ABSTRACT
The isolation of microorganims from the endogenous microbiota, which are generally considered to be little virulent, from sites of serious infections presents a warning that the role of these microorganims as contaminants should not be discarded immediately. On the contrary, it is possible that they have great clinical importance, mainly in highrisk individuals. Any failure in the exclusion of normal microbiota during sample collection procedures may lead to the need of longer time for analysis, or to the production of inaccurate data to be sent to the practicioner. On the other hand, inadequate transportation may lead to the loss of viability of certain microorganims, which are either not going to be isolated, or they will be isolated in small number, and, therefore, considered to be less important. The relative importance of different microorganims in a mixed infection should be judged based on the relative number of each isolated strain, presence in pure culture, presence in the blood stream or persistence in repeated cultures. Another important factor is the evaluation of the impact of antimicrobial compounds on indigenous microbiota, when it is considered that agents which produce a smaller disturbance on normal microbiota are the less susceptible to lead to a superinfection. It may be concluded, thus, that the traditional difference between pathogenic and non-pathogenic or virulent and non-virulent microorganisms is becoming more and more insignificant.
KEY WORDS:
Indigenous microbiota; endogenous aggression; anaerobes.