Les lactobacilles : propriétés, habitats, rôle physiologique et intérêt en santé humaine

Abstract

Regarding their morphology, their metabolism and their phylogeny, lactobacilli appear as a heterogeneous group of bacteria. Related to this diversity, the identification of lactobacilli at the species level is often problematic and in some cases, an accurate identification is only obtained using molecular or polyphasic approaches. Species identification remains essential for describing the bacterial population colonizing various niches and studying their dynamics. Lactobacilli are ubiquitous bacteria occurring in low numbers at all plant surfaces but they grow luxuriously in decaying plant material and fruits. These bacteria are used as a low-cost mean to preserve and transform plant and animal raw matters such as cereals, tubers, grass, vegetables, milk and dairy products, meat and fish. Thus, lactobacilli have a crucial role in human nutrition. Lactobacilli are commensals of human and animals. Lactobacillus jensenii, L. crispatus and L. gasseri are the predominant species in the normal vaginal microbial flora in women of reproductive age and their presence is correlated with a control of vaginal infections. L. ruminis, L. gasseri, L. reuteri and L. salivarius are the most frequent species detected in adult human faecal samples ( L. acidophilus is the species frequently found in human newborns faecal fluids) while L. plantarum, L. gasseri, L. rhamnosus and L. paracasei are detected in healthy human oral and rectal mucosa. The role of the autochthonous Lactobacillus flora of the human digestive tract is not yet completely elucidated. Lactobacilli may contribute to the intestinal microflora balance. In the mouth, they contribute to the development of dental plaques in association with Streptococcus mutans. Many applications of lactobacilli as probiotics are suggested but only few have shown clearly demonstrated effects on human health (e.g. treatment of lactase-deficiency, prevention and treatment of rotavirus induced diarrhoea in children). Recent data obtained with probiotics in the treatment of allergic diseases or inflammatory bowel diseases are particularly promising.