RESUMO
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.
Assuntos
Antibacterianos/farmacologia , Antibacterianos/uso terapêutico , Infecções por Escherichia coli/tratamento farmacológico , Infecções por Escherichia coli/microbiologia , Escherichia coli/efeitos dos fármacos , Imipenem/farmacologia , Imipenem/uso terapêutico , Proteínas da Membrana Bacteriana Externa/genética , Proteínas da Membrana Bacteriana Externa/metabolismo , Conjugação Genética , Farmacorresistência Bacteriana , Eletroforese em Gel de Campo Pulsado , Feminino , Genes Bacterianos/genética , Infecções por HIV/microbiologia , Humanos , Testes de Sensibilidade Microbiana , Pessoa de Meia-Idade , Mutação , Infecção da Ferida Cirúrgica/tratamento farmacológico , Infecção da Ferida Cirúrgica/microbiologia , Fatores de Virulência/genética , Fatores de Virulência/metabolismo , beta-Lactamases/genética , beta-Lactamases/metabolismoRESUMO
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