Expression of biofilm-associated genes in Staphylococcus epidermidis during in vitro and in vivo foreign body infections.

The expression of the genes icaA, icaC, aap, and atlE--with a putative role in the pathogenesis of Staphylococcus epidermidis foreign body infections--and of mecA and 3 housekeeping genes (gmk, tpi, and hsp60) was examined in vitro and in vivo. In vitro expression levels of ica, atlE, and gmk were higher in sessile than in planktonic bacteria. Exposure to foreign bodies in vitro and in vivo induced a sharp increase in ica expression that was followed by a progressive decrease. The in vivo expression of aap and mecA was high during early but low during late foreign body infections. The in vivo expression of atlE and gmk remained relatively high and stable. In conclusion, biofilm genes encoding for structural elements are mainly expressed during early foreign body infections. The ica genes are associated with initial colonization but not with persistence. The constant expression of atlE and gmk may indicate a role during the entire course of foreign body infections.