Julia Stewart:
Hello, this is Julia Stewart, and welcome back to PMA’s audio blog, “Ask Dr. Bob” with PMA’s Chief Science & Technology Officer Dr. Bob Whitaker. Bob, we’ve just devoted 10 posts to talking about the in’s and out’s of testing fresh produce for food safety. So, let’s hear it, bottom line, what’s your thinking?

Bob:
Let’s be straight, right up front, our industry has seen far too many outbreaks, and we must be fully committed to the safety of our products. If product testing could keep contaminated produce from getting into the supply chain and making people sick, then the issues of supply chain disruption and added cost would be moot. At the very least, the supply chain issues with regard to perishability and the costs associated with product testing would have to be considered in context with other costs involved in implementing a comprehensive food safety program – and the marketplace would ultimately determine how best to sustainably absorb those costs.

In our previous posts on product testing, we’ve tried to lay out some of the benefits and limitations of the various types of tests currently being used in the industry. We’ve discussed the very real issues associated with product sampling.  We have tried to do this with an eye on the perishable nature of our products, and some of the science that lies behind current testing methods.  I hope our listeners have picked up a few nuggets to help them as they assess how to set up their own product testing programs.  As far as whether you should or should not do product testing, that’s a decision that each producer has to address individually.

In reality, when it comes to product testing, it seems that the “horse is already out of the barn”.  While the scientific basis of product testing is arguable with current technologies, the marketplace is making some form of product testing a requirement of suppliers of some commodities.  Essentially, that moves the issue of product testing from a scientific debate to a business decision.  We can understand why buying organizations might want their suppliers to do product testing from a liability perspective.  I’ve even heard from some buying organizations that believe their requirements for product testing, while it may have limited preventative value presently, will actually help the industry to produce safer food in the future by forcing the supply side to examine all risk factors.  I have to admit, the issue of product testing has kept food safety in the forefront of industry’s focus.

Simultaneously, we see a science-based group like the Food and Drug Administration that, despite being clearly aware of the technical pitfalls of product testing, is nonetheless increasingly using product testing to do surveillance in the marketplace.  That reality alone means the produce industry has to continue to focus on some of the issues we’ve raised in this series. Each company must be sure they fully understand what these tests mean and what actions they will take should their in-house testing program or a government testing program turn up a “positive” result for their products. 

Julia:
So what’s the bottom line?

Bob:
Bottom line, Julia… product testing is just one tool in our food safety toolbox. Companies that think they can test their way to safety with today’s technologies are potentially whistling in the wind, as they say.  Product testing is clearly a part of our landscape, but sometimes I wonder if all the resources that went into testing were instead leveraged against preventing contamination in the first place, whether our industry’s overall food safety performance might be more improved.

Product testing and sampling is clearly an area where further research is needed and I urge our listeners to use the Center for Produce Safety, the local universities and cooperative extensions, and other resources to closely monitor new innovations and developments in this area.

Julia:
This is certainly a challenging area for the industry and for researchers alike. Well, this concludes our series on product testing.  In addition to listening to these and other Ask Dr. Bob blog posts, we invite PMA members to visit our new online Food Safety Resource Center on PMA.com. We are regularly posting new food safety content there to help you meet your company’s food safety needs.

Please email us at askdrbob@pma.com if you’ve got a question you’d like to see Dr. Bob address in a future post. Thanks for joining us! In addition to listening to these and other Ask Dr. Bob blog posts, we invite PMA members to visit our new online Food Safety Resource Center on PMA.com and check out the lab testing white paper in the Education section.

Julia Stewart:
Hello, this is Julia Stewart, and welcome back to PMA’s audio blog, “Ask Dr. Bob” with PMA’s Chief Science & Technology Officer Dr. Bob Whitaker. We’re continuing to talk about the benefits and challenges in product testing. Bob, there is a tremendous amount of product testing going on today in some commodities. What are some of the things we should consider when looking at all this testing and the resulting data?

Bob:
I think there are three basic questions we need to ask about testing, as well as what this data may mean and what we might do with it:
1. What pathogens should we be testing for?
2. Does a positive test result necessarily mean that the product would cause disease? And,
3. How can a company use the data generated for product testing programs to improve its food safety program?

First, let’s take the question “What pathogens should we be testing for?” Today, you’ll find many companies who test for E. coli O157:H7 and Salmonella species – others add a test for nterohaemorrhagic E. coli or EHECs – meanwhile still others are beginning to look at shigatoxin-producing E. colis or STEC’s – and a few even include Listeria monocytogenes in their product testing protocols.  Meanwhile, there are still some who look for indicator species like generic E. coli or total coliforms, even though the correlation between these and actual pathogen contamination is questionable in produce. 

So, which organisms should we test for?  A producer needs to make the decision on what to test for based on the risk profile of the particular products they grow and produce, the timing window they have between testing and when they need to ship, and the costs involved.  It’s important to avoid a “one size fits all” approach.  Instead, we should employ a science- and risk-based approach to determine commodity-specific and/or pathogen-specific testing strategies. 

For example, let’s say we’re a tomato grower. Then we’d clearly want to prioritize testing for Salmonella species, since this pathogen is most commonly associated with tomatoes.  On the other hand, if we are a leafy greens grower, then we’d want to broaden the pallet of tests to include Salmonella and E. coli O157:H7 and perhaps consider adding EHEC or STEC’s to cover all pathogenic strains historically associated with these foods. 

Julia:
So let’s look at the second question: Does a positive test result mean the product would cause disease? 

Bob:
You can look at this question from a number of perspectives.  Clearly, the most important is public health.  The Food, Drug and Cosmetic Act – that’s the federal food safety law we in the produce industry are currently subject to – considers product that tests positive to be adulterated, and prevents that product from being put into commerce.  The Food and Drug Administration will always act first and foremost to protect public health.  Further, as of September 2009, you have the obligation to report any products that may pose a public health risk via the Reportable Food Registry – so, if you had a positive test result and the product is in the marketplace, you’d need to report that to FDA. 

From a strictly scientific perspective, we know that new strains of E. coli have emerged in the last 30 years, most notably, E. coli O157:H7; and, unlike its harmless brethren, as few as 10 cells of O157:H7 can cause significant health issues in a person, particularly children, the elderly or other at-risk populations. Conversely, we can now identify more than 2,000 strains of Salmonella, whose illness-causing dose rates are much higher than with E. coli O157:H7, if they cause human illness at all.  Also, Salmonella infection is generally not lethal, and we’re learning that Salmonella may be more common in the environment than originally thought. 

So, while the zero-tolerance approach currently mandated by the FD&C Act is appropriate for a pathogen such as E. coli O157:H7, today’s science may or may not justify such a strict standard for other, perhaps less harmful pathogens.  We’re also starting to understand that perhaps a positive PCR test result or even a bacterial culture may not necessarily correlate to that organism’s ability to cause human illness.  Research is showing that our screening for DNA fragments that are associated with the pathogen’s ability to produce toxin, or to attach to the intestines, might not by themselves be proof that the organism can cause disease.  Other factors such as the pathogen’s acid tolerance and the physiological state of the pathogen likely play a critical role. 

Julia:
So, how can the data generated by a product testing program be used?

Bob:
Obviously, enacting a product testing program is an important decision and a significant financial commitment.  So, it seems reasonable that a company that chooses to do product testing should look to use the resulting data to improve their food safety programs.  In order to do that, you must have procedures in place to receive testing data from lab partners, to store and sort that data, and then analyze the data so that trends can be identified and acted upon.  For instance, you may be able to use product testing data in conjunction with additional data from your GAP or HACCP programs to identify and prioritize specific risk factors.  As an example, a preharvest risk assessment that identifies an animal intrusion event has occurred may be used in conjunction with a concentrated in-field product testing program to verify if the intruding animal species carried a pathogen, and perhaps even what buffer zone distances are necessary to manage the potential risk. 

Julia:
Bob, you’ve raised some interesting issues here to consider when setting up product testing programs.  How much data from product testing do you think is out there in the industry?

Bob:
Julia, that’s difficult to say.  Right now, the clear focus has been in leafy greens crops.  Some companies have large, sophisticated product testing programs that have generated thousands of data points.  In the last year there’s been a great deal of discussion around how industry might combine some of this data or “mine” it to see if it’s possible to prioritize risks.  We talked about this with FDA during a meeting after the Center for Produce Safety’s research symposium in June.  Sometime in the near future, we should do a blog series on data mining, as it’s a subject all unto itself with a number of positive and negative aspects.

Julia:
That sounds good, Bob; I’ll hold you to it!  Speaking of holding you to it, I promised our listeners that as we concluded this blog series, you’d sum up the real value of product testing.  So next time in our final blog in this series, let’s summarize some of the discussions we have had on this subject and see what the plusses and minuses are.  Until then, thank you, listeners, and we’ll see you back here next time.

Julia Stewart:
Hello, this is Julia Stewart, and welcome back to PMA’s audio blog, “Ask Dr. Bob” with PMA’s Chief Science & Technology Officer Dr. Bob Whitaker. This post is part of a continuing series we’ve been doing on product testing. In the last post we talked about the challenges of product sampling.  Today, we want to go back and look at sampling from an operational perspective.  Where and when you take samples can have very real impact on our bottom line. Previously, we’ve talked about the perishable nature of our products and the time it takes to perform testing; Bob, are there any options that might buy us some time?

Bob:
Well, Julia, as the industry has looked for ways to resolve the supply chain logistics issues versus the timing it takes to test products, some have implemented in-field or pre-harvest testing programs rather than testing and holding finished product.  This can be advantageous because the testing is done before harvest and before the shelf life “clock” starts ticking. Typically, these testing programs rely on field sampling 2 to 7 days prior to harvest. This permits enough time to sample the field, test the product, and get the results back from the lab so that a “negative” result can essentially “clear” the field for the scheduled harvest date.

For many commodities this is a better alternative than trying to hold harvested or even finished processed product. If testing does reveal a “positive” there is time to perform confirmation tests – then if these also come out positive, the affected product is not harvested and public health is not compromised in any way.  As a side benefit, since the contaminated product remains in the field, the event can be studied and perhaps the cause of contamination can be determined.  Recent work of this nature performed by Dr. Trevor Suslow and his team at University of California-Davis, with funding from the Center for Produce Safety and others, has shown some very interesting preliminary results regarding the importance of sample sizes, the presence of multiple pathogenic strains in a single contamination event, and the importance of temperature and rainfall for pathogen survivability. 

In-field testing also has the benefit of helping to manage costs.  Although growing costs are effectively committed just prior to harvest, in-field raw product testing permits evaluation prior to harvest so that harvest costs can be avoided if positive tests are uncovered.

Julia:
So what are its challenges?

Bob:
Well, although it generally avoids some of the issues we discussed in previous posts on perishability and test and hold practices, field-level raw product testing can still be highly disruptive to the supply chain. Harvest windows are often narrow due to rapidly changing market opportunities. Delaying harvest to permit product testing may impact a grower’s flexibility to hit a specific harvest window in a tight market.  In-field testing also leaves open a potential window of vulnerability. For example, if the raw product is tested in the field 2 to 7 days prior to harvest, any contamination occurring after sampling but before harvest could go undetected.  Indeed, data shared at the CPS Research Symposium in June 2010, indicated that attenuated E. coli O157:H7 purposely sprayed directly onto spinach or Romaine lettuce died off quickly, so that within two days, the attenuated strain could only be detected using enrichment procedures.  (I mentioned that research in a previous post in this series.) This may indicate that contamination events occurring within a few days of harvest may be more problematic than those occurring further away from the harvest date.  

There are also challenges in implementing raw product testing, whether it is implemented broadly across the produce industry, or even just targeted to “high risk commodities.” Aside from technical issues that may exist with the test itself and field sampling issues, pre-harvest or raw product testing requires active and complete communication between growers, shippers and processors. Test results obtained by any party sourcing raw products from common fields or lots must be shared in a timely fashion prior to harvest. This can be quite difficult to do in practice.

For example, a particular field could test positive by one shipper and would not be harvested by that company. However, a second company sourcing raw product from that same field might not have a field level testing program or if they do, their sampling scheme may not yield a positive result. That second company could then unknowingly harvest and ship the product only to find out later, if at all, that the field had potential contamination issues.  This lack of communication could easily translate into the second company having to perform a product recall with all the corresponding costs and damage to brands that encompasses.

So, while raw-product testing has some advantages over finished product testing from the perspective of perishability, it’s not without potential problems that could prove difficult to overcome if broadly implemented.     

Julia:
Thanks Bob. We’ve now talked about the issues of perishability, typical tests currently in use, product sampling issues, and raw versus finished product testing.  Next time I know you want to look at the significance of these testing programs and cover some additional thoughts on how all this data can be used.

Bob:
(laughing) OK.  I’ll be ready.  I look forward to it. 

Julia:
So will we, Bob.

Remember listeners, if you’d like to send Dr. Bob any comments or questions about product testing you can email him at AskDrBob@pma.com. In addition to listening to these and other Ask Dr. Bob blog posts, we invite PMA members to visit our new online Food Safety Resource Center on PMA.com and check out the lab testing white paper in the Education section. Until next time!