Detection of Stachybotrys chartarum isolates from faba beans dust during threshing

Abstract

Stachybotrys (S.) chartarum had been related to dangerous health problems in animals and humans that take place when exposure to S. chartarum toxins. S. chartarum had been isolated from various substrates, ranging from inappropriately stored feed and culinary herbs to damp buildings. To evaluate the pathogenic potential of isolates, it is essential to identify them with different methods. The occurrence and genetic diversity of S. chartarum isolates from faba beans dust during threshing in Upper Egypt were investigated. Low counts of Stachybotrys were found (six isolates) and identified morphologically by single-spore isolation and molecularly by the amplification of the specific internal transcribed spacer (ITS) region and glyceraldehydes-3-phosphate dehydrogenase (gpd). The genetic diversity of the collected isolates was studied by specific genes random primer polymerase chain reaction (SGRP-PCR). The phylogenetic analysis of S. chartarum showed that the specific primers IT51 and StacR3 used by commercial laboratories for detecting S. chartarum were not able to differentiate species of S. chartarum from S. chlorohalonata and unweighted pair group method of arithmetic averages (UPGMA) cluster analysis of SGRP fragments confirmed this result. The six isolates of S. chartarum were analyzed for the presence of trichodiene synthase (Tri5) gene, which needed in the early stage of the trichothecene synthesis path. All the tested isolates were positive for the Tri5 gene. Further study on the taxonomic status of the epithet S. chartarum is necessary and presence of sub species to S. chartarum might be acceptable depending on the variations of morphological characteristics which were confirmed by molecular techniques.

Keywords: SGRP-PCR; Specific primers; Stachybotrys chartarum; Tri5 gene.