Extracellular matrix in Staphylococcus epidermidis biofilms: a consequence of bacterial production or cell wall degradation?

Abstract

Staphylococcus epidermidis is a leading pathogen accounting for nosocomial infections. The ability to form biofilms is considered the major virulence factor of this bacterium. The hallmark of this type of infection is the presence of an extracellular polymeric matrix that, in the case of S. epidermidis biofilms, is mainly constituted by an N-acetylglucosamine polymer. We have identified a subpopulation of bacteria that we believe to be the responsible for the extracellular matrix accumulation in S. epidermidis biofilms as they have comparative significant higher amount of surface N-acetylglucosamine. Flow cytometric evaluation of cell wall permeability and transmission electronic microscopy are highly suggestive of primary wall degradation in these bacteria. In overall, these results suggest that the extracellular matrix in S. epidermidis biofilms is a consequence of the degradation of the bacteria cell wall and that propide iodium should be used with care when used as a marker for bacteria dead in biofilms.