Aflatoxin B1 (AFB1) is one of the most hazardous mycotoxins contamination in food and feed products, which leads to hepatocellular carcinoma in humans and animals. In the present study, we isolated and characterized an AFB1 degrading bacteria CG1061 from chicken cecum, exhibited an 93.7% AFB1 degradation rate by HPLC. 16S rRNA gene sequence analysis and a multiplex PCR experiment demonstrated that CG1061 was a non-pathogenic Escherichia coli. The culture supernatant of E. coli CG1061 showed an 61.8% degradation rate, whereas the degradation rates produced by the intracellular extracts was only 17.6%, indicating that the active component was constitutively secreted into the extracellular space. The degradation rate decreased from 61.8 to 37.5% when the culture supernatant was treated with 1 mg/mL proteinase K, and remained 51.3% when that treated with 100°C for 20 min. We postulated that AFB1 degradation was mediated by heat-resistant proteins. The content of AFB1 decreased rapidly when it was incubated with the culture supernatant during the first 24 h. The optimal incubation pH and temperature were pH 8.5 and 55°C respectively. According to the UPLC Q-TOF MS analysis, AFB1 was bio-transformed to the product C16H14O5 and other metabolites. Based on the results of in vitro experiments on chicken hepatocellular carcinoma (LMH) cells and in vivo experiments on mice, we confirmed that CG1061-degraded AFB1 are less toxic than the standard AFB1. E. coli CG1061 isolated from healthy chicken cerum is more likely to colonize the animal gut, which might be an excellent candidate for the detoxification of AFB1 in food and feed industry.

Enterotoxigenic Escherichia coli (ETEC) is primary pathogenic bacteria of piglet diarrhea, over two thirds of piglets diarrhea caused by ETEC are resulted from STa-producing ETEC strains. This experiment was conducted to construct the recombinant E. coli expressing STa and study the injury and mechanism of recombinant E. coli expressing STa on 7 days old piglets colon. Twenty-four 7 days old piglets were allotted to four treatments: control group, STa group (2 × 109 CFU E. coli LMG194-STa), LMG194 group (2 × 109 CFU E. coli LMG194) and K88 group (2 × 109 CFU E. coli K88). The result showed that E. coli infection significantly increased diarrhea rates; changed DAO activity in plasma and colon; damaged colonic mucosal morphology including crypt depth, number of globet cells, density of lymphocytes and lamina propria cell density; substantially reduced antioxidant capacity by altering activities of GSH-Px, SOD, and TNOS and productions of MDA and H2O2; obviously decreased AQP3, AQP4 and KCNJ13 protein expression levels; substantially altered the gene expression levels of inflammatory cytokines. Conclusively, STa group had the biggest effect on these indices in four treatment groups. These results suggested that the recombinant strain expressed STa can induce piglets diarrhea and colonic morphological and funtional damage by altering expression of proteins connect to transportation function and genes associated with intestinal injury and inflammatory cytokines.

Enterotoxigenic Escherichia coli (ETEC) is a common enteric pathogen that causes diarrhoea in humans and animals. Lactobacillus rhamnosus LB1 (formerly named Lactobacillus zeae LB1) has been shown to reduce ETEC infection to Caenorhabditis elegans and Salmonella burden in pigs. This study was to evaluate the effect of L. rhamnosus LB1 on the gut health of lactating piglets that were challenged with ETEC. Six-four piglets at 7 days of age were equally assigned into 8 groups (8 piglets per group): 1) control group (basal diet, phosphate buffer saline); 2) CT group (basal diet + 40 mg/kg colistin); 3) LL group (basal diet + 1 × 107 CFU/pig/day LB1); 4) HL group (basal diet + 1 × 108 CFU/pig/day LB1); 5) ETEC group: (basal diet + ETEC challenged); 6) CT + ETEC group (basal diet + CT + ETEC); 7) LL + ETEC group (basal diet + 1 × 107 CFU/pig/day LB1 + ETEC); 8) HL + ETEC group (basal diet + 1 × 108 CFU/pig/day LB1 + ETEC). The trial lasted ten days including 3 days of adaptation. Several significant interactions were found on blood parameters, intestinal morphology, gene, and protein expression. ETEC infection disrupted the cell structure and biochemical indicators of blood, undermined the integrity of the intestinal tract, and induced oxidative stress, diarrhoea, intestinal damage, and death of piglets. The supplementation of L. rhamnosus LB1 alleviated ETEC’s adverse effects by reducing pig diarrhoea, oxidative stress, and death, modulating cell structure and biochemical indicators of blood, improving the capacity of immunity and anti-oxidation stress of pigs, and restoring their intestinal integrity. At the molecular level, the beneficial effects of L. rhamnosus LB1 appeared to be mediated by regulating functional related proteins (including HSP70, Caspase-3, NLRP3, AQP3, and AQP4) and genes (including RPL4, IL-8, HP, HSP70, Mx1, Mx2, S100A12, Nrf2, GPX2 and ARG1). These results suggest that dietary supplementation of L. rhamnosus LB1 improved the intestinal functions and health of piglets.

This study was conducted to investigate the effect of Lactobacillus zeae LB2 on the gut microbiota in piglets infected with enterotoxigenic Escherichia coli (ETEC). Thirty-two healthy 7-day-old piglets were randomly divided into four treatment groups: control group (basal diet), LB2 group (supplemented with 1 × 10⁸ CFU/pig/day L. zeae LB2), ETEC group (infected with 1 × 10¹⁰ CFU/pig/day ETEC) and ETEC+LB2 group (LB2 supplementation + ETEC infection). Intestinal contents were collected for DNA extraction and Illumina sequencing. Significant result was observed for alpha diversity in the four intestinal sections, and both ETEC infection and LB2 supplementation showed a higher Chao1 alpha diversity. At the phylum level, Firmicutes and Bacteroidetes were dominant in the healthy piglets, while Proteobacteria were dominant in the ETEC-infected piglets. At the genus level, ETEC infection decreased the abundance of Prevotella, Ruminococcaceae, Lactobacillus, Alloprevotella, Flavobacterium, and Sutterella and increased the abundance of Actinobacillus. The LB2 supplementation reduced the abundance of Ruminococcaceae, Actinobacillus, Porphyromonas, and Alloprevotella, and increased the abundance of Prevotella and Lactobacillus. Both ETEC infection and LB2 supplementation affected several functional pathways associated with cellular processes, environmental information processing, genetic information processing, diseases, metabolism, and organismal systems. In summary, ETEC infection induced dysbiosis of the gut microbiome in piglets, while L. zeae supplementation could positively regulate the gut microbiome during ETEC infection. Therefore, L. zeae LB2 may be an ideal probiotic for the prevention or treatment of ETEC infection.

This research was to investigate beneficial impact and molecular mechanism of B. coagulans on piglets intestine. Twenty-four 21 days old weaned piglets were allotted to three treatments: control group (basal diet), B6 group (basal diet + 2×10 6 CFU/g B. coagulans), B7 group (basal diet + 2×10 7 CFU/g B. coagulans).The results showed that compared with control group, B6 and B7 group significantly decreased diarrhea rate and the concent of CHOL, GGT and DAO in plasma; decreased villus height and increase crypt depth in jejunum and ileum; increased the activities of SOD and CAT and decreased the concent of MDA and H2O2 in intestine. These data suggested that supplementing B. coagulans had beneficial impacts on promoting nutrients metabolism, maintaining intestinal integrity and alleviating oxidative stress and diarrhea. Futher research of molecular mechanisms showed that, these beneficial impacts were regulated by changing expression levels of related proteins (including HSP70, Caspase-3, Bax, Villin and Occludin), and genes (including RPL4, MX1, MX2, OAS1, AQP3, LPL, INSR and b 0,+ AT), and altering community composition of gut microbiota (particularly family Clostridiaceae, Enterobacteriaceae, and Veillonellaceae and genus Prevotella, Turicibacter, and Lactobacillus).