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Europe: Researcher studies two Clostridium perfringens strains in cooked beef for food safety in factories

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The control points that are critical to prevent foodborne outbreaks by Clostridium (C.) perfringens differ between two main groups of this bacterium, according to a research by Yinghua Xiao at NIZO food research.

C. perfringens isolates from foods were analysed using a functional genomics approach and their growth potential was assessed in cooked beef.

C. perfringens is one of the most common bacterial causes of foodborne illness.

The spores of this pathogen are resilient and can survive a range of processing steps in the food industry.

Spore germination and fast outgrowth can result in high numbers of this bacterium in foods, and upon consumption, this can lead to foodborne disease.

The doctoral study by Xiao was aimed at improved control of C. perfringens.

The work was carried out at NIZO within the frame work of TI Food and Nutrition, under the supervision of Marjon Wells-Bennik (NIZO) and Tjakko Abee (Laboratory of Food Microbiology, Wageningen University).

C. perfringens traits

Foodborne disease by C. perfringens is caused by certain strains that produce the C. perfringens enterotoxin (CPE) toxin.

A functional genomics approach based on conserved genes revealed that CPE producing C. perfringens food isolates in The Netherlands belong to two genetic clusters, each with different spore heat resistances and outgrowth potential in cooked beef.

One type, carrying the gene for CPE production on the chromosome, produces spores that are relatively heat resistant.

If such spores survive insufficient heat treatment and germinate, rapid growth to high numbers is possible if cooling regimes are not appropriate.

Their growth will be limited once the temperature drops below 12°C.

The second type, carrying the gene for CPE production on a plasmid, produces spores that are heat sensitive leading to full inactivation by appropriate heat treatments.

However, this type showed growth at 12°C.

This has practical implications and points to different critical control points to prevent foodborne illness due to C. perfringens.

For chromosomal CPE strains, an adequate heat treatment is required to inactivate spores, and rapid cooling is needed to prevent outgrowth in case any spores survive.”

For plasmid CPE strains, spores are rather sensitive and will be inactivated by heat.

However, as these strains grow quite well at relatively low temperatures, it is particularly important to prevent contamination after heating, for instance by food handlers, and maintain low storage temperatures of products.

Story by Marjon Wells-Bennik, NIZO food research.