Regional Distribution of Fusarium Verticillioides in Mexico and Its Implications in Animal, Human Nutrition and Health
Abstract
This study was designed to investigate the presence of Fusarium species in Mexican corn. Maize samples from 26 States were analyzed. Corn kernels were cultivated following a sequence of cultivation methods until obtaining spores which were transferred to carnation leaf agar medium. Taxonomic identification of fungi was carried out by microscopic examination. To evaluate the in vitro production of fumonisin B1, it was experimentally induced in un-contaminated maize. The quantitative determination of fumonisin B1 in the maize samples was performed by thin layer chromatography. Quality control and sensitivity were established using a standard solution of commercial origin whose purity was corroborated by both thin-layer chromatography and high-performance liquid chromatography.
Thirty-eight strains were isolated; 29 corresponded to Fusarium verticillioides and 9 to Fusarium subglutinans. Strains of Fusarium verticillioides exhibited a variable behavior in fumonisin B1 production. 4 strains produced fumonisin B1 in a range of 3.12 to 6.57 ppm.
In conclusion, two species of Fusarium; Fusarium verticillioides and Fusarium subglutinans were found in maize from 26 States of Mexico, their distribution is regionalized. Strains found in five States produced fumonisin B1 in concentrations that can be considered clinically relevant.
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Introduction
The fungi of the Fusarium genus are considered important food pollutants due to the deleterious effects they produce in vivo and the economic losses they cause during grain harvest and storage, both by reducing the food quality and by the production of mycotoxins (1). Fusarium verticillioides (moniliforme) and Fusarium proliferatum are two species that occur worldwide and are associated with infections in corn (2). Both species are known to produce the mycotoxins fumonisin B1, fumonisin B2 and fumonisin B3 (3), which have been stated to be associated with several diseases in animals and in humans (4-12). Fumonisin B1 is the major mycotoxin produced by Fusarium verticillioides (13) and related species (14) and is found most frequently in corn.
Some researchers have referred to the fumonisin B1 as the cause of equine leukoencephalomalacia with neurotoxic effects and hepatic damage (1). In addition, maize infected with Fusarium verticillioides that has been included in the diet or injected in animals in an experimental way exhibits cancer-promoting activity in rats (8) and in other animals such as swine, poultry, and rabbits causing pulmonary edema, hepatic necrosis and bone marrow cells disorder syndromes, respectively (15-18), in chicken embryos severe hemorrhages where evident after exposure to fumonisin B1 (19). Fusarium verticillioides has been suggested to be associated with esophageal cancer. It has been isolated frequently from some regions of China and southern Africa, where the highest incidences of human esophageal cancer have been reported (9-11). Fumonisin B1 has been detected in corn, corn forage, mash and tortillas from several states of Mexico, which may represent health risk for humans or animals (20-23). In addition, it has been found that the isolated strains of corn from the northwest region are strains that produce high fumonisin B1 levels (24). During the last 10 years, veterinarians from several academic institutions in Mexico have observed gross and microscopic lesions of equine leukoencephalomalacia in horses suffering from a nervous syndrome. In Oaxaca, horses that ingested corn containing fumonisin B1 died from equine leukoencephalomalacia (25). Such findings suggest the possibility of distribution of Fusarium fungi and fumonisin B1 throughout Mexico. This study was designed to investigate the presence of Fusarium species in Mexican corn and to evaluate the in vitro production of fumonisin B1 by this species of fungi.
Conclusion
In conclusion, two species of Fusarium; Fusarium verticillioides and Fusarium subglutinans were found in maize from 26 States of the Mexican Republic. About 50 % of the isolated strains produced toxins variable degree. Four States of the northeast region have strains with low production of fumonisin B1, which contrasts with previous results where this region was considered a high producer of this toxin. In addition, it was also found that in nine States there were non-producing strains of fumonisin B1. However, the south-central and southwestern regions, considered to be of low production, also betray an important change, since isolated strains in Oaxaca and Morelos produced fumonisin B1 in quantities of public health importance that exceeds that established by the FDA for corn intended for human consumption.
