A New TEM-Derived Extended-Spectrum β-Lactamase (TEM-91) with an R164C Substitution at the Ω-Loop Confers Ceftazidime Resistance

Abstract
A new plasmid-mediated TEM-derived extended-spectrum β-lactamase, TEM-91, was identified in a ceftazidime-resistant (MIC, >128 μg per ml)Escherichia colistrain isolated in 1996 in Japan. TEM-91 has three amino acid substitutions, R164C, M184T, and E240K, compared with TEM-1 penicillinase. The isoelectric point (pI),Km, andkcatof TEM-91 for ceftazidime were 5.7, 179 μM, and 29.0 s−1, respectively. TheKiof clavulanic acid for ceftazidime hydrolysis was 30.3 nM.
Keywords

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