Presenter: Simin Nikbin Meydani
Meydani began by commenting on how scientists have recently learned that dysregulation of immune and inflammatory response with aging not only contributes to greater susceptibility to infectious diseases and cancer, but also greater susceptibilities to other chronic diseases such as cardiovascular disease, Alzheimer’s disease, osteoporosis, and type 2 diabetes. She remarked that most of her talk, however, would focus on the former: how dysregulation of the immune and inflammatory systems, most of which is associated with changes in T-cell-mediated function, contribute to an increasing incidence of infectious diseases and cancer with aging.
Aging is associated with a higher incidence of morbidity and mortality from a number of different types of infectious diseases (e.g., pneumonia, tuberculosis, GI infections, urinary tract infections, and Herpes zoster). For example, pneumonia and influenza together are the fourth leading cause of death among older adults. Even when a diagnosis is cardiovascular disease, the cause of death is often pneumonia. While the incidence of GI infections is not necessarily any greater in the elderly population, morbidity and mortality from GI infections is much higher in older adults. For example, when a food poisoning episode occurs in a nursing home, the younger caregivers can usually recover, but the elderly people often suffer greater complications that may result in death.
To illustrate the impact that aging has on the severity of infectious disease, Meydani described a Salmonella typhimurium study that she and her colleagues conducted using a murine model system (Ren et al., 2009). They examined colonization of Salmonella after both young and old mice had been exposed to Salmonella. While in the beginning (one day post-infection), the young animals showed a higher colonization rate, the older animals showed a much higher colonization rate as their infections progressed (2–4 days post-infection). This was true at both low and high doses of exposure. Even early on, when the colonization rates were higher in the younger animals, the older animals nonetheless experienced greater weight loss because of the severity of the infection.
Meydani emphasized that the last observation is important to consider in relation to food safety because often efforts are directed toward preventing exposure to foodborne infectious agents without enough consideration