Open AccessSubstitution of Thr for Ala‐237 in TEM‐17, TEM‐12 and TEM‐26: alterations in β‐lactam resistance conferred on Escherichia coli
Author(s) -
Giakkoupi P.,
Hujer A.M.,
Miriagou V.,
Tzelepi E.,
Bonomo R.A.,
Tzouvelekis L.S.
Publication year - 2001
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.2001.tb10729.x
Subject(s) - aztreonam , ceftazidime , escherichia coli , cefepime , cefotaxime , enzyme , microbiology and biotechnology , cephalosporin , chemistry , threonine , mutant , biochemistry , biology , antibiotics , serine , bacteria , imipenem , antibiotic resistance , genetics , gene , pseudomonas aeruginosa
Non‐naturally occurring mutants of TEM‐17 (E104K), TEM‐12 (R164S) and TEM‐26 (E104K:R164S) extended‐spectrum (ES) β‐lactamases bearing threonine at position 237 were constructed by site‐specific mutagenesis and expressed under isogenic conditions in Escherichia coli . Quantification of β‐lactamase activities and immunoblotting indicated that Ala‐237→Thr did not significantly affect expression levels of these ES enzymes. Minimum inhibitory concentrations of β‐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‐β‐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.