title: Molecular characterization of amoxicillin-clavulanate resistance in a clinical isolate of Escherichia coli.
abstract: The resistance phenotype of the clinical isolate of Escherichia coli 1941 was characterized by high-level resistance to penicillins and to combinations amoxicillin-ticarcillin/clavulanate and ampicillin/sulbactam. This resistance was carried by the conjugative plasmid pEC1941 that encoded a beta-lactamase activity. The purified enzyme focused at pI 5.4 and was strongly inhibited in vitro by clavulanic acid (IC50 = 0.09 microM). Nucleotide sequence analysis revealed identity between the plasmid borne blaTEM gene of E. coli 1941 and the blaTEM-1B gene, except for a single C-to-T substitution at position 32 in the promoter region leading to the overlapping promoters Pa and Pb. No alterations in the expression of outer membrane porins OmpC and OmpF have been detected. These findings show that the resistance of E. coli 1941 to the combinations of beta-lactams with beta-lactamase inhibitors is related to high-level production of TEM-1 enzyme expressed from the strong promoters Pa and Pb.
authors.affiliation: Laboratoire de Biochimie et de Technobiologie, Faculté des Sciences de Tunis, 2092 EL-Manar II, Tunis, Tunisia.
authors.forename: Amel
authors.initials: A
authors.lastname: Bellaaj
authors.forename: Claude
authors.initials: C
authors.lastname: Bollet
authors.forename: Nejib
authors.initials: N
authors.lastname: Alfeddy
authors.forename: Ferid
authors.initials: F
authors.lastname: Limam
authors.forename: Cherifa
authors.initials: C
authors.lastname: Belhadj
authors.forename: Anne
authors.initials: A
authors.lastname: Regli
authors.forename: Renaud
authors.initials: R
authors.lastname: Chollet
authors.forename: Omrane
authors.initials: O
authors.lastname: Belhadj
authors.forename: Kamel
authors.initials: K
authors.lastname: Ben-Mahrez
mesh_terms: D019980:Amoxicillin-Potassium Clavulanate Combination / Q000494:pharmacology*; D001425:Bacterial Outer Membrane Proteins / Q000378:metabolism; D003001:Cloning, Molecular; D003227:Conjugation, Genetic; D004269:DNA, Bacterial / Q000032:analysis / Q000235:genetics; D004352:Drug Resistance, Microbial; D004359:Drug Therapy, Combination / Q000494:pharmacology*; D021902:Enterobacter aerogenes / Q000235:genetics; D004926:Escherichia coli / Q000187:drug effects*; D004927:Escherichia coli Infections / Q000188:drug therapy / Q000382:microbiology*; D006801:Humans; D015151:Immunoblotting; D007525:Isoelectric Focusing; D008826:Microbial Sensitivity Tests; D020133:Reverse Transcriptase Polymerase Chain Reaction; D001618:beta-Lactamases / Q000378:metabolism
chemical_list: D001425:Bacterial Outer Membrane Proteins; D004269:DNA, Bacterial; D019980:Amoxicillin-Potassium Clavulanate Combination; D001618:beta-Lactamases