Vibrio Parahaemolyticus Densities Research Articles

Temperature effects on the growth and survival of tdh positive Vibrio parahaemolyticus in tissues of postharvest Manila clam (Ruditapes philippinarum)

Bivalve storage at inadequate temperatures contains greater densities of Vibrio parahaemolyticus. The objective of the present study was to determine if there were any differences in growth and survival of potentially pathogenic V. parahaemolyticus (tdh positive) in relation to nonpathogenic V. parahaemolyticus (tdh-trh negative) levels in Manila clams (Ruditapes philippinarum) when exposed to different postharvest temperatures. Clams were depurated then exposed to known doses of both potential pathogenic and nonpathogenic V. parahaemolyticus for 24 h. Clams were then kept at the following temperatures corresponding to the Mediterranean summer (28 °C), winter (15 °C) and refrigeration (4 °C) for 96 h. Vibrio parahaemolyticus densities were determined at 0, 24, 48, 72 and 96 h of postharvest storage. Both isolates of V. parahaemolyticus multiplied rapidly in live clams held at 28 °C, (increase of 3 logs CFU/g at 72 h). Nonpathogenic V. parahaemolyticus in clams stored at 4 °C and 15 °C showed 1 log CFU/g and 2 log CFU/g decrease at 96 h, respectively, while no significant differences were detected for pathogenic V. parahaemolyticus at these temperatures after 96 h.

Snapshot of Vibrio parahaemolyticus densities in open and closed shellfish beds in Coastal South Carolina and Mississippi.

Vibrio parahaemolyticus is a Gram negative, halophilic bacterium that is ubiquitous in warm, tropical waters throughout the world. It is a major cause of seafood-associated gastroenteritis and is generally associated with consumption of raw or undercooked seafood, especially oysters. This study presents a snapshot of total V. parahaemolyticus densities in surface waters and shellstock American oysters (Crassostrea virginica) from open and closed shellfish harvesting areas, as well as "more rural areas" on two different US coasts, the Atlantic and the Gulf. Sampling was conducted from 2001 to 2003 at five sites near Charleston/Georgetown, SC and at four locations in the Gulfport/Pascagoula, MS area. V. parahaemolyticus numbers were determined by a direct plating method using an alkaline-phosphatase-labeled DNA probe targeting the species-specific thermolabile hemolysin gene (tlh) that was used for identification of bacterial isolates. The greatest difference between the two coasts was salinity; mean salinity in SC surface waters was 32.9ppt, whereas the mean salinity in MS waters was 19.2ppt, indicating more freshwater input into MS shellfish harvesting areas during the study period. The mean V. parahaemolyticus numbers in oysters were almost identical between the two states (567.4 vs. 560.1CFU/g). Bacterial numbers in the majority of surface water samples from both states were at or below the limit of detection (LOD = <10CFU/mL). The bacterial concentrations determined during this study predict a low public health risk from consumption of oysters in shellfish growing areas on either the Gulf or the Atlantic US coast.

The relationship of Vibrio parahaemolyticus densities and water quality factor during oyster culture

Vibrio parahaemolyticus(VP)is a pathogen of bacterial food poisoning associated with shellfish.VP,which is detected both in human and fish,has even higher concentrations in oysters and other filter-feeding shellfish.In order to study the relationship of VP densities versus water quality factor including water salinity,temperature,pH and dissolved oxygen in the course of oyster culture,we detected total VP densities in the oyster and water quality factor at the oyster farm in Yangxi,Guangdong from March to November in 2009.The results showed that the detection ratio of total VP in oysters was 94.38%.The water temperature was correlated positively with total VP in oysters,but the salinity was correlated negatively with total VP in oysters.The dissolved oxygen and pH didn't show correlation with total VP in oysters.Based on the regression analysis,a quadratic relationship for VP densities versus water temperature and salinity was found.The regression equation of VP densities versus water temperature was:LgVP=0.093T-0.685(R2=0.336);The regression equation of VP densities versus salinity was:LgVP=1.199+0.116S-0.004S2(R2=0.217);The best fit regression equation of VP densities versus water temperature and salinity was LgVP=-1.941+0.116T+0.058S-0.001S2(R2=0.414).The results of this paper may provide some reference data for the risk analysis of VP during oyster culture.

Growth and Survival of Vibrio parahaemolyticus in Postharvest American Oysters

Oysters at the retail stage of distribution generally contain greater densities of Vibrio parahaemolyticus than do oysters at harvest. The objective of this study was to determine the effects of postharvest storage at 26 and 3°C on the growth and survival of naturally occurring V. parahaemolyticus in shellstock American oysters (Crassostrea virginica). Oysters were collected monthly from May 1998 through April 1999 from Mobile Bay, Alabama, and their V. parahaemolyticus densities were determined after 0, 5, 10, and 24 h of postharvest storage at 26°C. After 24 h of storage at 26°C, oysters were transferred to a refrigerator at 3°C and analyzed 14 to 17 days later. V. parahaemolyticus numbers were determined by a direct plating method involving an alkaline-phosphatase-labeled DNA probe that targets the species-specific thermolabile hemolysin gene (tlh-AP) to identify suspect isolates. From April to December, when water temperatures at harvest were >20°C, the geometric mean harvest density of V. parahaemolyticus was 130 CFU/g. When water temperatures were <20°C, the geometric mean harvest density was 15 CFU/g. After harvest, V. parahaemolyticus multiplied rapidly in live oysters held at 26°C, showing a 50-fold increase (1.7 log CFU/g) at 10 h and a 790-fold increase (2.9 log CFU/g) at 24 h (April through December). Average V. parahaemolyticus numbers showed a sixfold decrease (0.8 log CFU/g) after approximately 14 days of refrigeration. These results indicate that V. parahaemolyticus can grow rapidly in unrefrigerated oysters.

Environmental investigation of potentially pathogenic Vibrio parahaemolyticus in the Seto-Inland Sea, Japan

Seawater and organic material (live and/or dead matter deposited on any substratum submersed in seawater) were collected during the cool weather season from a coast of the Seto-Inland Sea, Japan, and analyzed to determine Vibrio parahaemolyticus densities and the occurrence of pathogenic strains, defined as those possessing tdh and/or trh genes by the polymerase chain reaction (PCR), using isolated DNA from enrichment culture of the samples. About 95% of the samples were positive for V. parahaemolyticus (with densities of 3 to >1400 cells per 100 ml water or 10 g organic samples) by the most-probable-number (MPN)-PCR technique with species-specific toxR primers, but only 40% were positive by the conventional MPN-culture technique (with densities ranging from 3 to 240 cells per 100 ml water or 10 g organics). Furthermore, the tdh and trh genes were positive in 55% and 20% of samples, respectively, by the MPN-PCR technique. No tdh and trh gene-positive strains were isolated by the conventional MPN-culture procedure. The difference in detection between the MPN-culture and the MPN-PCR techniques appeared to be significant and may be attributed to different detection sensitivities and other factors.

Quantitative studies on Vibrio parahaemolyticus in market samples of finfish and shellfish from Cochin (South India)

This paper reports the results of a study conducted to determine the densities of Vibrio parahaemolyticus in market samples of finfish and shellfish from Cochin.

Incidence of Vibrio parahaemolyticus in U.S. coastal waters and oysters

Oyster and seawater samples were collected seasonally from May 1984 through April 1985 from shellfish-growing areas in Washington, California, Texas, Louisiana, Alabama, Florida, South Carolina, Virginia, and Rhode Island which had been designated as approved or prohibited by the National Shellfish Sanitation Program. Fecal coliforms counts, aerobic plate counts, and Vibrio parahaemolyticus densities were determined for the samples. Mean V. parahaemolyticus density was more than 100 times greater in oysters than in water, whereas density of fecal coliforms was approximately 10 times higher in oysters. Seasonal and geographical distributions of V. parahaemolyticus were related to water temperature, with highest densities in samples collected in the spring and the summer along the Gulf coast. The synthetic DNA probe for thermostable direct hemolysin hybridized with 2 of 50 isolates, 1 of which was positive by the Kanagawa test.

Effect of fecal pollution on Vibrio parahaemolyticus densities in an estuarine environment.

Vibrio parahaemolyticus densities in the Narragansett Bay, R.I., estuary were found to significantly correlate with the level of fecal pollution in the water. Results of field investigations showed a definite association between the levels of this organism and those of Escherichia coli, Clostridium perfringens, and enterococci. Densities of V. parahaemolyticus were greatest in the near-surface waters of contaminated areas and decreased sharply with both the distance from the sources of fecal pollution and the depth of the water column. A positive association with the amount of particulate matter in the water and specifically with its zooplankton content also was found. No association was obtained with any of the physical or chemical parameters examined except dissolved oxygen. The results of laboratory studies on the growth of V. parahaemolyticus in collected estuarine waters were consistent with the field observations in that nutrients in sewage did not directly produce any increase in natural or inoculated levels of the organism. Of several particulates added to the water, only chitin and net zooplankters (live or dead) supported the growth of V. parahaemolyticus. The addition of sewage to the water had no measurable effect, whether or not the various particulates also were present. The data show that wastewater effluents have an effect on V. parahaemolyticus densities in this estuary and indicate that the effect is indirect, probably mediated by biostimulation of the food chain and manifested at the level of the microfauna.