scholarly journals Effects of Intertidal Harvest Practices on Levels of Vibrio parahaemolyticus and Vibrio vulnificus Bacteria in Oysters

2016 ◽  
Vol 82 (15) ◽  
pp. 4517-4522 ◽  
Author(s):  
J. L. Jones ◽  
T. P. Kinsey ◽  
L. W. Johnson ◽  
R. Porso ◽  
B. Friedman ◽  
...  
Keyword(s):  
New Jersey ◽  
Vibrio Parahaemolyticus ◽  
Vibrio Vulnificus ◽  
Ambient Air ◽  
The United States ◽  
Washington State ◽  
Most Probable Number ◽  
Probable Number ◽  
Content Type ◽  
Handling Practices

ABSTRACTVibrio parahaemolyticusandVibrio vulnificuscan grow rapidly in shellfish subjected to ambient air conditions, such as during intertidal exposure. In this study, levels of total and pathogenic (tdh+and/ortrh+)V. parahaemolyticusand totalV. vulnificuswere determined in oysters collected from two study locations where intertidal harvest practices are common. Samples were collected directly off intertidal flats, after exposure (ambient air [Washington State] or refrigerated [New Jersey]), and after reimmersion by natural tidal cycles. Samples were processed using a most-probable-number (MPN) real-time PCR method for total and pathogenicV. parahaemolyticusorV. vulnificus. In Washington State, the mean levels ofV. parahaemolyticusincreased 1.38 log MPN/g following intertidal exposure and dropped 1.41 log MPN/g after reimmersion for 1 day, but the levels were dependent upon the container type utilized. PathogenicV. parahaemolyticuslevels followed a similar trend. However,V. vulnificuslevels increased 0.10 log MPN/g during intertidal exposure in Washington but decreased by >1 log MPN/g after reimmersion. In New Jersey, initial levels of all vibrios studied were not significantly altered during the refrigerated sorting and containerizing process. However, there was an increase in levels after the first day of reimmersion by 0.79, 0.72, 0.92, and 0.71 log MPN/g for total,tdh+andtrh+V. parahaemolyticus, andV. vulnificus, respectively. The levels of all targets decreased to those similar to background after a second day of reimmersion. These data indicate that the intertidal harvest and handling practices for oysters that were studied in Washington and New Jersey do not increase the risk of illness fromV. parahaemolyticusorV. vulnificus.IMPORTANCEVibrio parahaemolyticusandVibrio vulnificusare the leading causes of seafood-associated infectious morbidity and mortality in the United States.Vibriospp. can grow rapidly in shellfish subjected to ambient air conditions, such as during periods of intertidal exposure. When oysters are submersed with the incoming tide, the vibrios can be purged. However, data on the rates of increase and purging during intertidal harvest are scarce, which limits the accuracy of risk assessments. The objective of this study was to help fill these data gaps by determining the levels of total and pathogenic (tdh+and/ortrh+)V. parahaemolyticusandV. vulnificusin oysters from two locations where intertidal harvest practices are common, using the current industry practices. The data generated provide insight into the responses ofVibriospp. to relevant practices of the industry and public health, which can be incorporated into risk management decisions.

Effects of Dry Storage and Resubmersion of Oysters on Total Vibrio vulnificus and Total and Pathogenic (tdh+/trh+) Vibrio parahaemolyticus Levels

2015 ◽  
Vol 78 (8) ◽  
pp. 1574-1580 ◽  
Author(s):  
THOMAS P. KINSEY ◽  
KERI A. LYDON ◽  
JOHN C. BOWERS ◽  
JESSICA L. JONES
Keyword(s):  
Vibrio Parahaemolyticus ◽  
Storage Time ◽  
Vibrio Vulnificus ◽  
Ambient Air ◽  
Most Probable Number ◽  
Probable Number ◽  
Ambient Temperatures ◽  
Dry Storage ◽  
Hemolysin Gene ◽  
Thermostable Direct Hemolysin

Vibrio vulnificus (Vv) and Vibrio parahaemolyticus (Vp) are the two leading causes of bacterial illnesses associated with raw shellfish consumption. Levels of these pathogens in oysters can increase during routine antifouling aquaculture practices involving dry storage in ambient air conditions. After storage, common practice is to resubmerge these stored oysters to reduce elevated Vv and Vp levels, but evidence proving the effectiveness of this practice is lacking. This study examined the changes in Vv and in total and pathogenic (thermostable direct hemolysin gene and the tdh-related hemolysin gene, tdh+ and trh+) Vp levels in oysters after 5 or 24 h of dry storage (28 to 32°C), followed by resubmersion (27 to 32°C) for 14 days. For each trial, replicate oyster samples were collected at initial harvest, after dry storage, after 7 days, and after 14 days of resubmersion. Oysters not subjected to dry storage were collected and analyzed to determine natural undisturbed vibrio levels (background control). Vibrio levels were measured using a most-probable-number enrichment followed by real-time PCR. After storage, vibrio levels (excluding tdh+ and trh+ Vp during 5-h storage) increased significantly (P < 0.001) from initial levels. After 7 days of resubmersion, Vv and total Vp levels (excluding total Vp in oysters stored for 5 h) were not significantly different (P > 0.1) from levels in background oysters. Vv and total and pathogenic Vp levels were not significantly different (P > 0.1) from levels in background oysters after 14 days of resubmersion, regardless of dry storage time. These data demonstrate that oyster resubmersion after dry storage at elevated ambient temperatures allows vibrio levels to return to those of background control samples. These results can be used to help minimize the risk of Vv and Vp illnesses and to inform the oyster industry on the effectiveness of routine storing and resubmerging of aquaculture oysters.

scholarly journals Rapid Proliferation of Vibrio parahaemolyticus, Vibrio vulnificus, and Vibrio cholerae during Freshwater Flash Floods in French Mediterranean Coastal Lagoons

2015 ◽  
Vol 81 (21) ◽  
pp. 7600-7609 ◽  
Author(s):  
Kevin Esteves ◽  
Dominique Hervio-Heath ◽  
Thomas Mosser ◽  
Claire Rodier ◽  
Marie-George Tournoud ◽  
...  
Keyword(s):  
Vibrio Cholerae ◽  
Vibrio Parahaemolyticus ◽  
Vibrio Vulnificus ◽  
Coastal Lagoons ◽  
Flash Floods ◽  
Low Flow ◽  
Most Probable Number ◽  
Abrupt Decrease ◽  
Probable Number ◽  
Content Type

ABSTRACTVibrio parahaemolyticus,Vibrio vulnificus, andVibrio choleraeof the non-O1/non-O139 serotype are present in coastal lagoons of southern France. In these Mediterranean regions, the rivers have long low-flow periods followed by short-duration or flash floods during and after heavy intense rainstorms, particularly at the end of the summer and in autumn. These floods bring large volumes of freshwater into the lagoons, reducing their salinity. Water temperatures recorded during sampling (15 to 24°C) were favorable for the presence and multiplication of vibrios. In autumn 2011, before heavy rainfalls and flash floods, salinities ranged from 31.4 to 36.1‰ and concentrations ofV. parahaemolyticus,V. vulnificus, andV. choleraevaried from 0 to 1.5 × 103most probable number (MPN)/liter, 0.7 to 2.1 × 103MPN/liter, and 0 to 93 MPN/liter, respectively. Following heavy rainstorms that generated severe flash flooding and heavy discharge of freshwater, salinity decreased, reaching 2.2 to 16.4‰ within 15 days, depending on the site, with a concomitant increase inVibrioconcentration to ca. 104MPN/liter. The highest concentrations were reached with salinities between 10 and 20‰ forV. parahaemolyticus, 10 and 15‰ forV. vulnificus, and 5 and 12‰ forV. cholerae. Thus, an abrupt decrease in salinity caused by heavy rainfall and major flooding favored growth of human-pathogenicVibriospp. and their proliferation in the Languedocian lagoons. Based on these results, it is recommended that temperature and salinity monitoring be done to predict the presence of theseVibriospp. in shellfish-harvesting areas of the lagoons.

Vibrio vulnificus and Vibrio parahaemolyticus in U.S. Retail Shell Oysters: A National Survey from June 1998 to July 1999

2002 ◽  
Vol 65 (1) ◽  
pp. 79-87 ◽  
Author(s):  
DAVID W. COOK ◽  
PAUL O'LEARY ◽  
JEFF C. HUNSUCKER ◽  
EDNA M. SLOAN ◽  
JOHN C. BOWERS ◽  
...  
Keyword(s):  
United States ◽  
North Atlantic ◽  
Vibrio Parahaemolyticus ◽  
Vibrio Vulnificus ◽  
Gulf Coast ◽  
The United States ◽  
Most Probable Number ◽  
Probable Number ◽  
Hemolysin Gene ◽  
Thermostable Direct Hemolysin

From June 1998 to July 1999, 370 lots of oysters in the shell were sampled at 275 different establishments (71%, restaurants or oyster bars; 27%, retail seafood markets; and 2%, wholesale seafood markets) in coastal and inland markets throughout the United States. The oysters were harvested from the Gulf (49%), Pacific (14%), Mid-Atlantic (18%), and North Atlantic (11%) Coasts of the United States and from Canada (8%). Densities of Vibrio vulnificus and Vibrio parahaemolyticus were determined using a modification of the most probable number (MPN) techniques described in the Food and Drug Administration's Bacteriological Analytical Manual. DNA probes and enzyme immunoassay were used to identify suspect isolates and to determine the presence of the thermostable direct hemolysin gene associated with pathogenicity of V. parahaemolyticus. Densities of both V. vulnificus and V. parahaemolyticus in market oysters from all harvest regions followed a seasonal distribution, with highest densities in the summer. Highest densities of both organisms were observed in oysters harvested from the Gulf Coast, where densities often exceeded 10,000 MPN/g. The majority (78%) of lots harvested in the North Atlantic, Pacific, and Canadian Coasts had V. vulnificus densities below the detectable level of 0.2 MPN/g; none exceeded 100 MPN/g. V. parahaemolyticus densities were greater than those of V. vulnificus in lots from these same areas, with some lots exceeding 1,000 MPN/g for V. parahaemolyticus. Some lots from the Mid-Atlantic states exceeded 10,000 MPN/g for both V. vulnificus and V. parahaemolyticus. Overall, there was a significant correlation between V. vulnificus and V. parahaemolyticus densities (r = 0.72, n = 202, P < 0.0001), but neither density correlated with salinity. Storage time significantly affected the V. vulnificus (10% decrease per day) and V. parahaemolyticus (7% decrease per day) densities in market oysters. The thermostable direct hemolysin gene associated with V. parahaemolyticus virulence was detected in 9 of 3,429 (0.3%) V. parahaemolyticus cultures and in 8 of 198 (4.0%) lots of oysters. These data can be used to estimate the exposure of raw oyster consumers to V. vulnificus and V. parahaemolyticus.

scholarly journals Abundance of Vibrio cholerae, V. vulnificus, and V. parahaemolyticus in Oysters (Crassostrea virginica) and Clams (Mercenaria mercenaria) from Long Island Sound

2014 ◽  
Vol 80 (24) ◽  
pp. 7667-7672 ◽  
Author(s):  
Jessica L. Jones ◽  
Catharina H. M. Lüdeke ◽  
John C. Bowers ◽  
Kristin DeRosia-Banick ◽  
David H. Carey ◽  
...  
Keyword(s):  
Vibrio Cholerae ◽  
Vibrio Vulnificus ◽  
Long Island ◽  
Long Island Sound ◽  
The United States ◽  
Mitigation Strategies ◽  
Most Probable Number ◽  
Probable Number ◽  
Content Type ◽  
Island Sound

ABSTRACTVibriosis is a leading cause of seafood-associated morbidity and mortality in the United States. Typically associated with consumption of raw or undercooked oysters, vibriosis associated with clam consumption is increasingly being reported. However, little is known about the prevalence ofVibriospp. in clams. The objective of this study was to compare the levels ofVibrio cholerae,Vibrio vulnificus, andVibrio parahaemolyticusin oysters and clams harvested concurrently from Long Island Sound (LIS). Most probable number (MPN)–real-time PCR methods were used for enumeration of totalV. cholerae,V. vulnificus,V. parahaemolyticus, and pathogenic (tdh+and/ortrh+)V. parahaemolyticus.V. choleraewas detected in 8.8% and 3.3% of oyster (n= 68) and clam (n= 30) samples, with levels up to 1.48 and 0.48 log MPN/g in oysters and clams, respectively.V. vulnificuswas detected in 97% and 90% of oyster and clam samples, with median levels of 0.97 and −0.08 log MPN/g, respectively.V. parahaemolyticuswas detected in all samples, with median levels of 1.88 and 1.07 log MPN/g for oysters and clams, respectively. The differences betweenV. vulnificusand total and pathogenicV. parahaemolyticuslevels in the two shellfish species were statistically significant (P< 0.001). These data indicate thatV. vulnificusand total and pathogenicV. parahaemolyticusare more prevalent and are present at higher levels in oysters than in hard clams. Additionally, the data suggest differences in vibrio populations between shellfish harvested from different growing area waters within LIS. These results can be used to evaluate and refine illness mitigation strategies employed by risk managers and shellfish control authorities.

scholarly journals Seasonal and Geographical Differences in Total and Pathogenic Vibrio parahaemolyticus and Vibrio vulnificus Levels in Seawater and Oysters from the Delaware and Chesapeake Bays Determined Using Several Methods

2020 ◽  
Vol 86 (23) ◽  
Author(s):  
Salina Parveen ◽  
John Jacobs ◽  
Gulnihal Ozbay ◽  
Lathadevi K. Chintapenta ◽  
Esam Almuhaideb ◽  
...  
Keyword(s):  
Chesapeake Bay ◽  
Vibrio Parahaemolyticus ◽  
Vibrio Vulnificus ◽  
Seawater Temperature ◽  
False Negative ◽  
Delaware Bay ◽  
Most Probable Number ◽  
Probable Number ◽  
Content Type ◽  
Pathogenic Vibrio

ABSTRACT Oyster and seawater samples were collected from five sites in the Chesapeake Bay, MD, and three sites in the Delaware Bay, DE, from May to October 2016 and 2017. Abundances and detection frequencies for total and pathogenic Vibrio parahaemolyticus and Vibrio vulnificus were compared using the standard most-probable-number–PCR (MPN-PCR) assay and a direct-plating (DP) method on CHROMagar Vibrio for total (tlh+) and pathogenic (tdh+ and trh+) V. parahaemolyticus genes and total (vvhA) and pathogenic (vcgC) V. vulnificus genes. The colony overlay procedure for peptidases (COPP) assay was evaluated for total Vibrionaceae. DP had high false-negative rates (14 to 77%) for most PCR targets and was deemed unsatisfactory. Logistic regression models of the COPP assay showed high concordances with MPN-PCR for tdh+ and trh+ V. parahaemolyticus and vvhA+ V. vulnificus in oysters (85.7 to 90.9%) and seawater (81.1 to 92.7%) when seawater temperature and salinity were factored into the model, suggesting that the COPP assay could potentially serve as a more rapid method to detect vibrios in oysters and seawater. Differences in total Vibrionaceae and pathogenic Vibrio abundances between state sampling sites over different collection years were contrasted for oysters and seawater by MPN-PCR. Abundances of tdh+ and trh+ V. parahaemolyticus were ∼8-fold higher in Delaware oysters than in Maryland oysters, whereas abundances of vcgC+ V. vulnificus were nearly identical. For Delaware oysters, 93.5% were both tdh+ and trh+, compared to only 19.2% in Maryland. These results indicate that pathogenic V. parahaemolyticus was more prevalent in the Delaware Bay than in the Chesapeake Bay. IMPORTANCE While V. parahaemolyticus and V. vulnificus cause shellfish-associated morbidity and mortality among shellfish consumers, current regulatory assays for vibrios are complex, time-consuming, labor-intensive, and relatively expensive. In this study, the rapid, simple, and inexpensive COPP assay was identified as a possible alternative to MPN-PCR for shellfish monitoring. This paper shows differences in total Vibrionaceae and pathogenic vibrios found in seawater and oysters from the commercially important Delaware and Chesapeake Bays. Vibrio parahaemolyticus isolates from the Delaware Bay were more likely to contain commonly recognized pathogenicity genes than those from the Chesapeake Bay.

Evaluation of DNA Colony Hybridization and Real-Time PCR for Detection of Vibrio parahaemolyticus and Vibrio vulnificus in Postharvest-Processed Oysters

2009 ◽  
Vol 72 (10) ◽  
pp. 2106-2109 ◽  
Author(s):  
JESSICA L. JONES ◽  
KATHY E. NOE ◽  
ROBIN BYARS ◽  
ANGELO DePAOLA
Keyword(s):  
Real Time ◽  
Real Time Pcr ◽  
Vibrio Parahaemolyticus ◽  
Vibrio Vulnificus ◽  
The United States ◽  
Most Probable Number ◽  
Probable Number ◽  
Colony Hybridization ◽  
Alkaline Peptone Water ◽  
Peptone Water

The applicability of real-time PCR was examined for detection of vibrios from postharvest-processed (PHP) oysters to allow for a more rapid assay and higher sample throughput than currently used. During June to October 2004, 68 PHP oyster samples were collected directly from PHP firms or from retail markets across the United States. PHP oysters were examined to determine the effectiveness of treatments in the reduction of vibrio levels and to compare the analytical methods utilized. The latter is the focus of the data presented here. Each sample was analyzed for Vibrio parahaemolyticus and V. vulnificus by using a 2-dilution, three-tube most-probable-number (MPN) and a 25-g presence/absence enrichment in alkaline peptone water. Following 6-h and overnight enrichment, aliquots from each MPN tube and the 25-g sample were streaked onto selective media and tested by real-time PCR. Colonies from the selective agar were confirmed as V. parahaemolyticus or V. vulnificus by DNA colony hybridization. DNA hybridization and real-time PCR results for each MPN tube and the 25-g enrichment at both time points were analyzed individually for each organism. The methods were in agreement for 857 (95%) of 901 and for 882 (98%) of 903 tubes for detection of V. parahaemolyticus and V. vulnificus, respectively. Overall, there was 96% agreement between real-time and DNA colony hybridization. The results obtained by real-time PCR were comparable to those from DNA colony hybridization, but analysis time was significantly reduced for the detection of vibrios in PHP-treated oysters.

Selectivity and Specificity of a Chromogenic Medium for Detecting Vibrio parahaemolyticus†

2005 ◽  
Vol 68 (7) ◽  
pp. 1454-1456 ◽  
Author(s):  
YI-CHENG SU ◽  
JINGYUN DUAN ◽  
WEN-HSIN WU
Keyword(s):  
Vibrio Parahaemolyticus ◽  
Bile Salts ◽  
Vibrio Vulnificus ◽  
Enterobacter Cloacae ◽  
Most Probable Number ◽  
Chromogenic Medium ◽  
Probable Number ◽  
Vibrio Fluvialis ◽  
Vibrio Mimicus ◽  
Vibrio Spp

The thiosulfate–citrate–bile salts–sucrose agar (TCBS) used in the most-probable-number method for detecting Vibrio parahaemolyticus cannot differentiate growth of V. parahaemolyticus from Vibrio vulnificus or Vibrio mimicus. This study examined the selectivity and specificity of Bio-Chrome Vibrio medium (BCVM), a chromogenic medium that detects V. parahaemolyticus on the basis of the formation of distinct purple colonies on the medium. A panel consisting of 221 strains of bacteria, including 179 Vibrio spp. and 42 non-Vibrio spp., were examined for their ability to grow and produce colored colonies on BCVM. Growth of Salmonella, Shigella, Escherichia coli, Enterobacter cloacae, Yersinia enterocolitica, and Aeromonas was inhibited by both BCVM and TCBS. All 148 strains of V. parahaemolyticus grew on BCVM, and 145 of them produced purple colonies. The remaining 31 Vibrio spp., except one strain of Vibrio fluvialis, were either unable to grow or produced blue-green or white colonies on BCVM. Bio-Chrome Vibrio medium was capable of differentiating V. parahaemolyticus from other species, including V. vulnificus and V. mimicus. Further studies are needed to evaluate the sensitivity and specificity of BCVM for detecting V. parahaemolyticus in foods.

scholarly journals Long-Term Study of Vibrio parahaemolyticus Prevalence and Distribution in New Zealand Shellfish

2015 ◽  
Vol 81 (7) ◽  
pp. 2320-2327 ◽  
Author(s):  
C. D. Cruz ◽  
D. Hedderley ◽  
G. C. Fletcher
Keyword(s):  
New Zealand ◽  
Vibrio Parahaemolyticus ◽  
Most Probable Number ◽  
Pcr Analysis ◽  
Potential Hazard ◽  
Probable Number ◽  
Content Type ◽  
The North ◽  
Long Term Study ◽  
Food Borne

ABSTRACTThe food-borne pathogenVibrio parahaemolyticushas been reported as being present in New Zealand (NZ) seawaters, but there have been no reported outbreaks of food-borne infection from commercially grown NZ seafood. Our study determined the current incidence ofV. parahaemolyticusin NZ oysters and Greenshell mussels and the prevalence ofV. parahaemolyticustdhandtrhstrains. Pacific (235) and dredge (21) oyster samples and mussel samples (55) were obtained from commercial shellfish-growing areas between December 2009 and June 2012. TotalV. parahaemolyticusnumbers and the presence of pathogenic genestdhandtrhwere determined using the FDA most-probable-number (MPN) method and confirmed using PCR analysis. In samples from the North Island of NZ,V. parahaemolyticuswas detected in 81% of Pacific oysters and 34% of mussel samples, while the numbers ofV. parahaemolyticustdhandtrhstrains were low, with just 3/215 Pacific oyster samples carrying thetdhgene.V. parahaemolyticusorganisms carryingtdhandtrhwere not detected in South Island samples, andV. parahaemolyticuswas detected in just 1/21 dredge oyster and 2/16 mussel samples. Numbers ofV. parahaemolyticusorganisms increased when seawater temperatures were high, the season when most commercial shellfish-growing areas are not harvested. The numbers ofV. parahaemolyticusorganisms in samples exceeded 1,000 MPN/g only when the seawater temperatures exceeded 19°C, so this environmental parameter could be used as a trigger warning of potential hazard. There is some evidence that the totalV. parahaemolyticusnumbers increased compared with those reported from a previous 1981 to 1984 study, but the analytical methods differed significantly.

Effects of Flash Freezing, Followed by Frozen Storage, on Reducing Vibrio parahaemolyticus in Pacific Raw Oysters (Crassostrea gigas)

2009 ◽  
Vol 72 (1) ◽  
pp. 174-177 ◽  
Author(s):  
CHENGCHU LIU ◽  
JIANZHANG LU ◽  
YI-CHENG SU
Keyword(s):  
Crassostrea Gigas ◽  
Vibrio Parahaemolyticus ◽  
Vibrio Vulnificus ◽  
Frozen Storage ◽  
Most Probable Number ◽  
Freezing Process ◽  
Probable Number ◽  
Pacific Oysters ◽  
Subsequent Storage ◽  
Shellfish Sanitation

This study investigated the effects of flash freezing, followed by frozen storage, on reducing Vibrio parahaemolyticus in Pacific raw oysters. Raw Pacific oysters were inoculated with a five-strain cocktail of V. parahaemolyticus at a total level of approximately 3.5 × 105 most probable number (MPN) per gram. Inoculated oysters were subjected to an ultralow flash-freezing process (−95.5°C for 12 min) and stored at −10, −20, and −30°C for 6 months. Populations of V. parahaemolyticus in the oysters declined slightly by 0.22 log MPN/g after the freezing process. Subsequent storage of frozen oysters at −10, −20, and −30°C resulted in considerable reductions of V. parahaemolyticus in the oysters. Storing oysters at −10°C was more effective in inactivating V. parahaemolyticus than was storage at −20 or −30°C. Populations of V. parahaemolyticus in the oysters declined by 2.45, 1.71, and 1.45 log MPN/g after 1 month of storage at −10, −20, and −30°C, respectively, and continued to decline during the storage. The levels of V. parahaemolyticus in oysters were reduced by 4.55, 4.13, and 2.53 log MPN/g after 6 months of storage at −10, −20, and −30°C, respectively. Three process validations, each separated by 1 week and conducted according to the National Shellfish Sanitation Program's postharvest processing validation–verification interim guidance for Vibrio vulnificus and Vibrio parahaemolyticus, confirmed that a process of flash freezing, followed by storage at −21 ± 2°C for 5 months, was capable of achieving greater than 3.52-log (MPN/g) reductions of V. parahaemolyticus in half-shell Pacific oysters.

Survey of Postharvest-Processed Oysters in the United States for Levels of Vibrio vulnificus and Vibrio parahaemolyticus

2009 ◽  
Vol 72 (10) ◽  
pp. 2110-2113 ◽  
Author(s):  
ANGELO DePAOLA ◽  
JESSICA L. JONES ◽  
KATHY E. NOE ◽  
ROBIN H. BYARS ◽  
JOHN C. BOWERS
Keyword(s):  
Vibrio Vulnificus ◽  
Gulf Coast ◽  
Virulence Gene ◽  
Selective Advantage ◽  
The United States ◽  
Most Probable Number ◽  
Probable Number ◽  
Mild Heat ◽  
Thermostable Direct Hemolysin ◽  
The Mean

From June through October 2004, the U.S. Food and Drug Administration collected oysters (61 samples) that had been subjected to postharvest processing (PHP) methods, including mild heat treatment, freezing, and high hydrostatic pressure, from processors and retail markets in various states to determine Vibrio vulnificus and V. parahaemolyticus levels. Presence in a 25-g sample and most probable number (MPN) using standard enrichment and selective isolation procedures were utilized. Suspect colonies were isolated and identified using DNA probe colony hybridization. Neither species of vibrio was detected in 25-g portions of most samples regardless of the PHP. The lowest frequency of isolation of either pathogen (&lt;10%) was observed with the mild heat process. Few (12 to 13%) frozen samples collected at the processor but not at retail contained &gt;30 MPN/g of either pathogen. The mean levels of either organism in PHP oysters observed in the present study were 5 to 6 log less than in unprocessed raw Gulf Coast oysters. Of the 70 V. vulnificus isolates examined, only 5 possessed the putative virulence marker, type B 16S rRNA. Neither the thermostable direct hemolysin (tdh) nor the tdh-related hemolysin (trh) virulence gene was detected in any of the 40 V. parahaemolyticus isolates examined in the present study. These data suggest that if there is any selective advantage to pathogenic strains of V. vulnificus and V. parahaemolyticus, these differences are minimal. These results indicate that all PHP treatments greatly reduce exposure of V. vulnificus and V. parahaemolyticus to raw-oyster consumers. Consequently, these PHP oysters pose a much lower risk of illness to consumers due to these pathogens.

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