Probiotics: 'Living Drugs'

Gary W. Elmer


Am J Health Syst Pharm. 2001;58(12) 

In This Article

Mechanisms of Action of Probiotics

A common belief about how probiotics work (and one used in marketing these products) is that ingestion improves the "balance" of the intestinal and vaginal microflora so that pathogen growth is restricted. Recent studies indicate that this concept is simplistic and that probiotics probably work by multiple mechanisms. Furthermore, each agent may have unique actions.

Colonization resistance is the ability of the normal microbial flora to resist the establishment of pathogens. Perturbation by antimicrobials and other agents may diminish colonization resistance. An objective of probiotic therapy is to restore colonization resistance until the normal flora becomes reestablished. More specific mechanisms of action have been identified for individual probiotics ( Table 3 ). The ability of a probiotic to inhibit pathogen adhesion or to stimulate a local immunoglobulin A-mediated immune response would be highly desirable, because these properties would provide a broad spectrum of antipathogen activity. However, pathogen antagonism in vitro may not necessarily occur in vivo.


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