Abstract
In the last few years, there have been works in literature describing clinical cases of infections with bacteria previously considered to be non-pathogenic. So far, these bacteria have been commonly isolated from the natural environment: water, soil, plants, and isolation from a sample of clinical material has often been considered an impurity. Therefore, the aim of the paper was to draw attention to newly emerging bacterial species, their characteristics, biochemical properties, virulence factors and predisposition to selected forms of infection in groups of patients with specific risk factors. The impact on the more frequent isolation of species of bacteria previously considered to be non-pathogenic has several aspects: reliable diagnostic methods, including correct identification of the species, enabling the differentiation of closely related bacteria, the growing group of immune-compromised patients and with infectious risk factors (such as older age, diabetes, tumours, organ transplantation), more susceptible to infection, also with less pathogenic microorganisms. Greater adaptability of bacteria to new environmental conditions, including the human body, are also worth mentioning. The pathogenic effect of these bacteria, mainly related to the production of biofilms and factors conditioning adhesion to host cells or biomaterials, facilitating colonization and subsequent infection, is also important.
The progress in medicine that has taken place in recent years has positively influenced the life expectancy of patients with certain diseases and in many situations, it contributed to an improvement in its quality. Unfortunately, it also made it possible to cause infection with bacteria that were previously considered to be low or non-pathogenic.
1. Introduction. 2. Gram-positive rods 3. Streptococci with special nutritional requirements 4. Gram-negative rods. 5. Summary