Stalking the wild vibrio 



A quest for longer shelf life and better products 



Headache, diarrhea, abdominal pain? All-around 

 symptoms of Montezuma's revenge? 



If the feelings begin after a hefty seafood dinner, 

 Vibrio parahaemolyticus may be to blame. 



Vibrio parahaemolyticus is a small, curved bac- 

 teria which lives in most coastal waters. It's car- 

 ried by fish and causes gastroenteritis when con- 

 sumed in sufficient quantities. Vibrio is also the 

 pathogen most often found in North Carolina's 

 seafood, according to NCSU food scientists Marvin 

 Speck and Bibek Ray. 



"We've taken seafood from the coastal area and 

 from local markets here and we've done more than 

 400 samples looking for indicators such as coli- 

 forms and plate counts and done some work look- 

 ing for injured coliform. We've looked for patho- 

 gens such as salmonella, shigella, anaerobic 

 toxogenics and vibrio," Speck says. "And what 

 we've found in most cases is Vibrio parahaemoly- 

 ticus is the main contaminating pathogen. 



"Which is to be expected since it is a marine 

 organism," he adds. 



A new problem 



Scientists on the east coast were surprised, 

 however, when they discovered vibrio — which has 

 plagued Japan for years — was a problem here. 



"For some reason we thought the whole problem 

 was a Japanese problem because they ate so much 

 raw fish," Speck says. "Then in 1971 we had our 

 first outbreak of food poisoning traced to vibrio in 

 Maryland. From then on, after the methodology 

 was developed, vibrio was detected about every- 

 where you looked for it in coastal waters. Now we 

 think we have as much a problem as the Japanese." 



The NCSU tests have shown vibrio in about 85 

 percent of the clams, 80 percent of the shrimp, 75 

 percent of the oysters, 30 to 40 percent of the sea 

 scallops and varying amounts in finfish. 



The amounts of vibrio were not always enough 

 to cause trouble. But vibrio multiplies rapidly, and 

 any mishandling of the seafood could raise the 

 vibrio count to unhealthy numbers. 



Fortunately, vibrio is very sensitive to cold and 

 won't appear in water colder than 55 to 60 degrees 

 Farenheit. So it's not surprising that it stops 

 appearing in North Carolina seafood samples after 

 about November and isn't seen again until about 

 March. 



Hard to detect 



Unfortunately, according to Speck, vibrio often 

 isn't seen anytime of the year using the conven- 

 tional testing methods now used by the state and 

 other regulatory agencies. 



"We've found that the customary indicator, 

 (fecal) coliform, cannot be depended on to find 

 Vibrio parahaemolyticus ," Speck said. "We think 

 it's because this is a marine organism that it bears 

 no relationship to the indicator organisms. So we 



will have to look for this organism (vibrio) by it- 

 self." 



The most promising way to find vibrio — Speck 

 and Ray have been developing the method with Sea 

 Grant funds for the past two years — is called the 

 repair method. Vibrio is sensitive to cold and heat 

 and becomes "injured" when it is refrigerated or 

 heated to a certain degree. But the injured bacteria 

 remain harmful and can repair themselves. 



Another approach 



Using the new method — which determines the 

 number of injured and uninjured bacteria — Speck 

 and Ray have gotten very different results from the 

 tests now recommended by the Food and Drug 

 Administration. 



"Where under the FDA method we'll find no 

 vibrio, using the repair method there will be 43 to 

 200," says Hackney. "Or with FDA we'll find 

 23-100 and the repair method will find a 1,100 

 count. There's really that much of a difference. We 

 think we have a very good method." 



Once their study is complete, researchers plan 

 to recommend their method to the state. 



Marvin Speck 



