scholarly journals Azole-Resistance Development; How the Aspergillus fumigatus Lifecycle Defines the Potential for Adaptation

2021 ◽  
Vol 7 (8) ◽  
pp. 599
Author(s):  
Jianhua Zhang ◽  
Alfons J. M. Debets ◽  
Paul E. Verweij ◽  
Eveline Snelders
Keyword(s):  
Genetic Variation ◽  
Aspergillus Fumigatus ◽  
Scientific Work ◽  
Azole Resistance ◽  
Resistance Development ◽  
Genetic Changes ◽  
Genomic Changes ◽  
Metabolic Plasticity ◽  
Resistance Selection ◽  
Made In

In order to successfully infect or colonize human hosts or survive changing environments, Aspergillus fumigatus needs to adapt through genetic changes or phenotypic plasticity. The genomic changes are based on the capacity of the fungus to produce genetic variation, followed by selection of the genotypes that are most fit to the new environment. Much scientific work has focused on the metabolic plasticity, biofilm formation or the particular genetic changes themselves leading to adaptation, such as antifungal resistance in the host. Recent scientific work has shown advances made in understanding the natural relevance of parasex and how both the asexual and sexual reproduction can lead to tandem repeat elongation in the target gene of the azoles: the cyp51A gene. In this review, we will explain how the fungus can generate genetic variation that can lead to adaptation. We will discuss recent advances that have been made in the understanding of the lifecycle of A. fumigatus to explain the differences observed in speed and type of mutations that are generated under different environments and how this can facilitate adaptation, such as azole-resistance selection.

scholarly journals Relevance of heterokaryosis for adaptation and azole-resistance development in Aspergillus fumigatus

2019 ◽  
Vol 286 (1896) ◽  
pp. 20182886 ◽  
Author(s):  
Jianhua Zhang ◽  
Eveline E. Snelders ◽  
Bas J. Zwaan ◽  
Sijmen E. Schoustra ◽  
Ed J. Kuijper ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Human Lung ◽  
Spontaneous Mutation ◽  
Acquired Resistance ◽  
Fungal Mycelium ◽  
Azole Resistance ◽  
Resistance Level ◽  
Resistance Development ◽  
Genetic Changes ◽  
Lung Colonization

Aspergillus fumigatus causes a range of diseases in humans, some of which are characterized by fungal persistence. Aspergillus fumigatus , being a generalist saprotroph, may initially establish lung colonization due to its physiological versatility and subsequently adapt through genetic changes to the human lung environment and antifungal treatments. Human lung-adapted genotypes can arise by spontaneous mutation and/or recombination and subsequent selection of the fittest genotypes. Sexual and asexual spores are considered crucial contributors to the genetic diversity and adaptive potential of aspergilli by recombination and mutation supply, respectively. However, in certain Aspergillus diseases, such as cystic fibrosis and chronic pulmonary aspergillosis, A. fumigatus may not sporulate but persist as a network of fungal mycelium. During azole therapy, such mycelia may develop patient-acquired resistance and become heterokaryotic by mutations in one of the nuclei. We investigated the relevance of heterokaryosis for azole-resistance development in A. fumigatus. We found evidence for heterokaryosis of A. fumigatus in patients with chronic Aspergillus diseases. Mycelium from patient-tissue biopsies segregated different homokaryons, from which heterokaryons could be reconstructed. Whereas all variant homokaryons recovered from the same patient were capable of forming a heterokaryon, those from different patients were heterokaryon-incompatible. We furthermore compared heterokaryons and heterozygous diploids constructed from environmental isolates with different levels of azole resistance. When exposed to azole, the heterokaryons revealed remarkable shifts in their nuclear ratio, and the resistance level of heterokaryons exceeded that of the corresponding heterozygous diploids.

Basics of genetics

2013 ◽  
Author(s):  
Anne Barton
Keyword(s):  
Genetic Variation ◽  
Genetic Factors ◽  
Musculoskeletal Diseases ◽  
Disease Onset ◽  
Novel Therapies ◽  
Genetic Changes ◽  
Susceptibility Factors ◽  
Basic Concepts ◽  
Modern Technologies ◽  
Made In

Genetic factors are important in predisposing to nearly all of the conditions managed by rheumatologists; indeed, musculoskeletal diseases, like other complex diseases, are thought to be caused by environmental triggers in genetically susceptible individuals. Studying genetic susceptibility factors is more straightforward than environmental factors because, first, genetic changes are stable and do not vary throughout life; second, genetic changes exist before disease onset and so could be causative rather than occurring as a result of disease; and, third, genetic variation is easy to measure reliably using modern technologies. By comparison, environmental exposures can occur many years before disease onset, may vary during life, and are hard to accurately capture and measure. Enormous progress has been made in recent years in identifying susceptibility genes. This knowledge may allow better targeting of available therapies, the development of novel therapies, and an improved understanding of what determines disease severity in individual patients. In this chapter, the basic concepts in genetics are explained.

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

2020 ◽  
Vol 11 ◽  
Author(s):  
Bart Fraaije ◽  
Sarah Atkins ◽  
Steve Hanley ◽  
Andy Macdonald ◽  
John Lucas
Keyword(s):  
Aspergillus Fumigatus ◽  
Crop Production ◽  
Agricultural Soils ◽  
Acquired Resistance ◽  
Surface Protein ◽  
Health Concern ◽  
Azole Resistance ◽  
Arable Soils ◽  
Resistance Development ◽  
Resistance Evolution

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.

scholarly journals Environmental Hotspots for Azole Resistance Selection of Aspergillus fumigatus, the Netherlands

2019 ◽  
Vol 25 (7) ◽  
pp. 1347-1353 ◽  
Author(s):  
Sijmen E. Schoustra ◽  
Alfons J.M. Debets ◽  
Antonius J.M.M. Rijs ◽  
Jianhua Zhang ◽  
Eveline Snelders ◽  
...  
Keyword(s):  
The Netherlands ◽  
Aspergillus Fumigatus ◽  
Azole Resistance ◽  
Resistance Selection ◽  
Selection Of

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

2018 ◽  
Vol 4 (3) ◽  
pp. 103 ◽  
Author(s):  
Jochem Buil ◽  
Ferry Hagen ◽  
Anuradha Chowdhary ◽  
Paul Verweij ◽  
Jacques Meis
Keyword(s):  
Aspergillus Fumigatus ◽  
Minimal Inhibitory Concentration ◽  
Susceptibility Testing ◽  
Inhibitory Concentration ◽  
Azole Resistance ◽  
Wild Type ◽  
Gene Encoding ◽  
Environmental Resistance ◽  
Resistance Selection ◽  
Susceptibility Profiles

Azole resistance in Aspergillus fumigatus is most frequently conferred by mutations in the cyp51A gene encoding 14α-sterol demethylases. TR34/L98H and TR46/Y121F/T289A are the two most common mutations associated with environmental resistance selection. We studied the minimal inhibitory concentration (MIC) distribution of clinical A. fumigatus isolates to characterize the Clinical and Laboratory Standards Institute (CLSI) susceptibility profiles of isolates with the wild-type (WT) cyp51A genotype, and isolates with the TR34/L98H and TR46/Y121F/T289A cyp51A mutations. Susceptibility testing was performed according to CLSI M38-A2. The MICs of 363 A. fumigatus isolates were used in this study. Based on the CLSI epidemiological cut-off values (ECVs), 141 isolates were phenotypically non-WT and 222 isolates had a phenotypically WT susceptibility. All isolates with the TR34/L98H mutation had an itraconazole MIC > 1 mg/L which is above the CLSI ECV. Eighty-six of 89 (97%) isolates with the TR34/L98H mutation had voriconazole and posaconazole MICs above the CLSI ECV, i.e., MICs of 1 and 0.25 mg/L, respectively. The isolates with a TR46/Y121F/T289A mutation showed a different phenotype. All 37 isolates with a TR46/Y121F/T289A mutation had a voriconazole MIC above the CLSI ECV, while 28/37 (76%) isolates had an itraconazole MIC > 1 mg/L. Interestingly, only 13 of 37 (35%) isolates had a posaconazole MIC > 0.25 mg/L.

scholarly journals A Novel Environmental Azole Resistance Mutation inAspergillus fumigatusand a Possible Role of Sexual Reproduction in Its Emergence

mBio ◽  
2017 ◽  
Vol 8 (3) ◽  
Author(s):  
Jianhua Zhang ◽  
Eveline Snelders ◽  
Bas J. Zwaan ◽  
Sijmen E. Schoustra ◽  
Jacques F. Meis ◽  
...  
Keyword(s):  
Aspergillus Fumigatus ◽  
Sexual Reproduction ◽  
Crop Protection ◽  
Resistance Mutation ◽  
Azole Resistance ◽  
Wild Type ◽  
Resistance Mutations ◽  
Resistance Selection ◽  
Genotype 2

ABSTRACTThis study investigated the dynamics ofAspergillus fumigatusazole-resistant phenotypes in two compost heaps with contrasting azole exposures: azole free and azole exposed. After heat shock, to which sexual but not asexual spores are highly resistant, the azole-free compost yielded 98% (49/50) wild-type and 2% (1/50) azole-resistant isolates, whereas the azole-containing compost yielded 9% (4/45) wild-type and 91% (41/45) resistant isolates. From the latter compost, 80% (36/45) of the isolates contained the TR46/Y121F/T289A genotype, 2% (1/45) harbored the TR46/Y121F/M172I/T289A/G448S genotype, and 9% (4/45) had a novel pan-triazole-resistant mutation (TR463/Y121F/M172I/T289A/G448S) with a triple 46-bp promoter repeat. Subsequent screening of a representative set of clinicalA. fumigatusisolates showed that the novel TR463mutant was already present in samples from three Dutch medical centers collected since 2012. Furthermore, a second new resistance mutation was found in this set that harbored four TR46repeats. Importantly, in the laboratory, we recovered the TR463mutation from a sexual cross between two TR46isolates from the same azole-containing compost, possibly through unequal crossing over between the double tandem repeats (TRs) during meiosis. This possible role of sexual reproduction in the emergence of the mutation was further implicated by the high level of genetic diversity of STR genotypes in the azole-containing compost. Our study confirms that azole resistance mutations continue to emerge in the environment and indicates compost containing azole residues as a possible hot spot. Better insight into the biology of environmental resistance selection is needed to retain the azole class for use in food production and treatment ofAspergillusdiseases.IMPORTANCEComposting of organic matter containing azole residues might be important for resistance development and subsequent spread of resistance mutations inAspergillus fumigatus. In this article, we show the dominance of azole-resistantA. fumigatusin azole-exposed compost and the discovery of a new resistance mutation with clinical relevance. Furthermore, our study indicates that current fungicide application is not sustainable as new resistance mutations continue to emerge, thereby threatening the use of triazoles in medicine. We provide evidence that the sexual part of the fungal life cycle may play a role in the emergence of resistance mutations because under laboratory conditions, we reconstructed the resistance mutation through sexual crossing of two azole-resistantA. fumigatusisolates derived from the same compost heap. Understanding the mechanisms of resistance selection in the environment is needed to design strategies against the accumulation of resistance mutations in order to retain the azole class for crop protection and treatment ofAspergillusdiseases.

scholarly journals Contributions of both ATP-Binding Cassette Transporter and Cyp51A Proteins Are Essential for Azole Resistance in Aspergillus fumigatus

2017 ◽  
Vol 61 (5) ◽  
Author(s):  
Sanjoy Paul ◽  
Daniel Diekema ◽  
W. Scott Moye-Rowley
Keyword(s):  
Aspergillus Fumigatus ◽  
Azole Resistance ◽  
Atp Binding ◽  
Wild Type ◽  
Gene Encoding ◽  
Pathogenic Yeast ◽  
Genetic Changes ◽  
Content Type ◽  
Transporter Protein ◽  
Atp Binding Cassette

ABSTRACT While azole drugs targeting the biosynthesis of ergosterol are effective antifungal agents, their extensive use has led to the development of resistant organisms. Infections involving azole-resistant forms of the filamentous fungus Aspergillus fumigatus are often associated with genetic changes in the cyp51A gene encoding the lanosterol α14 demethylase target enzyme. Both a sequence duplication in the cyp51A promoter (TR34) and a substitution mutation in the coding sequence (L98H) are required for the full expression of azole resistance. A mechanism commonly observed in pathogenic yeast such as Candida albicans involves gain-of-function mutations in transcriptional regulatory proteins that induce expression of genes encoding ATP-binding cassette (ABC) transporters. We and others have found that an ABC transporter protein called Cdr1B (here referred to as AbcG1) is required for wild-type azole resistance in A. fumigatus. Here, we test the genetic relationship between the TR34 L98H allele of cyp51A and an abcG1 null mutation. Loss of AbcG1 from a TR34 L98H cyp51A-containing strain caused a large decrease in the azole resistance of the resulting double-mutant strain. We also generated antibodies that enabled the detection of both the wild-type and L98H forms of the Cyp51A protein. The introduction of the L98H lesion into the cyp51A gene led to a decreased production of immunoreactive enzyme, suggesting that this mutant protein is unstable. Our data confirm the importance of AbcG1 function during azole resistance even in a strongly drug-resistant background.

scholarly journals Parasexual recombination enables Aspergillus fumigatus to persist in cystic fibrosis

2020 ◽  
Vol 6 (4) ◽  
pp. 00020-2020
Author(s):  
Tobias Engel ◽  
Paul E. Verweij ◽  
Joost van den Heuvel ◽  
Dechen Wangmo ◽  
Jianhua Zhang ◽  
...  
Keyword(s):  
Cystic Fibrosis ◽  
Genetic Variation ◽  
Aspergillus Fumigatus ◽  
Cell Sorting ◽  
Biofilm Formation ◽  
Human Lung ◽  
Resistant Isolate ◽  
Resistance Development ◽  
Large Size ◽  
Different Origins

Aspergillus fumigatus is a saprobic fungus that causes a range of pulmonary diseases, some of which are characterised by fungal persistence such as is observed in cystic fibrosis (CF) patients. Creation of genetic variation is critical for A. fumigatus to adapt to the lung environment, but biofilm formation, especially in CF patients, may preclude mutational supply in A. fumigatus due to its confinement to the hyphal morphotype. We tested our hypothesis that genetic variation is created through parasexual recombination in chronic biofilms by phenotypic and genetic analysis of A. fumigatus isolates cultured from different origins.As diploids are the hallmark of parasex, we screened 799 A. fumigatus isolates obtained from patients with CF, chronic pulmonary lung disease and acute invasive aspergillosis, and from the environment for spore size. Benomyl sensitivity, nuclear content measurements through fluorescence-activated cell sorting and scanning electron microscopy were used to confirm the diploid state of large size spores. Whole genome sequencing was used to characterise diploid-associated genetic variation.We identified 11 diploids in isolates recovered from six of 11 (55%) CF patients and from one of 24 (4%) chronic aspergillosis patients, but not in 368 isolates from patients with acute Aspergillus infection and the environment. Diploid formation was associated with accumulation of mutations and variable haploid offspring including a voriconazole-resistant isolate.Parasexual recombination allows A. fumigatus to adapt and persist in CF patients, and plays a role in azole resistance development. Our findings are highly significant for understanding the genetics and biology of A. fumigatus in the human lung.

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