The Class A β-Lactamase FTU-1 Is Native to Francisella tularensis

Abstract

ABSTRACTThe class A β-lactamase FTU-1 produces resistance to penicillins and ceftazidime but not to any other β-lactam antibiotics tested. FTU-1 hydrolyzes penicillin antibiotics with catalytic efficiencies of 105to 106M−1s−1and cephalosporins and carbapenems with catalytic efficiencies of 102to 103M−1s−1, but the monobactam aztreonam and the cephamycin cefoxitin are not substrates for the enzyme. FTU-1 shares 21 to 34% amino acid sequence identity with other class A β-lactamases and harbors two cysteine residues conserved in all class A carbapenemases. FTU-1 is the first weak class A carbapenemase that is native toFrancisella tularensis.