Lysostaphin as a potential therapeutic agent for staphylococcal biofilm eradication.

The aim was to study the activity of lysostaphin in monotherapy or in combination with oxacillin, towards biofilms built by clinical and reference S. aureus and S. epidermidis strains in the wells of microplate, in the chambers of a LabTekII chamber slide or on the polyethylene catheter. MICs of oxacillin and lysostaphin for planktonic bacteria were determined according to the standards of NCCLS. BIC (Biofilm Inhibitory Concentration) was estimated by the MTT assay. The integrity of biofilm treated with antimicrobials was also examined: by staining with FITC and laser scanning fluorescence confocal microscopy and visually by TTC reduction assay. Despite the fact that susceptibility of planktonic cultures of 25 staphylococcal strains to lysostaphin action was various, we have demonstrated the effectiveness of lysostaphin in the treatment of biofilm, built not only on the flat surface of the microplates but also on catheter's surface. The synergistic effect of subBIC lysostaphin+oxacillin was observed for MSSA and MRSA biofilms but not for 1474/01 hVISA strain. Also BICOXA for S. epidermidis RP12 and A4c strains, but not for 6756/99 MRSE biofilms was reduced when lysostaphin was simultaneously used.