cagAnegative

cagAnegative refers to Helicobacter pylori strains that do not carry the cagA gene, and therefore do not produce the CagA protein. The cagA gene is part of the cag pathogenicity island (cag-PAI), a cluster of virulence genes associated with the type IV secretion system.

CagA-positive strains can translocate CagA into gastric epithelial cells, where it disrupts signaling pathways, promotes inflammatory responses such as interleukin-8 production, and is implicated in increased risk of atrophic gastritis, ulcers, and gastric cancer. In contrast, cagA-negative strains are generally associated with lower virulence, and some epidemiological studies link cagA-negativity to milder gastritis and lower risk of peptic ulcer disease and gastric cancer, though disease can still occur with cagA-negative strains due to other virulence factors.

Detection of cagA status is typically performed by molecular methods such as PCR assays targeting the cagA gene, or sequencing of the cagA locus. Serological tests detect antibodies to CagA but do not reliably distinguish between infection with cagA-positive or cagA-negative strains in an individual; immunodetection can confirm CagA protein expression in cultured isolates.

Geographic and population differences influence cagA prevalence, with prevalence of cagA-positive strains varying widely by region. The cagA status of H. pylori has clinical relevance for risk stratification in some settings, but is not the sole determinant of disease outcome.