Emerging Pathogens: Vibrio Cases in Oysters Expected to Continue Increasing

Ben Miller — Mon, 23 Sep 2013 05:01:19 +0000

With a nearly 50-percent mortality rate, Vibrio vulnificus is the most deadly foodborne pathogen in the world, according to University of North Carolina at Charlotte Biology Professor Jim Oliver. And instances of infection in the U.S., however rare, are rapidly rising. Fifteen years ago, there were 21 confirmed cases of Vibrio vulnificus and parahaemolyticus infections in the U.S. Last year, there were 193. While infections from either of the pathogens are still rare compared with, say, Salmonella and Campylobacter, the incidence rate grew faster than any of the other five microbes tracked in the Centers for Disease Control’s 2012 Food Safety Progress Report. The vulnificus strain is responsible for 95 percent of seafood-related illness fatalities in the U.S., according to a 2013 study by Oliver and Joanna Nowakowska. Another Vibrio strain, parahaemolyticus, is milder, causing diarrhea, nausea, fever and chills, according to CDC. Several studies have linked Vibrio’s quick growth rate with rising ocean temperatures, a critical condition favorable to the saltwater-based bacterium. Instances of Vibrio have started showing up in colder places where they were largely unheard-of before. “Most notably, they’ve been [seeing cases] in places like the Baltic and Germany,” Oliver said. While those cases usually involved Vibrio entering humans through wounds while they were swimming, a 2009 article by Oliver and Melissa Jones shows that about 93 percent of Vibrio cases in the U.S. manifest themselves in people who have consumed raw or undercooked oysters. Vibrio can also come from other undercooked seafood. Vibrio doesn’t harm the oysters in any way, according to Rohinee Paranjpye, a research microbiologist with the National Oceanic and Atmospheric Administration. “It appears to be a symbiotic relationship,” Paranjpye said. Several post-harvest processing methods exist, which have varying degrees of success at killing Vibrio, but they have several drawbacks, said Chris Nelson, a trustee of the Gulf & South Atlantic Fisheries Foundation. One of the largest barriers is cost. “There’s a huge barrier in terms of capitalization,” Nelson said. “Let’s say you needed a million dollars — and some of the post-harvest processing pieces of equipment are upwards of a million dollars — you have to be a certain size operation.” In addition to the costs of equipment, a 2011 report from the Interstate Shellfish Sanitation Conference found that processing methods incur staff time and transportation costs. Because such costs are passed on to the consumer, Nelson said the price of oysters can multiply. “Probably for every dollar spent processing, it’s going to result in at least three more dollars on the dinner plate,” he said. “And probably even more than that because, if you make the additional investment, you’re going to want an additional profit.” The least-expensive method, which involves freezing the oysters, is typically not used during the summer months when the water is warmer and Vibrio cases are more likely to rise, Nelson said. During the winter, when oysters are plumper, they can take the beating of post-harvest processing. But, when it gets warmer, the reproduction cycle takes much of the meat out of oysters, and processing can reduce the product’s quality, he said. However, the costs of processing vary depending on several factors, including the method used, the market intended for the oysters, and whether the company in question is using its own material or paying somebody else to process their catch. For instance, processing can actually reduce the price of shucked oysters, according to the ISSC’s report. Certain methods will help open oysters up, which almost cuts in half the amount of time it takes to shuck them. However, the report also showed that only 40 percent of oysters are sold to the shucked market, while 60 percent are sold to the half-shell market. Nelson said some regulations exist for post-harvest processing, but they vary by location and time of year. Cooking oysters can kill Vibrio as well. But, as long as ocean temperatures continue to rise, Oliver said Vibrio will continue to be a problem. “Vibrio cases in general, I’m very confident will increase,” he said.

Dishwasher Cooking Trend Raises Eyebrows Among Food-Safety Experts

Ben Miller — Tue, 17 Sep 2013 05:03:37 +0000

Food Network Host Bob Blumer, author Lisa Casali and National Public Radio all recommend cooking food in the dishwasher. General Electric and Whirlpool don’t. The phenomenon of dishwasher cooking, recently explored in an article by NPR Reporter Michaeleen Doucleff, has enjoyed exposure on blogs and in major news organizations. However, very little data exist to guide discussions on the safety of the practice. Casali, an Italian food author who has written a book on the subject of dishwasher cooking, spent some time studying the safety of the practice. Before writing “Cucinare in Lavastoviglie” (“Cooking in the Dishwasher”), she had an Italian chemical laboratory analyze samples of food cooked in various containers in a dishwasher. She said that the results showed that food cooked in vacuum-sealed plastic bags or hermetically sealed jars doesn’t risk contamination from the water or detergent used in the dishwasher. However, that’s not the only concern about the practice for North Carolina State University food specialist Ben Chapman. There’s also the question of whether dishwashers heat up the food enough to kill pathogens such as Salmonella enteritidis and clostridium botulinum. “I have no idea what temperature my dishwasher reaches,” Chapman said. “That matters here because, with fish, the recommended endpoint temperature is 145 degrees Fahrenheit.” Casali said Electrolux representatives told her that the dishwashers she used while researching for her book reach 131-167 degrees F. Chapman said the scientific literature provides specific cooking temperatures to make specific foods such as poultry, beef, pork and fish safe to eat, much in the 145 to 160 degree range. But, especially for eggs, the dishwasher would need to reach some of its highest temperatures to ensure that any pathogens in the food were destroyed. For fruits, vegetables and food that can be eaten raw, he said that cooking temperature might be less of a problem. Chapman’s concern with C. botulinum involves food being left in a sealed space for an extended period of time. He said that the best environment for the bacterium’s cells to vegetate in is one of less than 240 degrees F with little or no oxygen. “We’ve seen outbreaks of botulism from the environment people have created in their home, where they can their food, then leave it in their pantry for weeks,” Chapman said. Using a dishwasher over cooker for canning (or preserving) also concerns Chapman because, although boiling water (212 degrees) will kill vegetative cells, it is not enough to kill inactive spores. Cookers for canning reach 240 degrees for canning and other processes because they inactivate the spores. Less heat than that in an environment without oxygen can result in spores germinating and outgrow resulting in vegetative cells. Chapman said a byproduct of cell multiplication is toxin. “So you need to get to 240 to inactivate the spores – or once they are vegetative,” he said. U.S. Food and Drug Administration spokesman Sebastian Cianci said he could find no reports of illness related to dishwasher cooking, although he said cooking methods might not be included in such statements. Casali stressed that dishwasher cooking isn’t the only time people are served food prepared at low temperatures. “Cooking at low temperature is a popular technique in restaurants and … every day [such dishes] are served [by the] thousands,” she said. However, Chapman cautioned that people who are at high risk of contracting a foodborne illness – groups such as the young, old, pregnant women and those whose immune systems are compromised – could be putting themselves in danger by eating meals cooked at low temperatures. “If somebody’s going through chemotherapy, if someone’s been advised because of some other health condition that they shouldn’t be eating raw vegetables or raw foods, it could be a risky proposition,” he said. Representatives from General Electric and Whirlpool said that they didn’t recommend using their dishwashers to cook food. “Dishwashers are not intended to cook food. They are designed to clean dishes,” said Kim Freeman, a spokeswoman for General Electric. Samantha Smitala, a spokeswoman for Whirlpool, said the company advises its customers to use their products according to their use and care guides. One Whirlpool dishwasher care guide states, “Use the dishwasher only for its intended function.” Chapman, who contributed to food-safety website BarfBlog.com, said he hopes to conduct some testing soon on dishwasher cooking because there isn’t very much scientific information available on the practice right now. “I don’t think we know enough about cooking in the dishwasher to really, truly assess the risk,” he said.

Ben Miller | Food Safety News

Emerging Pathogens: Vibrio Cases in Oysters Expected to Continue Increasing

Dishwasher Cooking Trend Raises Eyebrows Among Food-Safety Experts