This Is AuburnElectronic Theses and Dissertations

Assessment of the Effects of Acid-Adaptation on the Thermal Tolerance of Listeria monocytogenes and Salmonella Heidelberg




Smith, Jacob

Type of Degree



Poultry Science


Foodborne illnesses attributed to major pathogens cause more than 9.4 million episodes, 55,000 hospitalizations and 1,351 deaths each year. Two of the most predominant pathogens contributing to these statistics are Listeria monocytogenes and Salmonella Heidelberg, largely attributed to Ready-To-Eat foods and raw chicken, respectively. In an attempt to eliminate these illnesses-causing pathogens from their respective foodborne vectors, processors may use combinations of acidic and thermal treatments. While such treatments are effective at reducing the microbial load on foods they may cause these pathogens to develop adaptations, both acid and thermal, and survive subsequent treatments. In this study various experiments were conducted and results demonstrated that while Salmonella Heidelberg and Listeria monocytogenes survive and grow under acid-adapted conditions their growth patterns are not different from their non-adapted counterparts (P > 0.05). Additionally, the reduction of non-adapted and acid-adapted cultures of Salmonella Heidelberg and Listeria monocytogenes, under both in vitro and in vivo conditions, are not significantly different (P > 0.05). These studies demonstrate that while these pathogens can become acid-adapted they are not able to develop cross-protection to additional stressors that could help them survive better than strains that are not acid-adapted.