Cefotaxime, des-Cefotaxime and Ceftazidime: in vitro activity and stability to hydrolysis from TEM-derived extended spectrum β-lactamases Cefotaxime, Cefotaxime-desacetil e Ceftazidime: attività in vitro e stabilità all’idrolisi delle β-lattamasi a spettro esteso

β-lactamases production represents a determining factor in bacterial resistance to β-lactam antimicrobial agents. Over 200 enzymes have been characterized for their nucleotidic sequences and/or biochemical properties [1]. Among class A β-lactamases [2] TEM-1 is the commonest enzyme in Enterobacteriaceae. Because of wide spread use of antibiotics there has been the emergence of different variants of this enzyme able to hydrolize oximino-cephalosporins, penicillins, monobactams and sometimes resistant to inhibitors used in clinical therapy [3, 4]. However, resistance levels due to TEM mutants can change towards each single β-lactam because of mutations able to influence and remodel the activesite of these β-lactamases [5]. In the present study we evaluated the phenotype of resistance induced by some extended spectrum β-lactamases (ESβLs) towards cefotaxime, desacetyl-cefotaxime, ceftazidime, piperacillin and cephalotin correlating kinetic parameters and susceptibility pattern. We decided to study desacetyl-cefotaxime, metabolic product of cefotaxime provided still with antimicrobial activity, to evaluate its sinergic role found “in vitro” as reported in literature [6].