Two carbapenem-resistant Escherichia coli strains isolated from blood and stool of a same patient / 中华传染病杂志

ABSTRACT

Objective To investigate the resistant mechanism of carbapenem-resistant Escherichia coli and its relationship with endogenous infection. Methods Two carbapenem-resistant Escherichia coli strains were isolated from blood and stool of a same patient, respectively. The minimal inhibition concentrations (MIC) of the two isolates against imipenem and meropenem were determined by E-test. The susceptibility against other antimicrobial agents were done by disc diffusion method. Isoelectric focusing electrophoresis (IEF), polymerase chain reaction (PCR) amplification,cloning and sequencing, conjugation, Southern blotting were carried out to analyze the encoding gene of β-lactamases. Homology analysis of the two strains was done by pulsed field gel electrophoresis (PFGE). Results MIC against imipenem and meropenem of the two strains were both≥32 mg/L.Both strains produced KPC-2 (pI 6.7) and SHV-12 (pI 8.2) β-lactamases. blaKPC2gene was located on a 54 kb transferable plasmid. PFGE showed that the two Escherichia coli strains were derived from the same clone. Conclusions The resistance and enzyme digestion map of chromosome DNA of the two Escherichia coli strains are coincident. The Escherichia coli septicemia of this patient is probably an endogenous infection caused by the immigration of Escherichia coli from the gut.