Food Safety Magazine

Rapid Micro Solutions | October/November 2017

Listeria Testing Results in under 60 Minutes

By Neogen

Listeria Testing Results  in under 60 Minutes

Neogen has developed the innovative Listeria Right Now™ test system that detects Listeria in environmental samples in under 60 minutes—with molecular-level accuracy and without the need to enrich samples.

This new test system can detect all species of Listeria, including the pathogenic Listeria monocytogenes, in under 60 minutes through their ribosomal RNA (rRNA). The system’s effectiveness has been validated by NSF International to detect low levels of Listeria in environmental samples with greater sensitivity and speed than any other method available. The test has also been submitted for AOAC Performance Tested certification to further validate its accuracy.

“The advanced technology in Listeria Right Now truly changes everything about testing the environment for Listeria. Contamination of Listeria in the environment can now be determined, and in the case of a positive, recleaned or remediated as necessary, before food production begins and the quality and safety of a food product is compromised,” says Ed Bradley, Neogen’s vice president of food safety. “The new test system enables food safety professionals to implement an immediate remedial action, which could include improving sanitation efforts or processes. Using Listeria Right Now also means that companies no longer have to be concerned about the growth of potentially dangerous organisms in their facilities during the testing process or store test cultures for potential follow-up testing. It allows our customers to adopt the ‘seek and destroy’ approach to Listeria detection that the U.S. Food and Drug Adminstration, U.S. Department of Agriculture and many auditors are promoting. Customers have described it as being ‘like ATP testing for Listeria.’”

Using Neogen’s Listeria Right Now, you can:
•    Conduct environmental monitoring for Listeria without enrichment

•    Perform corrective actions more quickly—fix the issue before it becomes a serious problem—then clean and retest

•    Conduct investigations in near real-time after positives

•    Perform contamination vectoring more easily

•    Be more flexible and proactive with your environmental testing program

•    Expand testing to include zone 1 surfaces if it’s possible to hold product pending results or as a preoperations screen

The innovative Listeria Right Now process starts with taking an environmental sample to capture any Listeria present. The entire sample is placed in a tube that contains a lysis buffer that breaks up any bacteria and releases its rRNA. If Listeria is in the sample, the test’s reagents will amplify thousands of copies of its rRNA and make the Listeria easily detectable by the Listeria Right Now assay.

“Because of the ease of use of the new test system, facilities will be able to enhance their environmental monitoring programs,” says Bradley. “In under 60 minutes, an operator will be able to analyze a sample and quickly make the decision to hold or quarantine product, reclean an area or move forward with production.”

NSF International Validated the Effectiveness of Listeria Right Now
After internal testing proved its effectiveness, Neogen requested that NSF International perform an independent validation study to evaluate the performance of the Listeria Right Now assay for detection of Listeria spp. in environmental swabs without enrichment.

In the study, surfaces of 4” × 4” squares of food-grade stainless steel were inoculated with different levels of L. monocytogenes and a mixture of competing organisms, including Pseudomonas aeruginosa, Bacillus subtilis and Enterococcus faecium. After the inoculum was allowed to partially dry, surface samples were collected using semipaired swabs. One swab was tested by the Listeria Right Now assay and the other swab was enriched by the culture method. The swab for the culture method was enriched overnight at 37 °C in growth medium and an aliquot plated on agar plates for detection on the following day.

In the Listeria Right Now test, the entire collected contents of the swab were subjected to sample processing and testing on the same day. After expression of the swab in the lysis buffer, one-half of the volume was taken for the lysis incubation steps. Next, a portion of the lysed sample was transferred to a strip tube containing lyophilized reaction reagents. The tubes were sealed and incubated at 56 °C in the Neogen reader. Results generated by the reader were displayed by the assay’s software.

In summary, no false negatives, false positives or invalids were observed during this study. The evaluation determined that under the conditions employed in this study, the enrichment-free Listeria Right Now method is as sensitive as the enrichment-based culture reference method for detection of L. monocytogenes on a stainless steel surface.

For a copy of the full study, please contact Neogen: www.neogen.com.

Categories: Testing and Analysis: Environmental Testing, Methods, Microbiological

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