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Tetracycline and rifampicin induced a viable but nonculturable state in Staphylococcus epidermidis biofilms
Virginia Carvalhais1,2, Begoña Pérez-Cabezas1, Cátia Oliveira1
1ICBAS - Instituto de Ciências Biomédicas Abel Salazar, University of Porto, Rua de Jorge Viterbo Ferreira 228, 4050-313 Porto, Portugal.
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.
