Salmonella-tainted ground beef could be the biggest challenge facing the industry, said a leading beef researcher. In March 2013, Salmonella Typhimurium in ground beef was linked to more than 20 human illnesses in six states.In September 2012, nearly 50 people in nine states became ill from eating ground beef tainted with Salmonella Enteritidis, according to the U.S. Centers for Disease Control and Prevention.
“It was always our working assumption that E. coli interventions should be controlling Salmonella,” said James Marsden, professor of animal science at Kansas State University. “E. coli is transferred from the beef hide to the carcass and works its way through the system. We thought this is what Salmonella did as well.”
“Incidences of E. coli have dropped sharply over the past 10 years, but Salmonella isn't dropping, which is perplexing,” Marsden added. “And some strains of Salmonella that have been observed in beef are drug-resistant strains, so they pose a public health problem.”
Scientists have realized they may have misidentified the source of Salmonella in beef cattle. They now realize it may be in the lymphatic system of cattle, making it harder to prevent than E. coli.
Researchers at Texas Tech University now believe that, unlike E. coli, Salmonella is in the lymphatic system of cattle. “In 2010, the industry was in a position to start asking questions,” said Guy Loneragan, professor of animal science and lead researcher at Texas Tech University. “We started looking at the lymph nodes, which are internal and exempt from current-prevention techniques.”
The rate of Salmonella-positive tests for ground beef increased each year from 2009 to 2011, according to a 2011 report from the Food Safety and Inspection Service (FSIS), the food-safety branch of the U.S. Department of Agriculture.
The scope and rate of sampling ground-meat products is different than those used for intact products such as whole chickens and turkeys. Any processing plant that produces at least 1,000 pounds of ground beef per day is subject to Salmonella testing.
If an egg facility has a Salmonella-positive test, eggs are not automatically recalled. They then do tests on the eggs. If the eggs are positive, they issue a recall. If not, then no recall. If ground beef tests positive for E.coli, it is recalled whether or not there are any illnesses. If ground beef tests positive for Salmonella, it is not automatically recalled. It is only recalled if there is a human illness.
Marsden, the Kansas State expert, said that USDA recalls beef with any level of E. coli because it considers E. coli an adulterant. When the agency finds Salmonella, it doesn’t issue a recall because Salmonella is not classified as an adulterant.
“If USDA decides it is an adulterant, that changes everything,” he said. “That would put this on the front burner and will cause problems for the industry.”
Marsden said there have been citizen requests to USDA to declare Salmonella an adulterant, but the agency has yet to do so.
Loneragan’s team is looking at what can be done pre-harvest to reduce Salmonella. He said what can be done in a beef packing plant is limited.
“There are many lymph nodes, and it is not practical or achievable to remove them,” said Loneragan. “We have downstream measures and we have upstream measures. Downstream measures would include irradiation or pasteurization. We are focusing upstream, on the live animal.”
Salmonella vaccinations and a diet that includes probiotics or direct-fed microbials are being used to reduce the prevalence of Salmonella in cattle.
Loneragan said that while research is preliminary, the findings are encouraging and warrant further consideration.
“There are benefits to feeding cattle for 30 days prior to slaughter with direct-fed microbial (probiotic) supplementation at the low- and medium-dose level,” she concluded..
“As for vaccines, the costs to a producer have not yet been determined. Probiotic costs could be about $2 per animal for the duration of time it is in a feed lot.
Reduction of Salmonella, not elimination, is the goal, Marsden said, adding that he believes it would be very difficult to get to zero cases of Salmonella or E. coli. Due to the drug-resistant nature of Salmonella in ground beef, there are few post-slaughter prevention options.
“You would need some form of pasteurization to eliminate it, or irradiation, but I am not a big advocate for it. Consumers are against it. Irradiation has been a dead issue for a few years, but there was discussion about doing it again in a more acceptable manner. It is a possible solution,” Marsden said.
Another possible postharvest solution would be to treat the ground beef with ammonium hydroxide. This practice of treating ground beef received mostly negative national media attention in 2012.
Ammonium hydroxide is used by Beef Products, Inc., a South Dakota ground-beef processor, in making lean finely textured beef, sometimes referred to as “pink slime.”
“I have done research with BPI for 10 years, and while their main concern was E. coli, we did look at Salmonella as well,” said James Dickson, professor of microbiology and animal science at Iowa State University. “Ammonium hydroxide does control E. coli and Salmonella in ground beef. It doesn’t eliminate it, but it does substantially reduce it.”
Ground beef trimmings were treated with Salmonella, E. coli and other pathogens during Dickson’s research. The ammonium hydroxide-treated beef displayed lower levels of pathogens. Further, when the treated beef was mixed with untreated beef, the new mix also displayed lower levels of pathogens.
“If meat is prepared properly, Salmonella is neutralized,” Marsden noted. “It can be in steaks and roast, not just in ground beef. But if it is all cooked well done this would solve the problem.
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