Itraconazole, Voriconazole, and Posaconazole CLSI MIC Distributions for Wild-Type and Azole-Resistant Aspergillus fumigatus Isolates

Evaluation of the Activity of Triazoles Against Non-fumigatus Aspergillus and Cryptic Aspergillus Species Causing Invasive Infections Tested in the SENTRY Program

The activity of isavuconazole and other triazoles against non-fumigatus (non-AFM) Aspergillus causing invasive aspergillosis was evaluated. A total of 390 non-AFM isolates were collected (1/patient) in 2017-2021 from 41 hospitals. Isolates were identified by matrix-assisted laser desorption ionization-time of flight mass spectrometry and/or internal spacer region/β-tubulin sequencing and tested by Clinical and Laboratory Standards Institute (CLSI) broth microdilution. CLSI epidemiological cutoff values were applied, where available. Isavuconazole showed activity against Aspergillus sections Flavi (n = 122; minimum inhibitory concentration [MIC]50/90, 0.5/1 mg/L), Terrei (n = 57; MIC50/90, 0.5/0.5 mg/L), Nidulantes (n = 34; MIC50/90, 0.12/0.25 mg/L), Versicolores (n = 7; MIC50, 1 mg/L), and Circumdati (n = 2; MIC range, 0.12-2 mg/L). Similar activity was displayed by other triazoles against those Aspergillus sections. Most of the isolates from Aspergillus sections Fumigati (n = 9), Nigri (n = 146), and Usti (n = 12) exhibited elevated MIC values to isavuconazole (MIC50/90, 2/-, 2/4, and 2/8 mg/L), voriconazole (MIC50/90, 2/-, 1/2, and 4/8 mg/L), itraconazole (MIC50/90, 2/-, 2/4, and 8/>8 mg/L), and posaconazole (MIC50/90, 0.5/-, 0.5/1, and >8/>8 mg/L), respectively. Isavuconazole was active (MIC values, ≤1 mg/L) against Aspergillus parasiticus, Aspergillus tamarii, Aspergillus nomius, Aspergillus nidulans, Aspergillus unguis, Aspergillus terreus, Aspergillus alabamensis, and Aspergillus hortai, while isavuconazole MIC values between 2 and 8 mg/L were observed against cryptic isolates from Aspergillus section Fumigati. Isavuconazole inhibited 96.1% of Aspergillus niger and 80.0% of Aspergillus tubingensis at ≤4 mg/L, the CLSI wild-type cutoff value for A niger. Voriconazole, itraconazole, and posaconazole showed similar activity to isavuconazole against most cryptic species. Isavuconazole exhibited potent in vitro activity against non-AFM; however, the activity of triazoles varies among and within cryptic species.

Susceptibility Testing of Environmental and Clinical Aspergillus sydowii Demonstrates Potent Activity of Various Antifungals

The genus Aspergillus consists of a vast number of medically and environmentally relevant species. Aspergillus species classified in series Versicolores are ubiquitous in the environment and include the opportunistic pathogen Aspergillus sydowii, which is associated with onychomycosis and superficial skin infections. Despite frequent clinical reports of A. sydowii and related series Versicolores species, antifungal susceptibility data are scarce, hampering optimal treatment choices and subsequent patient outcomes. Here, we employed antifungal susceptibility testing (AFST) based on microbroth dilution on a set of 155 series Versicolores strains using the common antifungals amphotericin B, itraconazole, voriconazole, posaconazole, isavuconazole and micafungin with the addition of luliconazole and olorofim. All strains were identified using partial calmodulin gene sequencing, with 145 being A. sydowii, seven A. creber and three A. versicolor, using the latest taxonomic insights. Overall, tested antifungals were potent against the entire strain collection. In comparison to A. fumigatus, azole and amphotericin B MICs were slightly elevated for some strains. AFST with luliconazole and olorofim, here reported for the first time, displayed the highest in vitro activity, making these antifungals interesting alternative drugs but clinical studies are warranted for future therapeutic use.

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

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

Trends in the activity of mold-active azole agents against Aspergillus fumigatus clinical isolates with and without cyp51 alterations from Europe and North America (2017-2021)

Azole resistance in Aspergillus fumigatus (AFM) is increasing and often associated with cyp51 alterations. We evaluated the activity of isavuconazole and other mold-active azoles against 731 AFM isolates causing invasive aspergillosis collected in Europe (EU; n = 449) and North America (NA; n = 282). Isolates were submitted to CLSI susceptibility testing and epidemiological cutoff value (ECV) criteria. A posaconazole ECV of 0.5 mg/L was used as no CLSI ECV was determined. Azole non-wild-type (NWT) isolates were submitted for cyp51 sequencing by whole genome sequencing. Overall, isavuconazole activity (92.7%/94.0% WT in EU/NA) was comparable to other azoles (WT rate range, 90.9%-96.4%/91.8%-98.6%, respectively), regardless of the region. A total of 79 (10.8%) azole NWT isolates were detected, and similar rates of these isolates were noted in EU (10.7%) and NA (11.0%). Although most AFM were WT to azoles, increasing azole NWT rates were observed in NA (from 6.0% in 2017 to 29.3% in 2021). Azole NWT rates varied from 4.9% (2019) to 20.6% (2018) in EU without an observed trend. cyp51 alterations occurred in 56.3%/54.8% of azole NWT from EU/NA, respectively. The cyp51A TR34/L98H alteration was observed only in EU isolates (72.0% of EU isolates), while cyp51A I242V occurred only in NA isolates (58.3%). Isavuconazole remained active (MIC, ≤1 mg/L) against 18.5/47.1% of azole NWT AFM exhibiting cyp51 alterations in EU/NA, along with voriconazole (29.6/82.4%; MIC, ≤1 mg/L) and posaconazole (48.1/88.2%; MIC, ≤0.5 mg/L). Fourteen different cyp51 alterations were detected in 44 of 79 NWT isolates. The in vitro activity of the azoles varied in AFM that displayed cyp51 alterations. IMPORTANCE A few microbiology laboratories perform antifungal susceptibility testing locally for systemically active antifungal agents. The identification of emerging azole-resistant Aspergillus fumigatus is worrisome. As such, there is a critical role for antifungal surveillance in tracking emerging resistance among both common and uncommon opportunistic fungi. Differences in the regional prevalence and antifungal resistance of these fungi render local epidemiological knowledge essential for the care of patients with a suspected invasive fungal infection.

Azole resistance in a clinical isolate of Aspergillus fumigatus from Chile

BACKGROUND

Aspergillus fumigatus is a ubiquitous opportunistic pathogen. This fungus can acquire resistance to azole antifungals due to different mutations in the cyp51A gene. Azole resistance has been observed in several continents and appears to be a globally distributed phenomenon. Specific mutations in cyp51A that lead to azole resistance, such as the TR34/L98H modification, have been reported.

AIMS

To evaluate the azole resistance in clinically isolated A. fumigatus strains.

METHODS

As a result of our passive surveillance strategy, a total of 23 A. fumigatus isolates from clinical origins were identified through a phylogenetic analysis using the ITS region and β-tubulin gene fragments, and typed with the CSP microsatellite. Azole susceptibility profiles were performed by disk diffusion and microdilution broth methodologies according to CLSI guidelines.

RESULTS

Here we describe, for the first time, the detection of azole-resistant A. fumigatus isolates from clinical origins in Chile with mutations in the cyp51A gene. In addition to the TR34/L98H mutation, one isolate exhibited an F46Y/M172V/E427K-type mutation. Furthermore, microsatellite typing based on cell surface protein (CSP) was performed, showing the t02 (TR34/L98H), t15 (F46Y/M172V/E427K) and t01 (susceptible clinical isolates) genotypes.

CONCLUSIONS

Our study demonstrates the presence of mutations related to azole resistance in A. fumigatus strains isolated from clinical samples in Chile. In order to obtain information that may help to tackle the spread of antifungal resistance among A. fumigatus populations, and to ensure the efficacy of future treatments against aspergillosis, a further research is necessary.

Susceptibility patterns of amphotericin B, itraconazole, posaconazole, voriconazole and caspofungin for isolates causing invasive mould infections from the SENTRY Antifungal Surveillance Program (2018-2021) and application of single-site epidemiological cutoff values to evaluate amphotericin B activity

We evaluated the activity of amphotericin B, itraconazole, posaconazole, voriconazole and caspofungin against 1468 invasive moulds collected worldwide from 2018 to 2021. Most (>92%) of the Aspergillus spp. isolates were wildtype (WT) to amphotericin B, caspofungin and the azoles. Azole-non-wildtype A. fumigatus rates were higher in Europe (9.5%) and North America (9.1%) than Latin America (0.0%; only 12 isolates) and the Asia-Pacific region (5.3%). Amphotericin B and caspofungin were active against azole-non-wildtype A. fumigatus isolates. Posaconazole and amphotericin B were the most active agents against the Mucorales. Among the less common moulds, several expressed a pan-azole-resistant phenotype; many of these species also showed elevated MIC values (MIC, >2 mg/L) for amphotericin B and caspofungin. Although most isolates of Aspergillus spp. remain WT to the azoles, azole resistance is increasing in both North America and Europe. Amphotericin B and caspofungin exhibit potentially useful activity against azole-resistant A. fumigatus.

The Transcriptome Response to Azole Compounds in Aspergillus fumigatus Shows Differential Gene Expression across Pathways Essential for Azole Resistance and Cell Survival

The opportunistic pathogen Aspergillus fumigatus is found on all continents and thrives in soil and agricultural environments. Its ability to readily adapt to novel environments and to produce billions of spores led to the spread of azole-resistant A. fumigatus across the globe, posing a threat to many immunocompromised patients, including critically ill patients with severe influenza or COVID-19. In our study, we sought to compare the adaptational response to azoles from A. fumigatus isolates that differ in azole susceptibility and genetic background. To gain more insight into how short-term adaptation to stressful azole compounds is managed through gene expression, we conducted an RNA-sequencing study on the response of A. fumigatus to itraconazole and the newest clinically approved azole, isavuconazole. We observed many similarities in ergosterol biosynthesis up-regulation across isolates, with the exception of the pan-azole-resistant isolate, which showed very little differential regulation in comparison to other isolates. Additionally, we found differential regulation of membrane efflux transporters, secondary metabolites, iron metabolism, and various stress response and cell signaling mechanisms.

Comparison of the Micronaut-AM System and the EUCAST Broth Microdilution Reference Method for MIC Determination of Four Antifungals against Aspergillus fumigatus

The Antifungal Susceptibility Testing method of the European Committee on Antimicrobial Susceptibility Testing (EUCAST-AFST) is a reference technique for the determination of the Minimum Inhibitory Concentration (MIC) of antifungals for Aspergillus fumigatus. However, it is time-consuming and requires expertise. Micronaut-AM (M-AM) is a fast, simple, time-saving, and ready-to-use new colorimetric method using an indicator (resazurin) to facilitate the visual reading. The aim of this retrospective study was to evaluate the performance of the M-AM system and compare it with the EUCAST broth microdilution reference method to determine the susceptibility of 77 A. fumigatus clinical strains to amphotericin B, itraconazole, voriconazole, and posaconazole. Overall, the essential agreements within ±2 dilutions were 100%, 62%, 58%, and 30% and the categorical agreements were 100%, 97%, 91%, and 87% for amphotericin B, itraconazole, voriconazole, and posaconazole, respectively. No categorical discrepancy was found for amphotericin B, but several categorical discordances were observed with azole antifungals. However, only 2 of the 16 azole-resistant strains confirmed by the cyp51A sequencing would have been misclassified by M-AM. The use of M-AM is probably suitable for the determination of the MICs of amphotericin B, but further evaluations are needed to confirm its usefulness for the determination of the MICs of azoles for A. fumigatus.

In Vitro Activity of Isavuconazole and Other Mould-Active Azoles against Aspergillus fumigatus with and without CYP51 Alterations

Azole resistance in Aspergillus fumigatus (AFM) is mainly associated with mutations in CYP51A and its promoter region or its homologue CYP51B. We evaluated the in vitro activity of isavuconazole, itraconazole, posaconazole, and voriconazole against 660 AFM collected during 2017-2020. Isolates were tested via CLSI broth microdilution. CLSI epidemiological cutoff values were applied. Non-wildtype (NWT) isolates to azoles were screened for alterations in the CYP51 sequences using whole genome sequencing. Azoles had similar activities against 660 AFM isolates. Overall, AFM displayed WT MIC values to isavuconazole (92.7%), itraconazole (92.9%), posaconazole (97.3%), and voriconazole (96.7%). Only 66 isolates (10.0%) were NWT to 1 or more of the azoles, and 32 harbored one or more alterations in the CYP51 sequences. Of these, 29/32 (90.1%) were NWT to itraconazole, 25/32 (78.1%) were NWT to isavuconazole, 17/32 (53.1%) were NWT to voriconazole, and 11/32 (34.4%) were NWT to posaconazole. The most frequent alteration was CYP51A TR34/L98H, carried by 14 isolates. Four isolates carried the alteration I242V in CYP51A, and G448S; A9T, or G138C was carried by one isolate each. Multiple alterations in CYP51A were detected in five isolates. Alterations in CYP51B were noted in seven isolates. Among 34 NWT isolates without -CYP51 alterations, WT rates to isavuconazole, itraconazole, voriconazole, and posaconazole were 32.4%, 47.1%, 85.3%, and 82.4%, respectively. Ten different CYP51 alterations were detected in 32/66 NWT isolates. Alterations in AFM CYP51 sequences can have variable effects on the in vitro activity of the azoles that are best delineated by testing all triazoles.

Progress of triazole antifungal agent posaconazole in individualized therapy

WHAT IS KNOWN AND OBJECTIVE

Posaconazole is the second-generation triazole antifungal agent with widespread clinical application. Posaconazole exposure is influenced by various factors such as drug interactions, disease state and diet, resulting in a high interindividual variability in many patients and failure to ensure therapeutic efficacy. Therefore, it is necessary to conduct individualized therapy on posaconazole to ensure the efficacy and safety of treatment.

METHODS

Articles were identified through PubMed using the keywords such as "posaconazole," "therapeutic drug monitoring" and "Population pharmacokinetics" from 1 January 2001 to 30 April 2022.

RESULTS AND DISCUSSION

In this paper, we review the individualized treatment studies of posaconazole from the three aspects of therapeutic drug monitoring, population pharmacokinetic study and Monte Carlo simulation to provide reference for in-depth individualized posaconazole dosing studies.

WHAT IS NEW AND CONCLUSION

This review suggests that therapeutic drug monitoring should be performed in patients taking posaconazole to adjust the dosage and assess the efficacy and cost-effectiveness of posaconazole under different clinical conditions and different dosing regimens through Monte Carlo simulations. In the future, a more detailed delineation and comprehensive examination of posaconazole PPK for specific populations requires further study.

Genetic Diversity and Azole Resistance Among Natural Aspergillus fumigatus Populations in Yunnan, China

The emergence and spread of azole resistance alleles in clinical and environmental isolates of Aspergillus fumigatus is a global human health concern and endangers the "One Health" approach in our fight against antifungal resistance (AFR) in this pathogen. A major challenge to combat AFR in A. fumigatus is the massive aerial dispersal ability of its asexual spores. Our recent fine-scale survey of greenhouse populations of A. fumigatus near Kunming, Yunnan, China, suggested that the use of azole fungicides for plant protection was likely a major driver of the high-frequency azole-resistant A. fumigatus (ARAF) in greenhouses. Here, we investigated the potential spread of those ARAF and the structure of geographic populations of A. fumigatus by analyzing 452 isolates from 19 geographic locations across Yunnan. We found lower frequencies of ARAF in these outdoor populations than those in greenhouses near Kunming, but there were abundant new alleles and new genotypes, including those associated with azole resistance, consistent with multiple independent origins of ARAF across Yunnan. Interestingly, among the four ecological niches, the sediments of a large lake near Kunming were found to have the highest frequency of ARAF (~ 43%). While most genetic variations were observed within the 19 local populations, statistically significant genetic differentiations were found between many subpopulations within Yunnan. Furthermore, similar to greenhouse populations, these outdoor populations of A. fumigatus in Yunnan were significantly different from those in other parts of the world. Our results call for increased attention to local and regional studies of this fungal pathogen to help develop targeted control strategies against ARAF.

Citizen Science Surveillance of Triazole-Resistant Aspergillus fumigatus in United Kingdom Residential Garden Soils

Compost is an ecological niche for Aspergillus fumigatus due to its role as a decomposer of organic matter and its ability to survive the high temperatures associated with the composting process. Subsequently, composting facilities are associated with high levels of A. fumigatus spores that are aerosolized from compost and cause respiratory illness in workers. In the UK, gardening is an activity enjoyed by individuals of all ages, and it is likely that they are being exposed to A. fumigatus spores when handling commercial compost or compost they have produced themselves. In the present study, 246 citizen scientists collected 509 soil samples from locations in their gardens in the UK, from which were cultured 5,174 A. fumigatus isolates. Of these isolates, 736 (14%) were resistant to tebuconazole: the third most-sprayed triazole fungicide in the UK, which confers cross-resistance to the medical triazoles used to treat A. fumigatus lung infections in humans. These isolates were found to contain the common resistance mechanisms in the A. fumigatus cyp51A gene TR34/L98H or TR46/Y121F/T289A, as well as the less common resistance mechanisms TR34, TR53, TR46/Y121F/T289A/S363P/I364V/G448S, and (TR46)2/Y121F/M172I/T289A/G448S. Regression analyses found that soil samples containing compost were significantly more likely to grow tebuconazole-susceptible and tebuconazole-resistant A. fumigatus strains than those that did not and that compost samples grew significantly higher numbers of A. fumigatus than other samples. IMPORTANCE The findings presented here highlight compost as a potential health hazard to individuals with predisposing factors to A. fumigatus lung infections and as a potential health hazard to immunocompetent individuals who could be exposed to sufficiently high numbers of spores to develop infection. Furthermore, we found that 14% of A. fumigatus isolates in garden soils were resistant to an agricultural triazole, which confers cross-resistance to medical triazoles used to treat A. fumigatus lung infections. This raises the question of whether compost bags should carry additional health warnings regarding inhalation of A. fumigatus spores, whether individuals should be advised to wear facemasks while handling compost, or whether commercial producers should be responsible for sterilizing compost before shipping. The findings support increasing public awareness of the hazard posed by compost and investigating measures that can be taken to reduce the exposure risk.

Fungal Genomics in Respiratory Medicine: What, How and When?

Respiratory infections caused by fungal pathogens present a growing global health concern and are a major cause of death in immunocompromised patients. Worryingly, coronavirus disease-19 (COVID-19) resulting in acute respiratory distress syndrome has been shown to predispose some patients to airborne fungal co-infections. These include secondary pulmonary aspergillosis and mucormycosis. Aspergillosis is most commonly caused by the fungal pathogen Aspergillus fumigatus and primarily treated using the triazole drug group, however in recent years, this fungus has been rapidly gaining resistance against these antifungals. This is of serious clinical concern as multi-azole resistant forms of aspergillosis have a higher risk of mortality when compared against azole-susceptible infections. With the increasing numbers of COVID-19 and other classes of immunocompromised patients, early diagnosis of fungal infections is critical to ensuring patient survival. However, time-limited diagnosis is difficult to achieve with current culture-based methods. Advances within fungal genomics have enabled molecular diagnostic methods to become a fast, reproducible, and cost-effective alternative for diagnosis of respiratory fungal pathogens and detection of antifungal resistance. Here, we describe what techniques are currently available within molecular diagnostics, how they work and when they have been used.

Aspergillus fumigatus and aspergillosis: From basics to clinics

The airborne fungus Aspergillus fumigatus poses a serious health threat to humans by causing numerous invasive infections and a notable mortality in humans, especially in immunocompromised patients. Mould-active azoles are the frontline therapeutics employed to treat aspergillosis. The global emergence of azole-resistant A. fumigatus isolates in clinic and environment, however, notoriously limits the therapeutic options of mould-active antifungals and potentially can be attributed to a mortality rate reaching up to 100 %. Although specific mutations in CYP 51A are the main cause of azole resistance, there is a new wave of azole-resistant isolates with wild-type CYP 51A genotype challenging the efficacy of the current diagnostic tools. Therefore, applications of whole-genome sequencing are increasingly gaining popularity to overcome such challenges. Prominent echinocandin tolerance, as well as liver and kidney toxicity posed by amphotericin B, necessitate a continuous quest for novel antifungal drugs to combat emerging azole-resistant A. fumigatus isolates. Animal models and the tools used for genetic engineering require further refinement to facilitate a better understanding about the resistance mechanisms, virulence, and immune reactions orchestrated against A. fumigatus. This review paper comprehensively discusses the current clinical challenges caused by A. fumigatus and provides insights on how to address them.

Intimate genetic relationships and fungicide resistance in multiple strains of Aspergillus fumigatus isolated from a plant bulb

Fungal infections are increasingly dangerous because of environmentally dispersed resistance to antifungal drugs. Azoles are commonly used antifungal drugs, but they are also used as fungicides in agriculture, which may enable enrichment of azole-resistant strains of the human pathogen Aspergillus fumigatus in the environment. Understanding of environmental dissemination and enrichment of genetic variation associated with azole resistance in A. fumigatus is required to suppress resistant strains. Here, we focused on eight strains of azole-resistant A. fumigatus isolated from a single tulip bulb for sale in Japan. This set includes strains with TR34 /L98H/T289A/I364V/G448S and TR46 /Y121F/T289A/S363P/I364V/G448S mutations in the cyp51A gene, which showed higher tolerance to several azoles than strains harbouring TR46 /Y121F/T289A mutation. The strains were typed by microsatellite typing, single nucleotide polymorphism profiles, and mitochondrial and nuclear genome analyses. The strains grouped differently using each typing method, suggesting historical genetic recombination among the strains. Our data also revealed that some strains isolated from the tulip bulb showed tolerance to other classes of fungicides, such as QoI and carbendazim, followed by related amino acid alterations in the target proteins. Considering spatial-temporal factors, plant bulbs are an excellent environmental niche for fungal strains to encounter partners, and to obtain and spread resistance-associated mutations.

Antifungal susceptibilities of opportunistic filamentous fungal pathogens from the Asia and Western Pacific Region: data from the SENTRY Antifungal Surveillance Program (2011-2019)

Antifungal surveillance is an important tool to monitor the prevalence of uncommon fungal species and increasing antifungal resistance throughout the world, but data comparing results across several different Asian countries are scarce. In this study, 372 invasive molds collected in the Asia-Western Pacific region in 2011-2019 were susceptibility tested for mold-active triazoles (isavuconazole, posaconazole, voriconazole, and itraconazole). The collection includes 318 Aspergillus spp. isolates and 53 non-Aspergillus molds. The MIC values using CLSI methods for isavuconazole versus Aspergillus fumigatus ranged from 0.25 to 2 mg l^-1. Isavuconazole, itraconazole, posaconazole, and voriconazole acted similarly against A. fumigatus. The mold-active triazoles exhibited a wildtype phenotype to most of the Aspergillus spp. isolates tested (>94%), but poor activity against Fusarium solani species complex and Lomentospora prolificans. Voriconazole was most active against the Scedosporium spp. and posaconazole was most active against the Mucorales. In summary, isavuconazole displayed excellent activity against most species of Aspergillus and was comparable to other mold-active triazoles against non-Aspergillus molds.

Point mutation or overexpression of A. fumigatus cyp51B, encoding lanosterol 14α-sterol demethylase, leads to triazole resistance

Aspergillus fumigatus is the most common cause of invasive fungal mold infections in immunocompromised individuals. Current antifungal treatment relies heavily on the triazole antifungals which inhibit fungal Erg11/Cyp51 activity and subsequent ergosterol biosynthesis. However, resistance, due primarily to cyp51 mutation, is rapidly increasing. A. fumigatus contains two Cyp51 isoenzymes, Cyp51A and Cyp51B. Overexpression and mutation of Cyp51A is a major cause of triazole resistance in A. fumigatus. The role of Cyp51B in generating resistance is unclear. Here we show that overexpression or mutation of cyp51B results in triazole resistance. We demonstrate that introduction of a G457S Cyp51B mutation identified in a resistant clinical isolate, results in voriconazole resistance in the naïve recipient strain. Our results indicate that mutations in cyp51B resulting in clinical resistance do exist and should be monitored.

Triazole resistant Aspergillus fumigatus in an Israeli patient with Chronic Cavitary Pulmonary Aspergillosis due to a novel E306K Substitution in Hmg1

Triazole resistance in the pathogenic mold Aspergillus fumigatus has increased worldwide, posing a growing therapeutic challenge. Recently, mutations in the 3-hydroxy-3-methyl-glutaryl-coenzyme A (HMG-CoA) reductase gene (hmg1) have been associated with triazole resistance. Here, we describe a novel E306K triazole resistance-conferring mutation in the HMG-CoA reductase gene from an Israeli patient with chronic cavitary pulmonary aspergillosis (CCPA).

In vitro activity of posaconazole and comparators versus opportunistic filamentous fungal pathogens globally collected during 8 years

The epidemiology of invasive filamentous fungal diseases requires monitoring due to changes in susceptibility patterns of new and established antifungal agents that may affect clinical practices. We evaluated the activity of posaconazole against 2,157 invasive moulds collected worldwide from 2010-2017. The isolates included 1,775 Aspergillus spp. and 382 non-Aspergillus moulds, including 81 Fusarium spp., 62 Mucorales group, and 57 Scedosporium spp. Isolates were tested using the CLSI reference broth microdilution method. Posaconazole showed similar activity to itraconazole and voriconazole against A. fumigatus. Applying published ECV, 98.0% of the A. fumigatus and 97.7% to 100.0% of other common Aspergillus species were wildtype to posaconazole. Categorical agreement between posaconazole and the other azoles tested against A. fumigatus was 98.7%. Notably, most of the Aspergillus spp. isolates recovered from this large collection were wildtype to echinocandins and all azoles. Posaconazole non-wildtype rates of A. fumigatus varied across the different geographic regions, with 2.1% in Europe, 2.2% in North America, 1.8% in Latin America, and 0.7% in the Asia-Pacific region. The frequency of azole non-wildtype A. fumigatus isolates from Europe increased steadily from 2010-2017 for all 3 triazoles (0.0%-5.0%). The azole non-wildtype A. fumigatus rates from the other geographic areas were stable over time. Fusarium and/or Scedosporium spp. isolates were highly resistant to azoles and echinocandins. Posaconazole and amphotericin B were the most active agents against the Mucorales. Posaconazole was very active against most species of Aspergillus and was comparable to itraconazole and voriconazole against the less common moulds. Posaconazole should provide a useful addition to the anti-mould grouping of antifungal agents.

In vitro interaction of isavuconazole and anidulafungin against azole-susceptible and azole-resistant Aspergillus fumigatus isolates

Background

The voriconazole and echinocandin combination has been found to be synergistic in vitro and in vivo against most Aspergillus fumigatus isolates, both with a WT azole phenotype and an azole-resistant phenotype. The interaction between isavuconazole and echinocandins is less well studied. This is especially true for azole-resistant isolates.

Objectives

We investigated the in vitro interaction between isavuconazole and anidulafungin for 30 A. fumigatus isolates including 18 azole-resistant isolates with various isavuconazole resistance phenotypes.

Methods

The isavuconazole/anidulafungin interaction was studied by using an adapted EUCAST-based 2D (12 × 8) chequerboard broth microdilution colorimetric assay using XTT. The interaction was analysed by FIC index (FICi) analysis and Bliss independence (BI) interaction analysis.

Results

Both the FICi analysis and the BI analysis showed synergistic interaction between isavuconazole and anidulafungin for the majority of WT and azole-resistant isolates. As we did not see significant beneficial effects of combination therapy in TR₄₆/Y121F/T289A isolates at clinically achievable drug concentrations, it is unlikely that TR₄₆/Y121F/T289A infections would benefit from isavuconazole and anidulafungin combination therapy.

Conclusions

In regions with high azole resistance rates this combination may benefit patients with WT disease, azole-resistant invasive aspergillosis and those with mixed azole-susceptible and azole-resistant infection, but may not be beneficial for aspergillosis due to isolates with high isavuconazole resistance, such as TR₄₆/Y121F/T289A isolates.

Azole resistance in Aspergillus species: promising therapeutic options

INTRODUCTION

Azoles are the first-line antifungal agents used for the treatment of Aspergillus infection. There is an increasing concern for azole resistance all over the world mainly from agricultural fungicide use. Choosing safe and effective antifungal regimens has become a challenge.

AREAS COVERED

Here, the authors review the epidemiology, mechanisms, and detection of azole resistance along with management options for azole-resistant Aspergillus infection, including new antifungal agents under development.

EXPERT OPINION

Routine global epidemiological surveillance is required to understand azole resistance prevalence. Azole-resistant Aspergillus infections are associated with high mortality. No good therapeutic options are currently available. High index of suspicion of resistance is required if a patient is not responding to 4-7 days of azole therapy, particularly in the areas of resistance. Susceptibility testing for Aspergillus is not routinely available in many parts of the world, which makes it difficult to diagnose azole resistance in Aspergillus infection. There are several new antifungal classes with novel mechanisms of action; clinical trials are ongoing.

Trends on Aspergillus Epidemiology-Perspectives from a National Reference Laboratory Surveillance Program

Identification of Aspergillus to species level is important since sibling species may display variable susceptibilities to multiple antifungal drugs and also because correct identification contributes to improve the knowledge of epidemiological studies. Two retrospective laboratory studies were conducted on Aspergillus surveillance at the Portuguese National Mycology Reference Laboratory. The first, covering the period 2017–2018, aimed to study the molecular epidemiology of 256 Aspergillus isolates obtained from patients with respiratory, subcutaneous, or systemic infections and from environmental samples. The second, using our entire collection of clinical and environmental A. fumigatus isolates (N = 337), collected between 2012 and 2019, aimed to determine the frequency of azole-resistant A. fumigatus isolates. Aspergillus fumigatus sensu stricto was the most frequent species in both clinical and environmental samples. Overall, and considering all Aspergillus sections identified, a high frequency of cryptic species was detected, based on beta-tubulin or calmodulin sequencing (37% in clinical and 51% in environmental isolates). Regarding all Fumigati isolates recovered from 2012–2019, the frequency of cryptic species was 5.3% (18/337), with the identification of A. felis (complex), A. lentulus, A. udagawae, A. hiratsukae, and A. oerlinghauensis. To determine the frequency of azole resistance of A. fumigatus, isolates were screened for azole resistance using azole-agars, and 53 possible resistant isolates were tested by the CLSI microdilution reference method. Nine A. fumigatus sensu stricto and six Fumigati cryptic isolates showed high minimal inhibitory concentrations to itraconazole, voriconazole, and/or posaconazole. Real-time PCR to detect cyp51A mutations and sequencing of cyp51A gene and its promoter were performed. The overall frequency of resistance to azoles in A. fumigatus sensu stricto was 3.0%. With this retrospective analysis, we were able to detect one azole-resistant G54R mutant A. fumigatus environmental isolate, collected in 2015. The TR₃₄/L98H mutation, linked to environmental transmission route of azole resistance, was the most frequently detected mutation (N = 4; 1.4%). Our findings underline the demand for correct identification and susceptibility testing of Aspergillus isolates.

Pharmacokinetics and Pharmacodynamics of Posaconazole

Posaconazole is typically used for preventing invasive yeast and mold infections such as invasive aspergillosis in high-risk immunocompromised patients. The oral suspension was the first released formulation and many pharmacokinetic and pharmacodynamic studies of this formulation have been published. Erratic absorption profiles associated with this formulation were widely reported. Posaconazole exposure was found to be significantly influenced by food and many gastrointestinal conditions, including pH and motility. As a result, low posaconazole plasma concentrations were obtained in large groups of patients. These issues of erratic absorption urged the development of the subsequently marketed delayed-release tablet, which proved to be associated with higher and more stable exposure profiles. Shortly thereafter, an intravenous formulation was released for patients who are not able to take oral formulations. Both new formulations require a loading dose on day 1 to achieve high posaconazole concentrations more quickly, which was not possible with the oral suspension. So far, there appears to be no evidence of increased toxicity correlated to the higher posaconazole exposure achieved with the regimen for these formulations. The higher systemic availability of posaconazole for the delayed-release tablet and intravenous formulation have resulted in these two formulations being preferable for both prophylaxis and treatment of invasive fungal disease. This review aimed to integrate the current knowledge on posaconazole pharmacokinetics, pharmacodynamics, major toxicity, existing resistance, clinical experience in special populations, and new therapeutic strategies in order to get a clear understanding of the clinical use of this drug.

Role and Interpretation of Antifungal Susceptibility Testing for the Management of Invasive Fungal Infections

Invasive fungal infections (IFIs) are associated with high mortality rates and timely appropriate antifungal therapy is essential for good outcomes. Emerging antifungal resistance among Candida and Aspergillus spp., the major causes of IFI, is concerning and has led to the increasing incorporation of in vitro antifungal susceptibility testing (AST) to guide clinical decisions. However, the interpretation of AST results and their contribution to management of IFIs remains a matter of debate. Specifically, the utility of AST is limited by the delay in obtaining results and the lack of pharmacodynamic correlation between minimal inhibitory concentration (MIC) values and clinical outcome, particularly for molds. Clinical breakpoints for Candida spp. have been substantially revised over time and appear to be reliable for the detection of azole and echinocandin resistance and for outcome prediction, especially for non-neutropenic patients with candidemia. However, data are lacking for neutropenic patients with invasive candidiasis and some non-albicans Candida spp. (notably emerging Candida auris). For Aspergillus spp., AST is not routinely performed, but may be indicated according to the epidemiological context in the setting of emerging azole resistance among A. fumigatus. For non-Aspergillus molds (e.g., Mucorales, Fusarium or Scedosporium spp.), AST is not routinely recommended as interpretive criteria are lacking and many confounders, mainly host factors, seem to play a predominant role in responses to antifungal therapy. This review provides an overview of the pre-clinical and clinical pharmacodynamic data, which constitute the rationale for the use and interpretation of AST testing of yeasts and molds in clinical practice.

Azole-Resistant Aspergillus fumigatus Harboring the TR34/L98H Mutation: First Report in Portugal in Environmental Samples

Introduction: The frequency in detection of azole-resistant Aspergillus fumigatus isolates has increased since 2010. In Portugal, the section Fumigati is one of the most frequent, and resistant strains to have been found in clinical and environmental contexts. Although several cryptic species within the Fumigati section show intrinsic resistance to azoles, one factor driving (acquired) resistance is selective pressure deriving from the extensive use of azoles. This is particularly problematic in occupational environments where high fungal loads are expected, and where there is an increased risk of human exposure and infection, with impact on treatment success and disease outcome. The mechanisms of resistance are diverse, but mainly associated with mutations in the cyp51A gene. Despite TR₃₄/L98H being the most frequent mutation described, it has only been detected in clinical specimens in Portugal. Methods: We analyzed 99 A. fumigatus isolates from indoor environments (healthcare facilities, spas, one dairy and one waste sorting unit) collected from January 2018 to February 2019 in different regions of Portugal. Isolates were screened for resistance to itraconazole, voriconazole and posaconazole by culture, and resistance was confirmed by broth microdilution. Sequencing of the cyp51A gene and its promoter was performed to detect mutations associated with resistance. Results: Overall, 8.1% of isolates were able to grow in the presence of at least one azole, and 3% (isolated from the air in a dairy and from filtering respiratory protective devices in a waste sorting industry) were pan-azole-resistant, bearing the TR₃₄/L98H mutation. Conclusion: For the first time in Portugal, we report environmental isolates bearing the TR₃₄/L98H mutation, isolated from occupational environments. Environmental surveillance of the emergence of azole-resistant A. fumigatus sensu stricto strains is needed, to ensure proper and timely implementation of control policies that may have a positive impact on public and occupational health.

The Multi-Fungicide Resistance Status of Aspergillus fumigatus Populations in Arable Soils and the Wider European Environment

The evolution and spread of pan-azole resistance alleles in clinical and environmental isolates of Aspergillus fumigatus is a global human health concern. The identification of hotspots for azole resistance development in the wider environment can inform optimal measures to counteract further spread by minimizing exposure to azole fungicides and reducing inoculum build-up and pathogen dispersal. We investigated the fungicide sensitivity status of soil populations sampled from arable crops and the wider environment and compared these with urban airborne populations. Low levels of azole resistance were observed for isolates carrying the CYP51A variant F46Y/M172V/E427K, all belonging to a cluster of related cell surface protein (CSP) types which included t07, t08, t13, t15, t19, and t02B, a new allele. High levels of resistance were found in soil isolates carrying CYP51A variants TR₃₄/L98H and TR₄₆/Y121F/T289A, all belonging to CSP types t01, t02, t04B, or t11. TR₄₆/Y121F/M172V/T289A/G448S (CSP t01) and TR₄₆/Y121F/T289A/S363P/I364V/G448S (CSP t01), a new haplotype associated with high levels of resistance, were isolated from Dutch urban air samples, indicating azole resistance evolution is ongoing. Based on low numbers of pan-azole resistant isolates and lack of new genotypes in soils of fungicide-treated commercial and experimental wheat crops, we consider arable crop production as a coldspot for azole resistance development, in contrast to previously reported flower bulb waste heaps. This study also shows that, in addition to azole resistance, several lineages of A. fumigatus carrying TR-based CYP51A variants have also developed acquired resistance to methyl benzimidazole carbamate, quinone outside inhibitor and succinate dehydrogenase (Sdh) inhibitor fungicides through target-site alterations in the corresponding fungicide target proteins; beta-tubulin (F200Y), cytochrome b (G143A), and Sdh subunit B (H270Y and H270R), respectively. Molecular typing showed that several multi-fungicide resistant strains found in agricultural soils in this study were clonal as identical isolates have been found earlier in the environment and/or in patients. Further research on the spread of different fungicide-resistant alleles from the wider environment to patients and vice versa can inform optimal practices to tackle the further spread of antifungal resistance in A. fumigatus populations and to safeguard the efficacy of azoles for future treatment of invasive aspergillosis.

Clonal Expansion of Environmental Triazole Resistant Aspergillus fumigatus in Iran

Azole-resistance in Aspergillus fumigatus is a worldwide medical concern complicating the management of aspergillosis (IA). Herein, we report the clonal spread of environmental triazole resistant A. fumigatus isolates in Iran. In this study, 63 A. fumigatus isolates were collected from 300 compost samples plated on Sabouraud dextrose agar supplemented with itraconazole (ITR) and voriconazole (VOR). Forty-four isolates had the TR34/L98H mutation and three isolates a TR46/Y121F/T289A resistance mechanism, while two isolates harbored a M172V substitution in cyp51A. Fourteen azole resistant isolates had no mutations in cyp51A. We found that 41 out of 44 A. fumigatus strains with the TR34/L98H mutation, isolated from compost in 13 different Iranian cities, shared the same allele across all nine examined microsatellite loci. Clonal expansion of triazole resistant A. fumigatus in this study emphasizes the importance of establishing antifungal resistance surveillance studies to monitor clinical Aspergillus isolates in Iran, as well as screening for azole resistance in environmental A. fumigatus isolates.

Aspergillus fumigatus and pan-azole resistance: who should be concerned?

PURPOSE OF REVIEW

Although clinical outcomes in the treatment of aspergillosis have markedly improved with the availability of newer triazoles, the development of resistance to these antifungals, especially in Aspergillus fumigatus, is a growing concern. The purpose of this review is to provide an update on azole resistance mechanisms and their epidemiology in A. fumigatus, the clinical implications of azole resistance, and to discuss future treatment options against azole-resistant aspergillosis.

RECENT FINDINGS

Resistance may develop through either patient or environmental azole exposure. Environmental exposure is the most prevalent means of resistance development, and these isolates can cause disease in various at-risk groups, which now include those with influenza, and potentially COVID-19. Although current treatment options are limited, newer therapies are in clinical development. These include agents with novel mechanisms of action which have in vitro and in vivo activity against azole-resistant A. fumigatus.

SUMMARY

Azole-resistant A. fumigatus is an emerging threat that hampers our ability to successfully treat patients with aspergillosis. Certain geographic regions and patient populations appear to be at increased risk for this pathogen. As new patient groups are increasingly recognized to be at increased risk for invasive aspergillosis, studies to define the epidemiology and management of azole-resistant A. fumigatus are critically needed. While treatment options are currently limited, new agents under clinical development may offer hope.

Anti-fungal activity of a novel triazole, PC1244, against emerging azole-resistant Aspergillus fumigatus and other species of Aspergillus

Objectives

The growing emergence of azole-resistant Aspergillus fumigatus strains worldwide is a major concern for current systemic antifungal treatment. Here we report antifungal activities of a novel inhaled triazole, PC1244, against a collection of multi-azole-resistant A. fumigatus strains.

Methods

MICs of PC1244 were determined for A. fumigatus carrying TR₃₄/L98H (n = 81), TR₄₆/Y121F/T289A (n = 24), M220 (n = 6), G54 (n = 11), TR₅₃ (n = 1), TR₄₆³/Y121F/T289A (n = 2), G448S (n = 1), G432C (n = 1) and P216S (n = 1) resistance alleles originating from either India, the Netherlands or France. The effects of PC1244 were confirmed in an in vitro model of the human alveolus and in vivo in temporarily neutropenic, immunocompromised mice.

Results

PC1244 exhibited potent inhibition [geometric mean MIC (range), 1.0 mg/L (0.125 to >8 mg/L)] of growth of A. fumigatus strains carrying cyp51A gene mutations, showing much greater potency than voriconazole [15 mg/L (0.5 to >16 mg/L)], and an effect similar to those on other azole-susceptible Aspergillus spp. (Aspergillus flavus, Aspergillus terreus, Aspergillus tubingensis, Aspergillus nidulans, Aspergillus niger, Aspergillus nomius, Aspergillus tamarii) (0.18–1 mg/L). In TR₃₄/L98H and TR₄₆/Y121F/T289A A. fumigatus-infected in vitro human alveolus models, PC1244 achieved superior inhibition (IC₅₀, 0.25 and 0.34 mg/L, respectively) compared with that of voriconazole (IC₉₀, >3 mg/L and >10 mg/L, respectively). In vivo, once-daily intranasal administration of PC1244 (0.56–70 μg/mouse) to the A. fumigatus (AF91 with M220V)-infected mice reduced pulmonary fungal load and serum galactomannan more than intranasal posaconazole.

Conclusions

PC1244 has the potential to become a novel topical treatment of azole-resistant pulmonary aspergillosis.

Azole-resistant Aspergillus and Echinocandin-resistant Candida - What are the treatment options?

Purpose of Review

This review summarizes current treatment options for echinocandin-resistant Candida spp. (ERC) and azole-resistant Aspergillus fumigatus (ARAF), emphasizing recent in vitro/in vivo data, clinical reports, and consensus statements.

Recent Findings

Advances in ERC and ARAF treatment are limited to specific antifungal combinations and dose optimization but remain reliant on amphotericin products. Although novel antifungals may provide breakthroughs in the treatment of resistant fungi, these agents are not yet available. Early identification and appropriate treatment remain a paramount, albeit elusive, task.

Summary

When either ERC or ARAF are suspected or proven, amphotericin products remain the cornerstone of initial therapy. For ERC, azoles are de-escalation options for susceptible isolates in stable patients to avoid amphotericin toxicities. Although combination echinocandin with high-dose salvage posaconazole or isavuconazole may be attempted in ARAF, it requires careful consideration following patient stabilization. Future research defining optimal therapies and early identification of ERC and ARAF is of extreme importance.

Comparison of the MICs Obtained by Gradient Concentration Strip and EUCAST Methods for Four Azole Drugs and Amphotericin B against Azole-Susceptible and -Resistant Aspergillus Section Fumigati Clinical Isolates

Reference methods used to assess the drug susceptibilities of Aspergillus fumigatus isolates consisted of EUCAST and CLSI standardized broth microdilution techniques. Considering the increasing rate and the potential impact on the clinical outcome of azole resistance in A. fumigatus, more suitable techniques for routine testing are needed. The gradient concentration strip (GCS) method has been favorably evaluated for yeast testing. The aim of this study was to compare the CGS test with EUCAST broth microdilution for amphotericin B (AMB), posaconazole (PCZ), itraconazole (ITZ), voriconazole (VRZ), and isavuconazole (ISA). A total of 121 Aspergillus section Fumigati strains were collected, including 24 A. fumigatus sensu stricto strains that were resistant to at least one azole drug. MICs were determined using GCS and EUCAST methods. Essential agreement between the 2 methods was considered when MICs fell within ±1 dilution or ±2 dilutions of the 2-fold dilution scale. Categorical agreement was defined as the percentage of strains classified in the same category (susceptible, intermediate, or resistant) with both methods. Essential agreements with ±1 dilution and ±2 dilutions were 96.7, 93.4, 90.0, 89.3, and 95% and 100, 99.2, 100, 97.5, and 100% for AMB, PCZ, ITZ, VRZ, and ISA, respectively. Categorical agreements were 94.3, 86.1, 89.3, and 88.5% for AMB, PCZ, ITZ, and VRZ, respectively. Detection of resistance was missed with the GCS for one strain (4.1%) for PCZ and for 2 strains (8.3%) for ISA. Determination of ITZ MICs using the GCS allowed the detection of 91.7% of azole-resistant strains. The GCS test appears to be a valuable method for screening azole-resistant A. fumigatus clinical isolates.

Detecting Azole-Antifungal Resistance in Aspergillus fumigatus by Pyrosequencing

Guidelines on the diagnosis and management of Aspergillus disease recommend a multi-test approach including CT scans, culture, fungal biomarker tests, microscopy and fungal PCR. The first-line treatment of confirmed invasive aspergillosis (IA) consists of drugs in the azole family; however, the emergence of azole-resistant isolates has negatively impacted the management of IA. Failure to detect azole-resistance dramatically increases the mortality rates of azole-treated patients. Despite drug susceptibility tests not being routinely performed currently, we suggest including resistance testing whilst diagnosing Aspergillus disease. Multiple tools, including DNA sequencing, are available to screen for drug-resistant Aspergillus in clinical samples. This is particularly beneficial as a large proportion of IA samples are culture negative, consequently impeding susceptibility testing through conventional methods. Pyrosequencing is a promising in-house DNA sequencing method that can rapidly screen for genetic hotspots associated with antifungal resistance. Pyrosequencing outperforms other susceptibility testing methods due to its fast turnaround time, accurate detection of polymorphisms within critical genes, including simultaneous detection of wild type and mutated sequences, and—most importantly—it is not limited to specific genes nor fungal species. Here we review current diagnostic methods and highlight the potential of pyrosequencing to aid in a diagnosis complete with a resistance profile to improve clinical outcomes.

Molecular Detection of Aspergillus: Application of a Real-Time PCR Multiplex Assay in Tissue Samples

Diagnosis of invasive fungal infections is complex, and the lack of standardization of molecular methods is still a challenge. Several methods are available for the diagnosis of invasive aspergillosis, but their effectiveness will depend on the studied population, the patients' comorbidities, and the use of mold active prophylaxis, among others. The ability to determine the identity of the infecting Aspergillus species, and to detect mutations conferring specific resistance patterns directly from DNA extracted from the biological product, is an advantage of nucleic acid testing compared with antigen-based assays. In this study, we to present laboratory cases where the diagnosis of aspergillosis was performed using a real-time multiplex PCR for the detection of Aspergillus DNA in tissue samples, showing its usefulness as one more tool in the diagnosis of aspergillosis in tissue samples. Aspergillus real-time multiplex PCR was also used to detect azole-resistance in some cases. In the majority of the PCR positive cases, cultures remained negative after 60 days. The PCR assay directed to Aspergillus gave positive signals for Aspergillus fumigatus sensu stricto. Results were confirmed by panfungal PCR, followed by sequencing, revealing 100% homology with Aspergillus fumigatus sensu stricto. Mutations conferring azole resistance were not detected.

Investigation of cgrA and cyp51A gene alternations in Aspergillus fumigatus strains exposed to kombucha fermented tea

BACKGROUND AND PURPOSE

Aspergillus fumigatus is one of the most common opportunistic fungus, which causes infection in immunocompromised and neutropenic patients. The current guidelines recommend voriconazole as the initial therapeutic and prophylactic agent for almost all cases, especially in patients with organ transplants, which leads to increased medication resistance in A. fumigatus. The aim of the present study was to evaluate the antifungal activity and effect of kombucha as a natural compound on A. fumigatus growth, as well as on the expression of cgrA and cyp51A genes.

MATERIALS AND METHODS

A panel of 15 A. fumigatus strains with two quality controls of CM237 and CM2627 as susceptible and resistant strains were obtained from Tehran Medical Mycology Laboratory, Tehran,Iran(TMML).Antifungal susceptibility testing assay was performed according to the Clinical and Laboratory Standards Institute (CLSI) M38-A2 document. Moreover, the mycelial dry weight of the fungus was calculated before and after being treated with kombucha. In addition, the quantitative changes in the expression of cgrA and cyp51A genes were analyzed by real-time polymerase chain reaction (real-time PCR) technique.

RESULTS

In the present study, the minimum inhibitory concentration ranges of kombucha were measured at 6,170 and 12,300 μg/mL for ten A. fumigatus azole-susceptible strains and 24,700 μg/mL for five A. fumigatus resistant strains. Moreover, changes in mycelial dry weight under kombucha treatment conditions underwent a significant reduction (P≤0.05). A coordinate down-regulation of expression in cgrA and cyp51A genes was observed in all azole-susceptible and -resistant A. fumigatus strains, after treating the fungus with different concentrations of kombucha (P≤0.05).

CONCLUSION

According to the obtained results, kombucha as a natural antioxidant , can exert inhibitory effects against the growth and expression of some genes in A. fumigatusstrains.