Evidence that inimical food-preservation barriers alter microbial resistance, cell morphology and virulence

Food manufacturing, distribution and storage rely on well-placed deleterious stresses or hurdles that either inhibit or inactivate contaminating microorganisms in food systems. Recent molecular and physiological evidence points to the fact that many food-borne pathogenic bacteria are adapting to these sub-lethal inimical stresses, and as a consequence, becoming more resistant to lethal levels of the same (homologous) or cross-protected against other (heterologous) stresses. Many stress-adapted microbial pathogens are also showing an enhanced virulence. As nonstressed exponentially-growing bacteria are often used in food safety studies, it is likely that predictive models using such data may be underestimating the actual survival capabilities of stress-challenged microorganisms. The 'stress-hardening' phenomenon has significant food-safety implications, especially in situations where the food industry explores levels of lethality that are close to the boundaries of microbial control. In this Viewpoint article, I wish to focus on the ability of environmental stress to augment or modulate virulence; the ability of stress-adapted microbial-pathogens to survive homologous or heterologous stresses commonly encountered in foods and in the mammalian host; and also to alter microbial cell morphological and physiological characteristics as a consequence of these inimical stresses. (C) 2000 Elsevier Science Ltd. All rights reserved.