Advances in the molecular diagnosis of ochratoxin A-producing fungi

Ochratoxin A (OTA) is detected worldwide in various food and feed sources. The compound is produced by Penicillium nordicum and P. verrucosum, as well as by various species within the sections Nigri and Circumdati of the genus Aspergillus, with A. ochraceus and A. carbonarius known to be the predominant producers. Recently, various pairs of PCR primers based on AFLP, RFLP, RAPD and the calmodulin gene were developed to set up novel diagnostic approaches for OTA producers in the Aspergillus and Penicillium genera. Real-time PCR assays based on well-characterized genomic sequences in A. ochraceus and P. nordicum have also been set up. Since the application of such assays to the analysis of contaminated sample material was demonstrated in only a few cases, future studies should be focused on applying such methods in rapid, robust and user-friendly applications, and implementing them in HACCP concepts. The recent detection and characterization of OTA biosynthetic pathway genes in the Penicillium genus is an important step towards understanding what mechanisms influence production of the toxin in order to redesign production processes in the food and feed industry and to keep de-novo synthesis to a minimum.