Rapid testing insight
Sept. 12, 2012
by Bryan Salvage
Meat and poultry processors want faster, more accurate rapid-test results to protect their products, customers, consumers and their own companies from potential food-safety dangers. And rapid-test suppliers are endeavoring to satisfy this demand.
Stronger regulations from the US Dept. of Agriculture’s Food Safety and Inspection Service, Food and Drug Administration as well as the Food Safety Modernization Act are leading to increased rapid-test usage by industry. Growing food-safety awareness from the public and government also are playing a role in the demand for faster, more accurate tests, says Chris Lopez, technical sales and pricing analyst with San Antonio-based Food Safety Net Services.
“Microbiological testing and high quality programs are a good starting point for a foundation to ensure the protocols of meat and poultry companies are protecting their products and their business,” he says.
Various platforms of rapid testing use different scientific approaches to detect the microorganism of interest, Lopez says. These platforms usually fall under three main approaches: antibody-based, nucleic acid-based or enzymatic.
Many rapid-test providers tout their tests are user-friendly and that anyone from a trained molecular microbiologist to entry-level lab technician can conduct them.
“When we chose our ATP [adenosine triphosphate] testing system, we looked for the system with accuracy, ease of use and understandable results,” says Darren Toczko, senior manager of food safety with Bar-S Foods Co., Phoenix, Ariz.
“I want accuracy, sensitivity, reproducibility, costs, time-saving and ease of use,” adds Carl Zerr, director of international food safety and quality assurance with Rastelli Foods Group, Swedesboro, NJ. “The most important thing to me is accuracy.”
Bar-S plants use ATP testing during pre-op inspections. At its corporate off-site laboratory, it uses a Listeria spp. test for processing environmental swabs.
“If the surface is not clean, we know it within seconds,” Toczko says. “ATP testing does not replace Aerobic Plate Count/total plate count or Listeria testing. It is an indication of cleanliness, not of microbe level or type.”
The Listeria spp. tests used in the Bar-S lab are fast, accurate and flexible to company sampling needs. This enables the processor to find and respond to any issues in a timely manner with confidence, he says. Bar-S’ Listeria spp. testing must be an AOAC method performed in an ISO 17025 laboratory.
“Our company lab, which processes samples for four plants, has been ISO17025-accredited since 2006, with Listeria spp. on its scope of accreditation,” he adds. “Any Listeria method without an enrichment step to allow very low numbers of cells to grow would not be considered. Since Listeria is a slow grower, faster is not always better.”
The test Bar-S uses requires a single-step enrichment and incubation for 40 to 48 hours, Toczko continues. “We stay away from methods which would lead to FSIS scrutiny of our results,” he adds. “It must also be flexible for increases in numbers of samples to be tested without excess increase in time, people or equipment,” he says.
Rastelli Foods Group, a major national US foodservice distributor of beef, lamb, veal, pork, poultry and seafood products, incorporates rapid testing for E. coli O157 and Salmonella. It currently uses the FoodChek MICT system for the E. coli O157 test and upon AOAC certification, will also use the Listeria spp test.
“I like the accuracy of the results, the ease of preparation and sample protocols to put everything together,” Zerr says of his E. coli O157 rapid test. “I didn’t need to hire a microbiologist to do the testing,” he adds. “The cost of the FoodChek Reader unit, test cassettes and pickup transportation savings I get by not sending every test to an independent lab is another factor.”
The company conducts many in-house screening tests. Zerr still sends bi-weekly samples to an independent lab to confirm that his in-house test results are consistent, but he has reduced this practice by about 90 percent.
Rastelli Foods now samples and tests products for the presence of E. coli O157 pathogens in its ground beef at 15-minute intervals. Before, tests may have been done two or three times a day. But over his first year despite increasing their testing, the company has saved around $14,000 with FoodChek’s system, Zerr says.
Examine each technology
A gap exists between current microbiology diagnostic products and technologies and what is ideally desired in rapid testing by plant QC managers, says William Hogan, president and CEO of FoodChek Systems Inc., Calgary, Alberta, Canada. Faster time-to-results (TTR) is the key requirement that enables better decision-making, improved economics and reduced risks, he adds.
FoodChek’s patented MICT magnetic nanotechnology system eliminates human error by using a testing process that includes a bench-top electronic magnetic diagnostic reader, Hogan says. The FoodChek system is the only food-safety pathogen screening test that uses nanotechnology, which consistently produces accurate results in as little as eight hours, including the sample enrichment growth phase, he adds.
FoodChek’s MICT Assay cassettes for E. coli O157 and Listeria spp provide very fast and accurate results in hours not days; are easy, five-step processes; and offer savings of up to 50 percent on the cost of pathogen testing, he continues. The company’s patent-pending Actero Enrichment Media also claim to have the fastest time-to-results in the bacteria growth phase; making the timeline to results up to 30 percent faster for E. coli and Listeria, and up to 70 percent faster for Salmonella. “Our MICT test cassettes give a quantitative result with a hard copy printout,” Hogan says.
Processors should use rapid tests as insurance to safeguard their business, Hogan insists. “I see [rapid tests] as a huge marketing tool,” he adds. “If you test more than your competitors, why would a consumer or retailer not buy from you? We’re creating the FoodChek symbol/brand for food safety to be like the Nike Swoosh. Rastelli Foods intends to be the first to put the FoodChek brand on its packaging.”
“[After the enrichment growth phase], our tests take 30 minutes to set up and 48 seconds to get results. We can find the results in the same production shift; nobody else can do this,” Hogan says.
FoodChek’s E. coli O157 rapid test is AOAC-approved and USDA/FSIS comparable. A new AOAC-approved, USDA/FSIS comparable Listeria spp rapid test is due for release this October; its Campylobacter test is expected out in January 2013; and its Salmonella spp; and its new STECs (shiga-toxin producing E. coli) tests are expected to be released in the second quarter of 2012.
More meat and poultry processors and testing labs are looking for technologies with faster turnaround times for their pathogen screening so decisions can be made earlier regarding releasing inventory or in-process product, concurs Christine Aleski, US pathogen specialist, 3M Food Safety Department, St. Paul Minn.
“Time is money and this axiom rules in the quality control lab as well,” she adds. “The sooner the results are available and the more accurate those results, with fewer retests required, the better financial circumstances for the company.”
Pathogen screening for Salmonella, E. coli O157(H7) and STECs are used most by 3M’s meat and poultry clients.
Rapid molecular testing offers earlier release from test-and-hold on inventories; increased specificity and sensitivity to help reduce the number of repeat tests; streamlined workflow to increase lab efficiency and technician productivity; real-time results to help make critical decisions faster; robust hardware with minimal maintenance requirements and less downtime for the lab; and powerful software that is easy to use and operate, she says.
3M’s Molecular Detection System is a simple, rapid, specific and cost-effective nucleic acid amplification and detection method, she adds.
“3M combined two unique technologies – Isothermal DNA amplification and bioluminescence detection – to offer the specificity and sensitivity required in a pathogen test solution that is also fast, simple and cost-effective,” she adds. “Compared to other rapid-detection methods, the system improves efficiencies in the lab process by offering users only one preparation protocol across all assays and all matrices allowing for batch processing, easier training and less chance for human error.”
Because the DNA amplification is detected via bioluminescence, the 3M Molecular Detection System offers the unique use of color-coded assay tubes to differentiate pathogen assays making it easier for technicians work with its system, she says. Bioluminescence provides real-time detection of the DNA amplification and simultaneous amplification and detection allows for detection of positive results before the end of the run (as early as 15 minutes).
With a smaller footprint that a standard notebook computer, the 3M Molecular Detection Instrument requires significantly less space than the market leading rapid methods, she says.
3M’s technology instrument is robust and portable with no need for recalibration, requires minimal maintenance and provides automatic diagnostics at start up. Isothermal DNA amplification proceeds at a constant temperature, removing the need for complicated instrumentation. Bioluminescence detection eliminates the need for high-cost excitation sources, fluorophores, fluorescent filters and detectors.
Assays are available for testing Salmonella, Listeria and E. coli including O157 H7.
Meat and poultry customers of Bio-Rad Laboratories Inc., Hercules, Calif., are using the company’s real-time PCR assays, says Wendy Lauer, senior product manager, food science division. These tests typically are for Salmonella and E. coli O157:H7. The company also offers an assay for STECs.
However, its most popular assay is its Listeria assay for environmental samples. “That’s where they test the processing environment instead of the food to use Listeria as an indicator of hygiene,” Lauer says.
Doing the culture method could be less expensive than a rapid method, but, regarding time-to-results – cost is a relative term. “If you have your food sitting in a warehouse waiting for test results, that’s an additional cost on top of your cost of testing,” Lauer says. “If you use a rapid test and get a result after 24 hrs. as opposed to 48 hrs., that’s one day more you have shelf-life on that product.”
Another rapid-test benefit is the ability of high-throughput screening. If a company is processing 100, 200 or more samples at one time, it needs something that can fit into that workflow. Usually, rapid methods are designed for that, Lauer says.
Sensitivity is key. “You want to have the right answer to your rapid testing [and not false negatives or positives],” Lauer says. “PCR methods detect DNA of the target, they’re extremely sensitive, which yield better results.”
iQ-Check is the company’s line of real-time PCR kits. “We have a full menu of different tests,” Lauer says. “We have iQ-Check Salmonella; iQ-Check Listeria (species and monocytogenes); iQ-Check Campylobacter; iQ-Check O157; and iQ-Check-STEC. All of our tests can all be run at the same time because chances are people aren’t just running one pathogen. Most people are running Listeria for their environmentals and Salmonella for their products, and they’re possibly running an O157 as well.
Enrichment times depend on the organism. Bio-Rad’s O157 test is validated for an eight hr. enrichment; STEC is 10 hours; Salmonella is 20 hrs. with no regrowth step; and Listeria 24 hrs. After the enrichment, the sample processing time is about 30-45 minutes and the run time is about an hour- and-a-half to two hrs. For the Listeria test, complete results are available between 26-27 hrs.; for O157 complete results are within 10-11 hrs.; Salmonella is less than 24 hrs. For all tests, the enrichment times are 24 hrs. or less.”
‘Time is money’
Expect rapid testing to increase among US meat and poultry processors in the future, all sources agree.
“Processors will be looking for ‘flawless information instantly,’” Hogan says. “It’s about gaining the fastest time-to-results. You’re going to see an entire movement towards technologies being the fastest because time is money.”