Proteobacteria: A Toolbox for Clinicians

Proteobacteria are a phylum of Gram-negative bacteria that, although normally a minor component of the healthy gut microbiota, can be markedly increased in many conditions. Their overgrowth is in fact linked to inflammation, impaired epithelial barrier function, and diseases such as inflammatory bowel disease, metabolic syndrome, and gastrointestinal cancers. Key species, like Escherichia coli and Helicobacter pylori, can promote disease through specific etiopathogenetic mechanisms, from genotoxin production to immune activation: this peculiarity can be used for diagnostic purposes, and in some cases even as therapeutics. Emerging microbiota-targeted therapies-such as dietary modulation, probiotics, fecal microbiota transplantation, bacteriophages, and engineered bacteria-aim to restore microbial balance. This narrative review deals with the dual role of Proteobacteria as both pathogens and diagnostic-therapeutic tools, which is crucial for advancing personalized microbiome-based medicine.