Epidemiological evidence of lesser role of thermostable direct hemolysin (TDH)-related hemolysin (TRH) than TDH on Vibrio parahaemolyticus pathogenicity.

Vibrio parahaemolyticus carrying the tdh gene, encoding the thermostable direct hemolysin (TDH), or the trh gene, encoding the TDH-related hemolysin (TRH), are both considered virulent strains. There are, however, disproportionally fewer reports of infections caused by seafood contaminated with trh-positive strains than by seafood contaminated with tdh-positive strains. Bivalves such as clams and oysters are the major seafood varieties associated with the infections.

Characteristics of bacterial and fungal growth in plastic bottled beverages under a consuming condition model.

Microbial contamination in unfinished beverages can occur when drinking directly from the bottle. Various microorganisms, including foodborne pathogens, are able to grow in these beverages at room temperature or in a refrigerator. In this study, we elucidated the characteristics of microorganism growth in bottled beverages under consuming condition models.

[Histamine formation in Japanese marine fish species and the effect of frozen storage].

To investigate histamine formation in Japanese marine fish, model samples were made from fish meat mixed with intestines of commercial 73 fish species. After the samples were stored at 25℃ for 12 hr, histamine was detected in 35 fish species at 50 mg/kg or more. These fish species might potentially be related to histamine poisoning.

Development of a density slicer for the simple collection of respective density layers after stepwise density gradient centrifugation.

Density gradient centrifugation (DGC) is useful for the separation of living microbial cells from food samples that are not filterable. After DGC, however, careful operation is necessary to collect each density layer. For a simple and reproducible collection after DGC, we have developed a seamless operation system composed of a 5-needle unit, a microchannel plate, and a microflow controller, and named this a density slicer system.

Separation of viable histamine-producing bacteria from yellowtail meat components by density gradient centrifugation.

Quantitative separation of live cells from food samples is essential for non-culture methods to be validated. In this viewpoint, the feasibility of density gradient centrifugation (DGC) was demonstrated for the first time using samples of yellowtail meat to which Morganella morganii, a histamine producing bacterium had been added. Using a Ficoll density gradient from 50 to 10 w/v % with 10 w/v % steps, meat-free fractions of M.