Flower Bulb Waste Material Is a Natural Niche for the Sexual Cycle in Aspergillus fumigatus

Widely dispersed clonal expansion of multi-fungicide-resistant Aspergillus fumigatus limits genomic epidemiology prospects

Invasive aspergillosis, caused by Aspergillus fumigatus, represents a critical public health concern, particularly due to increasing resistance to triazole antifungals linked to TR34/TR46 cyp51A haplotypes. In our genomic epidemiology study of 157 A. fumigatus isolates from Dutch environmental hotspots and two clinical centers, we identified near-identical genomes in several environmental and patient isolates, indicating a probable link. However, the geographic and temporal data alone are not sufficient to explain direct transmission pathways. Furthermore, a comparison with more than 1,200 globally sourced genomes revealed the extensive dissemination of certain clonal groups across multiple distant regions, raising significant challenges for the utility of genomic epidemiology. The discovery of high genetic diversity and the widespread distribution of some clonal groups challenges current understanding, suggesting that in most cases, tracing the precise source of individual infections will remain extremely difficult, even with increased sampling. In addition, we uncovered that the multi-triazole-resistant TR34/TR46 cyp51A haplotypes are associated with resistance to non-triazole fungicides such as benzimidazole, succinate dehydrogenase inhibitor, and quinone outside inhibitor classes, strongly suggesting an exposure history to multiple agricultural fungicides in these environmental hotspots. This resistance beyond the azole class suggests that strategies targeting only triazoles may be insufficient. Our findings challenge current paradigms and carry significant implications for One Health research and global public health strategies, underscoring the urgency of multidisciplinary approaches to tracking and monitoring fungal resistance.IMPORTANCEOur study links triazole-resistant A. fumigatus isolates cultured from three environmental hotspots to cases of aspergillus disease in two hospitals in the Netherlands. Genome comparisons of isolates from environmental hotspots and patients showed multiple near-identical linked genotypes, consistent with a route of transmission from the environment to patients. Linked cases without clear transmission routes emphasize the need to better understand the ecology of this fungus. Since patients often do not visit rural hotspots, research should explore complex, long-distance transmission mechanisms, including airborne dispersal of conidia or non-agricultural habitats. The multi-fungicide resistance phenotype suggests reducing one class of fungicides alone may not lower resistance selection. Instead, interventions should target modifying environments that promote the growth of fungicide-resistant A. fumigatus and prevent the escape of resistant spores from these hotspots to mitigate the burden of environmental resistance effectively.

Aspergillus fumigatus biology, immunopathogenicity and drug resistance

Aspergillus fumigatus is a saprophytic fungus prevalent in the environment and capable of causing severe invasive infection in humans. This organism can use strategies such as molecule masking, immune response manipulation and gene expression alteration to evade host defences. Understanding these mechanisms is essential for developing effective diagnostics and therapies to improve patient outcomes in Aspergillus-related diseases. In this Review, we explore the biology and pathogenesis of A. fumigatus in the context of host biology and disease, highlighting virus-associated pulmonary aspergillosis, a newly identified condition that arises in patients with severe pulmonary viral infections. In the post-pandemic landscape, in which immunotherapy is gaining attention for managing severe infections, we examine the host immune responses that are critical for controlling invasive aspergillosis and how A. fumigatus circumvents these defences. Additionally, we address the emerging issue of azole resistance in A. fumigatus, emphasizing the urgent need for greater understanding in an era marked by increasing antimicrobial resistance. This Review provides timely insights necessary for developing new immunotherapeutic strategies against invasive aspergillosis.

What in Earth? Analyses of Canadian soil populations of Aspergillus fumigatus

Aspergillus fumigatus is a globally distributed mold and a major cause of opportunistic infections in humans. Because most infections are from environmental exposure, it is critical to understand environmental populations of A. fumigatus. Soil is a major ecological niche for A. fumigatus. Here, we analyzed 748 soil isolates from 21 locations in six provinces and one territory in Canada. All isolates were genotyped using nine microsatellite markers. Due to small sample size and/or close proximities for some local samples, these isolates were grouped into 16 local geographic and ecological populations. Our results indicated high allelic and genotypic diversities within most local and provincial populations. Interestingly, low but statistically significant genetic differentiations were found among geographic populations within Canada, with relatively similar proportions of strains and genotypes belonging to two large genetic clusters. In Hamilton, Ontario, and Vancouver, BC, where two and three ecological populations were analyzed, respectively, we found limited genetic difference among them. Most local and provincial populations showed evidence of both clonality and recombination, with no population showing random recombination. Of the 748 soil isolates analyzed here, two were resistant to triazole antifungals. We discuss the implications of our results to the evolution and epidemiology of A. fumigatus.

Assessing thermal adaptation of a global sample of Aspergillus fumigatus: Implications for climate change effects

Aspergillus fumigatus is a common environmental mold and a major cause of opportunistic infections in humans. It's distributed among many ecological niches across the globe. A major virulence factor of A. fumigatus is its ability to grow at high temperature. However, at present, little is known about variations among strains in their growth at different temperatures and how their geographic origins may impact such variations. In this study, we analyzed 89 strains from 12 countries (Cameroon, Canada, China, Costa Rica, France, India, Iceland, Ireland, New Zealand, Peru, Saudi Arabia, and USA) representing diverse geographic locations and temperature environments. Each strain was grown at four temperatures and genotyped at nine microsatellite loci. Our analyses revealed a range of growth profiles, with significant variations among strains within individual geographic populations in their growths across the temperatures. No statistically significant association was observed between strain genotypes and their thermal growth profiles. Similarly geographic separation contributed little to differences in thermal adaptations among strains and populations. The combined analyses among genotypes and growth rates at different temperatures in the global sample suggest that most natural populations of A. fumigatus are capable of rapid adaptation to temperature changes. We discuss the implications of our results to the evolution and epidemiology of A. fumigatus under increasing climate change.