title: Emergence of imipenem resistance in clinical Escherichia coli during therapy.
abstract: The molecular epidemiology and the mechanisms of resistance of Escherichia coli isolated from two patients infected by imipenem-resistant strains are reported in this study. From one patient, three closely related consecutive isolates of E. coli were recovered; the first was carbapenem-susceptible but acquired imipenem resistance after treatment with ertapenem, and the third isolate was again imipenem-susceptible. An additional imipenem-resistant isolate was recovered from another patient who received imipenem. The genetic relatedness of the E. coli isolates was determined by pulsed-field gel electrophoresis (PFGE) after digestion with XbaI. Standard polymerase chain reaction (PCR) conditions were used to amplify several beta-lactamase genes coding for carbapenemases, extended-spectrum beta-lactamases (ESBLs) and plasmid-mediated AmpC; the E. coli ampC gene promoter was also amplified and sequenced. Primers OmpF-F/OmpF-R and OmpC-F/OmpC-R were used to amplify the ompF and ompC genes. The outer membrane protein (OMP) profiles were studied by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Imipenem-resistant E. coli isolates did not produce carbapenemases but lacked the two major OMPs OmpF and OmpC and had ampC promoter mutations; in addition, one of the imipenem-resistant isolates produced the CMY-2 cephalosporinase, whilst the other produced the new CTX-M-67 ESBL. Carbapenem resistance in this study was associated with lack of expression of OmpF and OmpC porins. Additional mechanisms of beta-lactam resistance, such as plasmid-mediated AmpC and ESBL production, were also found. Development of carbapenem resistance in a CTX-M-67-producing E. coli is first described in this study.
authors.affiliation: Antibiotic Laboratory, Bacteriology Service, Centro Nacional de Microbiología, Instituto de Salud Carlos III, Carretera Pozuelo a Majadahonda, 28220 Majadahonda, Madrid, Spain.
authors.forename: Jesús
authors.initials: J
authors.lastname: Oteo
authors.forename: Alberto
authors.initials: A
authors.lastname: Delgado-Iribarren
authors.forename: Dolores
authors.initials: D
authors.lastname: Vega
authors.forename: Verónica
authors.initials: V
authors.lastname: Bautista
authors.forename: María Cruz
authors.initials: MC
authors.lastname: Rodríguez
authors.forename: María
authors.initials: M
authors.lastname: Velasco
authors.forename: José María
authors.initials: JM
authors.lastname: Saavedra
authors.forename: María
authors.initials: M
authors.lastname: Pérez-Vázquez
authors.forename: Silvia
authors.initials: S
authors.lastname: García-Cobos
authors.forename: Luis
authors.initials: L
authors.lastname: Martínez-Martínez
authors.forename: José
authors.initials: J
authors.lastname: Campos
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use*; D001425:Bacterial Outer Membrane Proteins / Q000235:genetics / Q000378:metabolism; D003227:Conjugation, Genetic; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D004926:Escherichia coli / Q000187:drug effects*; D004927:Escherichia coli Infections / Q000188:drug therapy* / Q000382:microbiology*; D005260:Female; D005798:Genes, Bacterial / Q000235:genetics; D015658:HIV Infections / Q000382:microbiology; D006801:Humans; D015378:Imipenem / Q000494:pharmacology* / Q000627:therapeutic use*; D008826:Microbial Sensitivity Tests; D008875:Middle Aged; D009154:Mutation; D013530:Surgical Wound Infection / Q000188:drug therapy / Q000382:microbiology; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism; D001618:beta-Lactamases / Q000235:genetics / Q000378:metabolism
chemical_list: D000900:Anti-Bacterial Agents; D001425:Bacterial Outer Membrane Proteins; D037521:Virulence Factors; D015378:Imipenem; D001618:beta-Lactamases