Dissemination of the fosfomycin resistance gene fosA3 with CTX-M β-lactamase genes and rmtB carried on IncFII plasmids among Escherichia coli isolates from pets in China

Abstract

The presence and characterization of plasmid-mediated fosfomycin resistance determinants among Escherichia coli isolates collected from pets in China between 2006 and 2010 were investigated. Twenty-nine isolates (9.0%) were positive for fosA3, and all of them were CTX-M producers. The fosA3 genes were flanked by IS26 and were localized on F2:A-:B- plasmids or on very similar F33:A-:B- plasmids carrying both bla(CTX-M-65) and rmtB. These findings indicate that the fosA3 gene may be coselected by antimicrobials other than fosfomycin.

Fig 1

Comparison of regions flanking fosA3. (I)Escherichia coli 08-642 from Japan (23). (II) The size of the spacer region between the 3′ end of fosA3 and IS26 is 1,758 bp (GenBank accession no. JF411006). (III) The size of the spacer region between the 3′ end of fosA3 and IS26 is 536 bp (GenBank accession no. JF411007). (IV) The size of the spacer region between the 3′ end of fosA3 and IS26 is 370 bp (GenBank accession no. JF411008).

Fig 2

Analysis of F33:A−:B− plasmids carrying fosA3. Lanes 1 to 12, HN429, HN7A8, HN2B1, HN3D12, HN4B5, HN4A1, HN127, HN053, HN5E3, HN212, HN4E2, and HN131; lane M, λHindIII and DL15000 marker. (a) Plasmid profiles of transconjugants and transformants carrying F33:A−:B− plasmid. (b) EcoRI restriction digestion profiles of F33:A−:B− plasmids. (c) Southern blot hybridization of EcoRI-digested plasmids with a digoxigenin-labeled fosA3-specific probe.