The ability of biofilm formation does not influence virulence of Staphylococcus aureus and host response in a mouse tissue cage infection model.

The virulence of Staphylococcus aureus Sa113 (SA113) and an isogenic ica deletion mutant (ica-), deficient in the production of polysaccharide intercellular adhesin (PIA), which is crucial for biofilm formation, was compared in a mouse tissue cage infection model. The minimal infective doses for the induction of persistent tissue infections in C57BL/6 mice were 10(3) CFU for both SA113 and the ica- mutant. Bacterial growth, initial adherence to surfaces within the implants and the course of inflammation including growth-dependent host TNF and MIP-2 release, influx of phagocytes and an accumulation of dead leukocytes were similar as well. Since SA113 expressed PIA in vivo, we could demonstrate that PIA and the lack of biofilm formation did not influence the capacity of S. aureus to induce persistent infections and did not modulate host responses in the mouse tissue cage model.