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Aspergillus niger is an opportunistic pathogen commonly found in a variety of indoor and outdoor environments. An environmental isolate of A. niger from a pig farm were resistant to itraconazole and in-depth investigations were conducted to better understand cellular responses during growth when exposed to an antifungal.
Using a combination of cultivation techniques, antibiotic stress-testing, and label-free proteomics, this study has investigated the physiological and metabolic responses of A. niger to sublethal levels of antifungal stress.
Challenging A. niger with itraconazole inhibited the growth, and the minimum inhibitory concentration (MIC) was estimated to be >16 mg·L−1. Through the proteome analysis, 1305 unique proteins were identified. Differential expressed proteins during growth at 2 and 8 mg·L−1 itraconazole revealed that a total of 91 and 50 proteins were significantly differentially expressed, respectively. Challenged with itraconazole, A. niger decreased the expression of peroxidative enzymes, increased the expression of an ATP-binding cassette (ABC) transporter most likely involved as an azole efflux pump, and inhibited ergosterol synthesis, however, several ergosterol biosynthesis proteins increased in abundance. Furthermore, a reduced expression of proteins involved in the production of ATP and reducing power from both the TCA and glyoxylate cycle was observed. The mode of action of triazoles in A. niger therefore appears more complex than previously anticipated and showcase future targets for antifungal treatment.
This paper offers characteristic formula constructions in the realtime logic L ν for several behavioural relations between (states of) timed automata. The behavioural relations studied in this work are timed (bi)similarity, timed ready simulation, faster-than bisimilarity and timed trace inclusion. The characteristic formulae delivered by our constructions have size which is linear in that of the timed automaton they logically describe. This also applies to the characteristic formula for timed bisimulation equivalence, for which an exponential space construction was previously offered by Laroussinie, Larsen and Weise.
Antibiotic resistance in fungal isolates is increasing on a global scale. Despite knowledge that pig farmers are occupationally exposed to infectious species of fungi, such as Aspergillus spp., little is known regarding their potential exposure to antifungal-resistant Aspergillus spp. The aim of this study is to obtain knowledge regarding the antifungal resistance profiles of isolates of Aspergillus species taken from different source materials—including airborne dust, surface dust, faeces, and straw—within a pig farm. The EUCAST broth microdilution method was used for testing antifungal resistance from 43 isolates of Aspergillus sampled in 3 periods inside a Danish pig farm. Seven species of Aspergillus were obtained, including A. candidus (n = 5), A. fumigatus (n = 5), A. glaucus (n = 13), A. nidulans (n = 2), A. niger (n = 15), A. terreus (n = 1), and A. versicolor (n = 2). Overall, 27.9% of the Aspergillus isolates displayed resistance against at least one antifungal, and 11.6% of Aspergillus isolates displayed resistance against multiple antifungals. The most abundant group exhibiting antifungal resistance was affiliated with the species A. niger, with isolates exhibiting resistance to itraconazole, voriconazole, and caspofungin. One isolate of A. glaucus and two isolates of A. versicolor were resistant to amphotericin B (MIC ≥ 2 mg/L amphotericin B). Antibiotic-resistant fungi were found on all three sampling days.
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