Selective Survival of a Thermostable Direct Hemolysin-Producing Vibrio parahaemolyticus in the Alimentary Tract of a Juvenile Estuarine Gastropod (Clithon retropictus)

Abstract

Juvenile estuarine gastropods (Clithon retropictus), maintained in ultraviolet ray-irradiated recirculating artificial seawater with a salinity of 20% at 28°C, preserved thermostable direct hemolysin (TDH)-producing strain D-3 of Vibrio parahaemolyticus at a level of 10⁴-10⁵ colony forming units per gram (cfu/g) and TDH-non-producing strains N-18 and R-13 at a level of 10¹-10² cfu/g in the alimentary tract for at least 21 days after ingestion. In adults, the numbers of the three strains decreased to a level of 10⁰ cfu/g within 21 days under the same conditions. This evidence supports our recent observations that TDH-producing strains increased to a high level in the summer months in the presence of high levels of TDH-non-producing strains in the alimentary tract of juvenile C. retropictus at estuaries in Japan.