Characterisation/Quantification of the Impact of Food Structure on the Development of Antimicrobial Resistance of Food-related Pathogens

Nowadays, emerging industrial processing techniques are increasing rapidly and are progressively replacing the classical decontamination processes of food systems. One emerging alternative is the use of natural antimicrobials, produced by microorganisms such as lactic acid bacteria (LAB), as there is evidence that those components may act against food pathogens. However, the efficiency of such antimicrobial components is still unclear. Moreover, most of the available studies describe the action of antimicrobials against pathogens in liquid systems, although the majority of food products are solids. In a solid system immobilization of microorganisms leads to their evolution as colonies and due to diffusional limitations of oxygen and nutrients as well as the accumulation of acidic metabolic products around the colony microorganisms may experience a self-induced (acid) stress that could affect their overall response and tolerance to the antimicrobial component. Indeed, our recent findings point interesting differences in the development of antimicrobial resistance of Listeria in liquid vs solid state when exposed to natural antimicrobials. Development of antimicrobial resistance could lead to higher microbial tolerance on industrial processing conditions due to the action of the so-called cross-protection mechanism which enables cells adapted to a specific stress to resist other types of stress stimuli as well. Therefore, understanding and precisely quantifying the response of food related pathogens on the one hand to natural antimicrobials and on the other hands to natural antimicrobials in combination with an industrial(like) treatment in a food(like) in vitro models is of significant importance for the design of safe industrial processes and consequently for the achievement of food safety.