title: Mutant TEM beta-lactamase producing resistance to ceftazidime, ampicillins, and beta-lactamase inhibitors.
abstract: A derivative of the TEM-1 beta-lactamase producing clinically significant levels of resistance to ceftazidime and beta-lactamase inhibitors in the presence of penicillins was generated following five rounds of DNA shuffling and selection. This complex mutant enzyme contained three amino acid substitutions including those of residues 104 and 276 that are known to produce extended-spectrum resistance and, correspondingly, resistance to beta-lactamase inhibitors. Although the Glu104Lys substitution by itself produced low levels of ceftazidime resistance, additional amino acid replacements in the enzyme with the triple mutation resulted in further enhancement of resistance to ceftazidime. Kinetic studies of the purified beta-lactamase enzyme with the triple mutation indicated enhancement of the catalytic efficiency for turnover (kcat/Km) of ceftazidime. The increases in the Ki values of both clavulanic acid and tazobactam for the enzyme with the triple mutation were consistent with the observed bacterial resistance to the reversibility of beta-lactam resistance with these inhibitors.
authors.affiliation: Departments of Biochemistry and Molecular Biology, Wayne State University, Detroit, Michigan 48202, USA. svakulen@med.wayne.edu
authors.forename: Sergei
authors.initials: S
authors.lastname: Vakulenko
authors.forename: Dasantila
authors.initials: D
authors.lastname: Golemi
mesh_terms: D019943:Amino Acid Substitution; D000668:Ampicillin Resistance / Q000235:genetics*; D002442:Ceftazidime / Q000494:pharmacology*; D018550:Cephalosporin Resistance / Q000235:genetics*; D002511:Cephalosporins / Q000494:pharmacology*; D003001:Cloning, Molecular; D003470:Culture Media; D004269:DNA, Bacterial / Q000187:drug effects / Q000235:genetics; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007202:Indicators and Reagents; D008826:Microbial Sensitivity Tests; D016297:Mutagenesis, Site-Directed / Q000235:genetics; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D010957:Plasmids / Q000187:drug effects / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D065093:beta-Lactamase Inhibitors; D001618:beta-Lactamases / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D002511:Cephalosporins; D003470:Culture Media; D004269:DNA, Bacterial; D004791:Enzyme Inhibitors; D007202:Indicators and Reagents; D065093:beta-Lactamase Inhibitors; D002442:Ceftazidime; D001618:beta-Lactamases; C034413:beta-lactamase TEM-1