Molecular characterization and sensitivity to demethylation inhibitor fungicides of Aspergillus fumigatus from orange-based compost

Abstract

Aspergillus fumigatus, the causal agent of human aspergilloses, is known to be non-pathogenic in plants. It is present as saprophyte in different types of organic matter and develops rapidly during the high-temperature phase of the composting process. Aspergilloses are treated with demethylation inhibitor (DMI) fungicides and resistant isolates have been recently reported. The present study aims to estimate the abundance, genetic diversity and DMI sensitivity of A. fumigatus during the composting process of orange fruits. Composting of orange fruits resulted in a 100-fold increase in A. fumigatus frequency already after 1 week, demonstrating that the degradation of orange fruits favoured the growth of A. fumigatus in compost. Most of A. fumigatus isolates belonged to mating type 2, including those initially isolated from the orange peel, whereas mating type 1 evolved towards the end of the composting process. None of the A. fumigatus isolates expressed simultaneously both mating types. The 52 investigated isolates exhibited moderate SSR polymorphisms by formation of one major (47 isolates) and one minor cluster (5 isolates). The latter included mating type 1 isolates from the last sampling and the DMI-resistant reference strains. Only few isolates showed cyp51A polymorphisms but were sensitive to DMIs as all the other isolates. None of the A. fumigatus isolates owned any of the mutations associated with DMI resistance. This study documents a high reproduction rate of A. fumigatus during the composting process of orange fruits, requesting specific safety precautions in compost handling. Furthermore, azole residue concentrations in orange-based compost were not sufficient to select A. fumigatus resistant genotypes.

Aspergillus fumigatus population dynamics and sensitivity to demethylation inhibitor fungicides in whole‐crop corn, high moisture corn and wet grain corn silages

“…In this survey, ten silage A. fumigatus isolates contained the cyp51A E427K amino acid mutation. The polymorphism E427K has been already found in our previous reports in A. fumigatus deriving from composts of kitchen and garden wastes, and orange compost and brown compost from Italy and Spain. This mutation, detected now also in several corn silage isolates, is not related to DMI resistance, rather it represents a specific genotype existing at certain geographic sites.…”

“…The isolate resistant to voriconazole belonged to mat 2. This could be related to a higher aggressiveness of silage isolates as described previously for compost isolates (both environmental origin), where mat 2 was predominant and a high sensitivity to DMI fungicides was reported in northern Italy …”

“…Because DMI sensitivity evaluation of A. fumigatus from agricultural and environmental habitats, e.g. compost, is still limited, we carried out this study in corn silage, one of the preferred habitats of A. fumigatus on dairy farms. Silage is considered a major sources of conidia release of A. fumigatus into air and emphasis has been given to different corn silage types (whole‐crop corn, high moisture corn and wet grain silages) from corn harvest to conservation and aerobic deterioration of silage during feed‐out phase.…”

Citizen-science surveillance of triazole-resistantAspergillus fumigatusin UK residential garden soils

“…Sewell et al (2019) collected two samples from a compost heap in London that, combined with three samples collected from a flower bed ~500m away, gave a 60% prevalence of triazole-resistant A. fumigatus 60 . Pugliese et al (2018) sampled from composting orange peel in Italy and found A. fumigatus concentrations of 8.8 × 10 3 CFU/g at the start of the process rising to 605.7 × 10 3 CFU/g by the end, yet none of the 30 isolates selected for susceptibility testing were triazole-resistant 71 . Santoro et al (2017) sampled from 11 green and brown composts across Spain, Hungary and Italy and found concentrations of A. fumigatus ranging from 100 to 10.6 × 10 3 CFU/g, yet none of the 30 isolates selected for susceptibility testing were triazole-resistant 72 .…”

Molecular Epidemiology of Aspergillus fumigatus in Chronic Pulmonary Aspergillosis Patients

“…Several genotyping studies incorporating mating type loci in their analyses demonstrated their resolving power within otherwise isogenic groups [ 12 , 69 , 98 , 103 ], although mating markers do not play a role in virulence per se [ 104 ]. The existence of a sexual cycle in A. fumigatus was only discovered recently and seems to occur more frequently than previously thought [ 101 , 102 ], as evidenced by the high genetic diversity of environmental isolates obtained from a compost heap, suggesting sexual or parasexual recombination events, rather than clonal reproduction [ 105 ]. Confirmation of this theory was provided in a laboratory study in which the sexual cross between two TR 46 isolates from the same triazole-containing compost resulted in the recovery of a novel pan-triazole-resistant mutation (TR 46 (3)/Y121F/M172I/T289A/G448S) [ 106 ].…”