ARS | Publication request: Aflatoxin-Producing Aspergillus Species from Thailand

Submitted to: International Journal of Food Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 25, 2006
Publication Date: September 1, 2006
Citation: Ehrlich, K., Kobbeman, K., Montalbano, B.G., Cotty, P.J. 2007. Aflatoxin-Producing Aspergillus Species from Thailand. International Journal of Food Microbiology. 114:153-159.

Interpretive Summary: Aflatoxin contamination of food materials caused by Aspergillus molds is a worldwide problem. Aflatoxins are highly toxic and cause cancer. To be able to prevent aflatoxin contamination, it is important to recognize what molds are the main contaminants of foods. There are 5 known species of Aspergillus that make aflatoxin. In the United States, the main producing organism is Aspergillus flavus. A. flavus only makes aflatoxin B1. In Thailand, previous research found that an unusual Aspergillus was found as a contaminant of foods. This mold made both aflatoxin B1 and aflatoxin G1. The researchers claimed that this mold was a type of A. flavus. We now show that an unusual type of A. nomius, a more rare type found in soil, is widespread in Thai soil. This mold looks and behaves like a type of flavus. We did not find any of the B and G type A. flavus. We conclude that this may be the first report that A. nomius should be carefully looked at as a possible source of crop contamination with aflatoxin.

Technical Abstract: Aflatoxin-producing Aspergillus species were isolated from soil samples from ten different regions within Thailand. A. flavus was present in soil samples from all of the regions, but unlike previous studies, we found no A. parasiticus or A. flavus isolates capable of both B and G production in any of the samples. A. pseudotamarii, which had not been previously reported from Thailand, was found in four soil samples. In two soil samples, A. nomius was the most abundant aflatoxin-producing species. Based on DNA sequence alignments for genes for Taka-amylase, the rRNA internal transcribed spacer (ITS), and the intergenic region for two genes involved in regulation of aflatoxin biosynthesis, aflJ and aflR, the A. nomius isolates separated into three well-supported clades. Some of the A. nomius isolates had morphological properties similar to those found for S-type isolates capable of B and G aflatoxin production and could easily be mistaken for these isolates.