Human Bacterial Flora

, or communicating with the outside, such as the oral cavity, the gastrointestinal tract, the respiratory tract, the vagina and the lower urinary tract.

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Origin and development of the human bacterial flora

During fetal life, the organism does not have a real bacterial flora, since the placenta prevents the passage of the vast majority of microorganisms.

The situation changes radically at the moment of delivery, when the newborn comes into contact with microbes from the mother's genitourinary tract. In the following hours and days, the germs transmitted by people and by the environment with which the young body comes into contact will settle. From this moment on, the aforementioned body areas will begin to acquire their own complex "ecosystem", made up of different species microbial.

What at first glance might seem a passive process, is actually a complex and delicate system, strongly regulated by a bond made up of mutual advantages. The human organism supplies nutrient substrates to its bacterial flora, which in turn protects it from pathogens, preventing the development of other microorganisms in the same habitat. In these complex interactions, the immune system represents an attentive spectator, ready to intervene if the balance broke. Normally harmless bacteria can become so when they multiply out of control or migrate to other areas of the body.

Food deficiency, traumatic injuries, prolonged antibiotic therapies or a temporary lowering of the immune defenses, can cause an alteration of the human microbial flora.

it is exposed to a great variety of potential colonizers, from which it protects itself by adopting different defensive strategies:

• Lipids present in the sebum and in the hydrolipidic film;
• Poor hydration
• Frequent replacement of the outer cell layers;
• acid pH and sweat immunoglobulins.

For this reason, bacterial settlements are concentrated near the skin orifices and in the most humid areas, such as the armpit or the interdigital folds of the feet.

The decomposition of skin lipids and glandular secretions is responsible for bad smells which, coincidentally, become more intense in the aforementioned skin areas. Likewise, alterations in the normal skin bacterial flora can be responsible for unpleasant odors, which are not always an indication of bad personal hygiene.

Supported by an "excessive secretion of sebum, the proliferation of some microorganisms and in particular of the Propionibacterium acnes, favors the onset of inflammatory processes that manifest themselves with the appearance of boils and acne.

as you go down the respiratory tree, the concentration of these microorganisms decreases further, until it disappears in correspondence with the pulmonary alveoli.

The mucus secreted by the muciparous respiratory glands helps protect the organism from pathogens, entangling them inside and neutralizing them through the antibodies it is equipped with.

: functions of the bacterial flora

The digestive tract is colonized by an "impressive number of microorganisms, particularly numerous also from a qualitative point of view.

In the oral cavity we find the so-called bacterial plaque, a sort of patina adhered to the surface of the teeth on which bacteria develop. Main responsible for caries are lo Streptococcus mutans and the Lactobacillus acidophilus. The body defends itself from their cariogenic attack through saliva, but it can do little when an excessively high sugar diet is accompanied by poor oral hygiene.

Bad odor (halitosis) can be, also in this case, a sign of the presence of certain bacterial colonies, whose metabolism produces volatile sulphurous substances with an unpleasant odor.

Small colonies of pathogens can also be found in the oral cavity of healthy people, such as Candida albicans. However, these microorganisms are present in numerically insufficient quantities to carry out their pathogenic activity. When their virulence increases, for example due to a temporary decline in the body's defenses, they can give rise to specific pathological conditions (in this specific case, to thrush).

In the stomach, the presence of microorganisms is severely limited by "gastric acidity. The exception is"Helicobacter pylori which can cause an ulcer to form in the long run.

See also: vaginal bacterial flora, intestinal bacterial flora, oral bacterial flora.