Dissemination of plasmid-mediated fosfomycin resistance fosA3 among multidrug-resistant Escherichia coli from livestock and other animals.

Abstract

Aims: To investigate plasmid-mediated fosfomycin resistance related to fosA3 in Escherichia coli isolates collected from different animals in Hong Kong, China, 2008-2010. Methods and Results: In total, 2106 faecal specimens from 210 cattle, 214 pigs, 460 chickens, 398 stray cats, 368 stray dogs and 456 wild rodents were cultured. The faecal colonization rates of fosfomycin-resistant E. coli were as follows: 11·2% in pigs, 8·6% in cattle, 7·3% in chickens, 2·4% in dogs, 0·8% in cats and 1·5% in rodents. The cultures yielded 1693 isolates of which 831 were extended-spectrum β-lactamases (ESBL) producers. Fosfomycin-resistant isolates were more likely than fosfomycin-susceptible isolates to be producers of ESBL and to have resistance to chloramphenicol, ciprofloxacin, cotrimoxazole, gentamicin and tetracycline. Of the 101 fosfomycin-resistant isolates, 97 (96·0%) isolates were fosA3 positive and 94 (93·1%) were blaCTX-M positive. PCR mapping showed that the fosA3-containing regions were flanked by IS26, both upstream and downstream in 81 (83·5%) isolates, and by an upstream blaCTX-M-14-containing transposon-like structure (ΔISEcp1-blaCTX-M-14-ΔIS903 or ISEcp1-IS10 -blaCTX-M-14-ΔIS903) and a downstream IS26 in 14 (14·4%) isolates. For the remaining two isolates, fosA3 was flanked by a downstream IS26 but the upstream part cannot be defined. In a random subset of 18 isolates, fosA3 was carried on transferable plasmids with sizes of 50-200kb and the following replicons: F2:A-B- (n=3), F16:A1:B- (n=2), F24:A-B- (n=1), N (n=1), B/O (n=1) and untypeable (n=3). Significance and Impact of the Study: This study demonstrates the emergence of fosA3-mediated fosfomycin resistance among multidrug-resistant E. coli isolates from various animals. IS26 transposon-like structures might be the main vehicles for dissemination of fosA3. © 2012 The Society for Applied Microbiology.