General features of probiotics and their importance in our GITs:
Firstly, let us consider the general benefits of probiotics:
- Probiotics are defined as living micro-organisms which, on ingestion in certain numbers, exert health benefits beyond inherent general nutrition. In fact the mammalian gut is considered one of the most densely populated ecosystems on earth with a bacterial load in the region of 10 organisms/g of faecal material in the large intestine. The normal flora, which colonises the GI tract exert several functions:
- Synthesising and excreting vitamins in excess of their own needs, which can be absorbed as nutrients by their hosts (enteric bacteria secrete Vitamin K and Vitamin B12, and lactic acid bacteria produce certain B-vitamins
- Preventing the pathogens colonisation by competing for attachment sites or essential nutrients and being likely to produce substances, which inhibit or kill non indigenous species
- Stimulating the development of certain tissues, i.e., the caecum and certain lymphatic tissues (Peyer’s patches) in the GI tract and stimulating the production of natural antibodies
- Producing a variety of substances ranging from relatively non-specific fatty acids and peroxides to highly specific bacteriocins, which inhibit or kill other bacteria
- Gut microbiota are also know to influence energy balance and in turn, emerging evidence demonstrates the importance of guy microbiota in the pathophysiology of obesity
- The key observations are that these micro-organisms are essential to the normal immune development and the induction of oral tolerance. The bacteria are intimately involved in the development of immune competent cells and tuning the balance between Th1 and Th2 immunity during the development of gut-associated immune system. A child born by C-section is generally regarded as “sterile” since the acquisition of the micro-organisms is from its mother during the birthing process: there is now clear evidence that such children do not develop the correct balance between these important immune cells and therefore have “allergic” tendencies. These suggestions are supported by observations that germ-free mice do not develop tolerance in the absence of a gut microbiota in addition to the observed differences in the composition of the gut microbiota between infants living in countries with a high and a low prevalence of allergy and between healthy infants and infants with allergy.
- There is now good evidence that certain strains of lactobacilli and bifidobacteria can influence immune function through a number of different pathways including effects on enterocytes, antigen presenting cells (including both circulating monocytes and local dendritic cells [DCs]), regulatory T cells, and effector T and B cells. This has led to the notion of “dysbiosis” when the balance between symbionts and pathogens is disturbed and a state of chronic inflammation sets in. this is depicted in Figure 1 below:
Clinical use of probiotics in children:
Probiotics for the prevention of treatment of allergies: it is a well-established fact that allergies result from a fundamental imbalance in immune regulation between Th1 and Th2 cells. Microbial exposure arguably provides the strongest environmental signal for normal postnatal maturation of the immune system and also induces the maturation of antigen presenting cells and T-regulatory cells, which are essential for programming and regulating the T-cell response. It appears likely that microbial activation of regulatory pathways through microbial pattern recognition molecules (Toll like receptors [TLRs]) plays a central role in reducing the risk of immunologically mediated disease, including TH@-mediated allergic responses, and possibly also TH1-mediated autoimmune disease, such as type I diabetes.
Postoperative complications in GI surgery could involve bacteraemia and infectious complications. The main causes could be the translocation of the GI bacteria or its toxins as a consequence of bacterial overgrowth, the loss of intestinal epithelial integrity and the immunologic compromising of the host. Probiotics could be a good candidate to fight against these factors through the competition with potential pathogens for nutrients or enterocyte adhesion sites, degradation of toxins, production of antimicrobial factors, and local and systemic immunomodulation.
The prevalence of IBS is increasing in countries in the Asia-Pacific region, particularly in countries with developing economies. IBS mainly occurs between the ages of 15 and 65. The estimated prevalence of IBS in children is similar to that in adults. IBS is a common disorder of the intestines associated with cramping, stomach pain, gas, bloating, and changes in bowel habits. IBS can be characterised by constipation, diarrhoea or both. There is overwhelming scientific evidence in support of the use of various probiotic formulation s to treat patients with underlying IBS with very favourable outcomes.
Episodes of diarrhoea are frequent side effects of antibiotic therapy. Antibiotic therapy leads to an alteration of normal intestinal flora which may cause a loss of colonisation resistance and an alteration of the metabolic functions of the normal flora. The first situation is followed by an abnormal growth of pathogenic organisms such as C. Difficile, Candida albicans, K.caytoca, and Salmonella spp, which are responsible for toxigenic diarrhoea. The second situation leads to a diminished production of SCFAs resulting in diarrhoea. Several clinical studies have been conducted in children with acute Rotavirus diarrhoea whereby the outcomes identified the concomitant use of probiotics and routine supportive therapy lead to decreased stool volume losses and shortened period to recovery.
Probiotic formulations have been widely studied for the treatment of atopic dermatitis(AD), a pathology defined as an inflammatory chronically relapsing, non-contagious, and pruritic skin disease, which is associated with elevated IgE levels and Th2 responses. AD in animal models and human studies has been investigated using different probiotic strains such as Bifidobacterium, Lactobacillus, and Lactococcus. The use of probiotics lead to the suppression of specific or non-specific IgE production, reduction of infiltrated eosinophils and degranulated mast cells, potentiation of regulatory T cell cytokines such as IL-10 and TGF-beta relative to IL-4 and IL5, and potentiation of Th1/Th2 activity, along with reduced symptoms of AD.
In HIV disease, it has been shown by several authors of a translocation of gut pathogen-derived ligands (toxins) into the mesenteric lymph nodes leading to chronic immune activation and consequently disease progression. In this country with such a high burden of HIV disease perhaps the concomitant use of a good probiotic formulation with HAART could contribute to better management of our HIV-infected children.
Obesity in children is on the increase and results from alterations in the body’s regulation of energy intake, expenditure, and storage. Recent evidence, primarily from investigation in animal models, suggests that the gut microbiota affects nutrient acquisition and energy regulation. The microbiota profile has also been shown to differ in lean versus obese animals and humans. Existing evidence warrants further investigation of the microbial ecology of the human gut and points to modification of the gut microbiota as one means to treat people who are overweight or obese.