[Microbiological Testing] E. Coli Detection

According to a recent release from the U.S. Department of Agriculture’s Food Safety and Inspection Service (FSIS):

• Since January, there have been 15 recalls related to E. coli O157:H7 in beef. Eight were associated with human illness.
• In 2006, there were eight E. coli-related recalls, none of which were related to human illness.
• In 2005, there were five related recalls.

Whether this reflects a rise in incidents or the impact of the industry’s increased ability to detect the pathogen as the cause of illness, the statistics indicate a need for better controls, and experts recommend that these controls cross the supply continuum — for virtually any product. While the most recent outbreaks have been related to ground beef, the spinach and lettuce recalls of 2006 prove that few food processors are exempt from the potential contamination of this pathogen.

ACROSS THE CONTINUUM. “When somebody gets sick, when somebody has an illness, it’s a failure across the system,” said Wendy Warren-Serna, vice president of technical services for Food Safety Net Services. Food manufacturers have a role in and responsibility for ensuring that good practices are taking place at every step of the continuum, she said, including testing for verification of controls and practices at the supply and plant levels and communicating with and educating customers and consumers in proper handling and use.

“If you do everything under your own roof you can control it,” Warren-Serna said. But when a processor is buying mid-process items, receiving any food item for further production, “you have to have a very strong communication with your suppliers and effectively build them into your process.” This may include testing of incoming goods or auditing of the product and processes of the supplier’s facility. “Do you have a high level of confidence that (your suppliers) have everything under control?” she asked.

As related to E. coli in particular, “it would certainly be helpful to have a baseline database of the level of contamination on and in live animals,” said Skip Seward, vice president of regulatory stewardship for the American Meat Institute (AMI). Although studies have been done on this, information is still limited, in part because of the inconsistency of the results.

On the technical side, Seward asked, why has the E. coli vaccine not been approved for use on live animals? The vaccine, developed through a partnership of Bioniche Life Sciences in Canada and the University of British Columbia, was approved by the Canadian Food Inspection Agency last December for distributions to veterinarians. Reducing the occurrence in live animals, he said, “is an excellent place to start.”

“E. coli is naturally carried by cattle,” Warren-Serna added. “It just is and that’s something that everyone has to respect.” But the question is, “How does that organism get transferred from the animal hide?” It is the understanding and management of that risk — whether on the animal itself or through contamination of nearby produce — that will lead to greater food safety.

On the other end of the continuum, she said, it is important for processors to take steps to ensure that customers and consumers understand proper handling of each product. “Do you know what your customer is doing with this product?” she asked. For example if a grocer is grinding beef that was intended to stay intact, there could be a higher associated risk.

CONSUMER EDUCATION. “As an industry, we all have a responsibility to educate the consumer,” Warren-Serna said, noting that such a responsibility extends to the retailer. Instead of distributing cheese-and-cracker samples, she recommends, give consumers a meat thermometer after a presentation on its proper use.

One of the greatest issues of consumer education is ensuring beef is cooked to 160° F internal temperature.

Warren-Serna used a comparison with jelly beans to explain: Say you have a container of 2,000 jelly beans, five of which are blue and the others white. Your goal is take samples from various points of the container to find blue jelly beans. If the five are grouped together in one corner of the container, you would have to hit that exact place in your sampling to find any. But if all the jelly beans are then mixed together, with the blue ones now at random places throughout the container, there is a higher likelihood of chancing upon at least one of them.

The same holds true with beef, she explained. If E. coli is located at one spot in a piece of beef, you would have to sample that very spot to locate it; once the beef is ground and the E. coli is mixed throughout the beef, you are more likely to find it in sampling.

It is also because of this mixing that illness is more likely from E. coli in ground beef, she explained. The pathogen is most commonly associated with the surface fat layer of the beef. When on an unground piece of meat, this will generally remain on the surface, thus is subject to more direct heat and higher temperatures in cooking than the center. But because E. coli can have been mixed anywhere in the ground beef, a trace of the pathogen that reached the center of the patty may not get “cooked out,” particularly if the patty is cooked to only a rare or medium rare state.

In addition, Seward said, a fair number of the recalls occurred with frozen ground beef patties, which, if cooked directly from the frozen state, have an even lesser likelihood of reaching the necessary internal temperature.

Consumer education should include information such as this, as well as clear labeling and cooking instructions. “The consumer, we’ve always said, has a role,” Seward said, “but we need to be sure the instructions we’re providing for them are adequate — with a little room for error.”

TEST, BUT VERIFY. One step FSIS took earlier this year toward prevention was the testing of beef trim. “By testing earlier in the production chain to identify contaminated beef trim intended for ground beef, FSIS prevents this source from contaminating the ground beef available to consumers,” said Daniel Engeljohn, deputy assistant administrator at the Office of Policy, Program and Employee Development in an October media teleconference.
In addition to this, FSIS is now:

• expanding its ground beef component testing, increasing the number of tests of ground beef for the E. coli by more than 75 percent in July, and testing other materials used in raw ground beef in addition to trim. 
• requiring imported beef to be subject to the same, or equivalent, sampling requirements as domestic beef.
• requiring verification that beef plants are effectively controlling E. coli during slaughter and processing, and providing industry with minimum criteria for this verification.
• accelerating implementation of initiatives scheduled for spring 2008 and planning to review suppliers and processors based on a new checklist.
• targeting routine testing on larger-volume slaughter and grinding operations more frequently, and using data to determine testing frequency for an establishment.
• increasing the speed of recalls, taking into account a broader, more complete range of evidence when evaluating whether to seek a recall or take regulatory action.

SAMPLING. There is a relationship between the number of samples taken, the prevalence of the contaminant and the confidence rate of finding the contaminant if it exists, Seward said. FSIS currently recognizes sound surface sampling for raw beef trim to be based on “n=60.” That is, the taking of 60 samples per lot, which is generally defined as no more than five 2,000-pound combos, which is said to result in 95 percent confidence that the pathogen would be detected if it was present at a level of five percent or greater.

More samples could be taken to increase the level of sensitivity and the likelihood of detecting the pathogen. “But eventually you run up against the practicality of taking that many samples and the cost of that,” Seward said. “It is not really practical.”

A better improvement would be a reduction of lot sizes, he said. Not only would this increase detection sensitivity, it would reduce the beef processor’s liability should the test run positive, as less potentially contaminated product would need to be diverted.

Where a product is tested during the process also is an important factor, particularly as it relates to homogenized products such as ground beef, for which it may be more effective to test the finished product, but also is less efficient. The problem with testing after the beef is ground, Seward said, is “you have all that additional value in the product.” Discovering the pathogen in finished ground beef is very costly.

In addition to detecting a pathogen early, it is critical to have ongoing monitoring that any detection is quickly realized and communicated. “Early warning in the fresh food industry is paramount,” Warren-Serna said. “If we know right at the point of the problem, we can take care of it as soon as possible and take steps to keep it from being released into commerce.”

Such a system needs to include timing of sample collection, collection technique (“Are you taking a representative sample?” she asked), and analysis of testing data. Different plants will need different systems, with each specifically designed to the process. But, regardless of the specifics, the plant should develop a “robust sampling plan to try to find a defect if it’s there,” she said. “Try to do it in such a way that you have some of the odds in your favor. The more sampling you do and the more representative it is of your process, the more opportunity you will have for detection.”

USING THE DATA. A plant can have a robust sampling program with all the odds in its favor, but if it is not analyzing and applying the resulting data, it is virtually worthless. “Once you have the data,” Warren-Serna asks, “What are you doing with it?” One of the greatest fears of an auditor is to walk into a plant and see sealed, unopened lab reports. Lab results need to be reviewed and need to be applied back to the program. “Pulling a message out of that data is so important,” she said. Data should be trended and tracked, problems and artifacts identified, and corrective action developed to get to the root of any issue. All of which should be done by a knowledgeable, dedicated person. “What I like to see is a person responsible for this activity who doesn’t have 14 other hats that they’re wearing,” she said. “The person has to be able to be dedicated to it.”

Even if all the data is coming back negative, the question should be asked as to whether the program is robust enough or if testing should be more aggressive. “Don’t get too complacent with negatives,” she warned.

In addition, a plant should ensure that the lab doing the testing is fully accredited or being held to standards; that it is calculating the results correctly and using verifiable, standard testing methods. “Can you stand behind that result to make decisions?” a plant should ask itself.

PLANT PRACTICES. So what can a plant do? “That is the million dollar question. What can industry do to further ensure that contaminated product doesn’t reach the consumer?” Seward said. “You can’t test safety into the product,” he said, but you can follow best practices, such as following of n=60 standards, putting tested products on hold until results are reported, conducting proper sanitation of all equipment used in the process and in the entire plant environment, and increasing our understanding of the pathogenic association.

For example, he said, “Can E. coli harbor like Listeria? That’s a question that perhaps needs to be addressed.”

“Testing is not going to solve the problem, but it’s going to help us improve our processes,” Warren-Serna said. Prevention and the application of Good Manufacturing Practices (GMPs) are the real key to reducing incidents, with testing as a tool for verification. “It’s all about managing risk,” she said, “Testing will show that your processes and procedures are working to control those hazards.”

INTO THE FUTURE. Even with higher controls in place, both Warren-Serna and FSIS warned that detected incidents of E. coli levels could very likely increase in 2008, because of increased detection systems being put in place. “In January 2008 we will begin using a newly developed test that will detect lower levels of E. coli O157:H7 contamination in products that we test,” said David Goldman, FSIS Assistant Administrator, Office of Public Health Science. “I want to remind people that the outcome of this new test use may be that we find more positive results than in years past once we begin employing this new test.”

“As clinical surveillance gets better, it’s going to shift the balance a little bit, because with that increased awareness, we may see higher levels than we thought,” Warren-Serna added.

Consumers have more understanding of foodborne illness and doctors are more likely to test for them when a patient comes in with potential symptoms. Even when there is no actual product remaining for testing, the traceability of products back to a particular lot and analysis of multiple cases can detect a relationship and pathogenic source. “The incidents are not necessarily increasing, we just know what it is,” she said. “It’s a product of a better public health surveillance program.”

The author is Staff Editor of QA magazine.