To investigate the pathogenicity of viable but non-cultivable state (VBNC) Vibrio parahaemolyticus (Vp) from salmon consumed raw, the isolated strain VBNC-VpRS1 and the virulent strain Vp17802 were separately orally administered to C57BL/6J mice. The behavior of the mice was observed for the following 72 h, and the disease activity index (DAI) score, Vp load, intestinal damage, tight junction (TJ) protein expression and cytokine levels were measured. It was found that symptoms of infection with VBNC-VpRS1 appeared six hours later than those of infection with Vp17802. Compared with the control group, infection with VBNC-VpRS1 and Vp17802 significantly increased the DAI score, colonic Vp load and the levels of proinflammatory cytokines in mice (P < 0.01 and P < 0.001), and significantly decreased the colon length, anti-inflammatory factor levels and TJ protein expression (P < 0.01, P < 0.001 and P < 0.05). The infected mice showed severe intestinal mucosal tissue defects with hemorrhagic effusion and neutrophil infiltration. Moreover, the colonic Vp load and the degree of pathologic damage in the mice infected with VBNC-VpRS1 were higher than (P < 0.05) those in the mice infected with Vp17802, whereas VBNC-VpRS1 was less effective than Vp17802 in inhibiting the intestinal barrier function and promoting inflammatory responses (P < 0.05). VBNC-VpRS1 can be resuscitated in vivo and has strong colonic adhesion and invasion abilities. As VBNC Vp seriously threatens human health, seafood products consumed raw should be included in the monitoring of Vp.

Fish oil (FO) can modulate the gut ecosystem and improve intestinal health, but the specific role and mechanism of FO in preventing foodborne pathogen infection are still unclear. In this study, the effect of FO on enteritis damage and intestinal gene expression profiles in Vibrio parahaemolyticus (Vp) infected mice was investigated. The disease activity index (DAI) score, the colonic histopathological score (HIS), the expression of intestinal fibrosis biomarkers (type I and type III collagen), the contents of the cytokines interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α(TNFα), the activities of the antioxidant enzymes catalase (AT), superoxide dismutase (SOD) and total antioxidant enzymes (TAE) and the colonic gene expression profiles in the mouse model of Vp infection were measured before and after FO intervention. The results showed that gavage with 4.0 mg/d FO significantly reduced DAI scores and HIS, and alleviated colonic pathological damage. FO could also significantly down-regulate the expression of intestinal fibrosis-related proteins (P< 0.05), maintain intestinal barrier functions, and inhibit cytokine-mediated excessive inflammation and oxidative stress. Thus, FO reduced body damage induced by Vp infection by altering the gene expression pattern in the colon, up-regulating the gene expression of peroxisome proliferator activated receptor (PPAR), enriching the PPAR signaling pathway, and inhibiting the nuclear factor-κB signaling pathway. Hence, dietary supplementation of FO can protect the body against foodborne pathogens.

To investigate the metabolic characteristics of salmon muscle consumed raw under fluctuating temperature chilled conditions, differential metabolites in salmon samples stored for different periods (0, 4 and 9 days) at 4 or 10 ℃ were analyzed by ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS)-based metabolomics combined with multivariate statistical analysis. Results showed that the composition of metabolites was significantly different between fresh and stored salmon at each temperature (P < 0.05), and the difference was more obvious in samples stored at 10 ℃. By orthogonal partial least squares-discriminant analysis (OPLS-DA), 47 and 62 differential metabolites were identified between fresh salmon and samples stored at 4 and 10 ℃, respectively, including lipids and lipid-like compounds, amino acids and their derivatives, organic acids and their derivatives, nucleotides and their derivatives. Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis and metabolic path mapping showed that the biosynthesis of amino acids was the important metabolic pathway for salmon samples stored at 4 ℃. L-Histidine and L-tryptophan were involved in more metabolic pathways and, therefore, could be used as metabolic markers for raw salmon stored at 4 ℃. Additionally, the energy metabolism pathway was the major metabolic pathway for salmon samples stored at 10 ℃, and L-histidine, pyruvate, linolenic acid and purine metabolites played important roles and thus could be used as metabolic markers for raw salmon stored at 10 ℃.

The protective effect of Bacillus subtilis JZXJ-7 (JZXJ-7) on Vibrio parahaemolyticus (Vp) infected mice was investigated. Totally 28 male C57BL/6J mice were randomly divided into four groups: a Vp infection model group (infected with the standard virulence strain ATCC33847), two JZXJ-7 intervention groups (administered at low (10⁶ CFU) and high (10⁸ CFU) doses by gavage), and a control group. The control and model groups were administered with an equal volume of normal saline. Disease activity index (DAI), Vp load in the intestine tract (including the ileum, cecum, and colon), colonic pathological alterations, colonic cytokine contents, oxidative stress resistance, and changes in intestinal microbial community composition were detected in all groups. The results showed that the protective effect of JZXJ-7 was better at the high dose than at the low dose. High-dose JZXJ-7 significantly reduced the DAI and intestinal Vp load in Vp infected mice, alleviated inflammatory cell infiltration and collagen deposition, and increased the number of intestinal epithelial goblet cells (P < 0.05). Moreover, high-dose JZXJ-7 significantly inhibited cytokine-mediated inflammation, increased antioxidant enzyme activities and enhanced intestinal permeability. Furthermore, JZXJ-7 significantly increased (P < 0.05) intestinal microbial diversity, partially reversing intestinal flora disturbance, enriching Akkermansia, Bifidobacterium, Clostridium and other beneficial bacteria, and thus resulting in the restoration of intestinal microecological homeostasis. In summary, JZXJ-7 can effectively alleviate colonic pathological damage in Vp infected mice and maintain intestinal functions, and the underlying mechanism may be related to its regulatory effect on the intestinal microbiota.