Pancreatic ductal adenocarcinoma (PDAC) remains one of the most aggressive and lethal human malignancies, with five-year survival rates showing only marginal improvement despite decades of intensive research. Its dismal prognosis reflects a combination of intrinsic biological aggressiveness, late clinical presentation, and marked resistance to standard therapies, underscoring the urgent need for innovative diagnostic and therapeutic approaches. Growing evidence indicates that the microbiome is a modifiable factor influencing the onset, progression, and treatment response of PDAC. Microbial communities originating from the gut, oral cavity, and even the tumor microenvironment can shape carcinogenic pathways, modulate immune activity, and alter the efficacy of chemotherapy and immunotherapy. In addition to bacteria, fungal and viral populations are emerging as relevant contributors within this complex ecosystem. This review provides a comprehensive overview of the current mechanistic and translational evidence linking the microbiome to PDAC biology and therapy. It further explores microbiota-targeted interventions—such as probiotics, postbiotics, engineered bacterial strains, bacteriophages, oncolytic viruses, and fecal microbiota transplantation—as promising adjuncts to conventional treatments. A deeper understanding of host–microbiome interactions could yield novel biomarkers and open innovative avenues for precision medicine in PDAC, ultimately improving patient outcomes and reshaping therapeutic paradigms. Integrating microbiome-based strategies into PDAC management may thus represent a crucial step toward more effective and personalized oncologic care.

This narrative review explores the intricate dynamics of Small Intestinal Bacterial Overgrowth (SIBO), a condition marked by an excessive growth of bacteria in the small intestine. We delve into the multifaceted etiology of SIBO, including its associations with gastrointestinal disorders, motility issues, and alterations in gut architecture. The review examines current diagnostic methodologies, emphasizing the distinctions between breath testing and direct aspiration techniques. Furthermore, we assess the various treatment approaches, ranging from antibiotics and dietary modifications to emerging therapeutic options. By synthesizing the latest research findings, we aim to enhance understanding of SIBO’s implications for gut health and provide insights into effective management strategies.

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.