Christopher Hager

The Emerging Pathogen Candida auris: Growth Phenotype, Virulence Factors, Activity of Antifungals, and Effect of SCY-078, a Novel Glucan Synthesis Inhibitor, on Growth Morphology and Biofilm Formation

ABSTRACT Candida auris, a new multidrug-resistant Candida spp. which is associated with invasive infection and high rates of mortality, has recently emerged. Here, we determined the virulence factors (germination, adherence, biofilm formation, phospholipase and proteinase production) of 16 C. auris isolates and their susceptibilities to 11 drugs belonging to different antifungal classes, including a novel orally bioavailable 1,3-β-d-glucan synthesis inhibitor (SCY-078). We also examined the effect of SCY-078 on the growth, ultrastructure, and biofilm-forming abilities of C. auris. Our data showed that while the tested strains did not germinate, they did produce phospholipase and proteinase in a strain-dependent manner and had a significantly reduced ability to adhere and form biofilms compared to that of Candida albicans (P = 0.01). C. auris isolates demonstrated reduced susceptibility to fluconazole and amphotericin B, while, in general, they were susceptible to the remaining drugs tested. SCY-078 had an MIC90 of 1 mg/liter against C. auris and caused complete inhibition of the growth of C. auris and C. albicans. Scanning electron microscopy analysis showed that SCY-078 interrupted C. auris cell division, with the organism forming abnormal fused fungal cells. Additionally, SCY-078 possessed potent antibiofilm activity, wherein treated biofilms demonstrated significantly reduced metabolic activity and a significantly reduced thickness compared to the untreated control (P < 0.05 for both comparisons). Our study shows that C. auris expresses several virulence determinants (albeit to a lesser extent than C. albicans) and is resistant to fluconazole and amphotericin B. SCY-078, the new orally bioavailable antifungal, had potent antifungal/antibiofilm activity against C. auris, indicating that further evaluation of this antifungal is warranted.

In Vitro and In Vivo Evaluation of the Antifungal Activity of APX001A/APX001 against Candida auris

ABSTRACT Candida auris is an emerging multidrug-resistant yeast that has been responsible for invasive infections associated with high morbidity and mortality. C. auris strains often demonstrate high fluconazole and amphotericin B MIC values, and some strains are resistant to all three major antifungal classes. We evaluated the susceptibility of 16 C. auris clinical strains, isolated from a wide geographical area, to 10 antifungal agents, including APX001A, a novel agent that inhibits the fungal protein Gwt1 (glycosylphosphatidylinositol-anchored wall transfer protein 1). APX001A demonstrated significantly lower MIC50 and MIC90 values (0.004 and 0.031 μg/ml, respectively) than all other agents tested. The efficacy of the prodrug APX001 was evaluated in an immunocompromised murine model of disseminated C. auris infection. Significant efficacy (80 to 100% survival) was observed in all three APX001 treatment groups versus 50% survival for the anidulafungin treatment group. In addition, APX001 showed a significant log reduction in CFU counts in kidney, lung, and brain tissue (1.03 to 1.83) versus the vehicle control. Anidulafungin also showed a significant log reduction in CFU in the kidneys and lungs (1.5 and 1.62, respectively) but did not impact brain CFU. These data support further clinical evaluation of this new antifungal agent.

The mycobiome: Role in health and disease, and as a potential probiotic target in gastrointestinal disease.

The human gastrointestinal (GI) tract is home to trillions of microorganisms, some beneficial and others potentially harmful. Recent advances in science have allowed us to identify the multitude of organisms inhabiting the GI tract and parse out those that play a role in inflammatory bowel disease (IBD). Unfortunately, most research has focused on studying only the bacteria while ,overlooking a key player, fungus. In order to address this issue, we have focused our efforts on studying the fungal community in the GI tract known as the mycobiome. We found that patients with Crohns disease (CD) tend to have much higher levels of the fungus Candida tropicalis compared to their healthy family members, as well as two bacteria, Escherichia coli and Serratia marcescens. Furthermore, we showed that these three organisms worked together to form robust biofilms capable of exacerbating intestinal inflammation. Herein, we discuss the role of the mycobiome in health and disease, and highlight the importance of maintaining balance of the GI microbiota. Additionally, taking into consideration recent next generation sequencing data, we provide insight into potentially new therapeutic approaches in the treatment of IBD through the use of antifungals and/or probiotics aimed at establishing and maintaining a healthy balance of the GI total microbial community including fungi and bacteria.

Evaluation of the efficacy of rezafungin, a novel echinocandin, in the treatment of disseminated Candida auris infection using an immunocompromised mouse model

Abstract Background Multiple cases of Candida auris infection have been reported with high mortality rates owing to its MDR nature. Rezafungin (previously CD101) is a novel echinocandin with enhanced stability and pharmacokinetics that achieves high plasma drug exposure and allows for once weekly dose administration. Objectives Evaluate the efficacy of rezafungin in the treatment of disseminated C. auris infection using a mouse model of disseminated candidiasis. Methods Mice were immunosuppressed 3 days prior to infection and 1 day post-infection. On the day of infection, mice were inoculated with 3 × 107C. auris blastospores via the tail vein. Mice were randomized into four groups (n = 20): rezafungin at 20 mg/kg, amphotericin B at 0.3 mg/kg, micafungin at 5 mg/kg and a vehicle control. Treatments were administered 2 h post-infection. Rezafungin was given additionally on days 3 and 6 for a total of three doses, while the remaining groups were treated every day for a total of seven doses. Five mice from each group were sacrificed on days 1, 4, 7 and 10 of the study. Kidneys were removed from each mouse to determine the number of cfu for each respective day. Results Rezafungin had significantly lower average log10 cfu/g of tissue compared with amphotericin B- and vehicle-treated mice on all days when kidneys were harvested. Additionally, rezafungin-treated mice had significantly lower average log10 cfu/g of tissue compared with micafungin-treated mice on day 10. Conclusions Our findings show that rezafungin possesses potent antifungal activity against C. auris in a disseminated model of candidiasis.

The mycobiome in HIV

Purpose of review There are a limited number of studies investigating the association between the microbiome and HIV. Although the majority of these published investigations have focused on the role of the bacterial community (bacteriome) in this setting, a handful of studies have also characterized the role of the mycobiome in HIV-infected individuals. This review will summarize the most recent reports pertaining to the role of the fungal community in HIV. Recent findings Differences in the composition of the oral and respiratory mycobiome in HIV-infected individuals compared with uninfected individuals have been reported. Summary Our review shows that studies investigating the role of the mycobiome in the setting of HIV are severely lacking. With recent advances in our understanding of the composition of the human microbiome, investigations into the role of the bacteria and fungus comprising the overall microbiota and how the two interact to influence each other and the host is crucial.

Clinical Effects of Gamma-Radiation-Resistant Aspergillus sydowii on Germ-Free Mice Immunologically Prone to Inflammatory Bowel Disease

We report and investigated a case of inadvertent contamination of 125 mice (housed in two germ-free positive-pressurized isolators) with emerging human and coral pathogen Aspergillus sydowii. The infected mice correspond to genetic line SAMP1/YitFc, which have 100% immune predisposition to develop Crohns disease-like spontaneous pathologies, namely, inflammatory bowel disease (IBD). Pathogen update based on a scoping review of the literature and our clinical observations and experimentation are discussed. The unwanted infection of germ-free mice (immunologically prone to suffer chronic inflammation) with human pathogen A. sydowii resulted in no overt signs of clinical disease over 3-week exposure period, or during DSS-induced colitis experiments. Results and observations suggest that A. sydowii alone has limited clinical effect in immunocompromised germ-free mice or that other commensal microbial flora is required for Aspergillus-associated disease to occur.

Evaluation of the In Vitro and In Vivo Antifungal Activity of APX001A/APX001 Against Candida auris

Abstract Background Candida auris, an emerging multidrug-resistant yeast, causes deadly invasive infections with high mortality. C. auris strains often show high MICs to fluconazole and amphotericin B, and some are resistant to all 3 major antifungal classes, limiting treatment options. We tested 16 C. auris strains from a wide geographical area (Germany, Japan, S. Korea, and India) against 10 antifungals including APX001A (APXA), an antifungal with a novel mechanism of action (inhibition of the Gwt1 fungal enzyme). The prodrug APX001 (APX) is in clinical development and its efficacy was evaluated in an immunocompromised murine model of disseminated C. auris. Methods MICs were determined by CLSI M27-A3 method. Mice were immunocompromised for the study. Treatment was initiated 2 hours post challenge. IP treatment groups included a vehicle control, APX 78mg/kg (mpk) BID, 78mpk TID, and 104mpk BID, and anidulafungin (AFG) 10mpk BID. Survival was monitored for 16d post inoculation. Results Susceptibility. APXA had significantly lower MIC50 and MIC90 values (concentration that inhibits 50 and 90% of the tested isolates, respectively) than the other tested antifungals with a MIC90 of 0.031 µg/mL (Table 1). Survival. 100% mortality in the vehicle-treated control group occurred by 6d. Significant efficacy was observed in all APX treatment groups with 90, 100, and 80% survival observed respectively for APX 78 mpk BID; 78 mpk TID and 104 mpk BID. AFG treatment resulted in 50% survival at 16d. Mice in all of the APX treated groups had a significantly higher % survival compared with the AFG and vehicle groups. Conclusion APXA was the most active antifungal agent in vitro. The prodrug APX resulted in significantly better survival than AFG in a C. auris disseminated infection model. Thus APX may be a viable treatment for C. auris infections. Table 1: Susceptibility of 16 C. auris isolates against antifungals Disclosures K. J. Shaw, Amplyx Pharmaceuticals Inc.: Employee, Salary; M. Ghannoum, Amplyx Pharmaceuticals: Consultant, Research Contractor and Scientific Advisor, Consulting fee and Research grant; Cidara Therapeutics: Consultant and Research Contractor, Consulting fee and Research grant