A polyphasic method for the identification of aflatoxigenic Aspergillus species isolated from Camel feeds

The main goal of our study was to identify Aspergillius spp. isolates by polyphasic taxonomic techniques. Differential culture media, biochemical and molecular characterization were applied to 21 isolates of Aspergillus flavus and Aspergillus niger from Saudi Arabia camel feeds. Six aflatoxin producing culture media were used for characterizing and identifying aflatoxigenic isolates. The blue fluorescent ring visible under UV light which indicates the ability to produce aflatoxin, by aflatoxinogenic strains was not observed for any of the tested non aflatoxigenic isolates. Biochemical characterization involving the screening of the isolates for five aflatoxins was also performed. As found, most isolates were capable of producing detectable levels of both B and G type's aflatoxins (AFs) and maltoryzine, although 4 of the 7 A. niger isolates failed to produce any detectable amount of AFs. PCR was performed using one set of primers that specifically targets the aflatoxin regulatory gene (aflR) involved in aflatoxin biosynthetic pathway as well as four specific primers for A. flavus and A. niger. The presence of the aflR gene did not correlate with aflatoxigenicity. Most of the fungi belonging to A. flavus group reacted positively with aflR primers that cover the region from 540 to 1338 of aflatoxin regulatory gene with product size of 798 base pairs (bp). All A. flavus isolates had positive PCR results using the primer pair FLA1-FLA. A unique DNA fragment of the expected 500-bp size was amplified in all A. flavus isolates, while no PCR products were visualized in other Aspergillus species or members belong to other fungal genera. Using the primer pairs OMt1R-OMt1F, a single fragment of about 1232 bp A. niger isolates was amplified but did not amplify with DNA extracted from other Aspergillus species or species belonging to other fungal genera. Detection and quantification of these two important aflatoxin-producing Aspergilli could provide important information to predict the aflatoxin profiles which may be present in the feed matrix. © 2013.