New insights in the pathogenesis of foreign body infections with coagulasenegative staphylococci

Foreign body infections by coagulase negative Staphylococci are an importan t and growing problem in our hospitals. Only recently have we started to get some data on the specific virulence fa ctors that permit the otherwise non-pathogenic Coagulase Negative Staphyloc occi (CNS) to be so successful in causing foreign body infections. Adherence of the Coagulase Negative Staphylococci to the foreign body is a first and crucial step. Several genes and gene-products have been identifie d that enhance staphylococcal adherence to biomaterials. Adherence is follo wed by accumulation; in this phase the Coagulase negative Staphylococci org anise themselves into a complex multilayer of cells covered with polysaccha ride. This we call the biofilm. Finally coagulase negative Staphylococci un dergo complex and as yet non-defined metabolic changes that in combination with biofilm formation allow them to persist on the foreign body and become less susceptible to antibiotics. Few data are available on the factors inv olved in the accumulation and persistence phase.