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  • Title: Substitution of Thr for Ala-237 in TEM-17, TEM-12 and TEM-26: alterations in beta-lactam resistance conferred on Escherichia coli.
    Author: Giakkoupi P, Hujer AM, Miriagou V, Tzelepi E, Bonomo RA, Tzouvelekis LS.
    Journal: FEMS Microbiol Lett; 2001 Jul 10; 201(1):37-40. PubMed ID: 11445164.
    Abstract:
    Non-naturally occurring mutants of TEM-17 (E104K), TEM-12 (R164S) and TEM-26 (E104K:R164S) extended-spectrum (ES) beta-lactamases bearing threonine at position 237 were constructed by site-specific mutagenesis and expressed under isogenic conditions in Escherichia coli. Quantification of beta-lactamase activities and immunoblotting indicated that Ala-237-->Thr did not significantly affect expression levels of these ES enzymes. Minimum inhibitory concentrations of beta-lactam antibiotics showed that the presence of threonine at position 237 exerted a dominant effect increasing the enzymes' preference for various early generation cephalosporins over penicillins. Activity against broad-spectrum oxyimino-beta-lactams was also changed. The effect of Ala-237-->Thr on the activity against ceftazidime, aztreonam, cefepime and cefpirome of all three ES TEM enzymes was detrimental. Introduction of Thr-237 improved activity against cefotaxime and ceftriaxone in TEM-12 and TEM-26, but not in TEM-17.
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