Coexistence of SFO-1 and NDM-1 β-lactamase genes and fosfomycin resistance gene fosA3 in an Escherichia coli clinical isolate

This study aims to characterize antimicrobial resistance and antimicrobial resistance genetic determinants of an Escherichia coli clinical isolate HD0149 from China in 2012. This strain displayed high-level resistance to cephalosporins, carbapenems, fluoroquinolones, aminoglycosides and fosfomycin. A range of antimicrobial resistance genes was detected responsible for its multiple antimicrobial resistances, involving the bla(CMY-2), bla(CTX-M-65), bla(NDM-1), bla(SFO-1), bla(TEM-1), fosA3, rmtB, sul1 and sul2 genes. Four amino acid substitutions were detected in the quinolone resistance-determining regions (QRDRs) of GyrA (S83L and D87N), ParC (S80I) and ParE (S458A). Conjugation experiments revealed two multiresistance plasmids present in E. coli HD0149. The bla(SFO-1) gene associated with bla(NDM-1) gene was located in a 190 kb IncA/C plasmid and the bla(CTX-M-65), fosA3 and rmtB genes were located in a 110 kb IncF plasmid. This is the first identification of the bla(SFO-1) gene in an E. coli isolate and on a conjugative IncA/C plasmid. This may dramatically enhance the international prevalence and dissemination of bla(SFO-1) among Enterobacteriaceae.