Simultaneous production of two types of Beta-lactamase in Escherichia coli and Providencia stuartii

Abstract

The production of β-lactamase has been studied in two strains isolated from clinical samples: Providencia stuartii MULB 501 and Escherichia coli MULB 130. These strains were selected for their high resistance level to penicillins and cephalosporins. Determination and identification of β-lactamase activity were achieved by combining several up-to-date methods including (i) neutralization by anti-β-lactamase sera, (ii) purification by affinity chromatography on cephalosporin C linked Sepharose 4B, (iii) determination of substrate specificity and kinetic values (K_m and V_max) by a computerized microacidimetric method, and (iv) isoelectric focusing.The results clearly demonstrate that in these two strains there is a simultaneous production of different β-lactamases: the first one is similar to the TEM penicillinase and the second one shares a typical cephalosporinase profile. This double β-lactamase production is a relatively rare phenomenon.