Background: Porcine enterotoxigenic Escherichia coli (ETEC) is one of the primary pathogens causing severe diarrhea in piglets. The main pathogenic factors of this strain are K88ac, K99, and 987P proteins. Methods: The K88ac or K99-987P sequence was used to replace the central part of the AcmA gene, and the cell wall anchor-expressing recombinant pNZ8149-MD/Lactobacillus lactisstrain was constructed. The Usp45 signal peptide, dendritic cell-targeting peptide, and TAT sequence were added to the terminal, and the secretory protein-expressing recombinant pNZ8149-XDT /L.lactis strain was constructed. Mice were immunized with the recombinant strains, and mouse K88, K99, 987P, IgG, sIgA antibodies; IFN-γ; and IL-4 levels were quantified. Results: The experimental group showed increased levels of these immune proteins. sIgA level increased drastically, and the levels of K88, K99, 987P, IgG, and IL-4 also increased significantly. Immunized mice were challenged with a strain of ETEC. The XDT feeding group showed the lowest mortality rate, lower symptom score, lower levels of inflammatory cytokines IL-6 and TNF-α, and milder pathological changes, thus adequately protecting the mice from ETEC infection. Limitations: It remains unclear whether the vaccine can protect pigs from infection with ETEC. Conclusion: The XDT feeding vaccine with K88 or K99-987P antigen was developed.

To better guide microbial risk management and control, growth kinetic models of Salmonella with the coexistence of two other dominant background bacteria in pork were constructed. Sterilized pork cutlets were inoculated with a cocktail of Salmonella Derby (S. Derby), Pseudomonas aeruginosa (P. aeruginosa), and Escherichia coli (E. coli), and incubated at various temperatures (4–37 °C). The predictive growth models were developed based on the observed growth data. By comparing R2 of primary models, Baranyi models were preferred to fit the growth curves of S. Derby and P. aeruginosa, while the Huang model was preferred for E. coli (all R2 ≥ 0.997). The secondary Ratkowsky square root model can well describe the relationship between temperature and μmax(all R2 ≥ 0.97) or Lag (all R2 ≥ 0.98). Growth models were validated by the actual test values, with Bf and Af close to 1, and MSE around 0.001. The time for S. Derby to reach a pathogenic dose (105 CFU/g) at each temperature in pork was predicted accordingly and found to be earlier than the time when the pork began to be judged nearly fresh according to the sensory indicators. Therefore, the predictive microbiology model can be applied to more accurately predict the shelf life of pork to secure its quality and safety.