The laboratory investigation, management, and infection prevention and control of Candida auris: a narrative review to inform the 2024 national guidance update in England.

The emergent fungal pathogen Candida auris is increasingly recognised as an important cause of healthcare-associated infections globally. It is highly transmissible, adaptable, and persistent, resulting in an organism with significant outbreak potential that risks devastating consequences. Progress in the ability to identify C. auris in clinical specimens is encouraging, but laboratory diagnostic capacity and surveillance systems are lacking in many countries. Intrinsic resistance to commonly used antifungals, combined with the ability to rapidly acquire resistance to therapy, substantially restricts treatment options and novel agents are desperately needed. Despite this, outbreaks can be interrupted, and mortality avoided or minimised, through the application of rigorous infection prevention and control measures with an increasing evidence base. This review provides an update on epidemiology, the impact of the COVID-19 pandemic, risk factors, identification and typing, resistance profiles, treatment, detection of colonisation, and infection prevention and control measures for C. auris. This review has informed a planned 2024 update to the United Kingdom Health Security Agency (UKHSA) guidance on the laboratory investigation, management, and infection prevention and control of Candida auris. A multidisciplinary response is needed to control C. auris transmission in a healthcare setting and should emphasise outbreak preparedness and response, rapid contact tracing and isolation or cohorting of patients and staff, strict hand hygiene and other infection prevention and control measures, dedicated or single-use equipment, appropriate disinfection, and effective communication concerning patient transfers and discharge.

First detection of triazole-resistant aspergillus fumigatus harbouring the TR34/L98H Cyp51A mutation in Burkina Faso.

BACKGROUND: Triazole-resistant Aspergillus fumigatus (TRAF) isolates are a growing public health problem with worldwide distribution. Epidemiological data on TRAF is limited in Africa, particularly in West Africa. OBJECTIVES: This study aimed to screen for the environmental presence of TRAF isolates in the indoor air of two hospitals in Burkina Faso. MATERIALS AND METHODS: Air samples were collected in wards housing patients at risk for invasive aspergillosis, namely infectious diseases ward, internal medicine ward, nephrology ward, pulmonology ward, medical emergency ward and paediatric ward. Sabouraud Dextrose Agar supplemented with triazoles was used to screen the suspected TRAF isolates and EUCAST method to confirm the resistance of suspected isolates. Sequencing of cyp51A gene was used to identify the resistance mechanism of confirmed TRAF isolates. RESULTS: Of the 198 samples collected and analysed, 67 showed growth of A. fumigatus isolates. The prevalence of TRAF isolates was 3.23% (4/124). One TRAF isolate exhibited a pan-triazole resistance. Sequencing of cyp51A gene identified the TR34/L98H mutation for this pan-triazole resistant isolate. This study showed for the first time the circulation of the pan-azole resistant isolate harbouring the TR34/L98H mutation in Burkina Faso. CONCLUSIONS: These findings emphasise the need to map these TRAF isolates in all parts of Burkina Faso and to establish local and national continuous surveillance of environmental and clinical TRAF isolates in this country.

Clinical Situation, Species Distribution, and Antibiotic Resistance of Pathogenic Bacteria and Fungi in 626 Cases of Vulvovaginitis in Hangzhou, China.

BACKGROUND: Female vulvovaginitis was one of the most common gynecological diseases. It had a great negative impact on their work and quality of life. This retrospective study evaluated the clinical and laboratory data of patients with vulvovaginitis in Hangzhou, China. To analyze the clinical situation, species distribution and antibiotic resistance of pathogenic fungi and bacteria in 626 cases of vulvovaginitis in Hangzhou. Microorganism culture, identification, and antibiotic susceptibility testing were conducted. The study aimed to provide a theoretical value for an effective treatment of vulvovaginitis. METHODS: In total, 626 outpatients and inpatients diagnosed with vulvovaginitis were selected from January 2018 to January 2023. Data of all the patients were collected from the hospital's electronic medical records. Vaginal secretion was collected for testing and SPSS 25.0 software was used to perform statistical analysis. RESULTS: A total of 626 strains of fungi, Gram-positive, and -negative bacteria were detected. Clinical situations of patients infected with the top five pathogenic fungi and bacteria were analyzed. Pathogenic fungi and bacteria were slightly different in each age group and in each onset time group. The results of antibiotic susceptibility testing showed that the resistance rates of itraconazole and fluconazole were high and Gram- negative and -positive bacteria were multidrug resistant. Gram-negative bacteria were more sensitive to carbenicillins and compound antibiotics, while Gram-positive bacteria were sensitive to rifampicin and daptomycin. MRSA and non vancomycin-resistant strains were detected. CONCLUSIONS: Fungi and bacteria were usually detected as pathogenes in patients with vulvovaginitis in Hangzhou. Some factors, such as age and onset time, often affected the incidence. Pathogenic fungi and bacteria were resistant to some common antibiotics, and clinical treatments should be carried out in a timely and reasonable manner according to the results of antibiotic susceptibility testing.

Mapping the Global Spread of T. indotineae: An Update on Antifungal Resistance, Mutations, and Strategies for Effective Management.

INTRODUCTION: The global spread of Trichophyton indotineae presents a pressing challenge in dermatophytosis management. This systematic review explores the current landscape of T. indotineae infections, emphasizing resistance patterns, susceptibility testing, mutational analysis, and management strategies. METHODS: A literature search was conducted in November 2023 using Embase, PubMed, Scopus, and Web of Science databases. Inclusion criteria covered clinical trials, observational studies, case series, or case reports with T. indotineae diagnosis through molecular methods. Reports on resistance mechanisms, antifungal susceptibility testing, and management were used for data extraction. RESULTS AND DISCUSSION: A total of 1148 articles were identified through the systematic search process, with 45 meeting the inclusion criteria. The global spread of T. indotineae is evident, with cases reported in numerous new countries in 2023. Tentative epidemiological cut-off values (ECOFFs) suggested by several groups provide insights into the likelihood of clinical resistance. The presence of specific mutations, particularly Phe397Leu, correlate with higher minimum inhibitory concentrations (MICs), indicating potential clinical resistance. Azole resistance has also been reported and investigated in T. indotineae, and is a growing concern. Nevertheless, itraconazole continues to be an alternative therapy. Recommendations for management include oral or combination therapies and individualized approaches based on mutational analysis and susceptibility testing. CONCLUSION: Trichophyton indotineae poses a complex clinical scenario, necessitating enhanced surveillance, improved diagnostics, and cautious antifungal use. The absence of established clinical breakpoints for dermatophytes underscores the need for further research in this challenging field.

Antifungal susceptibility and virulence determinants profile of candida species isolated from patients with candidemia.

Candida is the most prevalent fungal bloodstream infection (BSI) with a high mortality rate among hospitalized patients. Another concern facing physicians is rising global incidence of drug-resistant Candida. This study aimed to characterize the prevalence, antifungal susceptibility, biofilm formation, and virulence genes (HWP1, ALS1, SAP2) of different Candida spp. isolated from patients with candidemia. 52 isolates of Candida spp. were identified from blood cultures by chromogenic Candida agar and confirmed by the VITEK 2 system. Isolates were tested for antifungal susceptibility by disk diffusion and VITEK 2 system. Biofilm formation and investigated genes were detected by the Congo red method and conventional PCR, respectively. Candida spp. caused 2.3% of detected BSIs, of which 32.7% were caused by Candida albicans (C. albicans) and 67.3% by non-albicans Candida (NAC), with the predominance of C. tropicalis (25%), followed by C. parapsilosis (17.3%), and C. krusei (13.5%). The susceptibility rates to fluconazole, voriconazole, caspofungin, micafungin, amphotericin B, and flucytosine were 64.7%, 76.5%, 100.0%, 100%, 100.0%, and 100.0% in C. albicans, while 53.6%, 71.4%, 91.4%, 91.4%, 94.3%, and 94.3% in NAC, respectively. Biofilm production, HWP1, ALS1, and SAP2 were detected in 70.6%, 82.4%, 76.5%, and 52.9% of C. albicans and 74.3%, 85.7%, 80.0%, and 48.6% of NAC, respectively. There is remarkable shift to NAC BSIs and high azole resistance. Antifungal stewardship and analysis of risk factors associated with this shift are needed.

The practice and evaluation of antifungal stewardship programs at a tertiary first-class hospital in China.

BACKGROUND: The sharp increase in fungal infections, insufficient diagnostic and treatment capabilities for fungal infections, poor prognosis of patients with fungal infections as well as the increasing drug resistance of fungi are serious clinical problems. It is necessary to explore the implementation and evaluation methods of antifungal stewardship (AFS) to promote the standardized use of antifungal drugs. METHODS: The AFS programme was implemented at a tertiary first-class hospital in China using a plan-do-check-act (PDCA) quality management tool. A baseline investigation was carried out to determine the utilization of antifungal drugs in pilot hospitals, analyse the existing problems and causes, and propose corresponding solutions. The AFS programme was proposed and implemented beginning in 2021, and included various aspects, such as team building, establishment of regulations, information construction, prescription review and professional training. The management effectiveness was recorded from multiple perspectives, such as the consumption of antifungal drugs, the microbial inspection rate of clinical specimens, and the proportion of rational prescriptions. The PDCA management concept was used for continuous improvement to achieve closed-loop management. RESULTS: In the first year after the implementation of the AFS programme, the consumption cost, use intensity and utilization rate of antifungal drugs decreased significantly (P < 0.01). The proportion of rational antifungal drug prescriptions markedly increased, with the proportion of prescriptions with indications increasing from 86.4% in 2019 to 97.0% in 2022, and the proportion of prescriptions with appropriate usage and dosage increased from 51.9 to 87.1%. In addition, after the implementation of the AFS programme, physicians' awareness of the need to complete microbial examinations improved, and the number of fungal cultures and serological examinations increased substantially. Statistics from drug susceptibility tests revealed a decrease in the resistance rate of Candida to fluconazole. CONCLUSION: This study indicated that the combination of AFS and the PDCA cycle could effectively reduce antifungal consumption and promote the rational use of antifungal drugs, providing a reference for other health care systems to reduce the overuse of antifungal drugs and delay the progression of fungal resistance.

Oral candidiasis in liver transplant patients: species identification and antifungal susceptibility profile.

OBJECTIVE: This study aimed to verify oral candidiasis, identify the causative species, and investigate the antifungal susceptibility of yeasts isolated from liver transplant patients. METHODS: A descriptive analysis of 97 patients who underwent liver transplantation was conducted at a hospital. Two clinical examinations (Collections A and B) of the oral cavity were performed. Oral material was collected from all patients, inoculated in Sabouraud Dextrose Agar, and incubated at 35℃ for 48 hours. Samples were identified by molecular sequencing of the internal trascribed space region of rDNA. RESULTS: An antifungal susceptibility test with fluconazole, amphotericin B, and micafungin was performed using the Clinical and Laboratory Standards Institute yeast broth microdilution method. Among the patients, 15 presented with oral candidiasis: eight in Collection A and seven in Collection B. The primary type of candidiasis was atrophic, followed by pseudomembranous candidiasis. The most prevalent species was Candida albicans (nine), followed by Candida glabrata (three), Candida tropicalis (two), and Candida dubliniensis (one). Regarding susceptibility to fluconazole, of the 15 samples, 11 were susceptible, three were susceptible in a dose-dependent manner, and one was resistant. CONCLUSION: The most commonly identified type of candidiasis was atrophic, with C. albicans and C. glabrata being the most prevalent causative species. One fluconazole-resistant isolate each of C. tropicalis and C. albicans were identified.

Loss of the yeast transporter Agp2 upregulates the pleiotropic drug-resistant pump Pdr5 and confers resistance to the protein synthesis inhibitor cycloheximide.

The transmembrane protein Agp2, initially shown as a transporter of L-carnitine, mediates the high-affinity transport of polyamines and the anticancer drug bleomycin-A5. Cells lacking Agp2 are hyper-resistant to polyamine and bleomycin-A5. In these earlier studies, we showed that the protein synthesis inhibitor cycloheximide blocked the uptake of bleomycin-A5 into the cells suggesting that the drug uptake system may require de novo synthesis. However, our recent findings demonstrated that cycloheximide, instead, induced rapid degradation of Agp2, and in the absence of Agp2 cells are resistant to cycloheximide. These observations raised the possibility that the degradation of Agp2 may allow the cell to alter its drug resistance network to combat the toxic effects of cycloheximide. In this study, we show that membrane extracts from agp2Δ mutants accentuated several proteins that were differentially expressed in comparison to the parent. Mass spectrometry analysis of the membrane extracts uncovered the pleiotropic drug efflux pump, Pdr5, involved in the efflux of cycloheximide, as a key protein upregulated in the agp2Δ mutant. Moreover, a global gene expression analysis revealed that 322 genes were differentially affected in the agp2Δ mutant versus the parent, including the prominent PDR5 gene and genes required for mitochondrial function. We further show that Agp2 is associated with the upstream region of the PDR5 gene, leading to the hypothesis that cycloheximide resistance displayed by the agp2Δ mutant is due to the derepression of the PDR5 gene.

Geldanamycin confers fungicidal properties to azole by triggering the activation of succinate dehydrogenase.

AIMS: Azoles have been widely employed for the treatment of invasive fungal diseases; however, their efficacy is diminished as pathogenic fungi tolerate them due to their fungistatic properties. Geldanamycin (GdA) can render azoles fungicidal by inhibiting the ATPase and molecular chaperone activities of heat shock protein 90 (Hsp90). Nonetheless, the clinical applicability of GdA is restricted due to its cytotoxic ansamycin scaffold structure, its induction of cytoprotective heat shock responses, and the conservative nature of Hsp90. Hence, it is imperative to elucidate the mechanism of action of GdA to confer fungicidal properties to azoles and mitigate the toxic adverse effects associated with GdA. MATERIALS AND METHODS: Through various experimental methods, including the construction of gene-deleted Candida albicans mutants, in vitro drug sensitivity experiments, Western blot analysis, reactive oxygen species (ROS) assays, and succinate dehydrogenase activity assays, we identified Hsp90 client proteins associated with the tolerance of C. albicans to azoles. KEY FINDINGS: It was observed that GdA effectively hindered the entry of Hsp90 into mitochondria, resulting in the alleviation of inhibitory effect of Hsp90 on succinate dehydrogenase. Consequently, the activation of succinate dehydrogenase led to an increased production of ROS. within the mitochondria, thereby facilitating the antifungal effects of azoles against C. albicans. SIGNIFICANCE: This research presents a novel approach for conferring fungicidal properties to azoles, which involves specifically disrupting the interaction of between Hsp90 and succinate dehydrogenase rather than employing a non-specific inhibition of ATPase activity of Hsp90.

Treatment of vaginitis caused by non-albicans Candida species.

INTRODUCTION: In the face of increased frequency of non-albicans Candida vulvovaginitis (VVC) reported worldwide, there is a paucity of effective oral and topical antifungal drugs available. Drug selection is further handicapped by an absence of data of clinical efficacy of available antifungal drugs for these infections. AREAS COVERED: In this review, attention is directed at the cause of drug shortage as well as increased frequency of non-albicans Candida (NAC) vulvovaginitis. There is widespread recognition of reduced in vitro azole drug susceptibility in NAC species. Moreover, antifungal susceptibility tests have not been standardized or validated for NAC isolates, hence clinicians rely on an element of empiricism especially given the absence of randomized controlled comparative studies targeting NAC species. Clinical spectrum of NAC species isolates is highly variable with ongoing difficulty in determining a causal role in symptomatic patients. EXPERT OPINION: We have entered the era of demand for Candida species-specific therapy and although consensus treatment guidelines are emerging, new antifungal agents that target these multiple-azole resistant or relatively resistant vaginal NAC species are urgently needed.

Genetic Mutations in FKS1 Gene Associated with Acquired Echinocandin Resistance in Candida parapsilosis Complex.

Candida parapsilosis complex has recently received special attention due to naturally occurring FKS1 polymorphism associated with high minimal inhibitory concentrations for echinocandin and the increase of clonal outbreaks of strains resistant to commonly used antifungals such as fluconazole. Despite the previous fact, little is known about the genetic mechanism associated with echinocandin resistance. Therefore, the present study was designed to investigate the mechanism of acquired echinocandin resistance in C. parapsilosis complex strains. A total of 15 clinical C. parapsilosis complex isolates were sub-cultured for 30 days at a low concentration of micafungin at ½ the lowest MIC value of the tested isolates (0.12 µg/ml). After culturing, all the isolates were checked phenotypically for antifungal resistance and genotypically for echinocandin resistance by checking FKS1 gene hot spot one (HS1) and HS2 mutations. In vitro induction of echinocandin resistance confirmed the rapid development of resistance at low concentration micafungin, with no difference among C. parapsilosis, C. metapsilosis, and C. orthopsilosis in the resistance development. For the first time we identified different FKS1 HS1 and or HS2 mutations responsible for echinocandin resistance such as R658S and L1376F in C. parapsilosis, S656X, R658X, R658T, W1370X, X1371I, V1371X, and R1373X (corresponding to their location in C. parapsilosis) in C. metapsilosis, and L648F and R1366H in C. orthopsilosis. Our results are of significant concern, since the rapid development of resistance may occur clinically after short-term exposure to antifungals as recently described in other fungal species with the potential of untreatable infections.

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.

Antimicrobial and anti-biofilm properties of oleuropein against Escherichia coli and fluconazole-resistant isolates of Candida albicans and Candida glabrata.

BACKGROUND: Side effects associated with antimicrobial drugs, as well as their high cost, have prompted a search for low-cost herbal medicinal substances with fewer side effects. These substances can be used as supplements to medicine or to strengthen their effects. The current study investigated the effect of oleuropein on the inhibition of fungal and bacterial biofilm in-vitro and at the molecular level. MATERIALS AND METHODS: In this experimental study, antimicrobial properties were evaluated using microbroth dilution method. The effect of oleuropein on the formation and eradication of biofilm was assessed on 96-well flat bottom microtiter plates and their effects were observed through scanning electron microscopy (SEM). Its effect on key genes (Hwp1, Als3, Epa1, Epa6, LuxS, Pfs) involved in biofilm formation was investigated using the quantitative reverse transcriptase-polymerase chain reaction (RT-qPCR) method. RESULTS: The minimum inhibitory concentration (MIC) and minimum fungicidal/bactericidal concentration (MFC/MBC) for oleuropein were found to be 65 mg/ml and 130 mg/ml, respectively. Oleuropein significantly inhibited biofilm formation at MIC/2 (32.5 mg/ml), MIC/4 (16.25 mg/ml), MIC/8 (8.125 mg/ml) and MIC/16 (4.062 mg/ml) (p < 0.0001). The anti-biofilm effect of oleuropein was confirmed by SEM. RT-qPCR indicated significant down regulation of expression genes involved in biofilm formation in Candida albicans (Hwp1, Als3) and Candida glabrata (Epa1, Epa6) as well as Escherichia coli (LuxS, Pfs) genes after culture with a MIC/2 of oleuropein (p < 0.0001). CONCLUSIONS: The results indicate that oleuropein has antifungal and antibacterial properties that enable it to inhibit or destroy the formation of fungal and bacterial biofilm.

Preventing multi-resistance: New insights for managing fungal adaptation.

Sustainable crop protection is vital for food security, yet it is under threat due to the adaptation of a diverse and evolving pathogen population. Resistance can be managed by maximising the diversity of selection pressure through dose variation and the spatial and temporal combination of active ingredients. This study explores the interplay between operational drivers for maximising the sustainability of management strategies in relation to the resistance status of fungal populations. We applied an experimental evolution approach to three artificial populations of Zymoseptoria tritici, an economically significant wheat pathogen, each differing in initial resistance status. Our findings reveal that diversified selection pressure curtails the selection of resistance in naïve populations and those with low frequencies of single resistance. Increasing the number of modes of action most effectively delays resistance development, surpassing the increase in the number of fungicides, fungicide choice based on resistance risk, and temporal variation in fungicide exposure. However, this approach favours generalism in the evolved populations. The prior presence of multiple resistant isolates and their subsequent selection in populations override the effects of diversity in management strategies, thereby invalidating any universal ranking. Therefore, the initial resistance composition must be specifically considered in sustainable resistance management to address real-world field situations.

Protoplast-mediated transformation of Madurella mycetomatis using hygromycin resistance as a selection marker.

Madurella mycetomatis is the main cause of mycetoma, a chronic granulomatous infection for which currently no adequate therapy is available. To improve therapy, more knowledge on a molecular level is required to understand how M. mycetomatis is able to cause this disease. However, the genetic toolbox for M. mycetomatis is limited. To date, no method is available to genetically modify M. mycetomatis. In this paper, a protoplast-mediated transformation protocol was successfully developed for this fungal species, using hygromycin as a selection marker. Furthermore, using this method, a cytoplasmic-GFP-expressing M. mycetomatis strain was created. The reported methodology will be invaluable to explore the pathogenicity of M. mycetomatis and to develop reporter strains which can be useful in drug discovery as well as in genetic studies.

Azole resistance mechanisms and population structure of the human pathogen Aspergillus fumigatus on retail plant products.

Aspergillus fumigatus is a ubiquitous saprotroph and human-pathogenic fungus that is life-threatening to the immunocompromised. Triazole-resistant A. fumigatus was found in patients without prior treatment with azoles, leading researchers to conclude that resistance had developed in agricultural environments where azoles are used against plant pathogens. Previous studies have documented azole-resistant A. fumigatus across agricultural environments, but few have looked at retail plant products. Our objectives were to determine if azole-resistant A. fumigatus is prevalent in retail plant products produced in the United States (U.S.), as well as to identify the resistance mechanism(s) and population genetic structure of these isolates. Five hundred twenty-five isolates were collected from retail plant products and screened for azole resistance. Twenty-four isolates collected from compost, soil, flower bulbs, and raw peanuts were pan-azole resistant. These isolates had the TR34/L98H, TR46/Y121F/T289A, G448S, and H147Y cyp51A alleles, all known to underly pan-azole resistance, as well as WT alleles, suggesting that non-cyp51A mechanisms contribute to pan-azole resistance in these isolates. Minimum spanning networks showed two lineages containing isolates with TR alleles or the F46Y/M172V/E427K allele, and discriminant analysis of principle components identified three primary clusters. This is consistent with previous studies detecting three clades of A. fumigatus and identifying pan-azole-resistant isolates with TR alleles in a single clade. We found pan-azole resistance in U.S. retail plant products, particularly compost and flower bulbs, which indicates a risk of exposure to these products for susceptible populations and that highly resistant isolates are likely distributed worldwide on these products.IMPORTANCEAspergillus fumigatus has recently been designated as a critical fungal pathogen by the World Health Organization. It is most deadly to people with compromised immune systems, and with the emergence of antifungal resistance to multiple azole drugs, this disease carries a nearly 100% fatality rate without treatment or if isolates are resistant to the drugs used to treat the disease. It is important to determine the relatedness and origins of resistant A. fumigatus isolates in the environment, including plant-based retail products, so that factors promoting the development and propagation of resistant isolates can be identified.

Taxonomy of Candida parapsilosis complex isolated from neonates and the role of Hsp90 inhibitors to enhanced the antifungal activity of micafungin.

Species from Candida parapsilosis complex are frequently found in neonatal candidemia. The antifungal agents to treat this infection are limited and the occurrence of low in vitro susceptibility to echinocandins such as micafungin has been observed. In this context, the chaperone Hsp90 could be a target to reduce resistance. Thus, the objective of this research was to identify isolates from the C. parapsilosis complex and verify the action of Hsp90 inhibitors associated with micafungin. The fungal identification was based on genetic sequencing and mass spectrometry. Minimal inhibitory concentrations were determined by broth microdilution method according to Clinical Laboratory and Standards Institute. The evaluation of the interaction between micafungin with Hsp90 inhibitors was realized using the checkerboard methodology. According to the polyphasic taxonomy, C. parapsilosis sensu stricto was the most frequently identified, followed by C. orthopsilosis and C. metapsilosis, and one isolate of Lodderomyces elongisporus was identified by genetic sequencing. The Hsp90 inhibitor geladanamycin associated with micafungin showed a synergic effect in 31.25% of the isolates, a better result was observed with radicicol, which shows synergic effect in 56.25% tested yeasts. The results obtained demonstrate that blocking Hsp90 could be effective to reduce antifungal resistance to echinocandins.

The Ptk2-Pma1 pathway enhances tolerance to terbinafine in Trichophyton rubrum.

The increasing prevalence of dermatophyte resistance to terbinafine, a key drug in the treatment of dermatophytosis, represents a significant obstacle to treatment. Trichophyton rubrum is the most commonly isolated fungus in dermatophytosis. In T. rubrum, we identified TERG_07844, a gene encoding a previously uncharacterized putative protein kinase, as an ortholog of budding yeast Saccharomyces cerevisiae polyamine transport kinase 2 (Ptk2), and found that T. rubrum Ptk2 (TrPtk2) is involved in terbinafine tolerance. In both T. rubrum and S. cerevisiae, Ptk2 knockout strains were more sensitive to terbinafine compared with the wild types, suggesting that promotion of terbinafine tolerance is a conserved function of fungal Ptk2. Pma1 is activated through phosphorylation by Ptk2 in S. cerevisiae. Overexpression of T. rubrum Pma1 (TrPma1) in T. rubrum Ptk2 knockout strain (ΔTrPtk2) suppressed terbinafine sensitivity, suggesting that the induction of terbinafine tolerance by TrPtk2 is mediated by TrPma1. Furthermore, omeprazole, an inhibitor of plasma membrane proton pump Pma1, increased the terbinafine sensitivity of clinically isolated terbinafine-resistant strains. These findings suggest that, in dermatophytes, the TrPtk2-TrPma1 pathway plays a key role in promoting intrinsic terbinafine tolerance and may serve as a potential target for combinational antifungal therapy against terbinafine-resistant dermatophytes.

A secondary mechanism of action for triazole antifungals in Aspergillus fumigatus mediated by hmg1.

Triazole antifungals function as ergosterol biosynthesis inhibitors and are frontline therapy for invasive fungal infections, such as invasive aspergillosis. The primary mechanism of action of triazoles is through the specific inhibition of a cytochrome P450 14-α-sterol demethylase enzyme, Cyp51A/B, resulting in depletion of cellular ergosterol. Here, we uncover a clinically relevant secondary mechanism of action for triazoles within the ergosterol biosynthesis pathway. We provide evidence that triazole-mediated inhibition of Cyp51A/B activity generates sterol intermediate perturbations that are likely decoded by the sterol sensing functions of HMG-CoA reductase and Insulin-Induced Gene orthologs as increased pathway activity. This, in turn, results in negative feedback regulation of HMG-CoA reductase, the rate-limiting step of sterol biosynthesis. We also provide evidence that HMG-CoA reductase sterol sensing domain mutations previously identified as generating resistance in clinical isolates of Aspergillus fumigatus partially disrupt this triazole-induced feedback. Therefore, our data point to a secondary mechanism of action for the triazoles: induction of HMG-CoA reductase negative feedback for downregulation of ergosterol biosynthesis pathway activity. Abrogation of this feedback through acquired mutations in the HMG-CoA reductase sterol sensing domain diminishes triazole antifungal activity against fungal pathogens and underpins HMG-CoA reductase-mediated resistance.