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infectious diseases

Microorganisms

The term microorganisms and its synonyms (microbes, germs, etc.) refers to very small living beings (in the order of a millionth of a meter), generally unicellular, that is, formed by a single cell, but with some features common to all other more complex living beings.

Microorganisms are divided into four groups:

  1. bacteria : in turn, they can be classified as gram positive and gram negative. They are found everywhere, in the earth, in water, in the air and in our skin, but also in environments
    hostile to life (high temperatures, absence of oxygen). Some of these microorganisms have the ability to produce spores comparable to particularly resistant shells, which allow the bacterium to survive in hostile conditions (heat, cold, lack of nutrients) for quite long times. As soon as the environmental conditions are favorable again, the spore is transformed again into its vegetative form and the bacterial cell regains the ability to replicate.

    Based on their shape, they are divided into cocci (cylindrical bacteria), bacilli (rod-shaped) and spirilli (a spiral stick).

  2. Mushrooms and molds : larger and more complex than bacteria, they develop on organic materials forming colonies that look like a cotton flake or a viscid substance with very variable colors. These micro-organisms reproduce by means of spores that can propagate in the environment transported by the air or by animals.

  3. Yeasts : a cross between fungi and bacteria; unlike molds, which are multicellular (for this reason, they do not represent micro-organisms properly), yeasts are single-celled organisms.

  4. Viruses : very small, more than real life forms are organic molecules that live at the expense of another life form and are defined, for this reason, forced parasites. Consequently, strictly speaking, they cannot be considered microorganisms, let alone living organisms

DIMENSIONS OF MICRO-ORGANISMS:

  • bacteria: 0.2 - 10 µm;
  • mold spores: 2.5 - 20 µm;
  • yeast spores: 4- 12 µm;
  • virus: 0.015 - 0.25 µ (visible only with the electron microscope).

Not all microorganisms are enemies of man; some of them, for example, have been used for centuries in the preparation of foods such as bread, wine, vinegar and cheese. Some bacteria that populate our intestines produce vitamins and antibiotics, protecting the body and strengthening the immune system; in the same way the lactobacilli that make up the vaginal flora protect the female organism from genital infections.

Only some microorganisms are therefore dangerous to health and have the ability to cause serious diseases. Examples are the plague, cholera, tetanus and tuberculosis, as regards bacteria, candida and aspergillosis for fungal microorganisms, mononucleosis, smallpox, AIDS and rubella for viruses.

On the basis of the relationships that these contract with the host, different types of microorganisms can be distinguished:

  • saprophytes or commensals: they live and multiply in contact with the host without causing damage; indeed, sometimes a relationship of mutual benefit can be established (symbiosis);
  • Pathogens: microorganisms that tend to cause disease;
  • Opportunists: normally harmless microorganisms, but capable of causing diseases, even serious ones, following a weakening of the organic defenses.

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