RESUMEN
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. In this study, the prevalence of strains possessing the tdh and trh genes was investigated in Japan in 74 samples collected in 2007-2008 and in 177 samples collected in 2010 of domestic bivalves, bloody clams, hen clams, short-neck clams, and rock oysters. The tdh-positive and trh-negative, tdh-negative and trh-positive, and tdh-positive and trh-positive samples represented 5.4%, 12.2%, and 4.1% of all samples collected in 2007-2008, and 5.1%, 18.6%, and 5.6% of all samples collected in 2010, respectively. As determined by polymerase chain reaction, the prevalence of tdh negative and trh positive in all samples was two to four times higher than that of tdh positive and trh negative. In the samples collected in 2010, the tdh-negative and trh-positive V. parahaemolyticus (20 samples) was more often isolated than tdh-positive and trh-negative V. parahaemolyticus (7 samples). The most common serotype of tdh-positive isolates (22 of 24 strains) was pandemic O3:K6. The trh-positive isolates (61 strains) were various serotypes including OUT:KUT. In 330 V. parahaemolyticus outbreaks and sporadic infections in Japan, most outbreaks and sporadic infections were caused by tdh-positive and trh-negative strains (89.4%). The frequencies of infections caused by tdh-negative and trh-positive, and both tdh- and trh-positive strains were 1.2% and 3.0%, respectively. This finding suggests that the virulence of trh might be less than that of tdh, although trh-positive V. parahaemolyticus frequently contaminated bivalves.
Asunto(s)
Proteínas Bacterianas/toxicidad , Bivalvos/microbiología , Proteínas Hemolisinas/toxicidad , Intoxicación por Mariscos/etiología , Mariscos/efectos adversos , Vibrio parahaemolyticus/patogenicidad , Factores de Virulencia/análisis , Animales , Arcidae/microbiología , Proteínas Bacterianas/análisis , Proteínas Bacterianas/química , Toxinas Bacterianas/análisis , Toxinas Bacterianas/química , Toxinas Bacterianas/toxicidad , Crassostrea/microbiología , Brotes de Enfermedades , Electroforesis en Gel de Campo Pulsado , Proteínas Hemolisinas/análisis , Proteínas Hemolisinas/química , Calor , Humanos , Japón/epidemiología , Tipificación Molecular , Reacción en Cadena de la Polimerasa , Estabilidad Proteica , Mariscos/análisis , Mariscos/economía , Mariscos/microbiología , Intoxicación por Mariscos/epidemiología , Intoxicación por Mariscos/microbiología , Vibriosis/epidemiología , Vibriosis/microbiología , Vibrio parahaemolyticus/clasificación , Vibrio parahaemolyticus/crecimiento & desarrollo , Vibrio parahaemolyticus/aislamiento & purificación , Virulencia , Factores de Virulencia/químicaRESUMEN
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. Furthermore, we provide insight into the safety of partially consumed bottled beverages with respect to food hygiene. We inoculated microorganisms, including foodborne pathogens, into various plastic bottled beverages and analysed the dynamic growth of microorganisms as well as bacterial toxin production in the beverages. Eight bottled beverage types were tested in this study, namely green tea, apple juice drink, tomato juice, carbonated drink, sport drink, coffee with milk, isotonic water and mineral water, and in these beverages several microorganism types were used: nine bacteria including three toxin producers, three yeasts, and five moulds. Following inoculation, the bottles were incubated at 35°C for 48 h for bacteria, 25°C for 48 h for yeasts, and 25°C for 28 days for moulds. During the incubation period, the number of bacteria and yeasts and visible changes in mould-growth were determined over time. Our results indicated that combinations of the beverage types and microorganism species correlated with the degree of growth. Regarding factors that affect the growth and toxin-productivity of microorganisms in beverages, it is speculated that the pH, static/shaking culture, temperature, additives, or ingredients, such as carbon dioxide or organic matter (especially of plant origin), may be important for microorganism growth in beverages. Our results suggest that various types of unfinished beverages have microorganism growth and can include food borne pathogens and bacterial toxins. Therefore, our results indicate that in terms of food hygiene it is necessary to consume beverages immediately after opening the bottle.
Asunto(s)
Bacterias/crecimiento & desarrollo , Bebidas/microbiología , Ingestión de Líquidos , Microbiología de Alimentos , Levaduras/crecimiento & desarrollo , Bacterias/aislamiento & purificación , Humanos , Concentración de Iones de Hidrógeno , Higiene/normas , Especificidad de la Especie , Temperatura , Levaduras/aislamiento & purificaciónRESUMEN
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 25â 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. In addition, the effect of frozen storage at -45â on histamine formation was examined. Although histamine was formed in some fish species, and Photobacterium damselae and Photobacterium iliopiscarium were isolated from the frozen samples, the amount of histamine formed in the model samples was reduced in all tested fish species after frozen storage. Therefore frozen storage of fish may be effective to control histamine formation, even though histamine forming bacteria survived under these conditions.
Asunto(s)
Productos Pesqueros/análisis , Contaminación de Alimentos/análisis , Almacenamiento de Alimentos , Congelación , Histamina/análisis , Animales , Productos Pesqueros/microbiología , Microbiología de Alimentos , Histamina/biosíntesis , Histamina/envenenamiento , Japón , Photobacterium/aislamiento & purificación , Photobacterium/metabolismo , Temperatura , Factores de TiempoRESUMEN
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. Two types of 5-needle units were devised and both showed nearly the same performance. Reproducible results with the automatic operation system could be demonstrated using an Escherichia coli cell suspension.
Asunto(s)
Técnicas Bacteriológicas/instrumentación , Separación Celular/instrumentación , Centrifugación por Gradiente de Densidad/métodos , Escherichia coli/aislamiento & purificaciónRESUMEN
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. morganii cells were collected in 20-50 w/v % layers. The total cell collection rate ranged from 73-86 % irrespective of the cell density in the range 10(2)-10(6) cells/200 microl.