Aim: The goal of this study was to determine the effectiveness of antibiotics on Staphylococcus epidermidis biofilms with different proportions of dormant bacteria, using clinical and commensal isolates.
Materials & methods: The ability of S. epidermidis isolates to develop a dormant state was determined. The susceptibility of biofilms with prevented or induced dormancy to antibiotics was evaluated by enumeration of viable and cultivable cells, and confocal microscopy.
Results: Dormancy was observed in the majority of tested strains. Tetracycline and rifampicin enhanced the development of a viable but noncultivable biofilm state.
Conclusion: Biofilms with induced dormancy were more likely to survive rifampicin. Furthermore, we found that the reduction of cultivable cells was not sufficient to reach definite conclusions on antimicrobial effectiveness.
Keywords: Staphylococcus epidermidis biofilms; antibiotics; culturability; dormancy; viability; viable but noncultivable cells.