TEM-8: a paradoxical ceftazidimase that owes its uniqueness to the presence of serine residues at positions 164 and 238

An extended-spectrum, TEM-type beta -lactamase (ESBL) markedly more active against ceftazidime than other beta -lactams was studied because its kinetic parameters differed from those previously described for ESBLs. None the less, analysis of the nucleotide sequence confirmed the TEM-8 gene. As a first step in attempting to explain this discrepancy, we determined the kinetic parameters of the reference strain synthesizing the TEM-8 ESBL, i.e. the Escherichia coli K-12 C600 transconjugant, CF704, according to a method described previously.