Submitted to: Journal of Applied Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/8/2009
Publication Date: 1/15/2010
Citation: Probst, C., Schulthess, F., Cotty, P.J. 2010. Impact of the Aspergillus Section Flavi Community Structure on the Development of Lethal Levels of Aflatoxins in Kenyan Maize (Zea mays). Journal of Applied Microbiology. 108:600-610. Interpretive Summary: Aflatoxins are poisonous metabolites of fungi that may contaminate several crops. Aflatoxin contamination of maize is a recurring problem in Kenya. Consumption of contaminated maize has killed several hundred people in 2004. The goal of the current study was to determine if the fungal community structure is an important contributor to the aflatoxin contamination that caused the Kenyan deaths. Fungal communities associated with maize were contrasted between provinces with aflatoxicosis and without. Individual Aspergillus isolates were screened for aflatoxin-producing ability and to evaluate the association of the fungal community structure with aflatoxicosis. An unusual fungal community structure was associated with the lethal contamination events. The results indicate the target through which aflatoxin management practices could be directed to prevent future outbreaks in Kenya and elsewhere.
Technical Abstract: Maize is the main staple for most of Kenya’s population. Fungal contamination events that lead to inedible and toxic crops have been frequently reported in Kenya. In order to gain insight on the fungal community structure capable of producing aflatoxins we analyzed maize samples that were collected in four Kenyan provinces with histories of repeated lethal aflatoxicoses. Maize samples were collected from Eastern and Central Kenya as well as the Rift Valley and Coastal region between 2004 and 2006. Aspergillus Section Flavi isolates were recovered from the maize by dilution plate technique on modified rose Bengal agar. The majority of the isolated aflatoxin-producing fungi belonged to Aspergillus flavus. The strain composition within A. flavus varied greatly between provinces, with the S strain being dominant in semi-arid regions and the L strain being dominant in tropical-humid regions. Aspergillus parasiticus and A. nomius were also detected, with the latter making up less than 0.001% of all isolates. To further clarify relationships among isolates from Kenya and morphologically similar isolates collected in West Africa, North America and Asia, phylogenetic studies were conducted.