RESUMEN
Objective This study was designed to determine the mechanisms of carbapenem and fosfomycin resistance in an Escherichia coli strain isolated from bloodstream infection in Huashan Hospital,Shanghai in 2010 and the mode of transmission of resistance genes.Methods The Escherichia coli isolate was characterized by antibiotic susceptibility testing,multilocus sequence typing (MLST),molecular identification of resistance genes,plasmid typing and the resistant genetic environment analysis.Results It was found that the isolate was resistant to carbapenem,fosfomycin and produced extended-spectrum β-1actamases.MLST genotyping showed it belonged to ST46.The carbapenem-resistant gene blaKPC-2 and fosfomycin resistant genefosA3 co-located on the same conjugative plasmid (～ 70 kb).The β-lactamases gene blaTEM and blaCTX-M located on another conjugative plasmid (～ 150 kb).PCR mapping showed that blaKPC-2 gene located in the structure Tn1721-blaKPC-2-Tn3 andfosA3 gene located between two IS26 elements.Conclusions This Escherichia coli strain isolated from bloodstream infection carried multiple antibiotic resistant genes,including blaKPC-2,fosA3,blaTEM,and blaCTX-M.More attention should be paid to the mechanisms of antibiotic resistance and transmission of resistance genes in Escherichia coli isolates for better control of hospital infections.