| Abstract: | The production of beta-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 beta-lactamase activity were achieved by combining several up-to-date methods including (i) neutralization by anti-beta-lactamase sera, (ii) purification by affinity chromatography on cephalosporin C linked Sepharose 4B, (iii) determination of substrate specificity and kinetic values (Km and Vmax) 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 beta-lactamases: the first one is similar to the TEM penicillinase and the second one shares a typical cephalosporinase profile. This double beta-lactamase production is a relatively rare phenomenon. |
