Biology subjects

Wiederhold, N. P.

Publications and source records attributed to Wiederhold, N. P..

8 recordsLinked to original sources

bioRxiv2025

Antifungal susceptibility profile of clinically relevant species of the genus Sporothrix: establishment of Epidemiological Cutoff Values (ECVs) according to CLSI broth microdilution methodology

Sporotrichosis is a globally distributed subcutaneous mycosis caused mainly by Sporothrix brasiliensis, S. schenckii, and S. globosa. Cat-transmitted sporotrichosis, primarily caused by S. brasiliensis in South America and to a lesser extent by S. schenckii in Southeast Asia, is emerging as a significant public health concern, due its outbreak potential. Itraconazole is the first-choice drug for treatment of human and cats, but reduced susceptibility has been reported based on previously proposed epidemiological cut-off values (ECVs). To support resistance surveillance, we aimed to establish CLSI-endorsed ECVs for these clinically relevant Sporothrix species. A total of 3,588 minimum inhibitory concentration (MIC) values for seven antifungal agents (amphotericin B, itraconazole, posaconazole, voriconazole, isavuconazole, olorofim, and terbinafine) were obtained from 19 international laboratories. Four of seven antifungals met the CLSI M57 guidelines criteria to determine the ECV. Established ECVs for amphotericin B were found to be high with 8 {micro}g/mL for S. brasiliensis and S. globosa, and 4 {micro}g/mL for S. schenckii. Itraconazole ECVs were 4 {micro}g/mL for S. brasiliensis and S. schenckii. Posaconazole ECVs were 4 {micro}g/mL for all three species (tentative for S. globosa), while the terbinafine ECV for S. brasiliensis was 0.12 {micro}g/mL. Olorofim demonstrated good in vitro activity, particularly against S. brasiliensis. Overall, this study establishes validated ECVs for key antifungals against Sporothrix species and identifies a low prevalence of non-wild type (NWT) isolates, supporting ongoing antifungal resistance monitoring.

microbiology↗

bioRxiv2025

Mutations in transcription factors that confer fluconazole resistance also confer reduced susceptibility to manogepix in Candida auris, Candida albicans, Candida parapsilosis, and Candida glabrata (Nakaseomyces glabratus)

The fungal pathogen Candida auris is of global concern due to high levels of multidrug resistance and its propensity to cause infectious outbreaks. Over 90% of isolates are resistant to fluconazole, the most commonly prescribed antifungal world-wide. Fluconazole resistance is multifactorial with many isolates carrying mutations in the gene encoding the transcriptional regulator Tac1B, leading to increased expression of the gene encoding the ATP Binding Cassette (ABC) transporter Cdr1. Recently, a study examining C. auris in vitro resistance mechanisms to manogepix, a promising antifungal agent currently in clinical trials, found a TAC1B mutation that confers reduced manogepix and fluconazole susceptibility. We hypothesized that mutations in C. auris TAC1B and similar transcription factors in other Candida species that confer fluconazole resistance might also confer reduced susceptibility to manogepix. We measured manogepix susceptibilities for selected isolates and strains and found C. auris TAC1B, C. albicans and C. parapsilosis TAC1, and C. glabrata PDR1 confer reduced manogepix susceptibility in a manner dependent on ABC transporters similar to Cdr1. Our findings raise the possibility of fluconazole and manogepix cross resistance for clinical isolates harboring mutations in these genes.

microbiology↗

bioRxiv2025

A Novel Sarocladium spinificis Strain Suppresses Coccidioides posadasii Growth: Morphological and Genetic Perspectives

Sarocladium is a diverse fungal genus with implications in both plant and human diseases, exhibiting roles in pathogenicity, endophytism, and biocontrol. This study characterizes two Sarocladium spinificis strains, CA16 (CBS 144516) and CA18 (CBS 144517), isolated from patients initially suspected of having coccidioidomycosis. Morphological, phylogenetic, and genomic analyses confirmed their classification within the Sarocladium genus, closely related to S. spinificis. Both strains exhibited growth at 24{degrees}C and 37{degrees}C, with distinct morphological features. Comparative genomic analysis identified unique orthologous clusters and functional gene families associated with adaptability and potential pathogenicity. Notably, these strains demonstrated enhanced production of secreted proteins, CAZymes, and peptidases, highlighting metabolic versatility. Co-cultivation experiments revealed that S. spinificis strains CA16 and CA18 inhibited the growth of Coccidioides posadasii, suggesting competitive interactions and potential antifungal properties. These findings underscore the ecological and clinical significance of S. spinificis and its impact on microbial communities, advancing our understanding of its diversity, pathogenic potential, and antifungal capabilities. ImportanceAccurate identification and characterization of emerging fungal pathogens are essential for improving diagnosis and treatment. Sarocladium spinificis, though not widely recognized as a human pathogen, exhibits traits suggesting a potential role in opportunistic infections. This study provides the first detailed morphological, phylogenetic, and genomic characterization of clinical S. spinificis isolates, highlighting its ability to survive at body temperature and its antifungal resistance. Additionally, we demonstrate that these strains inhibit Coccidioides posadasii, the agent of Valley fever, suggesting ecological competition or antifungal properties. These findings contribute to understanding fungal interactions in clinical and environmental settings, with implications for fungal pathogenesis and antifungal strategies. By uncovering new aspects of S. spinificis biology, this work expands knowledge of Sarocladium species in human health and lays the foundation for future research on its ecological role, pathogenic potential, and therapeutic applications.

microbiology↗

bioRxiv2025

Broad-Spectrum Activity and Mechanisms of Action of SQ109 on a Variety of Fungi

ABSTRACTWe investigated the activity of the tuberculosis drug SQ109 against sixteen fungal pathogens: Candida albicans, C. auris, C. glabrata, C. guilliermondi, C. kefyr, C. krusei, C. lusitaniae, Candida parapsilosis, C. tropicalis, Cryptococcus neoformans, Rhizopus spp., Mucor spp., Fusarium spp., Coccidioides spp., Histoplasma capsulatum and Aspergillus fumigatus. MIC values varied widely (125 ng/mL to >64 {micro}g/mL) but in many cases we found promising (MIC[~]4 {micro}g/mL) activity as well as MFC/MIC ratios of [~]2. SQ109 metabolites were inactive. The activity of 12 analogs of SQ109 against Saccharomyces cerevisiae correlated with protonophore uncoupling activity, suggesting mitochondrial targeting, consistent with the observation that growth inhibition was rescued by agents which inhibit ROS species accumulation. SQ109 disrupted H+/Ca2+ homeostasis in S. cerevisiae vacuoles, and there was synergy (FICI[~]0.31) with pitavastatin, indicating involvement of isoprenoid biosynthesis pathway inhibition. SQ109 is, therefore, a potential antifungal agent with multi-target activity.

microbiology↗

bioRxiv2023

Universal Digital High Resolution Melt for the detection of pulmonary mold infections

BackgroundInvasive mold infections (IMIs) such as aspergillosis, mucormycosis, fusariosis, and lomentosporiosis are associated with high morbidity and mortality, particularly in immunocompromised patients, with mortality rates as high as 40% to 80%. Outcomes could be substantially improved with early initiation of appropriate antifungal therapy, yet early diagnosis remains difficult to establish and often requires multidisciplinary teams evaluating clinical and radiological findings plus supportive mycological findings. Universal digital high resolution melting analysis (U-dHRM) may enable rapid and robust diagnosis of IMI. This technology aims to accomplish timely pathogen detection at the single genome level by conducting broad-based amplification of microbial barcoding genes in a digital polymerase chain reaction (dPCR) format, followed by high-resolution melting of the DNA amplicons in each digital reaction to generate organism-specific melt curve signatures that are identified by machine learning. MethodsA universal fungal assay was developed for U-dHRM and used to generate a database of melt curve signatures for 19 clinically relevant fungal pathogens. A machine learning algorithm (ML) was trained to automatically classify these 19 fungal melt curves and detect novel melt curves. Performance was assessed on 73 clinical bronchoalveolar lavage (BAL) samples from patients suspected of IMI. Novel curves were identified by micropipetting U-dHRM reactions and Sanger sequencing amplicons. ResultsU-dHRM achieved an average of 97% fungal organism identification accuracy and a turn-around-time of 4hrs. Pathogenic molds (Aspergillus, Mucorales, Lomentospora and Fusarium) were detected by U-dHRM in 73% of BALF samples suspected of IMI. Mixtures of pathogenic molds were detected in 19%. U-dHRM demonstrated good sensitivity for IMI, as defined by current diagnostic criteria, when clinical findings were also considered. ConclusionsU-dHRM showed promising performance as a separate or combination diagnostic approach to standard mycological tests. The speed of U-dHRM and its ability to simultaneously identify and quantify clinically relevant mold pathogens in polymicrobial samples as well as detect emerging opportunistic pathogens may provide information that could aid in treatment decisions and improve patient outcomes.

microbiology↗

bioRxiv2022

Genomic diversity across Candida auris clinical isolates shapes rapid development of antifungal resistance in vitro and in vivo

Antifungal drug resistance and tolerance poses a serious threat to global public health. In the human fungal pathogen, Candida auris, resistance to triazole, polyene, and echinocandin antifungals is rising, resulting in multidrug resistant isolates. Here, we use genome analysis and in vitro evolution of seventeen new clinical isolates of C. auris from clades I and IV to determine how quickly resistance mutations arise, the stability of resistance in the absence of drug, and the impact of genetic background on evolutionary trajectories. We evolved each isolate in the absence of drug as well as in low and high concentrations of fluconazole. In just three passages, we observed genomic and phenotypic changes including karyotype alterations, aneuploidy, acquisition of point mutations, and increases in MIC values within the populations. Fluconazole resistance was stable in the absence of drug, indicating little to no fitness cost associated with resistance. Importantly, two isolates substantially increased fluconazole resistance to [≥]256{micro}g/ml fluconazole. Multiple evolutionary pathways and mechanisms to increase fluconazole resistance occurred simultaneously within the same population. Strikingly, the sub-telomeric regions of C. auris were highly dynamic as deletion of multiple genes near the sub-telomeres occurred during the three passages in several populations. Finally, we discovered a mutator phenotype in a clinical isolate of C. auris. This isolate had elevated mutation rates compared to other isolates and acquired substantial resistance during evolution in vitro and in vivo supporting that the genetic background of clinical isolates can have a significant effect on evolutionary potential. ImportanceDrug resistant Candida auris infections are recognized by the CDC as an urgent threat. Here, we obtained and characterized a set of clinical isolates of C. auris including multiple isolates from the same patient. To understand how drug resistance arises, we evolved these isolates and found that resistance to fluconazole, the most commonly prescribed antifungal, can occur rapidly and that there are multiple pathways to resistance. During our experiment, resistance was gained, but it was not lost, even in the absence of drug. We also found that some C. auris isolates have higher mutation rates than others and are primed to acquire antifungal resistance mutations. Furthermore, we found that multidrug resistance can evolve within a single patient. Overall, our results highlight the high stability and high rates of acquisition of antifungal resistance of C. auris that allow evolution of pan-resistant, transmissible isolates in the clinic.

microbiology↗

bioRxiv2021

A Recombinant Multivalent Vaccine (rCpa1) Induces Protection for C57BL/6 and HLA Transgenic Mice Against Pulmonary Infection with Both Species of Coccidioides

Coccidioidomycosis is caused by Coccidioides posadasii (Cp) and Coccidioides immitis (Ci) that have 4-5% differences in their genomic sequences. There is an urgent need to develop a human vaccine against both species. A previously created recombinant antigen (rCpa1) that contains multiple peptides derived from Cp isolate C735 is protective against the autologous isolate. The focus of this study is to evaluate cross-protective efficacy and immune correlates by the rCpa1- based vaccine against both species of Coccidioides. DNA sequence analyses of the homologous genes for the rCpa1 antigen were conducted for 39 and 17 clinical isolates of Cp and Ci, respectively. Protective efficacy and vaccine-induced immunity were evaluated for both C57BL/6 and human HLA-DR4 transgenic mice against 5 highly virulent isolates of Cp and Ci. There are a total of 7 amino acid substitutions in the rCpa1 antigen between Cp and Ci. Both C57BL/6 and HLA-DR4 mice that were vaccinated with a rCpa1 vaccine resulted in significant reduction of fungal burden and increased numbers of IFN-{gamma}- and IL-17-producing CD4+ T cells in the first 2 weeks post-challenge. These data support that rCpa1 has cross-protection activity against Cp and Ci pulmonary infection through activation of early Th1 and Th17 responses.

immunology↗

bioRxiv2020

Differential thermotolerance adaptation between species of Coccidioides

Coccidioidomycosis, or Valley fever, is caused by two species of dimorphic fungi. Based on molecular phylogenetic evidence, the genus Coccidioides contains two reciprocally monophyletic species: C. immitis and C. posadasii. However, phenotypic variation between species has not been deeply investigated. We therefore explored differences in growth rate under various conditions. A collection of 39 C. posadasii and 46 C. immitis isolates, representing the full geographical range of the two species, were screened for mycelial growth rate at 37{degrees}C and 28{degrees}C on solid media. The radial growth rate was measured over 16 days on yeast extract agar. A linear mixed effect model was used to compare the growth rate of C. posadasii and C. immitis at 37{degrees}C and 28{degrees}C respectively. C. posadasii grew significantly faster at 37{degrees}C, when compared to C. immitis; whereas both species had similar growth rates at 28{degrees}C. These results indicate thermotolerance differs between these two species. As the ecological niche has not been well-described for Coccidioides spp., and disease variability between species has not been shown, the evolutionary pressure underlying the adaptation is unclear. However, this research reveals the first significant phenotypic difference between the two species that directly applies to ecological and clinical research.

microbiology↗