Large-Scale Evaluation of In Vitro Amphotericin B, Triazole, and Echinocandin Activity against Coccidioides Species from U.S. Institutions

Talaromyces marneffei, Coccidioides species, and Paracoccidioides species-a systematic review to inform the World Health Organization priority list of fungal pathogens

The World Health Organization, in response to the growing burden of fungal disease, established a process to develop a fungal pathogen priority list. This systematic review aimed to evaluate the epidemiology and impact of infections caused by Talaromyces marneffei, Coccidioides species, and Paracoccidioides species. PubMed and Web of Sciences databases were searched to identify studies published between 1 January 2011 and 23 February 2021 reporting on mortality, complications and sequelae, antifungal susceptibility, preventability, annual incidence, and trends. Overall, 25, 17, and 6 articles were included for T. marneffei, Coccidioides spp. and Paracoccidioides spp., respectively. Mortality rates were high in those with invasive talaromycosis and paracoccidioidomycosis (up to 21% and 22.7%, respectively). Hospitalization was frequent in those with coccidioidomycosis (up to 84%), and while the duration was short (mean/median 3-7 days), readmission was common (38%). Reduced susceptibility to fluconazole and echinocandins was observed for T. marneffei and Coccidioides spp., whereas >88% of T. marneffei isolates had minimum inhibitory concentration values ≤0.015 μg/ml for itraconazole, posaconazole, and voriconazole. Risk factors for mortality in those with talaromycosis included low CD4 counts (odds ratio 2.90 when CD4 count <200 cells/μl compared with 24.26 when CD4 count <50 cells/μl). Outbreaks of coccidioidomycosis and paracoccidioidomycosis were associated with construction work (relative risk 4.4-210.6 and 5.7-times increase, respectively). In the United States of America, cases of coccidioidomycosis increased between 2014 and 2017 (from 8232 to 14 364/year). National and global surveillance as well as more detailed studies to better define sequelae, risk factors, outcomes, global distribution, and trends are required.

Challenges Facing Antimicrobial Stewardship Programs in the Endemic Region for Coccidioidomycosis

Coccidioidomycosis poses a significant cost and morbidity burden in the United States. Additionally, coccidioidomycosis requires constant decision-making related to prevention, diagnosis, and management. Delays in diagnosis lead to significant consequences, including unnecessary diagnostic workup and antibacterial therapy. Antifungal stewardship considerations regarding empiric, prophylactic, and targeted management of coccidioidomycosis are also complex. In this review, the problems facing antimicrobial stewardship programs (ASPs) in the endemic region for coccidioidomycosis, consequences due to delayed or missed diagnoses of coccidioidomycosis on antibacterial prescribing, and excess antifungal prescribing for prevention and treatment of coccidioidomycosis are elucidated. Finally, our recommendations and research priorities for ASPs in the endemic region for coccidioidomycosis are outlined.

Galleria mellonella Model of Coccidioidomycosis for Drug Susceptibility Tests and Virulence Factor Identification

Coccidioidomycosis (CM) can manifest as respiratory and disseminated diseases that are caused by dimorphic fungal pathogens, such as Coccidioides species. The inhaled arthroconidia generated during the saprobic growth phase convert into multinucleated spherules in the lungs to complete the parasitic lifecycle. Research on coccidioidal virulence and pathogenesis primarily employs murine models typically associated with low lethal doses (LD100 < 100 spores). However, the Galleria model has recently garnered attention due to its immune system bearing both structural and functional similarities to the innate system of mammals. Our findings indicate that Coccidioides posadasii can convert and complete the parasitic cycle within the hemocoel of the Galleria larva. In Galleria, the LD100 is between 0.5 and 1.0 × 106 viable spores for the clinical isolate Coccidioides posadasii C735. Furthermore, we demonstrated the suitability of this model for in vivo antifungal susceptibility tests to validate the bioreactivity of newly discovered antifungals against Coccidioides. Additionally, we utilized this larva model to screen a Coccidioides posadasii mutant library showing attenuated virulence. Similarly, the identified attenuated coccidioidal mutants displayed a loss of virulence in a commonly used murine model of coccidioidomycosis. In this study, we demonstrated that Galleria larvae can be applied as a model for studying Coccidioides infection.

The dog as a sentinel and animal model for coccidioidomycosis

Coccidioidomycosis is a potentially fatal fungal disease of humans and animals that follows inhalation of Coccidioides spp. arthroconidia in the environment. The disease in dogs resembles that in people, and because dogs may be at increased risk of exposure due to their proximity to the ground and digging behavior, they are valuable models for the disease in humans. Dogs have been sentinels for identification of new regions of endemicity in Washington and Texas. Canine serosurveillance has also been used to predict variables associated with environmental presence of Coccidioides spp. Expansion of the endemic region of coccidioidomycosis with climate change-along with predicted population increases and increased development in the southwest United States-may result in 45.4 million additional people at risk of infection by 2090. Here we provide an overview of the value of dogs as sentinels for the disease and encourage the routine reporting of coccidioidomycosis cases in dogs to public health agencies. We also highlight the value of dogs as naturally occurring models for studying novel treatment options and preventatives, such as a novel live avirulent coccidioidomycosis vaccine.

Invasive fungal infections and oomycoses in cats 2. Antifungal therapy

CLINICAL RELEVANCE

Invasive fungal infections (IFIs) and oomycoses (hereafter termed invasive fungal-like infections [IFLIs]) are characterised by penetration of tissues by fungal elements. The environment is the most common reservoir of infection. IFIs and IFLIs can be frustrating to treat because long treatment times are usually required and, even after attaining clinical cure, there may be a risk of relapse. Owner compliance with medication administration and recheck examinations can also decline over time. In addition, some antifungal drugs are expensive, have variable interpatient pharmacokinetic properties, can only be administered parenterally and/or have common adverse effects (AEs). Despite these limitations, treatment can be very rewarding, especially when an otherwise progressive and fatal disease is cured.

AIM

In the second of a two-part article series, the spectrum of activity, mechanisms of action, pharmacokinetic and pharmacodynamic properties, and AEs of antifungal drugs are reviewed, and the treatment and prognosis of specific IFIs/IFLIs - dermatophytic pseudomycetoma, cryptococcosis, sino-orbital aspergillosis, coccidioidomycosis, histoplasmosis, sporotrichosis, phaeohyphomycosis, mucormycosis and oomycosis - are discussed. Part 1 reviewed the diagnostic approach to IFIs and IFLIs.

EVIDENCE BASE

Information on antifungal drugs is drawn from pharmacokinetic studies in cats. Where such studies have not been performed, data from 'preclinical' animals (non-human studies) and human studies are reviewed. The review also draws on the wider published evidence and the authors' combined expertise in feline medicine, mycology, dermatology, clinical pathology and anatomical pathology.

ABBREVIATIONS FOR ANTIFUNGAL DRUGS

AMB (amphotericin B); FC (flucytosine); FCZ (fluconazole); ISA (isavuconazole); ITZ (itraconazole); KCZ (ketoconazole); PCZ (posaconazole); TRB (terbinafine); VCZ (voriconazole).

Endemic mycoses - are we making progress in management?

PURPOSE OF REVIEW

The endemic fungi are a significant cause of morbidity and mortality in effected patients. The range of endemicity for these are expanding with infections observed outside of traditional locations. Enhanced diagnostic and treatment practices may significantly alter patient outcomes.

RECENT FINDINGS

Recently completed clinical trials have focused on an assessment of improving efficacy while minimizing patient toxicity. Practice changing trials have been completed in histoplasmosis showing the utility of a single up-front liposomal amphotericin B dose followed by standard itraconazole dosing. The recent evaluation of several antifungal options including isauvconazole in the treatment of coccidioidomycosis also show promise for additional therapeutic agents. A recently conducted trial has also shown the superiority of amphotericin B therapy over itraconazole in the treatment of talaromycosis.

SUMMARY

The increased range of endemic mycoses coupled with the growing immunocompromised patient population mandates continued investigation of improved diagnostic and therapeutic options. Advances in these areas have led to more rapid diagnosis and more efficacious antifungal therapy.

Coccidioides species antifungal susceptibility testing: Experience from a large healthcare system in the endemic region

The clinical utility of Coccidioides species antifungal susceptibility testing (AST) remains unclear. This study describes the clinical course of eight patients with severe or chronic coccidioidomycosis and subsequent Coccidioides AST. We present the clinical manifestations, antifungal treatment regimens, and clinical outcomes for these patients.

Isavuconazole in the Treatment of Chronic Forms of Coccidioidomycosis

Coccidioidomycosis is a fungal infection with a range of clinical manifestations. Currently used antifungal agents exhibit variable efficacy and toxicity profiles that necessitate evaluation of additional therapeutic options. Improvement was observed in the majority of patients treated with isavuconazole, with clinical failures observed only in those with coccidioidal meningitis.

Review of Clinical and Laboratory Diagnostics for Coccidioidomycosis

Coccidioidomycosis is a fungal disease associated with soil exposure that frequently goes undiagnosed due at least in part to its nonspecific presentation and the lack of clinical suspicion by health care providers. Currently available diagnostics for coccidioidomycosis offer qualitative results that can suffer from low specificity, while semiquantitative assays are labor-intensive and complex and can require multiple days to complete. Furthermore, significant confusion exists regarding the optimal diagnostic algorithms and appropriate usage of available diagnostic tests. This review aims to inform clinical laboratorians and treating clinicians about the current diagnostic landscape, appropriate diagnostic strategies, and future diagnostic directions for coccidioidomycosis, which is expected to become more prevalent due to increased migration into areas of endemicity and climate changes.

Advocating for Coccidioidomycosis to Be a Reportable Disease Nationwide in the United States and Encouraging Disease Surveillance across North and South America

Coccidioidomycosis (Valley fever) has been a known health threat in the United States (US) since the 1930s, though not all states are currently required to report disease cases. Texas, one of the non-reporting states, is an example of where both historical and contemporary scientific evidence define the region as endemic, but we don't know disease incidence in the state. Mandating coccidioidomycosis as a reportable disease across more US states would increase disease awareness, improve clinical outcomes, and help antifungal drug and vaccine development. It would also increase our understanding of where the disease is endemic and the relationships between environmental conditions and disease cases. This is true for other nations in North and South America that are also likely endemic for coccidioidomycosis, especially Mexico. This commentary advocates for US state and territory epidemiologists to define coccidioidomycosis as a reportable disease and encourages disease surveillance in other endemic regions across North and South America in order to protect human health and reduce disease burden.

Fluconazole Failure in the Treatment of Coccidioidal Meningitis

INTRODUCTION

Coccidioidal meningitis (CM) is the most lethal form of disseminated coccidioidomycosis. Current guidelines recommend fluconazole as initial therapy but there has been a paucity of data regarding failure of fluconazole and optimal fluconazole dosage in the treatment of CM. We conducted this study to understand risk factors for fluconazole failure.

METHODS

We conducted a single-center retrospective chart review of patients diagnosed with coccidioidal meningitis between 1 January 1988 and 15 May 2021. Relevant demographic and clinical variables were collected, along with outcomes including treatment failure and death at any point. Univariate tests were conducted using the chi-squared goodness of fit test and analysis of variance.

RESULTS

Among 71 patients who began treatment for CM with fluconazole, 22 (31%) developed worsening meningitis at a median time of 206 days. Longer time from symptom onset to diagnosis of CM was a risk factor for fluconazole failure. Although the absolute failure rate of fluconazole starting dose of 400 mg daily was higher than that of 800 mg daily, the differences did not achieve statistical significance (p = 0.39).

CONCLUSION

Fluconazole failure is not uncommon in the treatment of CM. A dose of 800 mg daily was not superior to a dose of 400 mg daily. All patients on fluconazole for CM require close monitoring.

Genomic Data Mining Reveals Abundant Uncharacterized Transporters in Coccidioides immitis and Coccidioides posadasii

Coccidioides immitis and Coccidioides posadasii are causative agents of coccidioidomycosis, commonly known as Valley Fever. The increasing Valley Fever cases in the past decades, the expansion of endemic regions, and the rising azole drug-resistant strains have underscored an urgent need for a better understanding of Coccidioides biology and new antifungal strategies. Transporters play essential roles in pathogen survival, growth, infection, and adaptation, and are considered as potential drug targets. However, the composition and roles of transport machinery in Coccidioides remain largely unknown. In this study, genomic data mining revealed an abundant, uncharacterized repertoire of transporters in Coccidioides genomes. The catalog included 1288 and 1235 transporter homologs in C. immitis and C. posadasii, respectively. They were further annotated to class, subclass, family, subfamily and range of substrates based on the Transport Classification (TC) system. They may play diverse roles in nutrient uptake, metabolite secretion, ion homeostasis, drug efflux, or signaling. This study represents an initial effort for a systems-level characterization of the transport machinery in these understudied fungal pathogens.

Update on the Epidemiology, Diagnosis, and Treatment of Coccidioidomycosis

Coccidioidomycosis is a fungal infection caused by Coccidioides immitis and Coccidioides posadasii. The dimorphic fungi live in the soils of arid and semi-arid regions of the western United States, as well as parts of Mexico, Central America, and South America. Incidence of disease has risen consistently in recent years, and the geographic distribution of Coccidioides spp. appears to be expanding beyond previously known areas of endemicity. Climate factors are predicted to further extend the range of environments suitable for the growth and dispersal of Coccidioides species. Most infections are asymptomatic, though a small proportion result in severe or life-threatening forms of disease. Primary pulmonary coccidioidomycosis is commonly mistaken for community-acquired pneumonia, often leading to inappropriate antibacterial treatment and unnecessary healthcare costs. Diagnosis of coccidioidomycosis is challenging and often relies on clinician suspicion to pursue laboratory testing. Advancements in diagnostic tools and antifungal therapy developments seek to improve the early detection and effective management of infection. This review will highlight recent updates and summarize the current understanding of the epidemiology, diagnosis, and treatment of coccidioidomycosis.

Controversies in the Management of Central Nervous System Coccidioidomycosis

Central nervous system infection with Coccidioides spp is fatal if untreated, and complications occur even when therapy is directed by experienced clinicians. We convened a panel of clinicians experienced in the management of coccidioidal meningitis to summarize current controversies and provide consensus for the management of this difficult infection.

Current Landscape of Coccidioidomycosis

Coccidioidomycosis, also known as Valley fever, is an endemic fungal infection commonly found in the southwestern parts of the United States. However, the disease has seen an increase in both in its area of residency and its prevalence. This review compiles some of the latest information on the epidemiology, current and in-development pharmaceutical approaches to treat the disease, trends and projections, diagnostic concerns, and the overlapping dynamics of coccidioidomycosis and COVID-19, including in special populations. This review provides an overview of the current diagnostic and therapeutic strategies and identifies areas of future development.

Coccidioidomycosis: A Contemporary Review

Coccidioidomycosis, colloquially known as Valley Fever, is an invasive dimorphic fungal infection caused by Coccidioides immitis and C. posadasii. The fungi are found in the arid desert soils of the southwestern US, as well as in parts of Mexico and Central and South America. Acquisition is typically via inhalation of arthroconidia which become airborne after both natural (e.g., earthquakes, dust storms, and fires) and human-related events (e.g., military maneuvers, recreational activities, agriculture, and construction). The incidence of infection in increasing likely a result of both climatic and populational changes. Further, the recognized geographic distribution of Coccidioides spp. is expanding, as cases are being diagnosed in new areas (e.g., eastern Washington, Oregon, and Utah). Most coccidioidal infections are asymptomatic (60%); however, approximately one-third develop a pulmonary illness which is a leading cause of community-acquired pneumonia in highly endemic areas. Uncommonly (0.5–2% of cases), the infection disseminates to extrapulmonary locations (e.g., skin, bones/joints, and the central nervous system), and is most commonly seen among persons with cellular immunodeficiencies (e.g., transplant recipients, HIV, and pregnancy) and non-Caucasian races (especially African Americans and Filipinos). The diagnosis of coccidioidomycosis requires astute clinical suspicion and laboratory findings, including positive serology, cultures, and/or histopathology results. Treatment is warranted among persons with pneumonia who have risk factors for complicated disease and among those with extrapulmonary disease. Novel antifungals with improved fungicidal activity and rapidity of action with fewer side effects and drug interactions are needed. Preventive strategies (e.g., education regarding the disease, dust avoidance, mask wearing, including among select groups, antifungal prophylaxis, and surveillance laboratory testing) are advised for residents and travelers to endemic areas. Currently, no preventive vaccine is available. Coccidioidomycosis has been recognized for over a century, and an expanding wealth of knowledge has been gained regarding this emerging infectious disease which will be reviewed here.

Coccidioidomycosis

Coccidioidomycosis, caused by the dimorphic pathogenic fungi Coccidioides immitis and Coccidioides posadassi, is endemic to the southwestern United states and Central and South America. The incidence of coccidioidomycosis continues to increase. Coccidioidomycosis is typically a self-limiting influenza-like respiratory illness; however, it can lead to disseminated disease outside of the lungs. Not all nondisseminated cases require therapy, but antifungal therapy is typically beneficial requiring treatment ranging from months to lifelong. Clinical factors related to treatment decisions include severity of symptoms, radiography, coccidioidomycosis serologic results, and concurrent medical problems including immunosuppression. This review summarizes the epidemiology, clinical manifestations, and treatment options.

Infected Aneurysm of the Native Aorta due to Coccidioides posadasii

Coccidioidomycosis is an endemic fungal infection that is typically asymptomatic or associated with pulmonary disease. Extrapulmonary disease may involve the skin, bones, or central nervous system, yet endovascular infections are exceedingly rare. We report the first case, to our knowledge, of coccidioidomycosis of the native aorta in an immunocompromised host.

Treatment for Early, Uncomplicated Coccidioidomycosis: What Is Success?

The care of primary pulmonary coccidioidomycosis remains challenging. Such infections produce a variety of signs, symptoms, and serologic responses that cause morbidity in patients and concern in treating clinicians for the possibility of extrapulmonary dissemination. Illness may be due to ongoing fungal growth that produces acute inflammatory responses, resulting in tissue damage and necrosis, and for this, administering an antifungal drug may be of benefit. In contrast, convalescence may be prolonged by other immunologic reactions to infection, even after fungal replication has been arrested, and in those situations, antifungal therapy is unlikely to yield clinical improvement. In this presentation, we discuss what findings are clinical indicators of fungal growth and what other sequelae are not. Understanding these differences provides a rational management strategy for deciding when to continue, discontinue, or reinstitute antifungal treatments.

Coccidioidomycosis: Changing Concepts and Knowledge Gaps

Although first described more than 120 years ago, much remains unknown about coccidioidomycosis. In this review, new information that has led to changing concepts will be reviewed and remaining gaps in our knowledge will be discussed. In particular, new ideas regarding ecology and epidemiology, problems and promises of diagnosis, controversies over management, and the possibility of a vaccine will be covered.

Diagnosis of Breakthrough Fungal Infections in the Clinical Mycology Laboratory: An ECMM Consensus Statement

Breakthrough invasive fungal infections (bIFI) cause significant morbidity and mortality. Their diagnosis can be challenging due to reduced sensitivity to conventional culture techniques, serologic tests, and PCR-based assays in patients undergoing antifungal therapy, and their diagnosis can be delayed contributing to poor patient outcomes. In this review, we provide consensus recommendations on behalf of the European Confederation for Medical Mycology (ECMM) for the diagnosis of bIFI caused by invasive yeasts, molds, and endemic mycoses, to guide diagnostic efforts in patients receiving antifungals and support the design of future clinical trials in the field of clinical mycology. The cornerstone of lab-based diagnosis of breakthrough infections for yeast and endemic mycoses remain conventional culture, to accurately identify the causative pathogen and allow for antifungal susceptibility testing. The impact of non-culture-based methods are not well-studied for the definite diagnosis of breakthrough invasive yeast infections. Non-culture-based methods have an important role for the diagnosis of breakthrough invasive mold infections, in particular invasive aspergillosis, and a combination of testing involving conventional culture, antigen-based assays, and PCR-based assays should be considered. Multiple diagnostic modalities, including histopathology, culture, antibody, and/or antigen tests and occasionally PCR-based assays may be required to diagnose breakthrough endemic mycoses. A need exists for diagnostic tests that are effective, simple, cheap, and rapid to enable the diagnosis of bIFI in patients taking antifungals.

Self-assembled natural phytochemicals for synergistically antibacterial application from the enlightenment of traditional Chinese medicine combination

The application of nanotechnology for antimicrobial delivery has capacity to improve antibacterial efficacy. Currently, the usage of various inorganic and organic carriers, such as metal ions, nano-silicon and surfactants, might increase the potential toxicity of nanoparticles and make their clinical transformation more difficult. Herein, a nano-delivery system was constructed by direct self-assembly of antibacterial phytochemicals (berberine and rhein) originated from traditional Chinese medicine Coptis chinensis Franch. and Rheum palmatum L., respectively. Combining X-ray single crystal diffraction, nuclear magnetic resonance and other spectra characterizations, the stacked structure of nanoparticles was profoundly demonstrated. Briefly, rhein acted as the layered backbone and berberine embedded in it. In vitro bacteriostasis experiment showed the minimum bactericidal concentration of nanoparticles was 0.1 μmol/mL, which was lower than that of berberine and rhein. The results of confocal laser scanning microscope, biofilm quantitive assay and scanning electron microscopy indicated that nanoparticles had strong inhibitory effects on Staphylococcus aureus biofilm. More importantly, transmission electron microscopy and mass spectra indicated the further bacteriostatic mechanism of nanoparticles. Meanwhile, the nanoparticles had well biocompatibility and safety. Current study will open up new prospect that the design of self-assemblies between active phytochemicals can be originated from traditional Chinese medicine combination.

Review of the Novel Investigational Antifungal Olorofim

The incidence of invasive fungal infections caused by molds and endemic fungi is increasing. There is also concern regarding increased rates of reduced susceptibility or frank resistance among Aspergillus and Coccidioides species, while Scedosporium species, Lomentospora prolificans, and Fusarium species are inherently less susceptible or intrinsically resistant to clinically available antifungals. Olorofim (formerly F901318) is the first member of the orotomide class of antifungals to be evaluated clinically for the treatment of invasive mold infections. This agent inhibits dihydroorotate dehydrogenase, a key enzyme in the biosynthesis of pyrimidines. Olorofim has activity against many molds and thermally dimorphic fungi, including species that are resistant to azoles and amphotericin B, but lacks activity against yeasts and the Mucorales. It is currently being developed for both oral and intravenous administration. Although published clinical outcome data have been limited to case reports to date, the results against invasive and refractory infections are promising. This review describes the mechanism of action of olorofim, its in vitro spectrum of activity, and what is currently known about its pharmacokinetic profile and clinical efficacy.

Review on Current Status of Echinocandins Use

Fungal infections are rising all over the world every year. There are only five medical compound classes for treatment: triazoles, echinocandins, polyenes, flucytosine and allylamine. Currently, echinocandins are the most important compounds, because of their wide activity spectrum and much lower sides effects that may occur during therapy with other drugs. Echinocandins are secondary metabolites of fungi, which can inhibit the biosynthesis of β-(1,3)-D-glucan. These compounds have fungicidal and fungistatic activity depending on different genera of fungi, against which they are used. Echinocandin resistance is rare—the major cause of resistance is mutations in the gene encoding the β-(1,3)-D-glucan synthase enzyme. In this review of the literature we have summarized the characteristics of echinocandins, the mechanism of their antifungal activity with pharmacokinetics and pharmacodynamics, and the resistance issue.

The mysterious desert dwellers: Coccidioides immitis and Coccidioides posadasii, causative fungal agents of coccidioidomycosis

The genus Coccidioides consists of two species: C. immitis and C. posadasii. Prior to 2000, all disease was thought to be caused by a single species, C. immitis. The organism grows in arid to semiarid alkaline soils throughout western North America and into Central and South America. Regions in the United States, with highest prevalence of disease, include California, Arizona, and Texas. The Mexican states of Baja California, Coahuila, Sonora, and Neuvo Leon currently have the highest skin test positive results. Central America contains isolated endemic areas in Guatemala and Honduras. South America has isolated regions of high endemicity including areas of Colombia, Venezuela, Argentina, Paraguay, and Brazil. Although approximately 15,000 cases per year are reported in the United States, actual disease burden is estimated to be in the hundreds of thousands, as only California and Arizona have dedicated public health outreach, and report and track disease reliably. In this review, we survey genomics, epidemiology, ecology, and summarize aspects of disease, diagnosis, prevention, and treatment.

Fungal Cell Wall: Emerging Antifungals and Drug Resistance

The cell wall is an essential component in fungal homeostasis. The lack of a covering wall in human cells makes this component an attractive target for antifungal development. The host environment and antifungal stress can lead to cell wall modifications related to drug resistance. Antifungals targeting the cell wall including the new β-D-glucan synthase inhibitor ibrexafungerp and glycosyl-phosphatidyl Inositol (GPI) anchor pathway inhibitor fosmanogepix are promising weapons against antifungal resistance. The fosmanogepix shows strong in vitro activity against the multidrug-resistant species Candida auris, Fusarium solani, and Lomentospora prolificans. The alternative carbon sources in the infection site change the cell wall β-D-glucan and chitin composition, leading to echinocandin and amphotericin resistance. Candida populations that survive echinocandin exposure develop tolerance and show high chitin content in the cell wall, while fungal species such as Aspergillus flavus with a higher β-D-glucan content may show amphotericin resistance. Therefore understanding fungal cell dynamics has become important not only for host-fungal interactions, but also treatment of fungal infections. This review summarizes recent findings regarding antifungal therapy and development of resistance related to the fungal cell wall of the most relevant human pathogenic species.

Early Events in Coccidioidomycosis

Since its description nearly 130 years ago, hundreds of studies have deepened our understanding of coccidioidomycosis, also known as valley fever (VF), and provided useful diagnostic tests and treatments for the disease caused by the dimorphic fungi Coccidioides spp. In general, most of the literature has addressed well-established infections and has described patients who have experienced major complications. In contrast, little attention has been given to the earliest consequences of the pathogen-host interaction and its implications for disease manifestation, progression, and resolution. The purpose of this review is to highlight published studies on early coccidioidomycosis, identify gaps in our knowledge, and suggest new or former research areas that might be or remain fertile ground for insight into the early stages of this invasive fungal disease.

The Rise of Coccidioides: Forces Against the Dust Devil Unleashed

Coccidioidomycosis (Valley fever) is a fungal disease caused by the inhalation of Coccidioides posadasii or C. immitis. This neglected disease occurs in the desert areas of the western United States, most notably in California and Arizona, where infections continue to rise. Clinically, coccidioidomycosis ranges from asymptomatic to severe pulmonary disease and can disseminate to the brain, skin, bones, and elsewhere. New estimates suggest as many as 350,000 new cases of coccidioidomycosis occur in the United States each year. Thus, there is an urgent need for the development of a vaccine and new therapeutic drugs against Coccidioides infection. In this review, we discuss the battle against Coccidioides including the development of potential vaccines, the quest for new therapeutic drugs, and our current understanding of the protective host immune response to Coccidioides infection.

Central Nervous System Infections Due to Coccidioidomycosis

Coccidioidomycosis is a common infection in the western and southwestern United States as well as parts of Mexico and Central and South America and is due to the soil-dwelling fungi Coccidioides. Central nervous system (CNS) infection is an uncommon manifestation that is nearly always fatal if untreated. The presentation is subtle, commonly with headache and decreased mentation. The diagnosis should be considered in patients with these symptoms in association with a positive serum coccidioidal antibody test. The diagnosis can only be established by analysis of cerebrospinal fluid (CSF), which typically demonstrates a lymphocytic pleocytosis, hypoglycorrhachia, elevated protein, and positive CSF coccidioidal antibody. Cultures are infrequently positive but a proprietary coccidioidal antigen test has reasonable sensitivity. Current therapy usually begins with fluconazole at 800 mg daily but other triazole antifungals also have efficacy and are often used if fluconazole fails. Triazole therapy should be lifelong. Intrathecal amphotericin B, the original treatment, is now reserved for those in whom triazoles have failed. There are several distinct complications of CNS coccidioidal infection, the most common of which is hydrocephalus. This is nearly always communicating and requires mechanical shunting in addition to antifungal therapy. Other complications include cerebral vasculitis, brain abscess, and arachnoiditis. Management of these is difficult and not well established.

Coccidioidomycosis: Epidemiology, Fungal Pathogenesis, and Therapeutic Development

Purpose of Review

Coccidioidomycosis can result from the inhalation of infectious spores of Coccidioides species (spp.) immitis or posadasii. Clinical manifestations range from mild flu-like disease to severe disseminated infection that can require life-long therapy. Burden of this mycosis is high in the southwest region of the USA where it is well characterized, and in many areas of Mexico and Latin America where it is inadequately characterized. Here, we provide historical data and current knowledge on Coccidioides spp. pathogenesis as well as recent progress in therapeutic and vaccine development against coccidioidomycosis.

Recent Findings

The virulence mechanisms of Coccidioides spp. are largely unknown; however, production and regulation of a spherule glycoprotein, ammonium production, and melanization have all been proposed as integral factors in Coccidioides spp.' pathogenesis. Therapeutic options are limited and not 100% effective, but individualized treatment with triazoles or amphotericin B over the course of pulmonary or disseminated infection can be effective in resolution of coccidioidomycosis. Human immunization has not been achieved but efforts are ongoing.

Summary

Advances in therapeutic and vaccine development are imperative for the prevention and treatment of coccidioidomycosis, especially for those individuals at risk either living or traveling to or from endemic areas.

Current Concepts and Future Directions in the Pharmacology and Treatment of Coccidioidomycosis

Coccidioidomycosis remains a significant clinical problem with substantial morbidity and mortality. The vast majority of infections are asymptomatic and the need for early primary therapy remains controversial. The use of triazole antifungals has improved tolerability of therapy but concerns about acute and long-term toxicities among available agents limit their use. In addition, recent findings of decreased in vitro fluconazole susceptibility to as many as 37% of Coccidioides spp. isolates raises concerns regarding optimal therapy for these infections as fluconazole is commonly used for therapy including central nervous system disease. Thus, new agents from novel antifungal classes are currently in preclinical and clinical development aimed at reducing toxicity and improving outcomes of these serious infections.

APX001 and Other Gwt1 Inhibitor Prodrugs Are Effective in Experimental Coccidioides immitis Pneumonia

Coccidioidomycosis is a systemic fungal infection caused by the inhalation of the arthroconidia of either of two closely related dimorphic fungi, Coccidioides immitis and C. posadasii, that are endemic in the southwestern United States and other areas in the Western Hemisphere. Chronic cavitary pulmonary infections and extrapulmonary sites of infection are very difficult to treat and often require lifelong azole therapy. APX001A is the first in a new class of broad-spectrum antifungal agents that inhibit Gwt1, an enzyme which is required for cell wall localization of glycosylphosphatidylinositol (GPI)-anchored mannoproteins in fungi. APX001A and several analogs were highly active against clinical isolates of Coccidioides, inhibiting hyphal growth at low nanogram/ml concentrations. APX001 is the N-phosphonooxymethyl prodrug of APX001A, currently in clinical trials for the treatment of invasive fungal infections. Mice were treated orally once daily with 26 mg/kg/day of APX001 and the prodrug analog APX2097, 2 h after administration of the pan-cytochrome P450 inhibitor 1-aminobenzotriazole, which was used to enhance drug half-life and exposures to more closely mimic human pharmacokinetics of APX001A. Five days of treatment reduced lung colony counts by nearly 3 logs and prevented dissemination, similar to the efficacy of fluconazole dosed orally at 25 mg/kg twice daily. In a survival experiment, both APX001- and APX2097-treated mice survived significantly longer than control and fluconazole-treated mice. APX001 and other members of this new class of antifungal agents may offer great promise as effective therapies for coccidioidomycosis.

The Orotomide Olorofim Is Efficacious in an Experimental Model of Central Nervous System Coccidioidomycosis

Olorofim (formerly F901318) is an advanced analog of the orotomide class that inhibits fungal pyrimidine biosynthesis. We evaluated the in vitro and in vivo activities of olorofim against Coccidioides species. In vitro activity was assessed against 59 clinical Coccidioides isolates. Central nervous system infections were established in mice via intracranial inoculation with Coccidioides immitis arthroconidia. Oral therapy began 48 h postinoculation and consisted of vehicle control, olorofim daily doses of 20 mg/kg (6.67 mg/kg three times daily or 10 mg/kg twice daily) or 40 mg/kg (13.3 mg/kg three times daily or 20 mg/kg twice daily), or fluconazole (25 mg/kg twice daily). Treatment continued for 7 and 14 days in the fungal burden and survival arms, respectively. Fungal burdens were assessed by CFU counts in brains. Olorofim demonstrated potent in vitro activity (MIC range, ≤0.008 to 0.06 μg/ml). Survival was significantly enhanced in mice treated with olorofim. Reductions in brain tissue fungal burdens were also observed on day 9 in the olorofim-treated groups. Improvements in survival and reductions in fungal burdens also occurred with fluconazole. More frequent dosing of olorofim was associated with enhanced survival and greater reductions in fungal burdens. In the group treated with 13.3 mg/kg olorofim three times daily, fungal burdens remained low on day 30 (15 days after treatment was stopped), with undetectable levels in 7 of 10 mice. In contrast, fungal burdens rebounded in all other groups after therapy stopped. Olorofim was highly active in vitro and in vivo against Coccidioides These results demonstrate that olorofim may have a role in the treatment of coccidioidomycosis.

Myelitis due to Coccidioidomycosis in an Immunocompetent Patient

Myelitis of the spinal cord is an uncommon presentation of disseminated coccidioidomycosis. Most infected patients present subclinically, but patients, especially those who are immunocompromised, may progress to disseminated disease. We present a 50-year-old immunocompetent patient with no significant past medical history exhibiting symptoms of altered mental status, dizziness, headache, nausea, and quadriplegia. Upon investigation with lumbar puncture, cerebrospinal fluid (CSF) culture, and coccidioidal antibody studies, the patient was found to have acute coccidioidomycosis. Magnetic resonance imaging (MRI) of the brain demonstrated meningeal enhancements suggestive of meningitis, and further MRI study of the cervical spine revealed myelitis. Treatment with IV fluconazole for 2 weeks and IV voriconazole therapy over 3 weeks yielded limited improvement. The presentation of myelitis due to coccidioidomycosis infection is very rare and has infrequently reported in the literature. Awareness of this potentially fatal complication in immunocompetent patients can aid in faster recognition and treatment.

The Novel Fungal Cyp51 Inhibitor VT-1598 Is Efficacious in Experimental Models of Central Nervous System Coccidioidomycosis Caused by Coccidioides posadasii and Coccidioides immitis

Coccidioidal meningitis can cause significant morbidity, and lifelong antifungal therapy is often required. VT-1598 is a fungus-specific Cyp51 inhibitor that has potent in vitro activity against Coccidioides species. We evaluated the in vivo efficacy of VT-1598 in murine models of central nervous system coccidioidomycosis caused by C. posadasii and C. immitis Infection was introduced via intracranial inoculation, and therapy began 48 h postinoculation. Oral treatments consisted of vehicle control, VT-1598, and positive controls of fluconazole in the C. immitis study and VT-1161 in the C. posadasii study. Treatment continued for 7 and 14 days in the fungal-burden and survival studies, respectively. Fungal burden was assessed in brain tissue collected 24 to 48 h posttreatment in the fungal-burden studies, on the days the mice succumbed to infection, or at prespecified endpoints in the survival studies. VT-1598 plasma concentrations were also measured in the C. posadasii study. VT-1598 resulted in significant improvements in survival in mice infected with either species. In addition, the fungal burden was significantly reduced in the fungal-burden studies. Plasma concentrations 48 h after dosing stopped remained above the VT-1598 MIC against the C. posadasii isolate, although levels were undetectable in the survival study after a 4-week washout. Whereas fungal burden remained suppressed after a 2-week washout in the C. immitis model, a higher fungal burden was observed in the survival arm of the C. posadasii model. This in vivo efficacy supports human studies to establish the utility of VT-1598 for the treatment of coccidioidomycosis.

Coccidioides immitis septic knee arthritis

A 78-year-old man developed right knee pain and swelling without other systemic symptoms. He had travelled frequently to the Central Valley of California. He was diagnosed with coccidioidomycosis based on joint fluid culture. Coccidioidal complement fixation antibody titres were extremely elevated. Arthroscopic debridement and fluconazole therapy did not lead to satisfactory improvement. Subsequent open debridement and change to itraconazole was followed by resolution of clinical signs of infection.