Characterization of Pathogens and Mycotoxins Associated with Cyperus Esculentus L. (Tiger Nuts) Sold in Ibadan, Oyo State, Nigeria

Tiger nuts (Cyperus esculentus) are a minor but important tuber crop noted mostly by their aphrodisiac properties that are consumed as a snack, due to their rich flavor and texture. Though consumed raw, if exposed to microbial contamination when handling impose public health. This present study therefore was aimed at determining the mycotoxin level and distribution of parasitic, bacterial, and fungal contaminants associated with tiger nuts (Cyperus esculentus) sold in ten major markets in Ibadan, Oyo state Nigeria. Two types of intestinal parasites were identified, Entamoeba Histolytica (37.5%) and Ascaris Lumbricodes (62.5%). Nuts contaminated with parasites were found only in six markets (Bodija, Oja-Oba, Molete, Oje, Agbeni and Ojo). Bacteriological examination showed five different groups of bacterial isolates (Pseudomonas putida, Klebsiella pneumoniae, Bacillus cereus, Escherichia coli, and Staphylococcus aureus) with the most prevalent being Staphylococcus aureus. Unlike parasites, bacteria isolates were found among samples from all the ten major markets. Antibiogram of bacterial isolates revealed a varying level of resistance and susceptibility to the antibiotics tested. In this current study, Bacillus cereus and Escherichia coli were the only isolates seen to be highly susceptible to all the antibiotics tested. However, Pseudomonas putida was seen resistant to ampicillin and Staphylococcus aureus was seen resistant to iminipem. Based on the result of these findings, it can be concluded that the bacterial isolates had varying levels of resistance to the antibiotics tested. The antibiotic resistance pattern expressed by the isolates from the tiger-nut samples is suggestive of possible abuse of antibiotics and that the consumption of this nut poses a potential public health threat. The fungal analysis from the test tiger nuts (Cyperus esculentus) samples revealed the presence of three fungal species: Aspergillus flavus, Aspergillus fumigatus and Aspergillus niger. Aspergillus niger and Aspergillus fumigatus had the same percentage occurrence (31.25%) while the highest occurrence was seen in Aspergillus flavus (37.50%). The highest TFC (17 log10 CFU/mL) was recorded from tiger nut samples from Orita-Aperin market while the lowest TFC (6 log10CFU/mL) was obtained in samples from Oje market. The occurrence of these fungi may cause diverse effects on human health, as they have the potential to produce mycotoxins. In this study, twenty-four different mycotoxins were analyzed in the tiger nuts samples. Of all the mycotoxins tested, Aflatoxin B1 had the highest occurrence which was seen only in two of the major markets; Gbagi market sample (95.7ug/kg) and the Ojo market sample (33.03ug/kg), and they are seen to be above the permissible limits set up by NAFDAC (20ug/kg). In conclusion, buying and eating nuts as well as other fruits taken raw from street vendors and marketplaces could pose a significant public health threat. There is a need for efficient monitoring systems for food-borne pathogens in Ibadan, Oyo state.