ABSTRACTA total of 47 extended-spectrum-cephalosporin-resistantEscherichia colistrains isolated from stray dogs in 2006 and 2007 in the Republic of Korea were investigated using molecular methods. Extended-spectrum β-lactamase (ESBL) and AmpC β-lactamase phenotypes were identified in 12 and 23E. coliisolates, respectively. All 12 ESBL-producing isolates carriedblaCTX-Mgenes. The most common CTX-M types were CTX-M-14 (n= 5) and CTX-M-24 (n= 3). Isolates producing CTX-M-3, CTX-M-55, CTX-M-27, and CTX-M-65 were also identified. Twenty-one of 23 AmpC β-lactamase-producing isolates were found to carryblaCMY-2genes. TEM-1 was associated with CTX-M and CMY-2 β-lactamases in 4 and 15 isolates, respectively. In addition toblaTEM-1, two isolates carriedblaDHA-1, and one of them cocarriedblaCMY-2. Both CTX-M and CMY-2 genes were located on large (40 to 170 kb) conjugative plasmids that contained the insertion sequence ISEcp1upstream of theblagenes. Only in the case of CTX-M genes was there an IS903sequence downstream of the gene. The spread of ESBLs and AmpC β-lactamases occurred via both horizontal gene transfer, accounting for much of the CTX-M gene dissemination, and clonal spread, accounting for CMY-2 gene dissemination. The horizontal dissemination ofblaCTX-MandblaCMY-2genes was mediated by IncF and IncI1-Iγ plasmids, respectively. The clonal spread ofblaCMY-2was driven mainly byE. colistrains of virulent phylogroup D lineage ST648. To our knowledge, this is the first report ofblaDHA-1inE. colistrains isolated from companion animals. This study also represents the first report of CMY-2 β-lactamase-producingE. coliisolates from dogs in the Republic of Korea.
Extended-spectrum ^|^beta;-lactamase (ESBL) Produced by Escherichia coli and Klebsiella pneumoniae Isolated from Teikyou University Hospital The First Report