Probiotics as modulators of the gut flora

Abstract

Probiotic ingestion can be recommended as a preventative approach to maintaining the balance of the intestinal microflora and thereby enhance ‘well-being’. Research into the use of probiotic intervention in specific illnesses and disorders has identified certain patient populations that may benefit from the approach. Undoubtedly, probiotics will vary in their efficacy and it may not be the case that the same results occur with all species. Those that prove most efficient will likely be strains that are robust enough to survive the harsh physico-chemical conditions present in the gastrointestinal tract. This includes gastric acid, bile secretions and competition with the resident microflora. A survey of the literature indicates positive results in over fifty human trials, with prevention/treatment of infections the most frequently reported output. In theory, increased levels of probiotics may induce a ‘barrier’ influence against common pathogens. Mechanisms of effect are likely to include the excretion of acids (lactate, acetate), competition for nutrients and gut receptor sites, immunomodulation and the formation of specific antimicrobial agents. As such, persons susceptible to diarrhoeal infections may benefit greatly from probiotic intake. On a more chronic basis, it has been suggested that some probiotics can help maintain remission in the inflammatory conditions, ulcerative colitis and pouchitis. They have also been suggested to repress enzymes responsible for genotoxin formation. Moreover, studies have suggested that probiotics are as effective as anti-spasmodic drugs in the alleviation of irritable bowel syndrome. The approach of modulating the gut flora for improved health has much relevance for the management of those with acute and chronic gut disorders. Other target groups could include those susceptible to nosocomial infections, as well as the elderly, who have an altered microflora, with a decreased number of beneficial microbial species. For the future, it is imperative that mechanistic interactions involved in probiotic supplementation be identified. Moreover, the survival issues associated with their establishment in the competitive gut ecosytem should be addressed. Here, the use of prebiotics in association with useful probiotics may be a worthwhile approach. A prebiotic is a dietary carbohydrate selectively metabolised by probiotics. Combinations of probiotics and prebiotics are known as synbiotics.

Probiotics and prebiotics in infant nutrition

“…production of anti-microbial substances: lactic acid bacteria produce a wide variety of anti-bacterial substances, as well as inhibitory metabolites such as organic acids, diacetyl and H 2 O 2 . They also produce bacteriocins and antibiotic-like substances with activity against both Gram-positive and Gram-negative bacteria (Rolfe, 2002); 2. competition for adhesion receptors or sites: the presence of some bacteria in the intestinal tract is dependent on their ability to adhere to the gut epithelium, such that they become immobilised on the gut wall and resist being flushed out by peristalsis, as well as occupying a niche at the expense of potentiallyharmful organisms (Fuller, 1992;Fooks & Gibson, 2002); 3. competition for nutrients; 4. stimulation of immunity: the underlying mechanisms of immune stimulation are not well understood, but specific cell-wall components or cell layers may act as an adjuvant and increase humoral immune response; 5. degradation of toxin receptors.…”

O papel dos probióticos e prebióticos na prática pediátrica

“…Both lactobacilli and bifidobacteria are able to produce these elements. 3 Also interesting is that Lactobacillus rhamnosus GG, in addition to producing bacteriocins, also produces a biosurfactant, which helps its own survival.…”

“…1,3,8,13 According to its own definition, a probiotic should be viable at the time of It should be highlighted that probiotics do not multiply quickly, and so they are not permanent colonizers of the digestive tube. 13 Probiotic microorganisms positively change the intestinal flora, inhibit the growth of pathogenic bacteria, promote adequate digestion, stimulate the local immune function and increase resistance to infection.…”

“…intestinal microbiota with large participation of bifidobacteria and lactobacilli is regarded as healthy. 1,3,7 In individuals with an already established microbiota, the influence of probiotics is usually restricted to the period in which they are used. Thus, in order for these individuals to keep the desired change in their intestinal microbiota, they should ingest these microorganisms continually and indefinitely.…”

“…: bifidobacteria) when they reach the colon, bringing health benefits to the host. 3 Symbiotics are defined as products that contain both prebiotics and probiotics. 3 The number of articles about probiotics and prebiotics indexed in MEDLINE between 1996 and 2005 has significantly increased.…”