Study of the complete trh gene sequence in clinical, environmental and food isolates of Vibrio parahaemolyticus from European countries

Vibrio parahaemolyticus is a natural inhabitant of estuarine and coastal environments, part of the natural biota of bivalve molluscs and a human pathogen that can be transmitted through consumption of raw or undercooked... [ view full abstract ]

Vibrio parahaemolyticus is a natural inhabitant of estuarine and coastal environments, part of the natural biota of bivalve molluscs and a human pathogen that can be transmitted through consumption of raw or undercooked seafood.

Foodborne infections caused by V. parahaemolyticus harbouring the tdh or both tdh and trh genes are relatively more common than those caused by V. parahaemolyticus tdh-/trh+ strains. This work extends a previous study on partial trh gene sequences amongst tdh-/trh+ V. parahaemolyticus isolates of different origin collected in Italy by: sequencing the entire trh gene of Italian isolates and relating these to MLST types; performing trh gene sequencing of isolates from bivalve molluscs from UK or clinical samples from other European countries; comparing trh sequences of tdh-/trh+ V. parahaemolyticus isolates of this study with trh  sequences of tdh-/trh+ V. parahaemolyticus isolates from public database.

Sequencing analysis of the entire trh gene of 19 and 16 tdh-/trh+ V. parahaemolyticus isolates from Italy and UK, respectively, revealed the presence of the trh2 variant in all isolates. Some variability was identified in the trh sequences of the Italian isolates, while 15 of the 16 isolates from a survey in UK had identical trh sequences. Isolates sharing the same MLST Sequence Type possessed identical trh sequences. The trh2 of the Italian clinical isolate grouped with other clinical tdh- /trh2 V. parahaemolyticus from Europe, USA or Canada.