Food processors beware: Salmonella biofilms incredibly resistant to powerful disinfectants

 Once Salmonella bacteria get into a food processing facility and have an opportunity to form a biofilm on surfaces, it is likely to be extraordinarily difficult, if not impossible, to kill it.

Researchers from National University of Ireland, Galway conducted a study in which they attempted to kill Salmonella biofilms on a variety of hard surfaces, using three types of disinfectant.

"We found that it was not possible to kill the Salmonella cells using any of the three disinfectants, if the biofilm was allowed to grow for seven days before the disinfectant was applied," says Mary Corcoran, a researcher on the study. Even soaking the biofilms in disinfectant for an hour and a half failed to kill them.

The impetus for the study was a European outbreak in which 160 people in 10 countries became ill with gastroenteritis (vomiting and diarrhea) from the Agona serotype of Salmonella, says Corcoran. That outbreak was traced to meat from a major food-processing facility.

The research uncovered nothing special about that specific strain. "We found that all of the types of Salmonella we looked at were able to adopt the specialized biofilm lifestyle on all of the surfaces we looked at, including glass, stainless steel, glazed tile, and plastic, and that the biofilm of Salmonella gets more dense over time, and becomes more firmly attached to the surface," she says.