title: Plasmid-mediated resistance to third-generation cephalosporins caused by point mutations in TEM-type penicillinase genes.
abstract: Infections due to strains of Klebsiella pneumoniae, Escherichia coli, and Citrobacter freundii resistant to third-generation cephalosporins have been observed recently in France and the Federal Republic of Germany. This resistance phenotype is due to the production of new plasmid-mediated, broad-substrate-range beta-lactamases designated TEM-3 to TEM-7. DNA-DNA hybridization analysis with a probe specific for TEM-1 indicated that the corresponding genes blaT-3 to blaT-7 were variants of the structural genes for TEM-type beta-lactamases. In the present studies, a 2.5-kilobase BamHI plasmid DNA fragment encoding TEM-3 was cloned in E. coli, and the entire nucleotide sequence of blaT-3 was determined. The deduced amino acid sequence of TEM-3 differed in two positions from that of the TEM-2 enzyme: lysine (TEM-3) was substituted for glutamic acid (TEM-2) at residue 104 and serine (TEM-3) for glycine (TEM-2) at residue 238 in the numbering system of Ambler. Spontaneous mutants of TEM penicillinases with increased activity against third-generation cephalosporins were obtained in vitro by selection on cefotaxime or ceftazidime. It therefore appears that mutations in TEM-type beta-lactamases contribute to resistance to new-generation cephalosporins.
authors.affiliation: Unité des Agents Antibactériens, Institut Pasteur, Paris, France.
authors.forename: W
authors.initials: W
authors.lastname: Sougakoff
authors.forename: S
authors.initials: S
authors.lastname: Goussard
authors.forename: G
authors.initials: G
authors.lastname: Gerbaud
authors.forename: P
authors.initials: P
authors.lastname: Courvalin
mesh_terms: D000595:Amino Acid Sequence; D001483:Base Sequence; D002511:Cephalosporins / Q000494:pharmacology*; D002954:Citrobacter / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D003001:Cloning, Molecular; D004269:DNA, Bacterial / Q000235:genetics; D004352:Drug Resistance, Microbial / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D006801:Humans; D007711:Klebsiella pneumoniae / Q000187:drug effects / Q000201:enzymology / Q000235:genetics*; D009154:Mutation; D009693:Nucleic Acid Hybridization; D010405:Penicillinase / Q000235:genetics*; D011815:R Factors; D012689:Sequence Homology, Nucleic Acid; D014169:Transformation, Bacterial
chemical_list: D002511:Cephalosporins; D004269:DNA, Bacterial; D010405:Penicillinase