- Helicobacter pylori strain 26695 is one of the most widely studied and referenced strains in the field of microbiology and infectious disease research.
- It was originally isolated from a female patient suffering from gastritis in the United Kingdom.
- This strain gained international prominence when it became the first H. pylori strain to be fully sequenced, published in 1997 by the Sanger Centre. The availability of its complete genome, consisting of approximately 1.67 million base pairs and encoding around 1,590 proteins, marked a major milestone in the study of H. pylori biology and laid the groundwork for large-scale comparative genomic analyses.
- The genome of 26695 revealed a highly dynamic and recombinogenic nature, with a substantial number of strain-specific genes, mobile genetic elements, and repetitive DNA sequences, all contributing to the extraordinary genomic plasticity of H. pylori.
- Strain 26695 is characterized by the presence of several key virulence factors. It harbors a complete and functional cag pathogenicity island (cagPAI), which encodes a type IV secretion system responsible for translocating the CagA oncoprotein into host gastric epithelial cells. Upon delivery, CagA becomes phosphorylated at EPIYA motifs, enabling it to interact with SHP-2 and other host signaling proteins, ultimately altering cell morphology and promoting pro-inflammatory and potentially oncogenic pathways. Strain 26695 carries the Western-type CagA, with EPIYA-C motifs, which are less oncogenic than the East Asian variants but still contribute significantly to pathogenicity.
- Additionally, this strain produces a fully active Vacuolating cytotoxin A (VacA), with the s1/m1 genotype, known to cause epithelial cell vacuolation, immune modulation, and enhanced bacterial persistence.
- In terms of phenotypic behavior, 26695 demonstrates strong adherence to gastric epithelial cells, induces interleukin-8 (IL-8) secretion, and triggers cytoskeletal rearrangements, making it a robust model for studying host-pathogen interactions.
- It also possesses a functional BabA adhesin, which binds to Lewis b blood group antigens on host cells, contributing to colonization and host specificity. Its naturally competent nature allows for high-efficiency transformation, making it a preferred choice for genetic manipulation, including the generation of knockouts and reporter constructs.
- In research, H. pylori 26695 serves as a reference strain for genomic annotation, virulence studies, and comparative analyses. Its genome has been used extensively to identify conserved and strain-specific genes among H. pylori isolates from different geographic regions and disease backgrounds. Numerous studies have utilized 26695 to understand the molecular mechanisms of CagA-dependent signaling, VacA-mediated cellular damage, and host immune evasion. It has also been a cornerstone in the development of molecular tools, including microarrays, CRISPR-based systems, and RNA interference approaches adapted for H. pylori.
- Despite its importance, it is worth noting that strain 26695 does not represent the full spectrum of H. pylori diversity, particularly the highly virulent East Asian strains. Nevertheless, it remains a foundational model organism for H. pylori research. Its historical role, genetic tractability, and well-characterized virulence profile continue to make it a central tool for unraveling the pathogenesis of this globally prevalent pathogen.
