Response to Listeria monocytogenes outbreak in frozen vegetables from Hungary

This article comes from Neogen Europe’s Microbiology Insider newsletter, a resource for the latest developments and news in microbiology testing and related technology. See here to read the rest of the latest issue of Microbiology Insider.

Last year, it was announced that frozen corn was the likely source of a widespread Listeria monocytogenes outbreak that has affected many European countries dating as far back as 2015.

Whole genome sequencing was able to trace the same strains of L. mono in frozen vegetables processed by a Hungarian company over a three-year period, suggesting that the strains have persisted in the processing plant despite cleaning and disinfection procedures.

Increase in environmental monitoring and auditing

In response to this revelation, frozen vegetable manufacturers have taken a systemic approaching in reviewing their sites, including zone segregation, factory layout, process flow and cleaning practices to assess and reduce the risk of Listeria within their sites. The frequency of monitoring the factory environment and finished products for Listeria was also increased significantly at many companies.

To determine the efficiencies of these improved control measures, Campden BRI Hungary, a founding member of the Hungarian Freezing and Canning Industry Association (MHKSZ), was appointed to perform factory audits. Campden’s appointment was based in its extensive industry knowledge and experience in frozen food technology.

Following initial fact-finding audits during the 2018 production season, further corrective actions were deployed.

Best practices to avoid cross-contamination

As there are so many possible routes of pathogen transmission within a food processing site, it’s important for manufacturers to be aware of potential cross-contamination risks.

“Best practices to avoid cross-contamination issues include frequented testing of the environmental samples and finished products,” Campden’s Dr. András Sebõk told Neogen’s Microbiology Insider newsletter. “The speed, accuracy and reliability of the testing methods is also important for basing timely corrective actions, as well as regular internal audits by the companies.”

Continuous improvement

For the 2019 processing season, Campden, supported by MHKSZ, is leading a working group of participating companies to create a voluntary standard, the “Control of Listeria monocytogenes in Frozen Vegetables and Fruit Products.” This joint bid brings together industry partners and gives processors the opportunity to share both their failures and successes within their sites to continually improve conformity and reduce the risk for future outbreaks.