INHIBITOR-RESISTANT TEM (IRT) BETA-LACTAMASES WITH DIFFERENT SUBSTITUTIONS AT POSITION-244

A novel inhibitor-resistant TEM (IRT) beta-lactamase was detected in a n Escherichia coli isolate resistant to amoxicillin-clavulanate and su sceptible to cephalothin. The substrate and inhibitor profiles of this beta-lactamase were similar to those of IRT-1 and IRT-2, The novel IR T's bla gene was sequenced, end the deduced amino acid sequence showed the amino acid replacement Arg for His-244 of the TEM-1 sequence. Sub stitutions for Arg-244 have been reported in three TEM-1 mutants: IRT- 1 (which corresponds to TEM-31) (Cys), IRT-2/TEM-30 (Ser), and TEM-41 (Thr). We designated this novel beta-lactamase, which corresponds to T EM-51, IRT-15.