tdh

tdh is an acronym that in microbiology most often refers to the thermostable direct hemolysin gene found in Vibrio parahaemolyticus, a Gram-negative marine bacterium associated with seafood-borne illness. The tdh gene encodes thermostable direct hemolysin, a pore-forming toxin that contributes to cytolysis and enterotoxic effects, helping to cause gastroenteritis in humans.

Virulence and detection: tdh-positive strains are commonly linked with more severe disease and have been used as a molecular marker for pathogenic V. parahaemolyticus. The Kanagawa phenomenon, a beta-hemolysis reaction on Wagatsuma (Kanagawa) agar, historically served as a phenotypic indicator of tdh expression, though not all tdh-positive strains display the reaction and vice versa. Modern detection relies on PCR assays targeting the tdh gene.

Genomic context: In V. parahaemolyticus, tdh is frequently discussed together with trh (TDH-related hemolysin). The presence of either gene is used, in part, to assess the virulence potential of isolates, but disease outcome depends on multiple factors including infectious dose and host susceptibility.

Other uses: The acronym tdh may appear in other disciplines with different meanings; this article focuses on the microbiological gene. For disambiguation, context should be used.