Molecular characterization of amoxicillin-clavulanate resistance in a clinical isolate of Escherichia coli.
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.
Bellaaj
Amel
A
Laboratoire de Biochimie et de Technobiologie, Faculté des Sciences de Tunis, 2092 EL-Manar II, Tunis, Tunisia.
Bollet
Claude
C
Alfeddy
Nejib
N
Limam
Ferid
F
Belhadj
Cherifa
C
Regli
Anne
A
Chollet
Renaud
R
Belhadj
Omrane
O
Ben-Mahrez
Kamel
K
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
D001425:Bacterial Outer Membrane Proteins; D004269:DNA, Bacterial; D019980:Amoxicillin-Potassium Clavulanate Combination; D001618:beta-Lactamases