Application of a feasible method for determination of biofilm antimicrobial susceptibility in staphylococci.

The aim of this study was to use a practical method to determine the minimal biofilm eradication concentration (MBEC) of vancomycin and to compare the MBEC with minimal inhibitory concentration (MIC) for biofilm-producing and non-biofilm-producing isolates of staphylococci. Forty Staphylococcus spp. isolates from central venous catheter, from distinct patients, were selected for this study. The vast majority (28/30) of isolates which were biofilm-producing, presented high MBEC values (≥8 μg/mL) and could be considered as non-susceptible to vancomycin. All non-biofilm-producing isolates presented low MBEC (≤2 μg/mL) and were susceptible to vancomycin, according to CLSI breakpoints. While the MBEC and MIC values for biofilm-producing isolates differ significantly, the MBEC and MIC values for non-biofilm producers were the same. The method we have used proved to be a feasible and rapid technique to measure MBEC of Staphylococcus spp. biofilms. The method presented herein might be an alternative tool to evaluate the antibiotic susceptibility in the biofilm mode of growth; the MBEC may be a more appropriate approach to correlate the susceptibility in vitro with clinical outcome resulting from the treatment of Staphylococcus spp. infection.