Aflatoxins in sunflower seeds: influence of Alternaria alternata on aflatoxin production by Aspergillus parasiticus

Mycotoxin production by Alternaria strains isolated from Argentinean wheat

The toxigenic potential of Alternaria strains isolated from Argentinean wheat was investigated. A total of 123 strains were assayed for the production of tenuazonic acid (TA), alternariol (AOH) and alternariol monomethyl ether (AME). All but one of the isolates were able to produce at least one of the three mycotoxins. TA was produced by 72% of the strains (1-14782 mg/kg), AOH by 87% (4-622 mg/kg) and AME by 91% (7-2625 mg/kg). The average level of TA detected for all strains (1757 mg/kg) was higher than the average level of both alternariols (162 mg/kg for AOH and 620 mg/kg for AME). TA was the toxin produced at the highest concentration but in lower frequency. Most of the strains were able to synthesize more than one toxin: 74 isolates (60%) were positive for all three toxins, 30 (24%) for both AOH and AME, 5 (4%) for both TA and AME, and 2 (2%) for TA and AOH. The widespread occurrence of Alternaria in wheat and its ability to produce mycotoxins suggests the possible occurrence of its toxins in wheat naturally infected with this fungus.

Risk from inhaled mycotoxins in indoor office and residential environments

Mycotoxins are known to produce veterinary and human diseases when consumed with contaminated foods. Mycotoxins have also been proposed to cause adverse human health effects after inhalation exposure to mold in indoor residential, school, and office environments. Epidemiologic evidence has been inadequate to establish a causal relationship between indoor mold and nonallergic, toxigenic health effects. In this article, the authors model a maximum possible dose of mycotoxins that could be inhaled in 24 h of continuous exposure to a high concentration of mold spores containing the maximum reported concentration of aflatoxins B1 and B2, satratoxins G and H, fumitremorgens B and C, verruculogen, and trichoverrols A and B. These calculated doses are compared to effects data for the same mycotoxins. None of the maximum doses modeled were sufficiently high to cause any adverse effect. The model illustrates the inefficiency of delivery of mycotoxins via inhalation of mold spores, and suggests that the lack of association between mold exposure and mycotoxicoses in indoor environments is due to a requirement for extremely high airborne spore levels and extended periods of exposure to elicit a response. This model is further evidence that human mycotoxicoses are implausible following inhalation exposure to mycotoxins in mold-contaminated home, school, or office environments.

IgE-reactive proteins from Stachybotrys chartarum

BACKGROUND

Stachybotrys chartarum has been associated with idiopathic pulmonary hemorrhage in infants. This is thought to be mycotoxin-related. There are increasing numbers of reports linking this fungus to the indoor environment of patients with other pulmonary problems, including allergies and asthma.

OBJECTIVE

Given the potential significance of this fungus as a pulmonary pathogen, this work evaluates the antigenic proteins of S. chartarum as to their molecular size and the prevalence of immunoglobulin (Ig)E and IgG directed against them in the general population.

METHODS

S. chartarum was isolated from a local home. S. chartarum for extract production was grown on minimum salts and glucose. Plasma from 132 healthy individuals was evaluated for IgE and IgG directed against S. chartarum using direct and inhibition enzyme immunoassay. The number and molecular size of those proteins that were bound by IgE from pooled sera known to contain IgE to S. chartarum were determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis immunoblotting.

RESULTS

Enzyme immunoassay indicated 65 of 132 (49.2%) sera tested contained IgG against S. chartarum and 13 of 139 (9.4%) sera tested contained IgE against S. chartarum. Pooled sera identified two IgE-binding proteins from extracts of S. chartarum spores and mycelia. These proteins are 34 and 52 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis immunoblot.

CONCLUSIONS

We conclude sensitivity to S. chartarum is potentially much more widespread than previously appreciated. This fungus may impact the asthmatic and allergic population through both immunologic and toxic mechanisms. Its significance in the milieu of allergenic fungi may need to be re-evaluated.

Microbial interaction ofAspergillus parasiticus andBacillus subtilis withalternaria alternata. production of alternariol, alternariol monomethylether and tenuazonic acid on sunflower seeds

Production of alternariol, alternariol mono-methylether and tenuazonic acid byAlternaría alternata was studied in competition withAspergillus parasiticus andBacillus subtilis on irradiated sunflower seeds at 0.90 aw.In cultures co-inoculated withAlternaría alternata andAspergillus parasiticus alternariol production decreased by 64%. Similar results were observed in cultures co-inoculated withAlternaría alternata andBacillus subtilis.

Inhibition of growth and mycotoxin production of Alternaria alternata inhabiting decayed fruits by pesticides

The effect of the two pesticides, cuprosan and sumi oil, on growth and mycotoxin production by two strains of Alternaria alternata isolated from decayed fruits was studied. Mycelial biomass of the two strains was significantly inhibited with most applied doses, however, cuprosan was most effective. Sumi oil exhibited significant inhibitory effect on the Alternaria strain isolated from decayed lemons, whereas, it suppressed mycelial biomass of that isolated from decayed tomatoes at only higher doses (250 ppm). Mycelial respiration of the two tested strains was mainly inhibited by most used does. However, CO2 evolution was occasionally promoted. Synthesis of alternariol (AOH) and its monomethyl ether (AME) by the examined strains was mainly inhibited by pesticide application in a manner similar to that of mycelial growth.