Probiotics are helpful microorganisms that are resistant to biliary, gastric,
and pancreatic secretions and can attach to the epithelial cells and colonize the surface
of the intestinal cells. These capabilities are the main mechanisms of probiotics that
allow them the adaptation to gut conditions. Probiotic cells attach to the intestinal cells
and inhibit the attachment of enteric pathogenic germs to the intestinal mucosa by
producing growth-inhibitory elements such as short-chain fatty acids, bacteriocin, and
toxic oxygen metabolites. Attaching to the mucosal layer is essential for their
functions, but it can increase the possibility of translocation and pathogenicity. On the
other hand, there are also concerns about the possible transmission of antimicrobial
resistance properties from probiotic strains to pathogenic bacteria in the gut
environment. Consequently, the use of probiotics is entirely safe only in healthy
people, and also it should be used with caution in children, the elderly, pregnant
women, and immunocompromised patients. In recent years, scientists take a new
approach to using probiotics in a non-viable form (currently known as postbiotics) to
overcome the technological, economic, and clinical problems regarding the application
of live probiotics. Hence, this chapter provides an overview of the nutritional and
clinical concerns caused by probiotic intake in vulnerable patients, with emphasis on
the application of a non-viable form of probiotics as a promising alternative.
Keywords: Antibiotic-resistance genes, Biogenic amines, D-lactic acid,
Functional foods, Postbiotic, Probiotic.
