The Role of Non-Helicobacter Pylori Bacteria in the Pathogenesis of Gastric Diseases

In the context of dysbiosis, chronic inflammation, and carcinogenesis, non-Helicobacter pylori bacteria are becoming more widely acknowledged as significant contributors to stomach diseases. The stomach contains a variety of bacterial communities, including Fusobacterium nucleatum, Streptococcus species, Lactobacillus species, Prevotella species, Veillonella species, and Propionibacterium acnes, according to studies employing next-generation sequencing. Because of adaptation processes like urease activity, acid-tolerant metabolism, and biofilm development, these organisms can survive in acidic environments. While some, like Lactobacillus, can create metabolites like lactic acid that may impact carcinogenic nitrosation reactions, others, including F. nucleatum and Streptococcus, cause inflammation through immune activation and cytokine production. A known stomach carcinogen, N-nitroso compound, may be formed more frequently if nitrate-reducing bacteria proliferate. Following H. pylori eradication, dysbiosis frequently involves elevated abundance of these taxa, which may impact stomach cancer risk and mucosal integrity. The need for more comprehensive microbiome-targeted therapeutic approaches is highlighted by mounting evidence that non-H. pylori bacteria interact either antagonistically or synergistically with H. pylori and host factors, causing intestinal metaplasia, gastritis, and tumour progression, even though causality is still being investigated.