Polyphasic approach for differentiating Penicillium nordicum from Penicillium verrucosum

Abstract

The aim of this research was to use a polyphasic approach to differentiate Penicillium verrucosum from Penicillium nordicum, to compare different techniques, and to select the most suitable for industrial use. In particular, (1) a cultural technique with two substrates selective for these species; (2) a molecular diagnostic test recently set up and a RAPD procedure derived from this assay; (3) an RP-HPLC analysis to quantify ochratoxin A (OTA) production and (4) an automated system based on fungal carbon source utilisation (Biolog Microstation™) were used. Thirty strains isolated from meat products and originally identified as P. verrucosum by morphological methods were re-examined by newer cultural tests and by PCR methods. All were found to belong to P. nordicum. Their biochemical and chemical characterisation supported the results obtained by cultural and molecular techniques and showed the varied ability in P. verrucosum and P. nordicum to metabolise carbon-based sources and to produce OTA at different concentrations, respectively.

Keywords:

• high-performance liquid chromatography
• polymerase chain reaction
• ochratoxin A
• meat

Acknowledgements

The authors would like to thank Biolog, Inc. Company and, in particular, Mr Fabio Zenna for skilled technical assistance and for providing part of the material used for biochemical characterisation of the strains tested. The authors are indebted to Dr Rolf Geisen and Dr Cristina Varese for providing some of the P. verrucosum strains and to Dr Antonio Bodini for English revision of the manuscript.