Coagulase negative staphylococci and their participation in pathogenesis of human infections.

Coagulase negative staphylococci are among the bacteria routinely isolated at various clinical microbiology departments. There are presently 41 recognized taxons, designated coagulase negative staphylococci. Although long considered nonpathogens as the components of normal human skin and mucosa, lately they turned into significant etiological agents causing nosocomial infections, mainly in link with the presence of foreign bodies in the human organism. In addition, their increasing resistance to antibacterial drugs evoked deepening concern of infections involving coagulase negative staphylococci. Problems already appear during interception of the coagulase negative staphylococci in the material and the subsequent determination, whether they are invaders or colonisers. Hence, major efforts have been made toward the development of methods enabling to recognize those properties of coagulase negative staphylococci, which would resolve this day-to-day dilemma, facing the clinical microbiologist. From the aspect of their pathogenic potential, the most important property of coagulase negative staphylococci is their capability to form biofilm on the surfaces of foreign bodies introduced (implanted) into the organism. In consequence of such formation they are protected in the biofilm against the effects of antibacterial drugs and of the immune system. Lately, major interest appeared in the study of factors, mainly S. epidermidis, which participate in the biofilm formation, as well as of the determination of virulence factors of other coagulase negative staphylococci (Tab. 2, Ref. 25).