Early expression of the aflatoxin gene cluster in Aspergillus nomiae isolated from Brazil nut.

Aspergillus nomiae is the most important contaminant in Brazil nut due to its high incidence in these nuts and its strong production of carcinogenic metabolites: aflatoxins (AF). Aflatoxin biosynthesis pathway in A. nomiae is poorly studied. Thus, in present investigation, aflatoxin production and gene cluster (aflC, aflQ, aflU, and aflX) expression profile were evaluated on two strains of A. nomiae isolated from Brazil nut samples collected in the Amazon region, and cultivated on Brazil nut-based medium. The results showed that the expression of the aflatoxin gene cluster in A. nomiae, started at day 2 and occurred before the production of aflatoxins. Aflatoxin production (AFB1 and AFG1) was detected on day 3 on both strains. From day 4 onwards, all four toxins were detected and their production kept at similar proportions (AFG1>AFB1>AFG2>AFB2). Thus, the anticipated information obtained through early expression profile results of aflC, aflQ, aflU, and aflX gene cluster in A. nomiae may foresee aflatoxin production before its detection in Brazil nuts.

A non-toxigenic Aspergillus flavus strain prevents the spreading of Fusarium verticillioides and fumonisins in maize.

We evaluated Fusarium verticillioides and fumonisin contamination in maize samples after application of a non-aflatoxigenic Aspergillus flavus strain in the field. The sampling was performed 150 days after planting. The results showed a reduction in F. verticillioides frequency, as well as in fumonisin levels when samples were obtained from field areas treated with non-aflatoxigenic A. flavus strain. These results suggested a competition for substrate or space between fungi reducing the frequency of F. verticillioides and, consequently, fumonisin production.

Mycobiota and mycotoxins in Brazil nut samples from different states of the Brazilian Amazon region.

The objective of this study was to evaluate the presence of fungi and mycotoxins (aflatoxins and cyclopiazonic acid) in Brazil nut samples collected in different states of the Brazilian Amazon region: Acre, Amazonas, Amapá, and Pará. A total of 200 husk samples and 200 almond samples were inoculated onto Aspergillus flavus-parasiticus agar for the detection of fungi. Mycotoxins were analyzed by high-performance liquid chromatography. The mycobiota comprised the following fungi, in decreasing order of frequency: almonds - Phialemonium spp. (54%), Penicillium spp. (16%), Fusarium spp. (13%), Phaeoacremonium spp. (11%), and Aspergillus spp. (4%), husks - Phialemonium spp. (62%), Phaeoacremonium spp. (11%), Penicillium spp. (10%), Fusarium spp. (9%), and Aspergillus spp. A polyphasic approach was used for identification of Aspergillus species. Aflatoxins were detected in 22 (11%) of the 200 almond samples, with 21 samples presenting aflatoxin B(1) levels above 8µg/kg, the limit established by the European Commission for Brazil nuts for further processing. Nineteen (9.5%) of the 200 husk samples contained aflatoxins, but at levels lower than those seen in almonds. Cyclopiazonic acid (CPA) was detected in 44 (22%) almond samples, with levels ranging from 98.65 to 161.2µg/kg. Aspergillus nomius and A. flavus were the most frequent Aspergillus species. The presence of fungi does not necessarily imply mycotoxin contamination, but almonds of the Brazil nut seem to be a good substrate for fungal growth.

Toxicological effects of chronic low doses of aflatoxin B(1) and fumonisin B(1)-containing Fusarium moniliforme culture material in weaned piglets.

The effects of chronic oral exposure (28 days) to aflatoxin B(1) (AFB(1)) and fumonisin B(1) (FB(1)) were studied in weaned piglets. Six experimental groups, each comprising two neutered males and two females, were fed ad libitum with rations containing: (A) 0 mg of FB(1) and 0 mg of AFB(1)/kg of feed (control); (B) 10 mg of FB(1)/kg of feed; (C) 30 mg of FB(1)/kg of feed; (D) 50 microg of AFB(1)/kg of feed; (E) 10 mg of FB(1) plus 50 microg of AFB(1)/kg of feed; (F) 30 mg of FB(1) plus 50 microg of AFB(1)/kg of feed. The animals were inspected twice daily and their body weight and feed consumption were recorded weekly and daily, respectively. Samples of feces and urine were collected 24 h after the start of the experiment, to check for fumonisin residues by HPLC analysis. Blood samples were drawn at the start of the experiment and after 28 days for quantification of hematological and biochemical parameters. Necropsies were performed after 28 days; at necropsy, the organs were weighed, inspected macroscopically and processed for histopathological and toxicological analyses. All piglets from groups C and F presented typical signs of pulmonary edema, with reduced feed consumption and body weight gain as well as pathological alterations. FB(1) was detected in feces and urine at 24 h of intoxication and in liver after 28 days of intoxication. Increases were detected regarding the following hematological and biochemical parameters in animals from treatments C and F: erythrocyte number; hematocrit; total bilirubin; total protein; activity of serum alkaline phosphatase, aspartate aminotransferase, and alanine aminotransferase. Cholesterol levels were significantly aumented only in animals from groups C and F, whereas albumin concentrations increased in groups C, F, B and E. The average organ/body weight ratio of piglets (hearth, liver and lung) were significantly greater in groups C and F. The only joint effects of FB(1) and AFB(1) detected (group F) were a decrease in feed consumption during the last week of intoxication and in feed conversion throughout the 28 days of intoxication. Chronic intoxication of piglets with AFB(1) and FB(1) leads to important losses of productivity.