Assessment of aflatoxigeinic Aspergillus species in food commodities from local market of Addis Ababa

Abstract

Background: Contamination of food commodities with spoilage fungi presents a problem of global concern, since the growth and metabolism of these organisms can cause serious food-borne illnesses and a rapid spoilage of food products. Aspergillus species, a type of opportunistic fungi linked to food spoilage is the leading cause of infection, mycotoxicosis and economic loss. Mycotoxins that produce are responsible for cancers and many diseases affecting the gastrointestinal, urogenital, vascular, kidney, and nervous systems. Within the African region, aflatoxin is a threat to public health. In parts of sub-Saharan Africa about 250,000-hepatocarcinoma-related deaths occur annually due to aflatoxin ingestion alone. Because the impact is so devastating, there should be continuous assessment mechanisms to monitor the occurrence of aflatoxigenic strains of Aspergillus species in food commodities. Objective: To assess the occurrence of aflatoxigenic Aspergillus species in food commodities collected from Addis Ababa. Method: The isolation of aflatoxin producing species of Aspergillus from food commodities sold in Addis Ababa market was investigated. A total of 108 food samples were bought from markets within Addis Ababa. All samples were separately analyzed for the presence of aflatoxigenic Aspergillus species. The isolation of these species was carried out using dilution plating and/or direct plating methods. Morphological and culture characters, along with secondary metabolite profiles derived from thin-layer chromatography, were used to sort and identify Aspergillus species cultured on potato dextrose and sabaroud dextrose agar along with their aflatoxin-producing potentials on SMKY medium. Result: A total of 90 Aspergillus species (A. flavus, A. parasiticus, A. niger and A. fumigatus) were isolated from 108 samples of food commodities. The least number (5 isolates of Aspergillus species isolates were counted from the sample cookies while the highest (19 isolates) were counted from both the peanut and emmer wheat flour samples. From 33 Aspergillus flavus isolates 9 isolates (27.3%) were isolated from the peanut sample, while the fewest were isolated from the pea flour and cookies sample (n=3 (9.1%)). Six out of eighteen samples of peanut, emmer wheat flour, maize, and roasted barley were contaminated with Aspergillus niger, accounting (22.2%). A total of 21 (23.3%) isolates of Aspergillus species produced aflatoxin in vitro in SMKY broth culture out of 90 different Aspergillus species isolated from food commodities. Among the aflatoxigenic species isolated, Aspergillus flavus were responsible for the majority of cases (66.67%) followed by Aspergillus parasiticus (33.33%). None of the Aspergillus fumigatus isolates were found to produce aflatoxin in vitro on SMKY broth medium. Within species, 36.36% of Aspergillus flavus isolates were found to produce aflatoxin in vitro, while 18% of Aspergillus parasiticus isolates produced aflatoxin in vitro on culture media. Conclusion: Our study conducted to evaluate the presence of toxigenic strains of Aspergillus species in food commodities in Addis Ababa, has indicated the presence of these strains. Further studies should be done to quantify the level of aflatoxin in food commodities and also to evaluate the presence of potential mycotoxigenic fungi other than Aspergillus species in commercial food commodities.