[The role of beta-lactamases and the permeability barrier in resistance to beta-lactam antibiotics].

The role played by beta-lactamases and by permeability barrier in resistance to beta-lactam antibiotics was investigated in 250 clinical isolates of Enterobacteriaceae. The data obtained showed that in 73 strains (52.9\%) was a significant correlation between the specific enzyme activity and resistance, however in 38 strains (27.5\%) an essential role was played by permeability barrier because the addition of subinhibitory levels of EDTA produced markedly reduction in the MIC.