Sporeforming Bacteria: Biodiversity and Prevalence in Food Industries

Introduction:  Aerobic and anaerobic Gram-positive sporeformers exhibit a wide range of phenotypic and genotypic characteristics. These organisms are ubiquitous in the environment and have the ability to form endospores which enable them to survive heat treatments and sanitation commonly used in food process. The presence of spores in food may be associated with characteristic spoilage activity when bacterial germination and outgrowth is possible. Indeed during the last decade, the achievement of commercial sterility requirements has been hampered by the presence of psychrotrophic or highly heat-resistant sporulated bacteria in pasteurized and sterilized products.

Purpose:  The aim of this study was to evaluated biodiversity and prevalence of various sporeforming bacteria commonly found in raw material, ingredient, dehydrated products and ready-to-eat food, with and without visible trace of spoilage.  

Methods:  Spore counts, 16SrDNA sequencing isolate identification and molecular detection of targeted sporeformers were performed on raw material, ingredient, ready-to-eat and after surface samplings along industrial production lines. Further phenotypic characterizations were also done on some isolates, such as spoilage properties, heat resistance and minimal growth conditions.

Results:  A wide diversity of sporeformers was recovered from the studied samples. Spore contamination was mainly associated to raw material, dehydrated ingredients, concentrates and environment. Even though multiple contamination sources were identified, no spore formation area nor cross contamination between surface/products was highlighted. For studied industrial sites, low contamination could be associated to good hygiene conditions and food product storage in conditions which do not allow bacterial growth.

Significance:  Sporeformer diversity and prevalence from raw material to end product strongly suggest the emergence of thermophilic strains. This phenomenon might be due to the use of food ingredients and modern processing technologies that select sporeformer contaminants which survive sub-lethal stress conditions, thus leading to the persistence of specific strains in food industries. When spore contamination is detected along a production, screening or pre-treating raw food and ingredients would be a wiser option than always increasing heat treatments or processing.