Probiotics as drugs against human gastrointestinal infections

The commensal gut microbiota confer health benefits to their host by helping dietary digestion, regulating gut immunity, maintaining the microbial balance, and preventing pathogen colonization. A number of probiotic strains have been introduced in the market in dietary and pharmaceutical forms. Lactic acid bacteria (e.g. Lactobacillus) and Bifidobacterium constitute the main group of probiotics commercialized for human consumption. The treatment of gastrointestinal infections continues to be complicated due to the expansion of antibiotic resistances. Of the benefits of probiotics, those related to their preventive and therapeutic uses against gastrointestinal infections have an outstanding position, as reflected in a large number of patents. The mechanisms of action of probiotics against gastrointestinal pathogens addressed in diverse patent applications include: (i) modification of the environmental conditions, (ii) competition for nutrients and adhesion sites, (iii) production of antimicrobial metabolites and (iv) modulation of the immune and non-immune defense mechanisms of the host. The bioactive components of probiotics include cell-wall fractions, surface proteins, nucleic acids, organic and short-chain fatty acids, antimicrobial proteins and other less-well identified soluble factors. The effectiveness of probiotics is supported by solid clinical studies mainly on treatment of acute diarrhea in children and prevention of antibiotic associated disorders. Currently, probiotics and their bioactive compounds constitute attractive alternative drugs that can help to reduce the use of antibiotics as well as to improve conventional pharmacological therapies. The advances on the knowledge of the intricate host-microbe dialogues within the intestine and extraintestinal sites will result in the future development of a new generation probiotic-based products targeting broader range of pathologies and their etiologic agents.