Cross infections due to coagulase-negative staphylococci in high-risk patients

Until recently, infections due to coagulase-negative staphylococci (CNS) have been regarded as endogenous in origin. However, there are now increasingly reports in the literature on the endemic occurrence of distinct strains of CNS. Several outbreaks due to CNS are reported in cardiac surgery or in neonates. The latter seem to be high risk populations in regard to CNS infections because of certain risk factors (i.e. degree of immunosupression, routine use of central venous catheters and parenteral lipids as well as broad spectrum antibiotic therapy). On the other hand, these newborn babies have no physiological skin flora and are therefore easily colonized by multiresistent bacteria. The persistence of certain well-defined Staphylococcus epidermidis (SE) strains in neonatal intensive care units have been demonstrated over periods as long as a decade. Specific putative virulence factors (i.e. slime production and polysaccharide/adhesin PS/A) were more common in endemic strains as compared to single isolates. Pulsed-field gel electrophoresis (PFGE) proves to be a powerful tool in the study of the epidemiology of CNS while other modern typing techniques (ribotyping, plasmid typing) were also used in the literature to investigate outbreaks of CNS infections.