Nucleotide Sequence and Characterization of a Novel Cefotaxime-Hydrolyzing β-Lactamase (CTX-M-10) Isolated in Spain

A cefotaxime-resistant, ceftazidime-susceptible Escherichia coli isolate was obtained from a patient with sepsis in 1997, from which a β-lactamase with a pI of 8.1 was cloned. Cephaloridine and cefotaxime relative hydrolysis rates were 167 and 81, respectively (penicillin G rate = 100), whereas ceftazidime hydrolysis was not detected. The nucleotide sequence revealed a bla gene related to that coding for CTX-M-3. Despite 21 nucleotide substitutions, only 2 determined amino acid changes (Ala27Val and Arg38Gln). The amino acid sequence identity between this enzyme, designated CTX-M-10, and the chromosomal β-lactamase of Kluyvera ascorbata was 81%.