Gram-Negative Bacterial Overgrowth Predominated by: Potential Association with Intestinal Barrier Impairment and Inflammatory Diarrhea in Cats

Abstract

Simple Summary Feline diarrhea is a common gastrointestinal disease in veterinary clinics. It is hypothesized that dysbiosis of Gram-negative bacteria serves as a critical predisposing factor for this disease; however, in vivo evidence confirming that such microbiota triggers intestinal inflammation and disrupts intestinal barrier function remains scarce. In this study, fecal microbiota from diarrheic cats was transplanted into antibiotic-pretreated mice to investigate its impacts on host intestinal health. The results demonstrated that fecal microbes from diarrheic cats reduced body weight in mice, induced infiltration of neutrophils and macrophages in colonic tissues, and elicited intestinal inflammation together with intestinal barrier injury. 16S rRNA sequencing revealed that the relative abundance of Escherichia–Shigella in feces of diarrheic cats were markedly higher than that in healthy cats. Quantitative assays also verified a significantly increased load of fecal Gram-negative bacteria in diarrheic cats. Collectively, fecal microbiota from diarrheic cats is capable of inducing intestinal inflammation and barrier damage in mice. Overproliferation of Gram-negative bacteria, represented mainly by Escherichia–Shigella, is closely associated with the occurrence of feline diarrhea.