Aspergillus fumigatus is a widespread opportunistic fungal pathogen causing an alarmingly high mortality rate in immunocompromised patients. Nosocomial infections by drug-resistant A. fumigatus strains are of particular concern, and there is a pressing need to understand the origin, dispersal and long-term evolution of drug resistance in this organism. The objective of this study was to investigate the diversity and putative origins of triazole resistance of A. fumigatus from India. Eighty-nine isolates, including 51 multiple triazole resistant (MTR) isolates and 38 azole-susceptible isolates, were genotyped using multilocus sequence typing (MLST), mating typing and PCR fingerprinting. MLST resolved the 51 MTR isolates into three genotypes, two of which have susceptible counterparts, suggesting that MTR isolates originated multiple times in India. The multiple-origin hypothesis was further supported by the diversity of sequences at the triazole target gene CYP51A among the MTR isolates, and by PCR fingerprints. Interestingly, there is abundant evidence for mating and recombination in natural population of A. fumigatus in India, suggesting that sexual spread of TR34 /L98H, the dominant MTR allele, is possible. Our results call for greater attention to MTR in A. fumigatus and for better management of antifungal drug use.

Both yeasts and nematodes are significant components of the soil biomass and biodiversity and fulfil a wide variety of ecological functions. However, relatively little is known about the interactions between yeasts and nematodes, including the potential use of yeasts by nematodes as a food source and potential diseases that these yeasts can cause in nematodes. To begin investigating their ecological relationships, we tested the in vitro attractive ability of representative yeast species on nematodes. A total of 15 yeast strains belonging to six species were assayed for their attraction abilities towards two nematode species. Our results suggest that nematodes are able to distinguish between their microbial food source and yeast pathogens. Furthermore, our analyses demonstrated that host nematodes, yeast species, and in some cases yeast strains all contributed to the variation in attraction abilities. We hypothesize that volatile and/or diffusible organic compounds released from the yeasts are involved in attracting the nematodes. These results suggest the attraction and consumption interaction between soil yeasts and nematodes may be common in the environment. These interactions may be significant in regulating the populations of both the yeasts and their nematode hosts in natural soil ecosystems. The data presented here could also help to develop nematode-based model systems for studying fungal pathogenesis.