A new study has highlighted a potential new way of battling the persistence of Campylobacter in the food chain.

False coloured scanning electron microscope (SEM) image of Campylobacter cells attached to chicken juice on a glass slide. Image: Louise Salt, IFR with colouring by Kathryn Cross, IFR

One of the unsolved mysteries about Campylobacter is that it is easy to kill in the laboratory, but surprisingly difficult to remove from the food chain. Recent work from the Institute of Food Research has shown that organic material on surfaces helps Campylobacter form biofilms, colonies of bacteria on a surface protected by a slime layer. This protects the bacteria in the biofilm from antimicrobials and other disinfection treatments, and from mechanical removal during cleaning, allowing the bacteria to persist for longer periods.

The importance of this slime layer has made it a target for investigation, and although little is still known about it, one common component is known to be DNA.

In a new study, published in the journal PLOS ONE Helen Brown and colleagues at IFR and Campden BRI have investigated the effect of DNA-degrading enzymes on Campylobacter biofilms.

A search of a large collection of Campylobacter genome sequences highlighted that almost half of Campylobacter isolates have the capability to make one or more DNA degrading enzymes (DNases). The ability of these DNases to act on the biofilms matrix was then tested using a Campylobacter isolate that naturally produces three such DNase enzymes. This isolate was able to remove existing Campylobacter biofilms, as well as prevent the formation of new Campylobacter biofilms. Interference with biofilms in the processing environment or on meat can potentiate cleaning and disinfection regiments, and assist in the development of safer foods in the future.

Dr Arnoud van Vliet, who leads the Campylobacter research at IFR, commented “Biofilms are a well-known problem in the food industry, as they shield bacteria from antibiotics, cleaning and disinfection treatments. This work shows that while we may not be able to target the bacteria in the biofilms directly, we can take an indirect route by first removing the protective layer with enzymes such as DNase, and then subsequently target the Campylobacter bacteria that were inside the biofilm. Knowing that Campylobacter can make the enzyme itself expands our possibilities, and points to the way forward with this important food safety problem.”

Campylobacter is the leading cause of bacterial foodborne illness in the UK, with more than a quarter of a million cases per year.  The main infection route for humans is consumption of undercooked chicken or improper handling such as washing chicken, however if chicken is cooked thoroughly and handled correctly it should pose no risk to the consumer.

The study was funded by the Biotechnology and Biological Sciences Research Council. Helen Brown’s PhD studentship was co-funded by an industrial partner, Campden BRI.

Reference

Brown HL, Reuter M, Hanman K, Betts RP, van Vliet AHM (2015) Prevention of Biofilm Formation and Removal of Existing Biofilms by Extracellular DNases of Campylobacter jejuni. PLOS ONE 10(3): e0121680. doi: 10.1371/journal.pone.0121680