Billions of friends
At birth, newborns come into the world with a sterile gastrointestinal system. Within a few days, a life-sustaining microbiota then develops in their digestive tract thanks to their mother’s milk and the new environment that surrounds them. The endogenous microbiota serves two principal functions. It promotes the digestive process by degrading indigestible sugars into lactic acid and volatile fatty acids. It also participates in intestinal motility, the secretion and absorption of nutrients and enables the synthesis of vitamins B and K.
The barrier effect
The microbiota has a protective capacity against opportunistic agents by inhibiting the proliferation and intestinal adhesion of undesirable bacteria, by producing specific metabolites, and by stimulating immune defenses. The intestinal microbiota constitutes a very large part of the bacterial population contained in the human organism and forms an extremely complex ecosystem. In a healthy subject, at least 17 families of bacteria can be found, in addition to more than 1,000 species and an indefinite number of sub-species. The onset of an illness, the ingestion of medications, and a lifestyle that does not respect the natural biological rhythm can all put the microbiota balance at risk. Under these circumstances, endogenous bacteria cannot fully accomplish their regulatory role. Moreover, the balance between the different bacterial populations becomes disturbed, and their health and wellness benefits are compromised.
Several studies have shown the complexity and the variability of the vaginal flora according to the menstrual cycle and the stage of life (mostly because of hormonal and physiological changes).
According to a recent American study, healthy women have 1 to 6 different bacteria commonly found in the vagina. Lactobacilli represent 83% of the total bacterial count. These different species could be grouped according to their concentration. In healthy adult women (post-puberty and pre-menopause), not pregnant and not during their period, the vaginal flora is predominantly composed of different species of Lactobacilli called the Doderleïn flora. The identity of these species was uncertain for a long time because the phenotypic identification methods were not discriminating enough. Using these methods, the main species from the vaginal flora were identified as: Lactobacillus acidophilus, L. fermentum, L. plantarum, L. brevis, L. jensenii, L. casei, L. cellobiosus, L. leichmanii, L. delbrueckii and L. salivarius.
The phenotypic method failed to differentiate subspecies members from the subgroups. As many as 10 to 20 different species of Lactobacillus are commonly present in the vagina including L. crispatus, L. gasseri, L. iners, L. jensenii and L. vaginalis. Furthermore, a Swedish team of researchers has recently shown that if the estrogen rate is very low, the Lactobacilli usually found in the vagina can be replaced by other Lactobacilli such as L. rhamnosus and L. reuteri (…).Estrogen supplementation may restore the vaginal flora. However, it has been shown that estradiol stimulates the colonization of Candida albicans in the vagina as this yeast expresses an “estrogen-binding” protein.
Even if the bifidobacteria are usually found in the vaginal flora, there are few studies related to this bacteria type. A study conducted by a Russian team in 1999 has shown that B.bifidum, B.breve, B.adolescentis and B.longum are predominant subspecies found in the vaginal flora (…).
The oral cavity harbors a specific microflora, which is often overlooked. Indeed, this warm, humid and nutrient-rich environment represents an extremely favorable habitat for a great variety of bacteria. Over 700 different bacteria species have been found in the mouth, 20% of which belong to the Streptococci genus. An estimated 60% of these microorganisms are located on the tongue surface. The dental surface, which represents a much smaller area, plays an important role for bacteria colonization, with the formation of an important biofilm adhering to its surface: the dental plaque. Each milligram of dental plaque may contain 100 million of bacteria. The oral microflora evolves with age, and in particular depending on the presence of teeth.
At birth, the sterile environment of the mouth is rapidly colonized within hours. S. salivarius is dominant in infants and may make up to 98% of the total flora until the appearance of the teeth. Together with the eruption of teeth, appears a specific flora able to colonize non-epithelial, hard surfaces: S. mutans and S. sanguis. Other strains of Streptococci adhere strongly to the gums and inside of the cheeks. The gingival crevice area represents a favorable habitat for a variety of anaerobic species. The oral microflora continues to evolve during lifetime, with for example the apparition of Bacteroides and spirochetes at puberty and a higher colonization by S. aureus and other aerobic organisms in elderly people with implanted teeth.