Abstract

Listeriosis, a foodborne disease caused by Listeria monocytogenes, is characterized by brain infection in elderly or immunosuppressed patients, maternal-fetal and neonatal infection. Although neurologic listeriosis is one of the most severe forms of the disease, animal models of L. monocytogenes-induced neurologic disease have not been thoroughly investigated. In this study, a model of oral infection in immunosuppressed gerbil was developed to verify the role of immunosuppression in L. monocytogenes infection affecting the brain. Female gerbils treated or not with dexamethasone were orally infected with 106, 108, 1010 CFU/animal of L. monocytogenes. Neurologic changes were evaluated up to 30 days post infection, and bacterial recovery determined in systemic organs as well as in the central nervous system. The group of immunocompromised gerbils infected with 1010 CFU/animal of L. monocytogenes had more severe clinical signs, and had higher bacterial loads in the brain. Bacteria were consistently isolated in the brainstem of infected immunosuppressed gerbils at 15 days post infection, which was associated with lower weight gain, higher neurologic deficit, and marked abscesses in the brainstem. Radiolabeled L. monocytogenes with technetium-99m disseminated at early time points of infection to the brain of immunocompetent and immunosuppressed gerbils. This animal model has great potential to contribute to the expansion of our knowledge on the pathogenesis of neurologic listeriosis.