Background: Shigellosis is an illness that affects young children all over the world and Shigella flexneri is one of the most common pathogens. The aim of this study was to investigate a potential beneficial effect of Weizmannia coagulans Long45 supplementation on feline-derived Shigella flexneri-induced colitis in mice, as well as potential mechanisms. Results: The results revealed that mice receiving fecal microbiota from diarrheic cats experienced significant weight loss, decreased survival rate, increased mRNA levels of inflammatory cytokines (TNF-α, IL-4, IFN-γ, IL-1β, IL-6, and IL-18), and increased cell apoptosis compared to the single DSS treatment. In contrast, mice that received fecal microbiota from healthy cats exhibited an increased body weight, increased mRNA level of ZO-1, claudin-3, and Muc2 and decreased apoptosis, indicating a protective effect. The 16S rDNA analysis revealed that the abundance of Shigella in the feces of diarrheic cats was significantly higher than that in healthy cats, while the abundance of Bacillus was lower. Using bacteria culture technology, 19 strains of Shigella flexneri were isolated from 27 fecal samples of diarrheic cats and a strain of Weizmannia coagulans Long45 was isolated from the feces of healthy cats. Further study showed that Weizmannia coagulans Long45 significantly alleviated pathological alterations and colonic barrier dysfunction by modulating the NF-κB and Nrf2 signaling pathways. Conclusions: Our data indicate that feline-derived Shigella flexneri may be a potential pathogen associated with diarrhea and intestinal barrier dysfunction. Weizmannia coagulans Long45, as a potential probiotic, can effectively alleviate Shigella-induced colitis by interfering with the Nrf2 and NF-κB signaling pathways.

Background: Canine intestinal sensitivity is a multifactorial functional gastrointestinal disorder characterized by recurrent soft feces, impaired nutrient utilization, and low-grade intestinal inflammation, and it acts as a major trigger for chronic gastrointestinal discomfort in dogs. Conventional antibiotic therapy causes side effects and drug resistance. Probiotics modulate host physiology, immunity, and metabolism, serving as promising alternatives for improving canine intestinal health. This study aimed to compare the gut microbiota of healthy and sensitive German shepherd dogs, screen and identify candidate probiotics, and verify their efficacy in ameliorating canine intestinal dysfunction and hypersensitivity. Results: Fecal microbiota transplantation from healthy dogs effectively improved these fecal indicators and was associated with enhanced serum antioxidant and anti-inflammatory capacities in intestinal-sensitive dogs (p < 0.05). Additionally, 16S rRNA sequencing revealed that healthy German Shepherd dogs had higher intestinal microbial α- and β-diversity, with Pediococcus acidilactici enriched in healthy dogs and Shigella increased in diarrheic dogs (p < 0.05). P. acidilactici Long21 intervention, either alone or combined with its fermentation supernatant, significantly improved fecal traits; reduced pathogenic bacterial abundance; increased the apparent digestibility of dry matter, crude fibre, and ether extract; and was associated with normalized antioxidant function and inflammatory indicators in German Shepherd dogs with intestinal sensitivity (p < 0.05). We identified 2085 differentially abundant metabolites enriched in amino-acid and energy metabolism using untargeted metabolomics, with glutamate, malate, and pyruvate as hub metabolites correlated with nutrient digestibility and fecal traits. Conclusions: Intestinal flora imbalance is associated with intestinal sensitivity-related diarrhea in dogs. P. acidilactici Long21 supplementation alleviated intestinal sensitivity-associated diarrhea and improved intestinal health, possibly through coordinated changes in gut microbiota, metabolic profiles, and nutrient utilization. These findings provide a theoretical basis and a candidate strain for microecological intervention, although causal mechanisms remain to be confirmed.

Itaconic acid has been reported to possess anti-inflammatory and antibacterial properties. However, its specific mechanisms of action against pathogenic bacteria, especially in the context of purine metabolism, remain poorly understood. Here, we investigate the impact of itaconic acid on the purine metabolism of PCN033, a highly pathogenic porcine extraintestinal pathogenic Escherichia coli (ExPEC) strain. Our in vitro and in vivo experiments demonstrated that itaconic acid significantly inhibited the proliferation of PCN033. Multi-omics analyses, including transcriptome and metabolome sequencing, revealed that itaconic acid severely disrupted the purine metabolism pathway of PCN033. Further mechanistic studies identified PRPP amidotransferase (PurF), a key enzyme in de novo purine synthesis, as a direct target of itaconic acid. Molecular docking and click chemistry experiments provided compelling evidence that itaconic acid specifically binds to the second cysteine residue (2C) of PurF, leading to the inhibition of its enzymatic activity. These data reveal a novel and critical mechanism by which itaconic acid exerts its antibacterial effects in response to bacterial infection. Importantly, our in vivo data show that supplementation with itaconic acid alleviated weight loss, organ damage, and inflammatory responses induced by PCN033 infection in mice and nursery pigs. These novel findings enhance our understanding of the antibacterial mechanisms of itaconic acid. Supplementation with itaconic acid could serve as a therapeutic strategy for treating pathogenic bacterial infections in humans and other animals.

Background: Feline diarrhea is one of the most common gastrointestinal disorders encountered in veterinary clinics. Dysbiosis of Gram-negative bacteria is widely presumed to be a key cause of this disease, yet adequate in vivo evidence demonstrating its roles in provoking inflammation and impairing intestinal barrier integrity is still lacking. In this study, we investigated the effects of bacterial flora in cats with diarrhea on gut health in mice. Results: The results show the following: (1) Microorganisms in feces of diarrheal cats can cause weight loss in antibiotic-treated mice; the histopathological section of the colon showed that neutrophil aggregation occurred in the colon of mice in the fecal bacteria transplantation group; this indicates that gavage using fecal microbes from diarrheic cats could impair intestinal barrier integrity in antibiotic-treated recipient mice. (2) In addition, microbes in cats with diarrhea can induce inflammation in the colon and aggregation of macrophages, which may be caused by some Gram-negative bacteria in feces of cats with diarrhea. (3) The composition of the intestinal microbial community was analyzed by 16S rRNA gene sequencing, and it was found that the relative abundance of Escherichia–Shigella in feces of cats with diarrhea was significantly higher than that of normal cats. (4) Quantitative analysis of fecal samples revealed that diarrheic cats exhibited a significantly higher load of fecal Gram-negative bacteria compared with healthy cats, verifying that excessive colonization of Gram-negative bacteria may be highly correlated with feline diarrhea. Conclusion: In summary, fecal microbes from diarrheic cats are capable of triggering intestinal inflammation and barrier damage in antibiotic-treated mice. Excessive proliferation of Gram-negative bacteria, mainly Escherichia–Shigella species, may be highly associated with feline diarrhea.

Background: The occurrence of dysentery has received widespread attention. However, the occurrence of dysentery may be caused by many factors, among which poor sanitation is the main cause of dysentery. However, whether family pets are the cause of dysentery is still unclear. In this study, we investigated the effects of bacterial flora in cats with diarrhea on gut health in mice. Results: The results showed as following: 1) Microorganisms in feces of diarrheal cats can cause weight loss of germ-free mice; the histopathological section of the colon showed that neutrophil aggregation occurred in the colon of mice in the fecal bacteria transplantation group, and Occludin expression of tight junction protein significantly increased, which confirmed that microorganisms in feces of diarrheal cats have the ability to destroy intestinal barrier integrity; 2) In addition, microbes in cats with diarrhea can induce inflammation in the colon and aggregation of macrophages, which may be caused by some gram-negative pathogenic bacteria in feces of cats with diarrhea; 3) The composition of intestinal microbial community was analyzed by 16sRNA sequencing, and it was found that the abundance of Shigella in feces of diarrhea cats was significantly higher than that of normal cats; 4) We then verified by agarose electrophoresis with specific primers of Shigella, and found that the detection rate of Shigella reached 81.48%. Since Shigella is a typical gram-negative bacterium that activates the TLR4/NF-kB signaling pathway through lipopolysaccharide, we conclude that Shigella is the core pathogen mediating the damage of weight loss and intestinal inflammation in mice. Conclusion: These findings confirmed for the first time that domestic cats may be a potential carrier of Shigella, and provided an important theoretical basis for improving the prevention and control system of zoonotic infectious diseases.