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Fumonisin B 1 (FB 1 ) is a mycotoxin that commonly occurs in maize. FB 1 causes a variety of toxic effects in different animal species and has been implicated as a contributing factor of esophageal cancers in humans. In the present study, we examined the effect of dietary exposure to FB 1 on intestinal colonization by pathogenic Escherichia coli associated with extraintestinal infection. Three-week-old weaned pigs were given FB 1 by gavage as a crude extract or as a purified toxin at a dose of 0.5 mg/kg of body weight daily for 6 days. On the last day of the toxin treatment, the pigs were orally inoculated with an extraintestinal pathogenic E. coli strain. All animals were euthanized 24 h later, necropsies were performed, and tissues were taken for bacterial counts and light microscopic examination. Ingestion of FB 1 had only a minimal effect on animal weight gain, did not cause any macroscopic or microscopic lesions, and did not change the plasma biochemical profile. However, colonization of the small and large intestines by an extraintestinal pathogenic E. coli strain was significantly increased. Our results show that FB 1 is a predisposing factor to infectious disease and that the pig can be used as a model for the study of the consequences of ingesting mycotoxin-contaminated food.

The decomposition of ochratoxin A (OTA) was examined, under different temperature and moisture conditions. The calculated half-lives, corresponding to 50% values, were 707, 201, 12, and 6 min, respectively, at 100, 150, 200, and 250؇C for dry wheat and 145, 60, and 19 min, respectively, at 100, 150, and 200؇C for wheat heated under wet conditions. The presence of water (50%) increased the decomposition of OTA at 100 and 150؇C; the opposite was observed at 200؇C. Complete destruction of OTA within the limits of this study (100 to 250؇C) was not obtained.

Fumonisin B1 (FB1) is a mycotoxin from Fusarium moniliforme that is frequently associated with corn. Thermal treatments are used in many processes concerning this cereal and its derivatives. The thermostablity of this toxin in dry contaminated corn, resulting from F. monUiforme culture, was studied in different time-temperature combinations. FB1 was quantified by instrumentalized thin-layer chromatography after a two-step sequential development and postchromatographic derivatization byp-anisaldehyde. The identity of FB1 in extracts, before and after heat treatments, was confirmed by high-pressure liquid chromatography. For each temperature, the natural logarithm of the ratio of resulting FB1 on initial content (In C/Co) is linearly correlated to exposure time. The calculated half-lives (L50), corresponding to the 50%o value, were 10 min, 38 min, 175 min, and 8 h at 150, 125, 100, and 75°C, respectively. There is a linear relationship between calculated Lsos on a logarithmic scale and temperature. Therefore FB1 is not significantly destroyed by the main drying processes of corn or thermal treatments used for its derivatives. Other associated means are required for detoxification.

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Diacetoxyscirpenol and deoxynivalenol, two trichothecene mycotoxins shown previously to exert immunosuppressive effects on the immune system were examined for their in vitro effects on some functions of murine peritoneal macrophages. The cells were pre-incubated for 4 hr with the mycotoxin concentrations of 0.1 ng/ml-1 micrograms/ml. At concentrations that did not affect the cell viability (Specific Lactate Dehydrogenase test), diacetoxyscirpenol and deoxynivalenol suppress microbicidal activity of phagocytic cells. The diacetoxyscirpenol concentrations, which reduce phagocytosis (2 ng/ml), microbicidal activity (1 ng/ml), superoxide anion production (1 ng/ml) and phagosome-lysosome fusion (0.1 ng/ml), indicate that the inhibition of killing mechanism arise from both oxidative and non-oxidative pathways. Phagocytosis, microbicidal activity and superoxide anion production are inhibited by deoxynivalenol at 1 ng/ml whereas phagosome-lysosome fusion is reduce above 100 ng/ml. These results suggest that microbicidal activity inhibition by deoxynivalenol did not depend on non-oxidative pathway (phagosome-lysosome fusion) impairment.

The occurrence of a few cases of equine leuko-encephalomalacia in France has indicated a potentially widespread, low-level contamination of corn by fumonisins. To develop strategies for prevention, biotic and abiotic factors in fumonisin B1 (FB1) production and stability were investigated. The potential for FB1 production from 2 groups of Fusarium moniliforme strains was tested in corn cultures. The first group consisted of 48 strains that were previously isolated from corn, asparagus, watermelon, and vanilla. The second group consisted of 25 strains that were freshly isolated from corn. Respective frequencies in the first and second groups of strains and in each toxigenic class were as follows: 23 and 0%, <50 μg/g; 16 and 12%, 50–200 μg/g; 23 and 4%, 200–800 μg/g; 33 and 68%, 800–3200 μg/g; and 5 and 16%, >3200 μg/g. The initial rate of FB1 production decreased in the following order of temperature: 20, 25, 15, 30, 10°C. FB1 was not detected at 5, 35, or 40ΰC. Also, no FB1 was detected in confined atmosphere at 25°C during 10 weeks. Significant amounts (>200 μg/g) of FB1 were produced within 12 days, in laboratory conditions, with moisture contents of corn frequently encountered at harvest (≥27%). Thermal decomposition of FB1 in dried corn culture followed a first-order reaction. Half-life times at 150, 125, and 100°C were 10, 38, and 175 min, respectively. Therefore, contamination of foods and feeds by this stable mycotoxin is, theoretically, a permanent threat.

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