Aspergillus tubingensis and Aspergillus niger as the dominant black Aspergillus, use of simple PCR-RFLP for preliminary differentiation

This work aimed to identify the species distribution of common clinical and environmental isolates of black Aspergilli based on simple restriction fragment length polymorphism (RFLP) analysis of the P-tubulin gene. A total of 149 clinical and environmental strains of black Aspergilli were collected and subjected to preliminary morphological examination. Total genomic DNAs were extracted, and PCR was performed to amplify part of the beta-tubulin gene. At first, 52 randomly selected samples were species-delineated by sequence analysis. In order to distinguish the most common species, PCR amplicons of 117 black Aspergillus strains were identified by simple PCR-RFLP analysis using the enzyme Tasl. Among 52 sequenced isolates, 28 were Aspergillus tubingensis, 21 Aspergillus niger, and the three remaining isolates included Aspergillus uvarum, Aspergillus awamori, and Aspergillus acidus. All 100 environmental and 17 BAL samples subjected to Tasl-RFLP analysis of the beta-tubulin gene, fell into two groups, consisting of about 59% (n = 69) A. tubingensis and 41% (n = 48) A. niger. Therefore, the method successfully and rapidly distinguished A. tubingensis and A. niger as the most common species among the clinical and environmental isolates. Although tardy, the Ehrlich test was also able to differentiate A. tubingensis and A. niger according to the yellow color reaction specific to A. niger. A. tubingensis and A. niger are the most common black Aspergillus in both clinical and environmental isolates in Iran. PCR-RFLP using Tasl digestion of B-tubulin DNA enables rapid screening for these common species. (C) 2016 Elsevier Masson SAS. All rights reserved.