Probiotic milk has been previously demonstrated to reduce the number of respiratory infections (RI) among children attending day care centres. Thus, this pilot study was aimed to assess the efficacy and the safety of 3 month treatment with Bacillus clausii in the prevention of recurrent respiratory infections (RRI) in children. Eighty children with RRI were studied: 40 of them were randomly treated with B. clausii for 3 months, and followed up for further 3 months; 40 were included in the control group during the same period. Children treated with B. clausii had shorter duration of RI in comparison with the control group both during the treatment phase (mean 11.7 days vs 14.37; p=0.037) and the follow-up period (mean 6.6 days vs 10.92; p=0.049). This effect was evident also in allergic children during the follow-up. In conclusion, this pilot study provides the first preliminary evidence that B. clausii may exert a significant and persistent impact on RI in children and is safe and well tolerated.
Respiratory infections (RI), mainly involving the upper airways, are common in children and their recurrence constitutes a demanding challenge for the paediatrician (BWHO 1998). It has been proposed that to diagnose recurrent RI (RRI) at least one of the following criteria has to be present: 1) >6 RI per annum, 2) >1 RI per month involving the upper airways from September to April, 3) >3 RI per annum involving the lower airways (Gruppo di Studio di Immunologia della società Italiana di Pediatria 1988). Moreover, RRI represent a social problem both concerning economic aspects and the influence on the family and social milieu of the child. In addition, allergic children have more frequent and severe respiratory infections than nonallergic children (Ciprandi et al 2006). In recent years, following the increase in the incidence of antibiotic resistance, interest in preventive treatment has intensified. Such treatment should contribute to the prevention of RRI, thus reducing the usage and excessive consumption of antibiotics. Furthermore, it has been established that the intestinal microflora plays an important role in the maturation of the immune system (Holt et al 1997).
Probiotics are vital bacteria that colonize the intestine and modify its microflora with benefits for the host. They are present in foodstuffs such as yogurt and other dairy products. To exert their beneficial effects, probiotics must be able to overcome the obstacle of gastric acidity, to proliferate and to colonize the intestine even in the presence of biliary acids and of drugs such as antibiotics. They must adhere to intestinal walls, reducing their permeability and potentiate the local immune response, especially through secretory immunoglobulin (Ig) A (Isolauri et al 2001).
Probiotics are not pathogens as they are not virulent and consequently, their intake is usually not associated with undesirable effects.
The beneficial effect of probiotics is also to be ascribed to its capacity to modulate the immune response. The immune response dependent on Th1 lymphocytes (Th1) deputy to defend from viruses and bacteria is not fully efficient because it has not completely matured. Whereas, the Th2 response to antigens prevails and is often enhanced due to contact with environmental allergens, resulting in early activation of allergic responses (type I IgE-mediated allergic responses). Probiotics are able to induce an antigenic stimulation that leads to release of interleukin (IL) 12 by antigen-presenting cells (APC), which promotes the maturation of the immune system and the Th1 response. Furthermore, they reduce the production of IL4, which specifically regulates the development of the Th2 phenotype and leads to an increase in the synthesis of IgE, eosinophilia and atopic disease. Probiotics have anti-inflammatory properties related to the stimulation of secretory IgA synthesis in mucous membranes and the production of cytokines (Hattakka et al 2001). They also stimulate the synthesis of interferon-gamma (IFN-γ) and have antimicrobial activity as a result of the production of lactic acid, H2O2 and natural antibiotic substances with potent antiviral and antibacterial activity.
It has been previously reported that the prophylactic use of a probiotic milk reduced the number and the severity of RI among children attending day care centres (Hattakka et al 2001). Probiotics are microorganisms that exhibit a beneficial effect on the health of the host (Kaur et al 200