Klebsiella pneumoniae (KP) is an important opportunistic pathogen that can persist in the gastrointestinal tract and serve as a reservoir for subsequent infection. The increasing prevalence of multidrug-resistant KP highlights the need for non-antibiotic strategies to limit intestinal KP burden and associated host injury. Lactiplantibacillus plantarum GUANKE (L. plantarum GUANKE) is a candidate probiotic strain with reported effects on mucosal barrier protection and inflammatory regulation, but its role in intestinal KP challenge remains unclear. In this study, the effects of L. plantarum GUANKE and its metabolite phenyllactic acid (PLA) on KP growth, intestinal KP burden, and associated inflammatory injury were investigated using antibacterial assays in vitro, metabolomic analyses, an antibiotic-pretreated mouse model of intestinal KP challenge, and an influenza A virus (IAV)/KP intestinal co-exposure model. L. plantarum GUANKE and its culture-derived products inhibited KP growth in vitro. Metabolomic analysis identified PLA as a metabolite enriched in L. plantarum GUANKE fermentation supernatants, and exogenous PLA directly inhibited KP growth in a dose-dependent manner. In an antibiotic-pretreated mouse model of intestinal KP challenge, oral administration of L. plantarum GUANKE reduced intestinal KP burden and was associated with changes in gut microbiota composition, increased cecal PLA abundance, improved intestinal barrier-related parameters, and reduced inflammatory responses, while exogenous PLA partially reproduced these effects. IAV infection increased susceptibility to intestinal KP expansion, and oral L. plantarum GUANKE reduced KP burden in the IAV/KP intestinal co-exposure model. In mice challenged with multidrug-resistant KP strain NK04152, L. plantarum GUANKE and PLA reduce intestinal KP burden and associated tissue injury in mice, supporting their potential as candidate microbiota and metabolite strategies against intestinal KP challenge.

Background: The global prevalence of hyperuricemia (HUA) has increased worldwide, and probiotics are considered an adjunctive treatment with fewer side effects. However, the effective strains and underlying mechanisms are not well understood. Objective: This study aimed to investigate the role of Lacticaseibacillus paracasei SUB12 (SUB12) in alleviating HUA and elucidate its potential molecular mechanisms. Methods: In this study, a HUA mouse model was established using potassium oxonate and adenine to evaluate the uric acid-lowering effect of SUB12. High-throughput metabolomics and 16S rRNA sequencing were used to identify key metabolites and altered microbiota. Results: Oral administration of SUB12 significantly reduced serum UA level, hepatic xanthine oxidase (XOD) activity, and renal inflammation and altered uric acid transport-related proteins. Sequencing analysis suggested that SUB12 not only had the capacity of consuming succinate but also reduced the abundance of succinate-producing Prevotellamassilia. Succinate supplementation significantly promoted XOD activity through the succinate receptor 1 (SUCNR1)/hypoxia-inducible factor 1-alpha (HIF-1α) axis. Conclusions: Our findings reveal that SUB12 attenuates hyperuricemia by down-regulating succinate, which promotes XOD activity and uric acid production through the SUCNR1/HIF-1α/XOD axis.