Toxigenic Fusarium spp. as Determinants of Trichothecene Mycotoxins in Settled Grain Dust

Trichothecenes are immunosuppressive mycotoxins produced mainly by Fusarium spp. and often are detected as natural contaminants of grain and other agricultural products. Exposure to trichothecenes through inhalation during grain work may represent possible health risks for grain farmers. We aimed, therefore, to investigate the level of Fusarium spp. and trichothecenes in settled grain dust collected during work on 92 Norwegian farms. Mycotoxins were determined by gas chromatography-mass spectrometry, whereas the Fusarium spp. were identified and quantified both by species-specific semiquantitative polymerase chain reaction (PCR) and by cultivation. All potential trichothecene-producing molds in the grain dust were quantified using a PCR assay specific for tri5, the gene coding for trichodiene synthase that catalyzes the first step in the trichothecene biosynthesis. We performed correlation analysis between mold-DNA and mycotoxins to assess whether the PCR-detected DNA could be used as indicators of the mycotoxins. The methodological problem of detecting small amounts of airborne mycotoxins during grain work may then be avoided. Whereas the trichothecene-producing Fusarium species in grain dust could not be identified or quantified to a sufficient extent by cultivation, all investigated Fusarium spp. could be specifically detected by PCR and quantified from the DNA agarose gel band intensities. Furthermore, we observed a strong correlation between the trichothecenes HT-2 toxin (HT-2) or T-2 toxin (T-2) and DNA specific for tri5 (r = 0.68 for HT-2 and r = 0.50 for T-2; p < 0.001), F. langsethiae (r = 0.77 for HT-2 and r = 0.59 for T-2; p < 0.001), or F. poae (r = 0.41 for HT-2 and r = 0.35 for T-2; p < 0.001). However, only a moderate correlation was observed between the trichothecene deoxynivalenol (DON) and the combination of its producers, F. culmorum and F. graminearum (r = 0.24, p = 0.02), and no significant correlation was observed between DON and tri5. PCR clearly improved the detection of toxigenic Fusaria as potential sources of health risks for farmers inhaling grain dust during work, but the use of Fusarium-DNA as indicators for trichothecenes should be used cautiously.

Keywords:

• Fusarium
• grain dust
• occupational exposure
• PCR
• trichothecenes
• tri5

ACKNOWLEDGMENTS

We thank Lene Madsø for valuable participation in collecting samples, and Grete Lund and Jafar Razzaghian for excellent technical assistance. We acknowledge the late Wenche Langseth for contributing her great knowledge of molds and mycotoxins in the early stages of this work. This study was supported by the Norwegian Research Council.

Notes

*p < 0.05

***p≤ 0.001.