Emergence Of Azole Resistance Research Articles

Variability in competitive fitness among environmental and clinical azole-resistant Aspergillus fumigatus isolates.

Azole resistance in the human fungal pathogen Aspergillus fumigatus presents a global public health challenge. Understanding the epidemic trends and evolutionary patterns of azole resistance is critical to prevent and control the spread of azole-resistant isolates. The primary cause is the mutation of the drug target 14α-sterol-demethylase Cyp51A, yet its impact on competitive ability remains uncertain. Our competition assays revealed a diverse range of fitness outcomes for environmental and clinical cyp51A-mutated isolates. We have shown that this fitness cost is not reliant on cyp51A mutations but might be linked to unknown mutations induced by stress conditions. Among these isolates, the majority displayed fitness costs, while a few displayed enhanced competitive ability, which may have a potential risk of spread and the need to closely monitor these isolates. Our observation reveals the variation in fitness costs among azole-resistant isolates of A. fumigatus, highlighting the significant role of fitness cost in the spread of resistant strains.

Aneuploidy Formation in the Filamentous Fungus Aspergillus flavus in Response to Azole Stress.

Aspergillus flavus is a mycotoxigenic fungus that contaminates many important agricultural crops with aflatoxin B1, the most toxic and carcinogenic natural compound. This fungus is also the second leading cause of human invasive aspergillosis, after Aspergillus fumigatus, a disease that is particularly prevalent in immunocompromised individuals. Azole drugs are considered the most effective compounds in controlling Aspergillus infections both in clinical and agricultural settings. Emergence of azole resistance in Aspergillus spp. is typically associated with point mutations in cyp51 orthologs that encode lanosterol 14α-demethylase, a component of the ergosterol biosynthesis pathway that is also the target of azoles. We hypothesized that alternative molecular mechanisms are also responsible for acquisition of azole resistance in filamentous fungi. We found that an aflatoxin-producing A. flavus strain adapted to voriconazole exposure at levels above the MIC through whole or segmental aneuploidy of specific chromosomes. We confirm a complete duplication of chromosome 8 in two sequentially isolated clones and a segmental duplication of chromosome 3 in another clone, emphasizing the potential diversity of aneuploidy-mediated resistance mechanisms. The plasticity of aneuploidy-mediated resistance was evidenced by the ability of voriconazole-resistant clones to revert to their original level of azole susceptibility following repeated transfers on drug-free media. This study provides new insights into mechanisms of azole resistance in a filamentous fungus. IMPORTANCE Fungal pathogens cause human disease and threaten global food security by contaminating crops with toxins (mycotoxins). Aspergillus flavus is an opportunistic mycotoxigenic fungus that causes invasive and noninvasive aspergillosis, diseases with high rates of mortality in immunocompromised individuals. Additionally, this fungus contaminates most major crops with the notorious carcinogen, aflatoxin. Voriconazole is the drug of choice to treat infections caused by Aspergillus spp. Although azole resistance mechanisms have been well characterized in clinical isolates of Aspergillus fumigatus, the molecular basis of azole resistance in A. flavus remains unclear. Whole-genome sequencing of eight voriconazole-resistant isolates revealed that, among other factors, A. flavus adapts to high concentrations of voriconazole by duplication of specific chromosomes (i.e., aneuploidy). Our discovery of aneuploidy-mediated resistance in a filamentous fungus represents a paradigm shift, as this type of resistance was previously thought to occur only in yeasts. This observation provides the first experimental evidence of aneuploidy-mediated azole resistance in the filamentous fungus A. flavus.

In Vivo Efficacy of Voriconazole in a Galleria mellonella Model of Invasive Infection Due to Azole-Susceptible or Resistant Aspergillus fumigatus Isolates.

Aspergillus fumigatus is an environmental filamentous fungus responsible for life-threatening infections in humans and animals. Azoles are the first-line treatment for aspergillosis, but in recent years, the emergence of azole resistance in A. fumigatus has changed treatment recommendations. The objective of this study was to evaluate the efficacy of voriconazole (VRZ) in a Galleria mellonella model of invasive infection due to azole-susceptible or azole-resistant A. fumigatus isolates. We also sought to describe the pharmacokinetics of VRZ in the G. mellonella model. G. mellonella larvae were infected with conidial suspensions of azole-susceptible and azole-resistant isolates of A. fumigatus. Mortality curves were used to calculate the lethal dose. Assessment of the efficacy of VRZ or amphotericin B (AMB) treatment was based on mortality in the lethal model and histopathologic lesions. The pharmacokinetics of VRZ were determined in larval hemolymph. Invasive fungal infection was obtained after conidial inoculation. A dose-dependent reduction in mortality was observed after antifungal treatment with AMB and VRZ. VRZ was more effective at treating larvae inoculated with azole-susceptible A. fumigatus isolates than larvae inoculated with azole-resistant isolates. The concentration of VRZ was maximal at the beginning of treatment and gradually decreased in the hemolymph to reach a Cmin (24 h) between 0.11 and 11.30 mg/L, depending on the dose. In conclusion, G. mellonella is a suitable model for testing the efficacy of antifungal agents against A. fumigatus.

The Emergence of Azole Resistance in Candida parapsilosis Isolates Causing Systemic Candidosis

The Emergence of Azole Resistance in Candida parapsilosis Isolates Causing Systemic Candidosis

Antibody-guided in vivo imaging of Aspergillus fumigatus lung infections during antifungal azole treatment

Invasive pulmonary aspergillosis (IPA) is a life-threatening lung disease of immunocompromised humans, caused by the opportunistic fungal pathogen Aspergillus fumigatus. Inadequacies in current diagnostic procedures mean that early diagnosis of the disease, critical to patient survival, remains a major clinical challenge, and is leading to the empiric use of antifungal drugs and emergence of azole resistance. A non-invasive procedure that allows both unambiguous detection of IPA and its response to azole treatment is therefore needed. Here, we show that a humanised Aspergillus-specific monoclonal antibody, dual labelled with a radionuclide and fluorophore, can be used in immunoPET/MRI in vivo in a neutropenic mouse model and 3D light sheet fluorescence microscopy ex vivo in the infected mouse lungs to quantify early A. fumigatus lung infections and to monitor the efficacy of azole therapy. Our antibody-guided approach reveals that early drug intervention is critical to prevent complete invasion of the lungs by the fungus, and demonstrates the power of molecular imaging as a non-invasive procedure for tracking IPA in vivo.

1598. Clinical implications of azole-resistant vs. azole-susceptible invasive aspergillosis in hematological malignancy (CLARITY) – a multicenter study

BackgroundAdvances in the survival of patients with invasive aspergillosis (IA) are jeopardized by the emergence of azole resistance in Aspergillus fumigatus, which has been associated with high probability of azole treatment failure. The clinical implications of azole-resistant IA compared to azole-susceptible IA remain unclear. Thus, we seek to describe the epidemiology and to determine the efficacy of antifungal therapy in patients with documented azole-resistant IA compared to azole-susceptible IA in patients with hematological malignancy.MethodsFor proven and probable IA (EORTC/MSG 2019) caused by A. fumigatus in patients with hematological malignancies retrospective data were documented, comprising demographics, diagnosis, treatment, response, and outcome. Sites provided susceptibility results or respective isolates for analysis in a central laboratory.ResultsSites in 16 countries worldwide enrolled 187 cases diagnosed with IA between 2010 and 2019; 31 (16.6%) were resistant to at least one of the clinical azoles. Fungal isolates were available from 42 cases. A mixed fungal infection was reported for 32 patients (17.1%), most were related to non-fumigatus Aspergillus and non-Aspergillus molds (n=22, 69%). Most patients were male (66.8%) and overall the majority of patients were in the age groups between 50 and 89 years (71%). Amphotericin B was used for treatment in 24 (77%) patients with azole-resistant IA, compared to 76 (49%) in the azole-susceptible group (lipid-based formulation in 98%); only five (16%) patients with azole-resistant IA were treated with an azole alone vs. 57 (36%) of those with azole-susceptible IA. Overall, all-cause mortality rate was higher for patients with azole-resistant compared to azole-susceptible IA (74.2% vs. 53.8%, log rank P=0.004), the 8 patients with an azole-resistant IA treated in the intensive care unit died within 1 month (Figure 1). Details on underlying disease and survival are given in Table 1.Table 1. Underlying hematological malignancy and clinical outcome of patients with azole-resistant and azole-susceptible invasive aspergillosis Figure 1. Intensive care unit 1-year survival probability for patients with azole-resistant and azole-susceptible invasive aspergillosis ConclusionAzole-resistance in IA is associated with worse outcome, especially in critically ill patients. Susceptibility testing should be considered in patients with a suspected azole-resistant IA to support treatment decisions.Disclosures Danila Seidel, PhD, Basilea (Other Financial or Material Support, travel grant) Oliver Cornely, Prof., Actelion (Grant/Research Support)Actelion (Other Financial or Material Support, Personal fees)Al Jazeera Pharmaceuticals (Consultant)Allecra Therapeutics (Other Financial or Material Support, Personal fees)Amplyx (Other Financial or Material Support, Personal fees)Amplyx (Grant/Research Support)Astellas (Grant/Research Support)Astellas (Other Financial or Material Support, Personal fees)Basilea (Other Financial or Material Support, Personal fees)Basilea (Grant/Research Support)Biosys UK Limited (Other Financial or Material Support, Personal fees)Cidara (Other Financial or Material Support, Personal fees)Cidara (Grant/Research Support)Da Volterra (Grant/Research Support)Da Volterra (Other Financial or Material Support, Personal fees)Entasis (Other Financial or Material Support, Personal fees)F2G (Other Financial or Material Support)F2G (Grant/Research Support)Gilead (Grant/Research Support)Gilead (Other Financial or Material Support, Personal fees)Grupo Biotoscana (Other Financial or Material Support, Personal fees)Janssen Pharmaceuticals (Grant/Research Support)Matinas (Other Financial or Material Support, Personal fees)Medicines Company (Grant/Research Support)MedPace (Grant/Research Support)MedPace (Other Financial or Material Support, Personal fees)Melinta Therapeutics (Grant/Research Support)Menarini Ricerche (Other Financial or Material Support, Personal fees)Merck/MSD (Other Financial or Material Support, Personal fees)Merck/MSD (Grant/Research Support)Mylan Pharmaceuticals (Consultant)Nabriva Therapeutics (Other Financial or Material Support, Personal fees)Octapharma (Other Financial or Material Support, Personal fees)Paratek Pharmaceuticals (Other Financial or Material Support, Personal fees)Pfizer (Other Financial or Material Support, Personal fees)Pfizer (Grant/Research Support)PSI (Other Financial or Material Support, Personal fees)Rempex (Other Financial or Material Support, Personal fees)Roche Diagnostics (Other Financial or Material Support, Personal fees)Scynexis (Other Financial or Material Support, Personal fees)Scynexis (Grant/Research Support)Seres Therapeutics (Other Financial or Material Support, Personal fees)Tetraphase (Other Financial or Material Support, Personal fees) Philipp Koehler, MD, Akademie für Infektionsmedizin e.V., (Other Financial or Material Support, Personal fees)Astellas Pharma GmbH (Other Financial or Material Support, Personal fees)Cologne Excellence Cluster on Cellular Stress Responses in Aging-Associated Diseases, University of Cologne, Cologne, Germany (Other Financial or Material Support, Other)Gilead Sciences GmbH (Other Financial or Material Support, Personal fees)GPR Academy Ruesselsheim (Speaker’s Bureau)Miltenyi Biotec GmbH (Other Financial or Material Support, Non-financial support)MSD Sharp & Dohme GmbH (Other Financial or Material Support, Personal fees)Noxxon N.V. (Speaker’s Bureau)University Hospital, LMU Munich (Other Financial or Material Support, Personal fees) Katrien Lagrou, n/a, FUJIFILM WAKO (Speaker’s Bureau)Gilead (Consultant, Speaker’s Bureau)MSD (Consultant, Speaker’s Bureau, Other Financial or Material Support, travel grant)Pfizer (Speaker’s Bureau, travel grant)SMB Laboratoires Brussels (Consultant) Zdenek Racil, n/a, Astellas (Grant/Research Support, Speaker’s Bureau, travel grant) Blandine Rammaert, n/a, Gilead (Speaker’s Bureau, Other Financial or Material Support, travel grant)Merck/MSD (Speaker’s Bureau)Pfizer (Other Financial or Material Support, travel grant) Nikolay Klimko, n/a, Astellas (Speaker’s Bureau)Gilead (Speaker’s Bureau)Merck/MSD (Speaker’s Bureau)Pfizer (Speaker’s Bureau) Sung-Yeon Cho, MD, Gilead (Grant/Research Support, Speaker’s Bureau)Merck Sharp & Dohme (Grant/Research Support, Speaker’s Bureau)Pfizer (Grant/Research Support, Speaker’s Bureau)

Aspergillosis, Avian Species and the One Health Perspective: The Possible Importance of Birds in Azole Resistance.

The One Health context considers health based on three pillars: humans, animals, and environment. This approach is a strong ally in the surveillance of infectious diseases and in the development of prevention strategies. Aspergillus spp. are fungi that fit substantially in this context, in view of their ubiquity, as well as their importance as plant pathogens, and potentially fatal pathogens for, particularly, humans and avian species. In addition, the emergence of azole resistance, mainly in Aspergillus fumigatus sensu stricto, and the proven role of fungicides widely used on crops, reinforces the need for a multidisciplinary approach to this problem. Avian species are involved in short and long distance travel between different types of landscapes, such as agricultural fields, natural environments and urban environments. Thus, birds can play an important role in the dispersion of Aspergillus, and of special concern, azole-resistant strains. In addition, some bird species are particularly susceptible to aspergillosis. Therefore, avian aspergillosis could be considered as an environmental health indicator. In this review, aspergillosis in humans and birds will be discussed, with focus on the presence of Aspergillus in the environment. We will relate these issues with the emergence of azole resistance on Aspergillus. These topics will be therefore considered and reviewed from the “One Health” perspective.

Antifungal susceptibility profile and molecular identification of Cyp51C mutations in clinical and environmental isolates of Aspergillus flavus from Argentina.

The emergence of azole resistance in non-fumigatus Aspergillus strains is on the raise. To study the susceptibility profiles and the molecular mechanisms of azole resistance of environmental and clinical strains of Aspergillus flavus from Argentina. Thirty-five Aflavus isolates (18 from soybean seeds and chickpea seeds and 17 from the clinic) were analysed for amphotericin B and azole resistance using the standard microbroth dilution method according to CLSI M38-A2 guidelines. Sequencing analysis of the cyp51 genes was conducted in those isolates displaying high MICs values to itraconazole, voriconazole and/or posaconazole. Among the environmental isolates, 33.3% of them showed high MIC values for at least one triazole whereas 23.5% of the clinical isolates displayed high MIC values for amphotericin B. Point mutations in the Cyp51C gene were recorded in most environmental isolates with non-wild-type MIC values. Susceptibility differences among environmental Aflavus isolates might suggest the possibility of native resistance to certain triazole antifungals used in the clinic. To the best of our knowledge, this is the first report of antifungal screening of environmental strains of Aflavus in soybean seeds and chickpea seeds from Argentina that showed increased resistance to voriconazole and itraconazole in comparison to clinical strains.

Prevalence and Antifungal Susceptibility of Pathogenic Yeasts in China: A 10-Year Retrospective Study in a Teaching Hospital.

To determine the dynamic changes of pathogenic yeast prevalence and antifungal susceptibility patterns in tertiary hospitals in China, we analyzed 527 yeast isolates preserved in the Research Center for Medical Mycology at Peking University, Beijing, China, between Jan 2010 and Dec 2019 and correctly identified 19 yeast species by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) and ribosomal DNA sequencing. Antifungal susceptibility testing was performed following a Sensititre YeastOne colorimetric microdilution panel with nine clinically available antifungals. The Clinical and Laboratory Standards Institute (CLSI)-approved standard M27-A3 (S4) and newly revised clinical breakpoints or species-specific and method-specific epidemiological cutoff values were used for the interpretation of susceptibility test data. In this study, although Candida albicans was the predominant single species, non-C. albicans species constituted >50% of isolates in 6 out of 10 years, and more rare species were present in the recent 5 years. The non-C. albicans species identified most frequently were Candida parapsilosis sensu stricto, Candida tropicalis, and Candida glabrata. The prevalence of fluconazole and voriconazole resistance in the C. parapsilosis sensu stricto population was <3%, but C. tropicalis exhibited decreased susceptibility to fluconazole (42, 57.5%) and voriconazole (31, 42.5%), and 22 (30.1%) C. tropicalis isolates exhibited wild-type minimum inhibitory concentrations (MICs) to posaconazole. Furthermore, fluconazole and voriconazole cross-resistance prevalence in C. tropicalis was 19 (26.1%). The overall prevalence of fluconazole resistance in the C. glabrata population was 14 (26.9%), and prevalence of isolates exhibiting voriconazole non-wild-type MICs was 33 (63.5%). High-level echinocandin resistance was mainly observed in C. glabrata, and the prevalence rates of isolate resistance to anidulafungin, micafungin, and caspofungin were 5 (9.6%), 5 (9.6%), and 4 (7.7%), respectively. Moreover, one C. glabrata isolate showed multidrug resistant to azoles, echinocandins, and flucytosine. Overall, the 10-year surveillance study showed the increasing prevalence of non-C. albicans species over time; the emergence of azole resistance in C. tropicalis and multidrug resistance in C. glabrata over the years reinforced the need for epidemiological surveillance and monitoring.

COVID-19 Associated Pulmonary Aspergillosis (CAPA)-From Immunology to Treatment.

Like severe influenza, coronavirus disease-19 (COVID-19) resulting in acute respiratory distress syndrome (ARDS) has emerged as an important disease that predisposes patients to secondary pulmonary aspergillosis, with 35 cases of COVID-19 associated pulmonary aspergillosis (CAPA) published until June 2020. The release of danger-associated molecular patterns during severe COVID-19 results in both pulmonary epithelial damage and inflammatory disease, which are predisposing risk factors for pulmonary aspergillosis. Moreover, collateral effects of host recognition pathways required for the activation of antiviral immunity may, paradoxically, contribute to a highly permissive inflammatory environment that favors fungal pathogenesis. Diagnosis of CAPA remains challenging, mainly because bronchoalveolar lavage fluid galactomannan testing and culture, which represent the most sensitive diagnostic tests for aspergillosis in the ICU, are hindered by the fact that bronchoscopies are rarely performed in COVID-19 patients due to the risk of disease transmission. Similarly, autopsies are rarely performed, which may result in an underestimation of the prevalence of CAPA. Finally, the treatment of CAPA is complicated by drug–drug interactions associated with broad spectrum azoles, renal tropism and damage caused by SARS-CoV-2, which may challenge the use of liposomal amphotericin B, as well as the emergence of azole-resistance. This clinical reality creates an urgency for new antifungal drugs currently in advanced clinical development with more promising pharmacokinetic and pharmacodynamic profiles.

2268. Clinical Implications of Azole-Resistant vs. Azole-Susceptible Invasive Aspergillosis in Hematological Malignancy (CLARITY): A Multicenter Study

BackgroundIn recent years, survival of patients with invasive aspergillosis (IA) has improved mainly due to availability of extended spectrum triazoles. These advances are jeopardized by the emergence of azole resistance in Aspergillus fumigatus, the most common causative pathogen of IA. Despite several studies suggesting high probability of azole treatment failure in patients with azole-resistant isolates, the clinical implications of azole-resistant IA compared with azole-susceptible IA remain unclear.MethodsIn patients with hematological malignancies, cases of proven or probable IA (EORTC/MSG 2008) caused by A. fumigatus are registered. Retrospective data are documented, comprising demographics, diagnosis, treatment, response and outcome. Participating sites provided susceptibility results or isolates. Provided isolates were analyzed in a central laboratory.ResultsSince January 2018, 51 sites in 15 countries worldwide enrolled 154 cases diagnosed with IA between 2010 and 2019, of which 23 (14.9%) had azole-resistant IA. Of 44 cases, the respective clinical fungal isolate was analyzed in the central laboratory. A mixed fungal infection was reported for 34 patients (22.1%), 1 (2.9%) in the azole-resistant group; most were related to non-fumigatus Aspergillus species (n = 12, 35.3%) and non-Aspergillus molds (n = 10, 29.4). Most patients were male (n = 98, 63.6%); 19 (82.6%) in the azole-resistant group, 79 (60.3%) in the azole-susceptible group. Age was documented in categories instead of the exact age. Median age group was 50–69 years in both groups (ranging from 7–11 to 70–89 years for azole-resistant cases, 1–12 months to 70–89 years for azole-susceptible cases). Underlying disease and survival are shown in the table.ConclusionA worldwide network of investigators contributes to the CLARITY registry study. Completion of recruitment and subsequent data analysis are planned for 2019. Further sites may be added if azole-resistant cases are encountered. Disclosures All authors: No reported disclosures.

Aspergillus collected in specific indoor settings: their molecular identification and susceptibility pattern

ABSTRACT Exposure to Aspergillus conidia is an increased risk factor for the development of respiratory symptoms. The emergence of azole resistance in Aspergillus fumigatus is a major concern for the scientific community. The aim of this study was to perform the molecular identification of Aspergillus species collected from different occupational and non-occupational indoor settings and to study the azole susceptibility profile of the collected Fumigati isolates. The selected Aspergillus isolates were identified as belonging to the sections Fumigati, Nigri Versicolores, Terrei, Clavati and Nidulantes. All the Aspergillus fumigatus were screened for azole resistance using an agar media supplemented with itraconazole, voriconazole and posaconazole. None of the tested isolates showed resistance to those azoles. Knowledge of Aspergillus epidemiology in specific indoor environments allows a better risk characterization regarding Aspergillus burden. This study allowed the analysis of the molecular epidemiology and the determination of the susceptibility pattern of Aspergillus section Fumigati found in the studied indoor settings.

Molecular Detection of Azole-Resistant Aspergillus fumigatus in Clinical Samples.

Aspergillus diseases are often caused by Aspergillus fumigatus. Azoles are the mainstay of therapy, but the management of aspergillosis is hampered by the emergence of azole resistance. Rapid detection of azole resistance might benefit treatment outcome by early treatment modifications. However, the yield of fungal culture in invasive aspergillosis is low and susceptibility testing requires several days to be completed. To overcome the low yield of fungal cultures and slow detection of resistance, it is possible to use molecular tools directly on clinical specimens in order to rapidly detect molecular markers of azole resistance. Molecular tools to detect resistant markers in the Cyp51A gene can be expected to be less sensitive compared to molecular tools to detect Aspergillus DNA as the Cyp51A gene is a single copy gene and the target for Aspergillus DNA is often a multi-copy gene. In this mini-review, we summarize the current molecular tools for detection of azole-resistant A. fumigatus directly in clinical material. Several in-house PCR assays have been applied directly on clinical material. Furthermore, two assays are commercial available; the AsperGenius and MycoGENIE. The amplification of resistance markers was successful in 70–100% of samples that were positive for Aspergillus DNA in BAL samples using the AsperGenius assay. Despite using several samples per patient, amplification of resistance markers was only successful in 33–57% of patients with Aspergillus DNA in blood. Furthermore, several sequence based methods have been applied with the benefit of the ability to detect other Cyp51A gene alterations.

Pharmacodynamics of Voriconazole against Wild-Type and Azole-Resistant Aspergillus flavus Isolates in a Nonneutropenic Murine Model of Disseminated Aspergillosis.

Invasive aspergillosis (IA) due to Aspergillus flavus is associated with high mortality. Although voriconazole (VRC) is widely recommended as the first-line treatment for IA, emergence of azole resistance in Aspergillus spp. is translating to treatment failure. We evaluated the efficacy of voriconazole in a nonneutropenic murine model of disseminated A. flavus infection using two voriconazole-resistant isolates (one harboring the Y319H substitution in the cyp51C gene) and two wild-type isolates without mutations. All isolates exhibited a dose-response relationship, and voriconazole treatment improved mouse survival in a dose-dependent manner. At 40 mg/kg of body weight, 100% efficacy was observed for 1 susceptible isolate and 1 resistant isolate (with mutation), whereas for another susceptible isolate and resistant isolate (without mutation), survival rates were 81% and 72%, respectively. The Hill equation with a variable slope fitted the relationship between the area under the concentration-time curve (AUC)/MIC ratio and 14-day survival well for each strain. An F test showed the 50% effective doses to be significantly different from each other (P = 0.0023). However, contrary to expectation, there was a significant difference in exposure-response relationships between strains, and it appeared that the susceptible strains required a relatively higher exposure than the resistant ones to result in the same treatment effect, the 50% effective pharmacokinetic/pharmacodynamic (PK/PD) index (EI50) required being negatively and log-linearly related to the MIC (P = 0.04). We conclude that the efficacy of voriconazole depended on drug exposure and the voriconazole MIC of the isolates, but lower exposures are required for strains with higher MICs. These findings may have profound significance in clinical practice with respect to dosing and drug choice.

Emergence of Azole Resistance in Aspergillus.

Resistance to the azole antifungals itraconazole, voriconazole, and posaconazole in Aspergillus species is a growing concern. This is especially alarming for A. fumigatus, where acquired resistance has been documented in patients with invasive disease caused by this species that were exposed to these agents, as well as in azole-naive individuals. The primary mechanisms of resistance that have been described in clinical strains include different point mutations in the CYP51A gene, which encodes the enzyme responsible for converting lanosterol to ergosterol via demethylation. Some resistant isolates also contain a tandem repeat in the promoter region of this gene that causes increased expression. These mutations, including TR34/L98H and TR46/Y121F/T289A have also been found in the environment in several areas of the world and have been demonstrated to cause resistance to azole fungicides used in agriculture, thus raising the concern of environmental spread of resistance. Treatment options are limited in patients with infections caused by azole-resistant isolates and include amphotericin B formulations or combination therapy involving an echinocandin. However, there are few clinical data available to help guide therapy, and infections caused by resistant A. fumigatus isolates have been reported to have high mortality rates.

Asexual sporulation facilitates adaptation: The emergence of azole resistance in Aspergillus fumigatus.

Understanding the occurrence and spread of azole resistance in Aspergillus fumigatus is crucial for public health. It has been hypothesized that asexual sporulation, which is abundant in nature, is essential for phenotypic expression of azole resistance mutations in A. fumigatus facilitating subsequent spread through natural selection. Furthermore, the disease aspergilloma is associated with asexual sporulation within the lungs of patients and the emergence of azole resistance. This study assessed the evolutionary advantage of asexual sporulation by growing the fungus under pressure of one of five different azole fungicides over seven weeks and by comparing the rate of adaptation between scenarios of culturing with and without asexual sporulation. Results unequivocally show that asexual sporulation facilitates adaptation. This can be explained by the combination of more effective selection because of the transition from a multicellular to a unicellular stage, and by increased mutation supply due to the production of spores, which involves numerous mitotic divisions. Insights from this study are essential to unravel the resistance mechanisms of sporulating pathogens to chemical compounds and disease agents in general, and for designing strategies that prevent or overcome the emerging threat of azole resistance in particular.

Genesis of Azole Antifungal Resistance from Agriculture to Clinical Settings

Azole fungal resistance is becoming a major public health problem in medicine in recent years. However, it was known in agriculture since several decades; the extensive use of these compounds results in contamination of air, plants, and soil. The increasing frequency of life-threatening fungal infections and the increase of prophylactical use of azoles in high-risk patients, taken together with the evolutionary biology evidence that drug selection pressure is an important factor for the emergence and spread of drug resistance, can result in a dramatic scenario. This study reviews the azole use in agricultural and medical contexts and discusses the hypothetical link between its extensive use and the emergence of azole resistance among human fungal pathogens.

In vivo efficacy of voriconazole and posaconazole therapy in a novel invertebrate model of Aspergillus fumigatus infection

The emergence of azole resistance in Aspergillus fumigatus is a clinically important issue in the management of invasive aspergillosis as it could limit therapeutic options. Accurate measurement of in vitro antifungal activity in terms of minimum inhibitory concentration (MIC) is considered of clinical relevance and often gives useful therapeutic information for physicians. However, the lack of in vitro–in vivo correlation is frequent and the observed in vitro phenotype does not always correlate with the in vivo response. In this regard, a wild-type strain and five A. fumigatus cyp51A mutated strains showing different azole susceptibility profiles were used to investigate whether the greater wax moth (Galleria mellonella) is an alternative model to assess the in vivo efficacy of voriconazole and posaconazole. Administration of both azoles improved the survival of larvae infected with susceptible strains. However, those larvae infected with resistant strains did not respond to treatment. The phenotype observed in vitro was found to correlate with the efficacy observed in vivo. Moreover, using this in vivo model, the pharmacodynamic target predicting therapeutic success (AUC0–24/MIC) was in the same range as previously described, allowing the use of the G. mellonella model to predict the azole susceptibility profile of A. fumigatus strains.

Azole-resistant Aspergillus fumigatus with TR34/L98H mutations in the cyp51A gene in Iran

Introduction Triazole antifungal drugs such as itraconazole, posaconazole and voriconazole are the mainstay of therapy in the management and prophylaxis of aspergillosis. However, in recent years, triazole-resistant clinical isolates of Aspergillus fumigatus have emerged in Europe (the Netherlands, Denmark, Spain, UK, Belgium, Germany and France) and Asia (China, India) resulting in several cases of therapeutic failure caused by triazole-resistant A. fumigatus. Azole resistance may develop in patients who are treated with long-term azole therapy or may develop in the environment through the exposure of the fungus to the azole fungicides used in agriculture. Methods In the present study, we investigated the presence of azole resistance in environmental and clinical A. fumigatus isolated both from hospital surroundings area and infected patients. Results In vitro antifungal susceptibility testing has shown high MICs of itraconazole (> 16 mg/L) and voriconazole (> 8 mg/L). The TR34/L98H mutation was the only resistance mechanism with no mutation in G54, M220, G138C, T289A, Y121F and G432C. Azole-resistant A. fumigatus isolates had the same TR34/L98H STRAf genotype with Netherlands and India. It is emphasized that routine resistance surveillance studies focusing on environmental and clinical samples are warranted to yield the true prevalence of azole resistance in A. fumigatus in Iran. Conclusion The widespread application of triazole fungicides in the environment in Iran could have contributed to the emergence of environmental azole-resistant A. fumigatus. Given the emergence of azole resistance in environmental strains, continued surveillance of resistance in clinical A. fumigatus strains in Iran is desirable for successful therapy of aspergillosis. Furthermore, the need for enhanced understanding of the evolution of azole resistance and measures to prevent the emergence of multiple-azole-resistant A. fumigatus strains in countries using fungicides can hardly be over-emphasized.

In Vitro Interaction of Voriconazole and Anidulafungin against Triazole-Resistant Aspergillus fumigatus

Voriconazole is the recommended drug of first choice to treat infections caused by Aspergillus fumigatus. The efficacy of voriconazole might be hampered by the emergence of azole resistance. However, the combination of voriconazole with anidulafungin could improve therapeutic outcomes in azole-resistant invasive aspergillosis (IA). The in vitro interaction between voriconazole and anidulafungin was determined against voriconazole-susceptible and voriconazole-resistant (substitutions in the cyp51A gene, including single point [M220I and G54W] and tandem repeat [34-bp tandem repeat in the promoter region of the cyp51A gene in combination with substitutions at codon L98 and 46-bp tandem repeat in the promoter region of the cyp51A gene in combination with mutation at codons Y121 and T289] mutations) clinical A. fumigatus isolates using a checkerboard microdilution method with spectrophotometric analysis and a viability-based XTT {2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl]-2H-tetrazolium hydroxide} assay within 2 h of exposure after 24 and 48 h of incubation at 35 °C to 37 °C. Fractional inhibitory concentration (FIC) indexes (FICis) were determined using different MIC endpoints and Bliss independence analysis performed based on the response surface calculation of the no-drug interaction. Significant synergistic interactions obtained based on measuring the FIC index were dependent on the MIC endpoint, in which FICs were inversely related to voriconazole and anidulafungin MICs and were influenced by the CYP51A genotype. A statistically significant difference was observed between FIC indexes of isolates harboring tandem repeat mutations and wild-type controls (P = 0.006 by one-way analysis of variance [ANOVA]), indicating that synergy is decreased in azole-resistant strains. Our results indicated that a combination of voriconazole and anidulafungin might be effective against infections caused by both azole-susceptible and azole-resistant A. fumigatus isolates, but the combination could possibly be less effective in voriconazole-resistant strains with high MICs. Studies in vivo and in vitro-in vivo correlation investigations are required to validate the potential synergy of voriconazole and anidulafungin.