Rapid tests under development improve pathogen testing - The Packer

Rapid tests under development improve pathogen testing

07/01/2013 11:15:00 AM
Melissa Shipman

Advances in pathogen testing are coming soon, according to Trevor Suslow, extension research specialist for preharvest to post-harvest produce safety at the University of California-Davis.

“We’re trying to develop a rapid system or index for assessing the likelihood that pathogens will be present,” Suslow said.

In fact, Suslow says several systems are in development.

“Everyone’s searching for a validated approach for predicting food safety,” he said.

In particular, listeria is at the forefront of many industry discussions.

“We get a lot of questions of listeria contaminations, and what it takes to be compliant with the increasing expectations of retailers and buyers,” Suslow said.

United Fresh is taking the lead in pulling together a white paper that will be released shortly, according to Suslow. The goal is to present a sort of how-to manual for the industry, in which best practices for prevention and environmental monitoring of listeria are detailed.

New testing systems

These systems focus on delivering answers faster.

“You have to have an answer on if pathogens are present before you ship, so the latest advancements are in the sensitivity of the detection,” Suslow said.

“These new testing systems focus on placing the samples in an enrichment culture to help encourage those pathogens to multiply and increase in number so they can be more easily detected,” he said. “You are basically just growing enough of what may be present so you can more easily detect it.”

Then, there are several techniques to sort out any potential pathogens.

“There are a number of creative and sophisticated systems, either using magnetic or specially formulated viruses that will attach to something like E. coli or salmonella,” Suslow explained.

These processes will help to reduce the amount of time needed for labs to come to a conclusion on whether the sample needs to be rejected or accepted.

In some cases, traditional tests may have taken somewhere between three and four days, whereas these new rapid systems can have results in 12-24 hours.

Suslow said there are other various lab techniques and specifics that can affect the specific time each test takes to finish.

For example, listeria, which grows slower, needs to be grown for 20-24 hours to prevent what Suslow calls a false negative, while E. coli or even salmonella can be detected in about 12 hours.

Still, the improvements are noticeable.

“If you are going to be testing, there are much better platforms out there now than there have been for the last couple of years,” he said.

Of course, Suslow doesn’t want everyone to immediately start testing using this new system in hopes of avoiding an outbreak situation.

For one thing, it can be costly and time consuming for growers to do this, despite that the more tests that are done, the more cost effective each one becomes.

Prevention’s best

Instead, Suslow said he thinks contamination is really best if it’s simply prevented in the first place.

“Testing for pathogens won’t give you any better results than if you just have a well-managed, audited food safety system in place,” he said.

In cases where an issue or a specific case does arise, that’s when Suslow said pathogen testing is most effective.

“If a situation comes up, and you want to try and assure it doesn’t represent an actual contamination, that’s where I’d recommend you spend the target dollars to pathogen test,” he said.

He also said the industry needs to continue to work on evaluating environmental testing in packing facilities, which already is becoming more widespread at fresh processing locations.



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