The role of the microbiota-gut-brain axis on the neurobiology of infectious diseases

The microbiota-gut-brain axis is the bidirectional signaling mechanism between the gastrointestinal tract and the central nervous system (CNS). The intestinal ecosystem is remarkably complex, as it includes about 100 trillion microbial cells that inhabit the small and large intestines, and the ratio of human to bacterial cells is about 1:1, with 70% of bacteria living in the gut. The gut microbiota's composition and the production of its metabolites appear to be influenced by several factors, including the nature of the nutritional provision, use of antibiotic medications, peripheral infection, CNS infection, and neuroinflammation. Consequently, chemical substances with the potential for neuro- and immuno-logical modulations are released in the intestine, modifying the peripheral inflammatory profile and influencing both the blood-brain barrier (BBB) permeability and glial cell homeostasis in the brain. In this chapter, we will elucidate the microbiota-gut-brain axis and its connection to the neurobiology of infectious diseases.