232 patients, being 89 isolates retrieved from patients that remained colonised at D5 and D8. AFST was conducted for all Candida isolates. The overall rate of resistance to fluconazole was 2.7%, with 3 out of 133 C. albicans, 2 out of 89 C. parapsilosis and 2 out of 24 C. glabrata isolates identified as resistant. Voriconazole susceptibility was observed in 99.2% of the isolates, with only one C. albicans isolate identified as resistant to this triazole. All isolates were susceptible to amphotericin B and 98.5% to anidulafungin. Three Candida spp. exhibited resistance to anidulafungin, C. albicans, C. tropicalis, and C. parapsilosis.

Conclusions

This study highlights the importance of C. albicans as a frequent coloniser and showed that antifungal resistance remains uncommon among Candida isolates from ICUs in Portugal. The results may contribute to better management within institutions to guide therapeutic decision making.

In the flow of molecular miniaturized fungal diagnosis

The diagnosis of fungal infections presents several challenges and limitations, stemming from the similarities in symptomatology, diversity of underlying pathogenic species, complexity of fungal biology, and scarcity of rapid, affordable, and point-of-care approaches. In this review, we assess technological advances enabling the conversion of cutting-edge laboratory molecular diagnostic methods to cost-effective microfluidic devices. The most promising strategies toward the design of DNA sequence-based fungal diagnostic systems, capable of capturing and deciphering the highly informative DNA of the pathogen and adapted for resource-limited settings, are discussed, bridging fungal biology, molecular genetics, microfluidics, and biosensors.

Exploring the effects of culture conditions on Yapsin (YPS) gene expression in Nakaseomyces glabratus

Nakaseomyces glabratus, previously known as Candida glabrata, has the great potential to cause systemic fungal infections despite its similarity to baker's yeast. Its pathogenicity is attributed to the production of numerous virulence factors, among which the YPS genes (YPS1-YPS11) encoding aspartyl proteases have yet to be sufficiently characterized, and limited studies suggest their involvement in cellular homeostasis. The study's novelty is an investigation of the role of YPS in N. glabratus's ability to adapt to different host environments. For this purpose, we isolated RNA from N. glabratus cells grown in both host niche-mimicking culture media, such as artificial saliva (AS) and vagina-simulating media (VS), as well as standard yeast media (RPMI 1640 and YPDA). We then performed quantitative real-time PCR to evaluate YPS gene expression at different growth phases. At the early logarithmic phase, we observed a general increase in the expression levels of YPS genes; however, at the stationary phase, high expression levels were maintained for YPS7 in RPMI 1640 and YPDA media and YPS6 in RPMI 1640 and AS media. In addition, although the VS medium does not promote the proliferation of N. glabratus, the yeast can survive in an acidic environment, and the significantly overexpressed gene is YPS7. These findings underscore the significant modulation of N. glabratus YPS gene expression in response to external environmental conditions. This research provides insights into the molecular basis of N. glabratus pathogenicity and highlights new potential targets for antifungal therapy.

Shining a light on Candida-induced epithelial damage with a luciferase reporter

Host cell damage is a key parameter for research in infection biology, drug testing, and substance safety screening. In this study, we introduce a luciferase reporter system as a new and reliable assay to measure cell damage and validate it with the pathogenic yeast, Candida albicans, as a test case. We transduced human epithelial cell lines with a lentiviral vector to stably express an optimized luciferase enzyme, Nanoluc. Upon cell damage, the release of cytoplasmic luciferase into the extracellular space can be easily detected by a luminometer. We used the luciferase reporter system to investigate the damage caused by C. albicans to different newly generated epithelial reporter cell lines. We found that fungus-induced cell damage, as determined by established methods, correlated tightly with the release of the luciferase. The new luciferase reporter system is a simple, sensitive, robust, and inexpensive method for measuring host cell damage and has a sensitivity comparable to the standard assay, release of lactate dehydrogenase. It is suitable for high-throughput studies of pathogenesis mechanisms of any microbe, for antimicrobial drug screening, and many other applications.IMPORTANCEWe present a quick, easy, inexpensive, and reliable assay to measure damage to mammalian cells. To this end, we created reporter cell lines which artificially express luciferase, an enzyme that can be easily detected in the supernatant when these cells are damaged. We used infections with the well-investigated fungal pathogen of humans, Candida albicans, as a test case of our system. Using our reporter, we were able to recapitulate the known effects of strain variability, gene deletions, and antifungal treatments on host cell damage. This easily adaptable reporter system can be used to screen for damage in infection models with different microbial species, assay cell-damaging potential of substances, discover new non-toxic antibiotics, and many other damage-based applications.

Single-cell detection of copy number changes reveals dynamic mechanisms of adaptation to antifungals in Candida albicans

Genomic copy number changes are associated with antifungal drug resistance and virulence across diverse fungal pathogens, but the rate and dynamics of these genomic changes in the presence of antifungal drugs are unknown. Here we optimized a dual-fluorescent reporter system in the diploid pathogen Candida albicans to quantify haplotype-specific copy number variation (CNV) and loss of heterozygosity (LOH) at the single-cell level with flow cytometry. We followed the frequency and dynamics of CNV and LOH at two distinct genomic locations in the presence and absence of antifungal drugs in vitro and in a murine model of candidiasis. Copy number changes were rapid and dynamic during adaptation to fluconazole and frequently involved competing subpopulations with distinct genotypes. This study provides quantitative evidence for the rapid speed at which diverse genotypes arise and undergo dynamic population-level fluctuations during adaptation to antifungal drugs in vitro and in vivo.

The In Vitro Activity of Rezafungin Against Uncommon Species of Candida

BACKGROUND

Invasive candidiasis (IC) is increasing due to the rising numbers of immunocompromised patients. Increasing azole resistance rates and daily dosing required for most echinocandins have complicated its treatment. The approval of rezafungin has provided an option for weekly echinocandin treatment. The susceptibility of less common Candida spp. to rezafungin is unclear. We looked at the minimum inhibitory concentrations (MICs) of rezafungin and comparator agents against Candida spp. collected as part of a global surveillance program.

METHOD

The CLSI reference broth microdilution method was performed to test 590 clinical isolates of 28 different Candida species, including Candida auris. Species-specific interpretative criteria by breakpoints or epidemiological cutoff values were applied where available.

RESULTS

Rezafungin was within ±2-fold MIC50/90 values of other echinocandins against all Candida spp. The lowest rezafungin MIC50/90 values were noted against C. kefyr (0.03/0.06 mg/L) and C. pelliculosa (0.015/0.03 mg/L). Higher rezafungin MIC50/90 values were noted for C. guilliermondii (1/1 mg/L) and for isolates in the C. parapsilosis complex (C. orthopsilosis, 0.5/1 mg/L, C. metapsilosis, 0.12/0.5 mg/L). Rezafungin was active against 97.7% of C. dubliniensis and 95.4% of C. auris by CLSI breakpoints. For fluconazole, 69.7% of C. guilliermondii, 85.7% of C. orthopsilosis, and 100% of C. metapsilosis were wildtype by ECV, and 10.8% of C. auris were susceptible by CDC breakpoint.

CONCLUSIONS

Rezafungin was highly active by in vitro testing against less common Candida spp. Rezafungin MICs were comparable to other echinocandins. Rezafungin is a desirable therapeutic alternative due to its reduced dosing frequency.

High-Resolution Melting Assay to Detect the Mutations That Cause the Y132F and G458S Substitutions at the ERG11 Gene Involved in Azole Resistance in Candida parapsilosis

BACKGROUND

Candida parapsilosis is a pathogenic yeast that has reduced susceptibility to echinocandins and ranks as the second or third leading cause of candidaemia, depending on the geographical region. This yeast often causes nosocomial infections, which are frequently detected as outbreaks. In recent years, resistance to azoles in C. parapsilosis has increased globally, primarily due to the accumulation of mutations in the ERG11 gene.

OBJECTIVES

In this study, we have developed an assay based on real-time PCR and high-resolution melting (HRM) curve analysis to detect two of the most prevalent mutations at ERG11 that confer resistance to fluconazole (Y132F and G458S).

METHODS

We designed allele-specific oligonucleotides that selectively bind to either the wild type or mutated sequences and optimised the conditions to ensure amplification of the specific allele, followed by detection via high-resolution melting (HRM) analysis.

RESULTS

The designed oligonucleotides to detect the Erg11Y132F and Erg11G458S mutations produced specific amplification of either WT or mutated alleles. We conducted a duplex real-time PCR combining oligonucleotides for the wild-type sequences in one mix, and oligonucleotides for the mutated alleles in another. Following this, we performed an analysis of the HRM curve to identify the amplified allele in each case. This technique was blindly evaluated on a set of 114 C. parapsilosis isolates, all of which were unequivocally identified using our approach.

CONCLUSION

This technique offers a new method for the early detection of azole resistance mechanism in C. parapsilosis.

Most azole resistance mutations in the Candida albicans drug target confer cross-resistance without intrinsic fitness cost

Azole antifungals are the main drugs used to treat fungal infections. Amino acid substitutions in the drug target Erg11 (Cyp51) are a common resistance mechanism in pathogenic yeasts. How many and which mutations confer resistance is, however, largely unknown. Here we measure the impact of nearly 4,000 amino acid variants of Candida albicans Erg11 on the susceptibility to six clinical azoles. This was achieved by deep mutational scanning of CaErg11 expressed in Saccharomyces cerevisiae. We find that a large fraction of mutations lead to resistance (33%), most resistance mutations confer cross-resistance (88%) and only a handful of resistance mutations show a significant fitness cost (9%). Our results reveal that resistance to azoles can arise through a large set of mutations and this will probably lead to azole pan-resistance, with little evolutionary compromise. This resource will help inform treatment choices in clinical settings and guide the development of new drugs.

Investigating role of positively selected genes and mutation sites of ERG11 in drug resistance of Candida albicans

The steep increase in acquired drug resistance in Candida isolates has posed a great challenge in the clinical management of candidiasis globally. Information of genes and codon sites that are positively selected during evolution can provide insights into the mechanisms driving antifungal resistance in Candida. This study aimed to create a manually curated list of genes of Candida spp. reported to be associated with antifungal resistance in literature, and further investigate the structure-function implications of positively selected genes and mutation sites. Sequence analysis of antifungal drug resistance associated gene sequences from various species and strains of Candida revealed that ERG11 and MRR1 of C. albicans were positively selected during evolution. Four sites in ERG11 and two sites in MRR1 of C. albicans were positively selected and associated with drug resistance. These four sites (132, 405, 450, and 464) of ERG11 are predictive markers for azole resistance and have evolved over time. A well-characterized crystal structure of sterol-14-α-demethylase (CYP51) encoded by ERG11 is available in PDB. Therefore, the stability of CYP51 in complex with fluconazole was evaluated using MD simulations and molecular docking studies for two mutations (Y132F and Y132H) reported to be associated with azole resistance in literature. These mutations induced high flexibility in functional motifs of CYP51. It was also observed that residues such as I304, G308, and I379 of CYP51 play a critical role in fluconazole binding affinity. The insights gained from this study can further guide drug design strategies addressing antimicrobial resistance.

Development of multiplex real-time PCR for simultaneous detection of common fungal pathogens in invasive mycoses

Background

Fungi are common opportunistic pathogens that pose a significant threat to immunocompromised patients, particularly when late detection occurs.

Methods

In this study a multiplex real-time PCR has been developed for simultaneous detection of common fungal pathogens associated with invasive mycoses in a diagnostic setting.

Results

The specificity of the assay was rigorously tested on 40 types of organisms (n = 65), demonstrating 100% specificity. The limit of detection was determined to be 100 pg/μl (106 copies/μl), achievable within a rapid 3-h timeframe. The PCR assay efficiency exhibited a range between 89.77% and 104.30% for each target organism, with linearity falling between 0.9780 and 0.9983.

Conclusion

This multiplex real-time PCR assay holds promise for enhancing the timely and accurate diagnosis of invasive mycoses, particularly in immunocompromised patient populations.

Bloodstream infections: mechanisms of pathogenesis and opportunities for intervention

Bloodstream infections (BSIs) are common in hospitals, often life-threatening and increasing in prevalence. Microorganisms in the blood are usually rapidly cleared by the immune system and filtering organs but, in some cases, they can cause an acute infection and trigger sepsis, a systemic response to infection that leads to circulatory collapse, multiorgan dysfunction and death. Most BSIs are caused by bacteria, although fungi also contribute to a substantial portion of cases. Escherichia coli, Staphylococcus aureus, coagulase-negative Staphylococcus, Klebsiella pneumoniae and Candida albicans are leading causes of BSIs, although their prevalence depends on patient demographics and geographical region. Each species is equipped with unique factors that aid in the colonization of initial sites and dissemination and survival in the blood, and these factors represent potential opportunities for interventions. As many pathogens become increasingly resistant to antimicrobials, new approaches to diagnose and treat BSIs at all stages of infection are urgently needed. In this Review, we explore the prevalence of major BSI pathogens, prominent mechanisms of BSI pathogenesis, opportunities for prevention and diagnosis, and treatment options.

The first prevalence and antifungal susceptibility profile of Candida infections in Palestine, 2022

BACKGROUND

Candida spp. are the most common cause of opportunistic fungal infections and are associated with a high mortality rate worldwide. In Palestine, the prevalence of Candida spp. infections remains elusive.

METHODS

We performed our study at two hospitals in Palestine (Istishari Arab Hospital, and Najah National University Hospital). All patients diagnosed with candidiasis during the year 2022 have participated in the study. The prevalence of Candida spp., their distribution, and the activity of selected antifungals against Candida pathogens were assessed. In combination with phenotypic properties, Candida isolates were identified and tested for antifungal susceptibility using the colorimetric VITEK-2 Compact system.

RESULTS

Our results showed that the prevalence of Candida spp. among infected samples was 11.6%. A total of eleven different Candida spp. were identified. Among these isolates, C. albicans (46.54%) was the most frequent, followed by C. glabrata (16.14%), C. tropicalis (13.83%), C. parapsilosis (4.82%), C. krusei (3.56%), C. dubliniensis (2.09%), C. ciferrii (1.67%), C. lusitaniae (0.83%), C. guilliermondii (0.62%), C. kefyer (0.41%) and C. spherica (0.20%). Among C. albicans, all isolates were 100% susceptible to fluconazole and micafungin. The susceptibility rates to Amphotericin B and flucytosine were 95% and 99%, respectively. The susceptibility rates of non-albicans Candida spp. (NAC) to fluconazole, voriconazole, amphotericine B, caspofungin, flucytosine and micafungin were 70%, 99%, 97%, ,72%, 92% and 100%, respectively. The incidence of Candida infections was higher in the intensive care unit and surgery department as compared to other hospital departments.

CONCLUSIONS

Four pathogens are responsible for the most invasive infections: C. albicans, C. glabrata, C. tropicalis, and C. parapsilosis. A notable characteristic of this study was the high frequency of NAC species which were often more resistant to antifungal agents. A quick and accurate system like Vitek 2 compact was suggested for the careful species identification of clinical isolates of Candida. We suggest that continued surveillance of species distribution and susceptibility to antifungals will enhance future burden estimates and assist in evaluating preventative measures' effectiveness.

Prevalence, Species Distribution and Resistance of Candidemia in Pediatric and Adult Patients in a Northeast Italy University Hospital

Candidemia and invasive candidiasis (IC) are causes of morbidity and mortality in healthcare settings, with notable differences between children and adults. Understanding the species distribution and antimicrobial susceptibility profiles of clinical isolates can guide empiric therapy in patients at risk of IC. This study investigated the incidence and antifungal susceptibility patterns of yeasts involved in IC in pediatric and adult patients from 2019 to 2023. The average incidence of IC was 0.715 per 1000 patients, increasing over the study period; infants had the highest incidence rates. Over half of the IC episodes occurred in intensive care units (ICUs). Non-albicans Candida (NAC) species represented the most frequently isolated species in adults and children (55.96% and 50.0%, respectively), with the prevalence of C. parapsilosis (26.45% and 14.7%, respectively), N. glabratus (14.97% and 8.82%, respectively) and C. tropicalis (4.36% and 2.94%, respectively). C. lusitaniae was identified in 14.7% of pediatric IC cases. In NAC species, antifungal resistance has also increased over the five years of the study: 69.12% were resistant to azoles and 7.35% were resistant to micafungin. Resistance was higher in pediatric patients. Our study highlights differences in IC characteristics between pediatric and adult populations and emphasizes the importance of targeted antifungal stewardship in ICU patients with NAC invasive infections.

The Increasing Trend of Triazole-Resistant Candida from Vulvovaginal Candidiasis

Purpose

Candida vaginitis is widely prevalent worldwide and is one of the common gynecological disorders. The aim of this study is to analyze the sensitivity of recurrent vulvovaginal (RVVC) candidiasis to antifungal drugs and its relationship with vaginal microbiota.

Patients and Methods

We Isolated and cultured Candida from RVVC patients, mass spectrometry and broth microdilution method were used to identify and determine MIC values of antifungal drugs. Clinical medical records and vaginal microbiota of RVVC patients were also collected.

Results

The main pathogens causing RVVC are predominantly Candida albicans (70.26%), but in recent years, there has been an increasing proportion of Candida glabrata(24.46%). However, only 15.70% of Candida albicans were sensitive to Voriconazole, 35.84% to Fluconazole and 25.60% to Itraconazole. No fluconazole-resistant Candida glabrata was found. Most Candida krusei strains were sensitive to voriconazole (81.80%). More important MIC values of triazoles were increased in Candida species, when exposed to clotrimazole. In addition, we found that the vaginal microecology of candida vaginitis and bacterial vaginitis was significantly different.

Conclusion

Triazoles resistant Candida species have emerged, leading to the failure of empirical anti-infective therapy. At the same time, the vaginal microecology of candida vaginitis and bacterial vaginitis was significantly different. In addition, a new breakpoint for Candida from RVVC needs to be established.

Nosocomial transmission of fluconazole-resistant Candida glabrata bloodstream isolates revealed by whole-genome sequencing

The clonal transmission of fluconazole-resistant Candida glabrata isolates within hospitals has seldom been analyzed by whole-genome sequencing (WGS). We performed WGS on 79 C. glabrata isolates, comprising 31 isolates from three premature infants with persistent C. glabrata bloodstream infection despite antifungal treatment in the same neonatal intensive care unit (NICU) in 2022 and 48 (27 fluconazole-resistant and 21 fluconazole-susceptible dose-dependent) bloodstream isolates from 48 patients in 15 South Korean hospitals from 2010 to 2022. Phylogenetic analysis based on WGS single-nucleotide polymorphisms (SNPs) distinguished the 79 isolates according to multilocus sequence typing (MLST) (17 sequence type [ST]3, 13 ST7, two ST22, 41 ST26, four ST55, and two ST59 isolates) and unveiled two possible clusters of nosocomial transmission among ST26 isolates. One cluster from two premature infants with overlapping NICU hospitalizations in 2022 encompassed 15 fluconazole-resistant isolates harboring pleiotropic drug-resistance transcription factor (Pdr1p) P258L (13 isolates) or N1086I (two isolates), together with 10 fluconazole-susceptible dose-dependent isolates lacking Pdr1p SNPs. The other cluster indicated unforeseen clonal transmission of fluconazole-resistant bloodstream isolates among five patients (four post-lung transplantation and one with diffuse interstitial lung disease) in the same hospital over 8 months. Among these five isolates, four obtained after exposure to azole antifungals harbored distinct Pdr1p SNPs (N1091D, E388Q, K365E, and R376Q). The findings reveal the transmission patterns of clonal bloodstream isolates of C. glabrata among patients undergoing antifungal treatment, exhibiting different levels of fluconazole susceptibility or distinct Pdr1p SNP profiles.

IMPORTANCE

The prevalence of fluconazole-resistant bloodstream infections caused by Candida glabrata is increasing globally, but the transmission of these resistant strains within hospitals has rarely been documented. Through whole-genome sequencing and epidemiological analyses, this study identified two potential clusters of C. glabrata bloodstream infections within the same hospital, revealing the transmission of clonal C. glabrata strains with different levels of fluconazole susceptibility or distinct transcription factor pleiotropic drug resistance protein 1 (Pdr1p) single-nucleotide polymorphism profiles among patients receiving antifungal therapy.

Intra-Abdominal Candidiasis in Cancer Patients: A 10-Year Experience in a Middle-Income Country

BACKGROUND

Invasive candidiasis (IC) represents a significant threat to both mortality and morbidity, especially among vulnerable populations. Intra-abdominal candidiasis (IAC) frequently occurs in critically ill and cancer patients, with these specific groups carrying a heightened risk for such invasive fungal infections. Despite this, there is a noticeable lack of attention to IAC in cancer patients within the literature, highlighting a critical gap that requires urgent consideration.

OBJECTIVES

This study aimed to explore the clinical and epidemiological characteristics of IAC and identify prognostic factors in a cancer centre in a middle-income country over 10 years.

PATIENTS/METHODS

A retrospective cohort observational study of adults diagnosed with IAC was conducted at the Instituto do Cancer do Estado de São Paulo (ICESP), a tertiary hospital specialising in oncological diseases with 499 beds, including 85 intensive care unit (ICU) beds, from December 2009 through May 2021.

RESULTS

A total of 128 episodes were included: 67.2% admitted to the ICU; 54.7% males; and median age 62 years. The predominant diagnosis was peritonitis (75.8%). Blood culture samples were collected from 128 patients upon admission, revealing candidemia in 17.2% (22). The most frequently isolated were C. albicans (n = 65, 50.8%) and C. glabrata (n = 42, 32.8%). Antifungal treatment was administered to 91 (71%) patients, with fluconazole (64.8%) and echinocandins (23.4%) being the most common choices. A significant proportion of these patients had a history of abdominal surgery or antibiotic use. Independent factors associated with 30-day mortality included the median Sequential Organ Failure Assessment (SOFA) score of 6 (OR = 1.30, 95% CI 1.094-1.562, p = 0.003), days of treatment (median 10.5) (OR = 0.93, 95% CI 0.870-0.993, p = 0.031) and abdominal source control (78.1%) (OR = 0.148, 95% CI 0.030-0.719, p = 0.018). The 30-day mortality rate was 41.1%.

CONCLUSIONS

Our study underscores the critical importance of implementing effective source control as a key strategy for reducing mortality in IAC.

Antibiotics stimulates the development of persistent cells in biofilms of Candida albicans bloodstream isolates

Candida albicans invasive candidiasis is considered a global health problem. In such cases, biofilm formation on implanted devices represents a therapeutic challenge and the presence of metabolically inactive persistent cells (PCs) in these communities increases their tolerance to fungicidal drugs. This study investigated the influence of amoxicillin, AMX; cefepime, CEF; gentamicin, GEN; amikacin, AMK; vancomycin, VAN; and ciprofloxacin, CIP; on the production of PCs in biofilms of C. albicans bloodstream isolates. 48 h-mature biofilms (n = 6) grown in RPMI-1640 supplemented with antibiotics were treated with 100 μg ml-1 amphotericin B and then evaluated for PCs. Biofilms grown in the presence of antibiotics produced more PCs, up to 10×, when exposed to AMX and CIP; 5 × to CEF; and 6 × to GEN and VAN. The results indicate that antibiotics can modulate PC production in C. albicans biofilms. This scenario may have clinical repercussions in immunocompromised patients under broad-spectrum antibiotic therapy.

Understanding the clinical and environmental drivers of antifungal resistance in the One Health context

Antifungal drugs have had a tremendous impact on human health and the yields of crops. However, in recent years, due to usage both in a health setting and in agriculture, there has been a rapid emergence of antifungal drug resistance that has outpaced novel compound discovery. It is now globally recognized that new strategies to tackle fungal infection are urgently needed, with such approaches requiring the cooperation of both sectors and the development of robust antifungal stewardship rationales. In this review, we examine the current antifungal regimes in clinical and agricultural settings, focusing on two pathogens of importance, Candida auris and Aspergillus fumigatus, examining their drivers of antifungal resistance, the impact of dual-use azoles and the impact agricultural practices have on driving the emergence of resistance. Finally, we postulate that a One Health approach could offer a viable alternative to prolonging the efficacy of current antifungal agents.

Tracking Candidemia Trends and Antifungal Resistance Patterns across Europe: An In-Depth Analysis of Surveillance Systems and Surveillance Studies

BACKGROUND

The WHO fungal priority list classifies Candida species as critical and high-priority pathogens, and the WHO GLASS fungi initiative seeks to establish a standardised global framework for antifungal resistance monitoring. We aimed to review resistance rates and antifungal resistance patterns across European surveillance systems and studies in response to these recent calls for action.

METHODS

A systematic review of national and international surveillance systems and peer-reviewed surveillance studies available up to June 2024 was conducted. Descriptive and trend analyses were performed on surveillance data reporting resistance to different antifungals in Candida spp.

RESULTS

In total, 6 national surveillance systems and 28 studies from 13 countries provided candidemia resistance data, mostly about the C. albicans, C. glabrata and C. parapsilosis complex. Azole resistance was most frequently reported (6/6 surveillance systems and 27/28 studies) with the highest resistance rate, especially for C. glabrata, in Croatia (100%, 28/28 isolates) and Slovenia (85.7%, 82/96) and C. parapsilosis in Croatia (80.6%, 54/67) and Italy (72.6%, 106/146). Echinocandin and polyene resistance rates were nearly zero. The number of isolates included in the surveillance systems increased over the years, particularly for C. albicans (+40-60 isolates/year), C. glabrata, and C. parapsilosis (+15-30 isolates/year). No surveillance system or study reported resistance data for C. auris. Pooled data from national surveillance revealed a decreasing trend in azole resistance in C. albicans and C. glabrata. The increasing azole-resistance trend in C. parapsilosis disappeared after adjusting for between-country heterogeneity. Overall, echinocandin and polyene resistance trends appeared relatively stable.

CONCLUSIONS

Awareness of antifungal resistance is growing, but further actions are needed to strengthen surveillance capacity and knowledge-sharing networks across Europe.

Enhancement of ROS Production by Catechin Is a Primary Effect of Increased Azole Efficacy in Nakaseomyces glabratus (Candida glabrata) Cells Lacking the ERG6 Gene

Fungal infections have become an important public health problem. Currently, there are only three available classes of antifungals for the treatment of invasive infections. Two of them, azoles and polyenes, target the synthesis of ergosterol or bind to sterols. A promising strategy to improve current therapies is the use of natural compounds in combinational therapies with the existing antifungals. In this work, we analyzed the changes in the susceptibility of the mutant strain of Nakaseomyces glabratus (Candida glabrata) lacking the ERG6 gene (encoding the sterol C-24 methyltransferase in ergosterol biosynthesis) in the presence of catechin and antifungal azoles. The reduced content of ergosterol in the Cgerg6Δ mutant resulted in the increased tolerance of the mutant cells to both azoles and polyenes. The combination of catechin with fluconazole or miconazole led to the growth inhibition of the azole-resistant Cgerg6Δ mutant strain. In the presence of catechin and miconazole, the Cgerg6Δ mutant fails to properly activate the expression of genes encoding the transcription factors CgYap1p and CgMsn4p, as well as the gene expression of CgCTA1, which are involved in oxidative stress response and lead to the intracellular accumulation of ROS. Finally, we show that catechin administration reduces mortality in a Galleria mellonella model infected with C. glabrata. Our work thus supports the use of catechin in combination therapies for fungal infections and shows that the CgERG6 gene could be a potential new drug target.

Nanomaterial-based therapeutics for enhanced antifungal therapy

The application of nanotechnology in antifungal therapy is gaining increasing attention. Current antifungal drugs have significant limitations, such as severe side effects, low bioavailability, and the rapid development of resistance. Nanotechnology offers an innovative solution to address these issues. This review discusses three key strategies of nanotechnology to enhance antifungal efficacy. Firstly, nanomaterials can enhance their interaction with fungal cells via ingenious surface tailoring of nanomaterials. Effective adhesion of nanoparticles to fungal cells can be achieved by electrostatic interaction or specific targeting to the fungal cell wall and cell membrane. Secondly, stimuli-responsive nanomaterials are developed to realize smart release of drugs in the specific microenvironment of pathological tissues, such as the fungal biofilm microenvironment and inflammatory microenvironment. Thirdly, nanomaterials can be designed to cross different physiological barriers, effectively addressing challenges posed by skin, corneal, and blood-brain barriers. Additionally, some new nanomaterial-based strategies in treating fungal infections are discussed, including the development of fungal vaccines, modulation of macrophage activity, phage therapy, the application of high-throughput screening in drug discovery, and so on. Despite the challenges faced in applying nanotechnology to antifungal therapy, its significant potential and innovation open new possibilities for future clinical antifungal applications.