title: Klebsiella oxytoca: resistance to aztreonam by overproduction of the chromosomally encoded beta-lactamase.
abstract: Aztreonam-resistant Klebsiella oxytoca strain SL7811 was selected on agar containing 1 microgram of aztreonam per ml from a susceptible strain SL781. The MICs for the resistant mutant towards penicillins, aztreonam and ceftriaxone were much higher, to cefotaxime slightly higher and to ceftazidime unchanged. Synthesis of beta-lactamase was 223-fold greater in the mutant compared with the susceptible strain. SL781 and its resistant mutant SL7811 produced beta-lactamase with the same isoelectric point and substrate profile. The beta-lactamase genes from SL781 and SL7811 were cloned in plasmid pBGS18 giving pBOF-1 and pBOF-4 respectively. The sequences of the two putative promoters indicated two modifications in the resistant plasmid pBOF-4: a transversion (G-->T) in the first base of the -10 consensus sequence and a deletion of one C residue four base pairs upstream of the -10 hexamer.
authors.affiliation: Laboratoire de Microbiologie, Hôpital Saint-Louis (Université Paris VII), France.
authors.forename: B
authors.initials: B
authors.lastname: Fournier
authors.forename: G
authors.initials: G
authors.lastname: Arlet
authors.forename: P H
authors.initials: PH
authors.lastname: Lagrange
authors.forename: A
authors.initials: A
authors.lastname: Philippon
mesh_terms: D000595:Amino Acid Sequence; D001398:Aztreonam / Q000494:pharmacology*; D001483:Base Sequence; D002439:Cefotaxime / Q000494:pharmacology; D002876:Chromosomes, Bacterial; D003001:Cloning, Molecular; D004269:DNA, Bacterial; D004352:Drug Resistance, Microbial / Q000235:genetics; D004926:Escherichia coli; D007709:Klebsiella / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics; D008969:Molecular Sequence Data; D009154:Mutation; D011401:Promoter Regions, Genetic; D001618:beta-Lactamases / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D004269:DNA, Bacterial; D001618:beta-Lactamases; D001398:Aztreonam; D002439:Cefotaxime