Cloning and Sequence of the Gene Encoding a Novel Cefotaxime-Hydrolyzing β-Lactamase (CTX-M-9) from Escherichia coli in Spain

A new CTX-M-type β-lactamase (CTX-M-9) has been cloned from a clinical cefotaxime-resistant Escherichia coli strain. Despite the close identity that exists between the CTX-M-9 and Toho-2 β-lactamases (88%), the 35 amino acids located between residues Ala-185 and Ala-219 are totally different in both enzymes. Outside of this region there are only six amino acids substitutions between both proteins.