The frequency distribution of Aspergillus section Nigri from clinical and environmental samples in Iran.

Background: Aspergillus section Nigri is widely distributed in decaying plant materials in our environment. Although most of these species are known for food spoilage and some have industrial applications, some of these species, including Aspergillus tubingensis, A. welwitschiae, and A. niger, are etiologic agents of human and animal aspergillosis. Moreover, the frequency of each species in different environments is correlated with meteorological conditions. The present study aimed to investigate the frequency of Aspergillus section Nigri in clinical samples and environmental sources in several Iranian provinces.

Methods: A total of 629 samples, including 261 clinical materials and 368 environmental materials, were collected from seven Iranian provinces. The Aspergillus section Nigri was initially screened on the basis of colony morphology and then subjected to sequencing via the calmodulin (CaM) gene. Maximum likelihood phylogenies were constructed via MEGA 11 software.

Results: Of the 192 Aspergillus section Nigri isolates, 41.15% were identified as A. tubingensis, followed by A. welwitschiae (35.94%), A. niger (sensu stricto) (17.71%), A. neoniger (1.56%), A. piperis (1.56%), A. aculeatus (1.04%), and A. luchuensis (1.04%). The most prevalent species were A. tubingensis and A. welwitschiae from clinical and environmental samples, respectively. In addition, the frequency of these species varied across Iranian provinces.

Conclusions: This study determined the presence and frequency, distribution, and phylogenetic relationships of eight black aspergilli, A. tubingensis, A. welwitschiae, A. niger, A. neoniger, A. piperis, A. aculeatus, and A. luchuensis, associated with clinical and environmental samples from several Iranian provinces. In terms of the source of isolation, A. tubingensis was most common in the both environmental and clinical samples, whereas A. welwitschiae was most common in the clinical samples.