Biofilm baddies and Campylobacter – the importance of thoroughly cleaning food preparation surfaces

The foodborne bacterium Campylobacter has hit the headlines in the last few months, as it was the focus of the Food Safety Week 2014: ‘Don’t wash raw chicken‘. Campylobacter is the leading cause of bacterial foodborne infection in the UK, with the number of cases reaching up to half a million per year in the UK. Although symptoms of infection are unpleasant (to say the least), they usually resolve themselves, however many people with Campylobacter infection will need to take time off work or school to recover. This leads to a high economic burden, estimated to be £583 million in 2008. The main infection route for humans is consumption of undercooked chicken or improper handling, however if chicken is cooked thoroughly (so the meat is no longer pink and juices run clear) and handled correctly, it should pose no risk to health.

One of the unsolved puzzles about Campylobacter is that it is easy to kill in the laboratory, but surprisingly difficult to remove from the food chain. One of the goals of the Campylobacter research in the Gut Health and Food Safety programme is to gain a better understanding of how Campylobacter grows and survives in the food chain, and in order to do this this we have been looking at its ability to form biofilms on surfaces.

Scanning electron microscope image of a glass slide containing a Campylobacter jejuni biofilm. Image by Louise Salt, IFR

A biofilm is a colony of bacteria adhered to a surface and covered with a layer of self-produced slime (called the extracellular matrix). This extracellular matrix is very important to the biofilm, providing a scaffold for the cells to sit in, keeping nutrients near to the cells and protecting the bacteria in the biofilm from antimicrobials and disinfection treatments. Bacteria can also be shed from the biofilm and go on to contaminate new surfaces in the food chain. Biofilms are a very common mode of bacterial life and many foodborne bacterial pathogens (such as Salmonella, E. coli and Listeria) have the ability to form biofilms. Biofilms are thought to be one of the most important ways for bacteria to survive in the food chain, allowing them to persist in on surfaces within processing plants or kitchens for long periods of time.

Exciting new work by PhD student Helen Brown of the IFR Campylobacter research group has shown that soiling of surfaces with organic materials can assist Campylobacter biofilm formation in the food chain.  About this work Helen commented

Picture of chicken juice ‘being made’

“Using ‘chicken juice’, which is a solution prepared by defrosting frozen whole chickens and collecting all the liquid that is produced, we have shown that Campylobacter biofilms grown in medium supplemented with meat juices leads to enhanced biofilm formation by Campylobacter. We have discovered that this increase in biofilm formation was due to chicken juice coating the surfaces we used with a protein-rich film. This film then makes it much easier for the Campylobacter bacteria to attach to the surface, and it provides them with an additional rich food source. This study highlights the importance of thorough cleaning of food preparation surfaces to limit the potential of bacteria to form biofilms.”