Induction of Staphylococcus epidermidis biofilm formation by environmental factors: the possible involvement of the alternative transcription factor sigB.

Staphylococcus epidermidis is a major cause of nosocomial infections associated with the use of indwelling medical devices1. Chronic infection of a prosthetic implant can serve as a septic focus that can lead to osteomyelitis, acute sepsis, and death, especially in immunocompromised patients 2 . The ability of S. epidermidis to generate thick biofilms on smooth polymer surfaces is regarded as the crucial step in the pathogenesis of these infections. It is associated with the production of a polysaccharide intercellular adhesin (PIA). The PIA represents a linear β -1,6-linked glucosaminoglycan and the bacteria become embedded in this slimy extracellular matrix during the accumulative phase of biofilm formation 3 . The enzymes involved in the PIA synthesis are encoded by the ica ADBC operon which was found to be widespread in S. epidermidis clinical isolates 4,5,6. The expression of this operon undergoes strong intrastrain variation and the investigation of the varying ica -expression revealed that this phenomenon is based on different genetic mechanisms including phase variation, ica -deletions and large chromosomal rearrangements 6,7. In this work we give evidence that S. epidermidis biofilm expression can also be