Mycotoxin fumonisin B1 increases intestinal colonization by pathogenic Escherichia coli in pigs

Abstract

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.

FIG. 1.

In situ visualization of bacteria in colon tissue by immunohistochemistry using an anti-O75 serum and Vector red staining. Piglets were treated with FB₁ (A), or left untreated (B), inoculated with E. coli strain 28CNal^r, and euthanized 24 h postinoculation. (A) Bacteria, stained red on direct microscopic observation, were found in aggregates closely associated with the colon surface epithelium (arrow) and in the serosa (arrowhead). (B) Similar bacteria were occasionally found individually associated with the colon surface epithelium (arrow) but not in the serosa. Bar size, 100 μm.