When harmful bacteria are found in food products, things can quickly spin out of control for processors. A white paper recently released by the Food Science Institute at Kansas State University details the shutdown of a facility in Wheeling, IL leased and operated by a specialty food manufacturer. According to the report, the company experienced two food pathogen-related events (Listeria monocytogenes in its products), resulting in voluntary product recalls in May 2014. Only two months later, the company terminated its lease for the facility, surrendered the property to the owner and laid off all the remaining staff.
In 2000, the US Department of Agriculture’s Economic Research Service estimated that $6.9 billion per year was lost due to illness caused by five major foodborne pathogens. A 2012 report estimated that illness from 14 major pathogens in the US cost $14.1 billion annually, and the economic analysis does not stop there. “Economists have forecasted that pathogens alone can result in as much as $83 billion dollars in total annual losses worldwide,” says John David, global marketing supervisor for 3M Food Safety.
Clearly, the incentive to test for pathogens is present, but until several years ago, safety testing was a time-consuming, costly process. “Over five years ago, 3M conducted needs assessments with a number of its top food and beverage processor clients regarding safety testing,” says David. “Two top needs that emerged were accuracy and speed.”
Many of the new rapid testing methods designed for processors provide better in-house results and are faster and more convenient to use. Additionally, with microbial testing as an integral part of Hazard Analysis and Critical Control Point (HACCP) plans for quality assurance, detecting pathogenic organisms will become even more vital. As reported by Food Engineering last year, the food safety testing market is predicted to grow to $13.9 billion by 2019.
“Today, many retailers are providing their suppliers with stricter testing requirements to ensure both ingredients and finished products are safe,” says Morgan Wallace, senior microbiologist and validations leader for diagnostics at DuPont Nutrition and Health. “Rapid testing methods are quickly becoming the most cost-effective way to meet these retailer expectations.”
Traditionally, harmful pathogens have been detected through culture plating, which has long been considered the gold standard. The method involves the suspension of a sample in a solution, preparing an optimal bacterial growth medium and then plating the sample and media and incubating them in an ideal growth environment. Finally, the presence or absence of bacterial colonies is assessed. Because a number of adjustments might have to be made to any of the components, this approach could take over a week to obtain a result.
Although this method was long considered to be the most accurate, it was not easy to use and required a trained lab technician. Plus, it required a delay in food products going to market. However, advancements in enzyme-linked immunosorbent assay (ELISA) technology in the 1970s, as well as work on polymerase chain reaction (PCR) in the 1980s, ushered in an era of commercially available rapid foodborne pathogen detection tools.
“For products like refrigerated foods, where the cost of holding product for testing can be high, rapid testing can clear product for market faster and increase usable product life on the shelves,” says Wallace.
The ELISA method reduces the amount of time needed to produce a result by relying on antibodies to detect specific bacterial proteins. However, its sensitivity has limitations. The molecular methods of PCR are sensitive to pathogens and provide faster result times.
“An increasing number of food processors and laboratories are requiring and implementing molecular detection methods for pathogen testing,” says David. “Molecular methods can offer faster time to result, reducing the process by days, not just hours. In comparison to traditional culture methods or immunoassay-based methods, they also bring the benefits of higher sensitivity and specificity.”
PCR platforms have been improved and developed to now offer real-time PCR, says Stephanie Wilkins, microbiology product manager for Mérieux NutriSciences. “Real-time [RT] PCR is a type of rapid method that detects a pathogenic organism’s DNA sequence target in as little as an hour and a half after the DNA has been extracted,” she says.
The InstantLabs Hunter Real-Time PCR system provides food processors with a compact, portable solution that detects problematic foodborne pathogens. CEO Steve Guterman recalls a seafood processor that recently came to InstantLabs because of receiving too many false positive results from its ELISA system. “Protein testing systems—immunoassays or ELISA—can run into a matrix-specific limitation when encountering specific food or beverage types,” he says. Seafood companies sometimes have problems with false positives because of the protein-protein interactions within the test.
MOCON’s GreenLight microbial detection system uses sensor technology to measure the changes in oxygen levels in samples. Since the system does not require time for incubation or serial dilutions or plating, it produces results within a range of less than five hours to 11 hours, depending on the amount of contamination.
“In addition to testing for safety, testing for potential spoilage is a huge economic concern for food producers,” says Alan Traylor, business manager for MOCON. “There are new rapid methods that can detect and sometimes enumerate spoilage bacteria that make it through to final packaging. These include spore-forming bacteria that might only become active much later in the delivery chain, causing recalls and producer losses. By using highly sensitive oxygen detection assays, spore formers and other bacteria [even in the cold chain] can be detected in less than 24 hours without long pre-enrichment and testing cycles.”
Isothermal amplification is another relatively new, emerging rapid testing technology. “In contrast to PCR technology in which the reaction is carried out with a series of alternating temperature steps or cycles to achieve amplification, isothermal amplification [testing occurs] at a constant temperature,” says Wilkins. “Due to this approach, it does not require a thermal cycler and is very simplistic, allowing for a smaller footprint instrument.”
Enrichment times have been considered to be the leading barrier to time to result with the PCR method, but new advancements in rapid technologies are working on “enrichment-free” detection. For example, the Sample6 method utilizes naturally occurring bacteriophages that carry a specific reporter gene and is expressed once it is attached to a target cell, explains Wilkins.
“In this way, the Sample6 DETECT method completely eliminates the need for enrichment and significantly reduces the total time to results,” says Shana Cooper, director of product management for Sample6. “What previously took days and often required a testing sample be sent offsite to a third party only takes a maximum of seven hours and can easily be completed onsite.”
However, the molecular method for pathogen detection still requires a food or food surface sample to go through the enrichment media phase. The Canadian company FoodChek Systems Inc. is working to knock down that time. “To increase faster time to results, many food safety testing manufacturers have upgraded their testing systems or hardware, but they forgot about the enrichment media or software phase,” says William Hogan, president and CEO of FoodChek.
To remedy this situation, the company has developed the 20-hour, single-stage Actero enrichment media which, together with the DuPont BAX System Real-Time PCR Listeria monocytogenes assay, produces detection of this pathogen in 22 hours, one of the fastest time to results available.
“If facilities have shorter enrichment times, they determine much sooner whether they have a contamination problem,” he says. “Plus, they can increase the shelf life of a product and standardize their sample collection system. All of these benefits result in bottom line profits for processors.”
To achieve faster and more accurate results, manufacturers of rapid detection tools are focusing on different areas. One of these is reducing hands-on time by automating the DNA or RNA extraction step and PCR assay setup.
“Automation can not only remove the complexity associated with molecular methods, it can also provide safeguards to ensure the reported result is accurate,” says Phillip Berry, marketing communications manager for Roka Bioscience, Inc., which makes the Atlas System, a fully automated molecular pathogen detection method. “Automation removes the opportunity for the operator to influence the final result and provides a level of traceability and fidelity in the assay that is not attainable with more manual methods.”
A closed system and minimal technician interaction prevent cross-contamination and human error, says Wilkins of Mérieux NutriSciences. “This also enables the testing laboratory to be more efficient and process samples in a more timely manner,” she adds.
Advancements in microbial testing have eliminated counting methods that use manual labor, says Traylor. For instance, optical techniques have enabled automated readings. “Measurement systems can now be connected to the laboratory information management system to eliminate errors made in reporting and documenting test results,” he says.
Other companies are making rapid detection tools easier to use to improve the accuracy of the diagnostics. The American Proficiency Institute recently conducted a study on pathogen testing and found trained operators had an accuracy range of 2 to 10 percent in detecting Salmonella.
“Technologies that are easier to use help reduce operator error,” says Cooper. “For plants or small labs, technologies like the Sample6 DETECT method limit the number of steps and leverage standard lab practices to reduce the risk of user error.”
Simplifying the process so non-expert technicians can reliably perform tests is key, says DuPont’s Wallace. “For example, advancements are being made to simplify the testing process by eliminating complex steps such as centrifugation, minimizing required transfer steps and reducing the potential for cross-contamination events in the laboratory,” he says.
According to Guterman, InstantLabs products streamline the extraction process, so individuals without years of scientific training can run tests with accuracy and confidence. “Improved analysis algorithms parse the sample data much more efficiently,” he says. “Testing systems can provide highly accurate ‘yes-or-no’ results quickly to the end-user.”
3M Food Safety’s David says the problems with traditional PCR technology are that it requires complicated sample preparation steps that can lead to errors, and it uses complicated instrumentation involving thermal cycling and fluorescence detection. To eliminate these issues, 3M has taken a new approach to molecular pathogen testing by including in its molecular detection system two technologies: loop-mediated isothermal DNA amplification (LAMP) and bioluminescence detection.
“The molecular detection system contains pre-dispensed, ready-to-use reagents that require no measuring or mixing,” David explains. “It also provides matchless laboratory efficiencies through its single assay protocol across all the different pathogen tests— things like batch processing, easier training and less chance for human errors.”
The bioluminescence technology improves on automation by employing a special temperature-stable luciferase, an enzyme found in fireflies, to generate light during the amplification reaction. “This light is then read by the 3M molecular detection system’s instrument, automatically determining the presence or absence of the organism being tested for in the sample, without the potential for human error,” David says.
When choosing a rapid detection method, processors should consider a number of factors based on their manufacturing and business processes, including the type of food they test and what they test for.
“The type of matrix that is being tested will sometimes work better on one type of rapid method versus another,” says Wilkins. “Dark-colored matrices, emulsifiers and matrices with inhibitory ingredients are a challenge for some rapid method assays.”
“Food processors want to be confident that a pathogen detection solution will work with their specific food products, so they should conduct an extensive in-house evaluation to ensure the method’s performance meets their expectations,” says David. “Time to result, ease of use, productivity and system throughput are also important considerations.”
The affordability of bringing testing in house has been an additional factor, but costs have been trending downward in recent years. “For many processors, reducing storage costs and being able to get products to market faster more than offset the costs of installing a laboratory,” Guterman says.
Wallace agrees that processors that must release a product as soon as possible will benefit from a method with the fastest time to result, even if the price per test is higher than other available options. “On the other hand, a processor that must detect very low levels of a pathogen may benefit more from a method with a superior limit of detection, rather than speed or simplicity,” he says.
Sample6’s Cooper says many plants have found bringing testing in house saves both time and money. “Biosensor technologies such as the Sample6 offer capital equipment and kit costs that are half of third-party laboratory rates,” she says.
With in-house testing, processors also have the option of performing more tests more frequently. For example, after Rastelli Foods Group purchased the FoodChekMICT system, it went from testing only two times a week to testing 25 to 30 times a day. “Rastelli has gotten more customers due to its food safety testing program and protected its brand,” Hogan says.
The processor and supplier worked together to develop the FoodChek-Tested program, designed to communicate to consumers the objective of providing quality and safe, fresh food products. To convey this message, Rastelli Foods now has the FoodChek-Tested label on its products. Carl Zerr, the director of international food safety and quality assurance at Rastelli Foods Group, Inc., says the testing helps reduce potential recalls. “You want to know if you have a pathogen problem before [product] gets out,” he says. “Because of our test-and-hold program, nothing is out of our control.”
Additionally, Rastelli uses its food safety program as a marketing tool. Zerr says he’s received questions about the FoodChek-Tested label, and when he explains it signifies Rastelli’s robust food safety program, which goes above and beyond what the regulations mandate, people ask why everyone else doesn’t do it. “I can’t speak for anyone else, but we’re doing it to protect our consumers, and when you protect your consumers, you protect your brand,” he says.
When considering the implementation of any rapid testing method, processors should factor in its full cost, a step which is often overlooked, according to MOCON’s Traylor.
“[Processors] see the reagent cost and compare one method to another based solely on this variable. Labor costs, including physical demands and the extra shifts need to perform quality control work, are sometimes ignored,” he says. “Another cost is the energy needed to enrich and incubate samples. In many countries, the energy cost is so high that a rapid method with three or more times the reagent cost will still be advantageous because the test will be complete in less than 24 hours compared to three days for the classic microbiology method.”
Finally, the complexity of the testing system also should also be taken into account, according to Guterman, since processors may be reluctant to invest in systems with complicated protocols that require highly trained staff.
“Most manufacturers want a one-stop shop to test all their products, no matter how varied, with confidence,” he says. “Long story short: The best testing systems for the food and beverage processing industry are easy to use, require little hands-on time, have a small footprint and are adaptable to a large variety of sample types.”
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