Abstract
As a multifactorial cause, gastric ulceration-mediated diarrhea is widely prevalent in the weaned piglets, impairing pig health and economic benefits. With full implementation of antibiotic stewardship programs in China, Bacillus cereus (B. cereus) and Aspergillus fumigatus (A. fumigatus) were identified frequently in porcine feedstuffs and feeds of the animal industry. Association between feed-borne B. cereus and frequent diarrhea remains unclear. In the present study, we conducted a survey of B. cereus and A. fumigatus from feeds and feedstuffs in pig farms during hot season. Interestingly, B. cereus, B. subtilis, B. licheniformis and B. thuringinesis were isolated and identified from piglets’ starter meals to sow feeds, accounting for 56.1%, 23.7%, 13.7% and 6.5%, respectively. Obviously, both B. cereus and B. subtili were dominant contaminants in the survey. In an in vitro study, Deoxynivalenol (DON) contents were determined in a dose-dependent manner post fermentation with B. cereus (405 and DawuC). Subsequently, 36 weaned piglets were randomly assigned to four groups and the piglets simultaneously received the combination of virulent B. cereus (Dawu C) and A. fumigatus while animals were inoculated with B. cereus (Dawu C), A. fumigatus or PBS as the control group. Clinically, piglets developed yellow diarrhea on day 5 and significant reductions of relative body weight were observed in the B. cereus group, and co-infection group. More importantly, IgG titers against Classical swine fever virus (CSFV) and Porcine epidemic diarrhea (PED) were reduced dramatically during 14-day observation in co-infection group, the B. cereus (Dawu C) group or the A. fumigatus group. However, lower Foot and mouth disease (FMD) -specific antibodies were reduced on day 7 compared to those of the control group. Additionally, lower lymphocyte proliferations were found in the B. cereus group and the co-infection group compared to the control group. Postmortem, higher lesions of gastric ulceration were observed in the B. cereus group and the co-infection group from day 7 to day 14 compared with those of the A. fumigatus group and the control group. Compared to the A. fumigatus group, higher DON contents were detected in the stomach inoculated with B. cereus and the co-infection with A. fumigatus. In conclusion, our data support the hypothesis that B. cereus might be associated with severe diarrhea by inducing gastric ulcerations and A. fumigatus might aggravate immune suppression, threating a sustainable swine industry. It is urgently needed to control feed-borne B. cereus contamination.
Highlights
Diarrhea induced by gastric ulceration has been observed frequently both in poultry flock and livestock in the past decades
Extensive research confirms that the intoxicated emetic syndrome is caused by an emetic toxin, termed cereulide, the diarrheal syndrome is associated with pore-forming cytotoxins hemolysin HBL (Hbl), nonhaemolytic enterotoxin (Nhe) and cytotoxin K (CytK) [8]
B. cereus and B. subtilis Were Highly Contaminated in Swine Feed
Summary
Diarrhea induced by gastric ulceration has been observed frequently both in poultry flock and livestock in the past decades. As a common opportunistic pathogen involved in food poisoning, B. cereus causes vomiting and diarrhea in humans frequently, which seriously leads to death [5,6]. Extensive research confirms that the intoxicated emetic syndrome is caused by an emetic toxin, termed cereulide, the diarrheal syndrome is associated with pore-forming cytotoxins hemolysin HBL (Hbl), nonhaemolytic enterotoxin (Nhe) and cytotoxin K (CytK) [8]. It is known as a pathogen, B. cereus is licensed as a pesticide for agricultural plants and probiotics for animal additives. The virulent Bacillus spp and other emerging pathogens in animal-used probiotics pose an emerging threat to food safety
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