Bacteria are microorganisms that are found widely throughout nature. Bacteria can be pathogenic and cause diseases when entering the body. Their capacity for developing infections and associated pathologies depends on the type of bacteria and its location as well as the resistance (immunity) of the individual. Frequent infectious diseases such as those affecting the air waves, sinuses and ears, are caused by pathogenic bacteria that can normally be present in the pharynx or the nose. In situations in which our defense mechanisms are weakened, for example due to a viral infection (common cold or flu), bacteria can infect surrounding tissue causing rhinitis, otitis, sinusitis, pharyngitis bronchitis and pneumonia.

There is an enormous diversity of bacteria species grouped in families, genders and strains.