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Antunes ALS, Trentin DS, Bonfanti JW, Pinto CCF, Perez LRR, Macedo AJ, Barth AL. Application of a feasible method for determination of biofilm antimicrobial susceptibility in staphylococci. APMIS 2010; 118: 873-7. 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. [ABSTRACT FROM AUTHOR]

Coagulase-negative Staphylococcus spp. was considered nonpathogenic until the emergence of multiresistance and the demonstration of their participation as infectious agents. In Brazil, oxacillin resistance may be present in over 80% of isolates, and the Clinical and Laboratory Standards Institute standardized a disk-diffusion method to predict this resistance in Staphylococcus. The aim of this study was to evaluate the variability among commercial disks of oxacillin (1 microg) and cefoxitin (30 microg) widely used in clinical laboratories of microbiology, compared with mecA gene and minimum inhibitory concentration (MIC) of oxacillin. The use of oxacillin and cefoxitin disks simultaneously allowed the detection of important differences, particularly, in less frequent species such as S. cohnii, S. haemolyticus, S. saprophyticus, and S. sciuri. Disks of cefoxitin of the brand 2 displayed good correlation with the mecA gene (98.7%) and oxacillin MIC (97.8%), while major discrepancies were observed using disks of brand 1. One of the critical points in the diffusion disk test is the quality of the disks: the use of better quality disks associated with molecular methods lead to better results to define the best antibiotic therapy.