Research by Dr Mary Corcoran was prompted by 2012 European Salmonella Agona outbreak resulted in over 160 cases of gastroenteritis in 10 countries.

An NUI Galway researcher has discovered that once Salmonella gets into a food processing facility it is very difficult to remove it. Microbiologist Dr Mary Corcoran attempted to kill Salmonella biofilms on a variety of hard surfaces, using three types of disinfectant.

The research, to be published in the Journal of Applied and Environmental Microbiology, shows that once Salmonella has established itself for seven days, it was not possible to kill Salmonella using three disinfectants, even by soaking the Salmonella in disinfectant for an hour and a half.

The research found that all of the types of Salmonella studied were able to adopt the specialised biofilm lifestyle on all of the surfaces looked at. These included glass, stainless steel, glazed tile, concrete and plastic. It shows that the biofilm of Salmonella gets more dense over time, and becomes more firmly attached to the surface.

The findings will serve as a warning to food processors in particular highlighting that once Salmonella gets into a food processing facility and has an opportunity to form a biofilm on surfaces, it is likely to be extraordinarily difficult, if not impossible, to kill it.

Dr Mary Corcoran said “Food processing facilities must take strict care to keep Salmonella out of the clean areas where cooked foods get further processing and packaged, and ask whether disinfectants that are promoted as killing various types of bacteria are really as effective as claimed.”

The research was prompted by the Salmonella outbreak in Europe in which over 160 people in 10 countries developed gastroenteritis from the Salmonella Agona strain of Salmonella. That outbreak was traced to meat from a major food-processing facility. 

Dr Corcoran said “it seems that the outbreak entered into the environment in the part of the facility where meat that was already cooked was being handled, and it had survived and contaminated the cooked meat. Interested in finding out that Salmonella might have something special about it that makes it better at surviving in the environment of a food processing facility, we asked was it better at forming a dense biofilm, or was it more resistant to disinfectants than other Salmonella? We discovered it was not.”

The three disinfectants used against Salmonella in the research were sodium hypochlorite (household bleach), sodium hydroxide, and benzalkonium chloride.

The research shows that a lot of the time, the disinfectant may add very little, if anything, to good cleaning and appropriate food handling practices and that there is a need for more research to define better methods for killing Salmonella biofilm.”

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