Non-pigmented, rapidly growing mycobacteria are among the most common non-tuberculous mycobacteria isolated in laboratories of clinical microbiology. They are well-documented human pathogens (especially the species Mycobacterium fortuitum, Mycobacterium chelonae and Mycobacterium abscessus), able to cause a broad spectrum of diseases, including nosocomial infections. In many cases foreign bodies are present, and proper removal of them is necessary for a good outcome. Despite that clinical, taxonomic and even epidemiological data are abundant in the literature, our knowledge of pathogenic mechanisms presented by these bacteria is scanty. There are data suggesting that some strains are able to adhere to several cell lines, and even to grow intracellularly which could serve as an important pathogenic factor. However, there are also some data that suggest that this ability is not enough to explain the differences between true human pathogens and strains isolated as colonizators. Another well-documented factor is the ability of these species to adhere to foreign bodies and form biofilms. Epidemiological data suggest that these organisms form biofilms in medical devices, such as catheters, sutures or prosthetic devices, and that resistance against antibiotics appears in mature biofilm, as described in other bacteria. Also experimental data has demonstrated that some of these species of mycobacteria can form biofilms, and that antiseptic resistance appears when the biofilm is established. Molecular mechanisms of biofilm development has been recently described from related species of mycobacteria, such as M. smegmatis, and it is probable that similar mechanisms could be found in pathogenic species of these organisms.
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