Conditionally pathogenic flora These are bacteria that are present in a healthy person in amounts that are safe for the body. Moreover, they do not cause him any harm. Nevertheless, when a person is exposed to certain external or internal factors, the number of opportunistic microorganisms begins to exceed this permissible norm. This leads to the development of an inflammatory process (disease) of various kinds. One of the leading causes of the development of "pathogenicity" of the opportunistic flora is immunodeficiency.