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Updated: Oct 9, 2026

Isolation and Identification of Waterborne Antibiotic-Resistant Bacteria and Molecular Characterization of their Antibiotic Resistance Genes
Published on: March 3, 2023
Molecular and biochemical analysis of AST-1, a class A beta-lactamase from Nocardia asteroides sensu stricto
1Service de Bactériologie-Virologie, Hôpital de Bicêtre, Assistance Publique/Hôpitaux de Paris, Faculté de Médecine Paris-Sud, 94275 Le Kremlin-Bicêtre Cedex, France.
Abstract:
A beta-lactamase gene was cloned from a Nocardia asteroides sensu stricto clinical isolate. A recombinant plasmid, pAST-1, expressed the beta-lactamase AST-1 in Escherichia coli JM109. Its pI was 4.8, and its relative molecular mass was 31 kDa. E. coli JM109(pAST-1) was resistant to penicillins and narrow-spectrum cephalosporins. The beta-lactamase AST-1 had a restricted hydrolytic activity spectrum. Its activity was partially inhibited by clavulanic acid but not by sulbactam and tazobactam. AST-1 is an Ambler class A beta-lactamase sharing 65% amino acid identity with beta-lactamase FAR-1, the most closely related enzyme.
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