When E. coli O157:H7 made headlines in the 1990s and posed a threat to consumer health, especially consumers of ground beef and hamburger, meat processors thought first they had only one pathogen to attempt to control – albeit a formidable one.
Since then, scientists have discovered that there’s more than one E. coli STEC – Shiga toxin-producing E. coli – pathogen out there. And although O157:H7 probably shows up more than other STEC pathogens in food products, in recent years, six more pathogens have been discovered and found to be sources of food safety threats to consumers, not only in meat, but produce as well. The number of food safety cases from these non-O157:H7 strains of E. coli has been increasing.
Progressive food safety companies providing testing kits and products to detect dangerous pathogens in meat, poultry and other foods have developed more advanced technology and options to testing laboratories and processors that can identify seven pathogens that come from Shiga toxin-producing E. coli – seven STEC E. coli bacteria producing powerful toxins that can cause severe illnesses, and in some cases even death.
E. coli bacteria normally live in the intestines of people and animals and most are harmless and, in fact, are an important part of a healthy human intestinal tract. But some E. coli strains, including the seven STECs, are pathogenic.
Bio-Rad Laboratories, a food safety company based in Hercules, California, has recently introduced a testing kit that can find all seven Shiga toxin-producing E. coli pathogens in food products, including meat and poultry, and in water.
PCR technology itself isn’t new and is an established method used in food safety testing, looking for the presence or absence of pathogens. The problem with this more traditional technology is that when detecting STEC, determining the presence of different toxin genes in a single bacterium, it is not possible to determine if the genes are in the same organism or two different ones. “While PCR is highly effective at detection of foodborne pathogens, ‘false positives’ are often a reality using PCR for STEC detection,” says Mike Clark, International Group Manager for PCR Food at Bio-Rad.
Bio-Rad’s new kit to find STEC pathogens, called “dd-Check STEC” has some new twists, according to Clark. “The term ‘ddPCR’ stands for droplet-digital PCR and by dividing one sample into several thousand water-oil droplets, can concretely detect and verify that the positive STEC pathogen genes are present within single bacterium, giving an unambiguous true positive result.
“The droplets are essentially 20,000 individual reactions, encapsulating intact E. coli bacteria,” Clark says. “After PCR is performed in each one, the droplet reader scans each droplet individually and identifies if the target genes are present. This technology has the possibility to revolutionize STEC testing.”
Cari Lingle, a microbiologist for 3M Food Safety in St. Paul, Minnesota, talks about two methods the company offers for E. coli testing. One is called 3M Petrifilm Rapid E. coli/Coliform Count Plate. The other is 3M Molecular Detection System.
“The 3M Petrifilm Plate is next-day results for both E. coli and coliforms. It’s a two-in-one indicator test giving both an E. coli and coliform count within 18 to 24 hours. If a processor is doing ‘hold and release,’ the products can be released from inventory faster, meaning their products can have a longer shelf life,” Lingle says. “The Petrifilm plate count is used in meat, poultry and egg products to look for E. coli and coliforms as indicators of process control. They help meat processors, for example, to see how well their plant processes are working, and if any changes need to be made,” she says.
“The coliform count indicates a wider group of bacteria that might be there. If there’s a heavy load of microorganisms on beef, for example, coming into the plant, it might be more than the processor wants to accept into his plant,” she says.
“On the other hand, the Molecular Detection System, including the assay for E. coli detection, is not used to find an indicator organism, but to find E. coli O157:H7, the presence of the pathogen, as well as other pathogens like Salmonella and Listeria,” Lingle points out. She feels processors should probably use both systems: one to look for the pathogen itself, and the other to determine the “background level” of organisms to make sure processors are controlling their processes. “What’s in the plant environment? Is the sanitation up to the level it should be? Those are questions that can be answered by these tests,” she notes.
Both main methods are rapid test methods, allowing laboratories and processors to get results as quickly as possible. And both systems have the added benefit of being able to detect multiple organisms.
Because plant sanitation, as well as monitoring plant environments is so important, the company has just published a handbook on environmental testing – “The Environmental Monitoring Handbook for the Food and Beverage Industries.” Lingle is one of the book’s authors.
Neogen, based in Lansing, Michigan, offers rapid testing kit options for E. coli and coliforms, according to Rick Kanaby, director of sales for the food safety company’s meat, poultry and seafood group. One is the Soleris platform for testing products like meat and poultry and the environment.
He says the purpose of these tests is to facilitate the growth of target organisms, like generic E. coli and general coliforms. It’s an indicator organism and it’s helpful for processors to find if there is a lot of it in meat and poultry products, or in the plant environment. The idea is to keep generic E. coli at a low level.
Kanaby says Neogen has two primary testing platforms for detecting pathogenic E. coli bacteria – Reveal and ANSR. Reveal delivers results in 20 minutes after a 12- to 20-hour incubation for E. coli O157:H7. The ANSR system detects DNA to find the pathogen in 18 minutes after a 12- to 26-hour incubation.
When Kanaby talks about finding STECs, typically one specific pathogen is targeted, like E. coli O157:H7. To confirm the presence of one or more of the STECs, Neogen offers its NeoSeek service, that provides users with next-day results from submitted samples. This technology can detect all STEC pathogens.
Neogen’s Kanaby notes that E. coli is not a food safety problem limited to the meat industry. There have been high-profile outbreaks in the past year including a large recall of romaine lettuce, which was blamed for the most part on contamination in the environment. But he thinks the meat and poultry industry does a good job of moderating the risks of pathogenic contamination.
“While some people may assert the growing number of recalls must mean things are getting worse, we believe the numbers may reflect a higher level of more sophisticated and capable surveillance by the industry and auditing bodies,” Kanaby says. “They find it more because they’re getting better at looking for it.”
Kanaby also believes that sanitation in meat and poultry plants plays a critical role in preventing E. coli O157:H7 and other STECs. “The establishment of a robust environmental monitoring program provides plants with information they need to be effective in food safety. If we’re not cleaning our production equipment and the environment around it effectively, we’re going to get in all sorts of trouble.”
“There’s a saying in the food industry that states ‘you can’t test your way to safe food.’ The tests that Neogen and others supply are really sources of information from which responsible processors make important decisions. If they incorporate the knowledge they are gaining from our tests to make good decisions, then our tests have played an important role in helping assure the food supply is safe,” Kanaby says.
“Plant managers who want to prevent contamination of the food focus a lot of testing on the environment and develop robust environmental monitoring programs. By doing that, if you find it in the environment first, you can prevent it from getting into your product.”