Study reveals food poisoning bacteria on meat factory surfaces

The food poisoning bacterium Listeria could survive on surfaces in meat processing factories if certain other bacteria are present, scientists have been told.

Speaking at the Society for General Microbiology's Autumn meeting Christine Dodd, professor of Food Microbiology in the Division of Food Sciences, University of Nottingham, says: "Factories handling raw and processed meat products can become plagued by persistent harmful Listeria monocytogenes bacteria stuck to their work surfaces and machinery from where they can enter food products and potentially cause food poisoning."

"We have examined which factors affect attachment and have shown that the presence of a common food spoilage bacteria called Pseudomonas fluorescens may affect the ability of Listeria monocytogenes to stick to surfaces."

The team of Nottingham scientists found that Listeria was not as successful at attaching to stainless steel surfaces when in competition with other bacteria.

However, when Pseudomonas fluorescens was allowed to attach to the surface first, Listeria was able to attach to the same surface much more effectively.

The scientists say bacteria which form communities on surfaces, known as biofilms, are much more highly resistant to cleaning products and even antibiotics.

Listeria's success in persisting in factories comes partly from this ability to form resistant biofilms and partly from its extraordinary tolerance to drying out thereby allowing it to survive on what should be clean surfaces.

Professor Dodd said: "We also looked at the influence of different cooked meat juices including beef, pork, lamb, chicken and duck. We found significant differences between the ability of Listeria to stick to stainless steel surfaces at different temperatures, depending upon which meat was used."

"Cooked duck juices at 25 deg C allowed the highest levels of Listeria attachment."

The different meat residues may affect the ability of Listeria monocytogenes to attach by causing changes in the surface of the bacterial cells.

This means that meat factories may need to modify their cleaning and disinfecting procedures according to the type of meat product being processed, if food poisoning outbreaks are to be avoided.