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

Abstract

BACKGROUND: Aspergillus fumigatus, the causal agent of aspergillosis in humans, is commonly present as a saprophyte in various organic substrates, such as spoiled silages. Aspergillosis is generally combated with demethylation inhibitor (DMI) fungicides, but the recent appearance of resistant medical and environmental strains made current treatment strategies less reliable. The goal of this study was to determine the evolution of A. fumigatus populations during the ensiling process of whole-crop corn, high moisture corn and wet grain corn, and to monitor the sensitivity of isolates from treated and untreated fields to one medical and one agricultural DMI fungicide. RESULTS:A. fumigatus was isolated from fresh forage at harvest at rather low concentrations (10 2 cfu g −1 ). The low frequency lingered during the silage process (at 60 and 160 days), whereas it significantly increased during air exposure (at 7 and 14 days of air exposure). Field treatment of corn with a mixture of prothioconazole and tebuconazole did not affect the sensitivity of A. fumigatus isolates. One of 29 isolates from the untreated plot was resistant to voriconazole. A unique amino acid substitution (E427K) was detected in the cyp51A gene of 10 of 12 sequenced isolates, but was not associated with DMI resistance. CONCLUSION: A. fumigatus significantly increased during aerobic deterioration of ensilaged corn after silo opening, compared with the low presence in fresh corn and during ensiling. Field treatment of corn with DMI fungicides did not affect the sensitivity of A. fumigatus isolates collected from fresh and ensiled corn.

Crossover between the control of fungal pathogens in medicine and the wider environment, and the threat of antifungal resistance

“…fumigatus concentrations (below 10 2 cfu/g), whereas 1-2 weeks after silo opening, the concentration increased drastically to 10 5 -10 8 cfu/g (Spadaro et al, 2019). In the majority of samples collected from corn silage and compost made of oranges, both mating types were present, with mat-2 being more frequent than mat-1 (Pugliese et al, 2018;Spadaro et al, 2019). According to simple sequence repeats (SSR, microsatellite molecular markers) analysis, a high genetic diversity was detected in compost populations (Santoro et al, 2017) suggesting frequent sexual and/or parasexual processes.…”

“…fumigatus concentrations (below 10 2 cfu/g), whereas 1-2 weeks after silo opening, the concentration increased drastically to 10 5 -10 8 cfu/g (Spadaro et al, 2019). In the majority of samples collected from corn silage and compost made of oranges, both mating types were present, with mat-2 being more frequent than mat-1 (Pugliese et al, 2018;Spadaro et al, 2019).…”

Selection and Amplification of Fungicide Resistance in Aspergillus fumigatus in Relation to DMI Fungicide Use in Agronomic Settings: Hotspots versus Coldspots

“…Fraaije et al [60] found ARAf in soil from one of three maize fields sampled in Hungary and the Netherlands. Freshly harvested maize samples from continental European locations carried either no A. fumigatus or a small population only [94,95]. However, maize soils showed the highest frequency of detection (15%) of resistant isolates in soil samples among the various crop settings sampled in the UK by Tsitsopoulou et al [83].…”

“…In South America, Bedin Denardi et al [96] showed that 25% of samples from maize crops sampled in Brazil showed itraconazole resistance (but no pan-DMI resistance), and about half of soil samples taken from maize fields in Colombia contained ARAf [97]. Maize silage carried either no A. fumigatus [5] or low populations, up to the point at which it was exposed to air, after which the population increased significantly [94,95]. A comparison of maize silage from DMI-treated (double-dose) and untreated plots showed no effect on the DMI-susceptibility of A. fumigatus isolates; the single (non-TR) voriconazole-resistant isolate detected was recovered from silage from an untreated plot [95].…”

Tebuconazole resistance of Fusarium graminearum field populations from wheat in Henan Province

“…Over the years, due to the constant application of tebuconazole and other DMI fungicides, strains acquired resistance have emerged in wheat fields. The mechanisms of the resistance to DMI are usually attributed: (a) CYP51 gene mutation (Cools et al., 2010; Liu et al., 2011; Loffler et al., 1997; Sanglard et al., 1998; Spadaro et al., 2020; Wyand & Brown, 2005; Yin et al., 2009); (b) overexpression of the CYP51 gene (Becher et al., 2010; Chong et al., 2019; Hamamoto et al., 2000; Kildea et al., 2019; Liu et al., 2011; Ma et al., 2006); and (c) overexpression of efflux pumps (Gisi et al., 2000; Ma et al., 2006; Paulsen et al., 1997; Waard, 1997).…”