AUTHOR=Deng Hui , Si Hong-Bin , Zeng Shu-Yi , Sun Jian , Fang Liang-Xing , Yang Run-Shi , Liu Ya-Hong , Liao Xiao-Ping 

TITLE=Prevalence of extended-spectrum cephalosporin-resistant Escherichia coli in a farrowing farm: ST1121 clone harboring IncHI2 plasmid contributes to the dissemination of blaCMY-2

JOURNAL=Frontiers in Microbiology

VOLUME=6

YEAR=2015

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2015.01210

DOI=10.3389/fmicb.2015.01210

ISSN=1664-302X

ABSTRACT=<p>During a regular monitoring of antimicrobial resistance in a farrowing farm in Southern China, 117 <italic>Escherichia coli</italic> isolates were obtained from sows and piglets. Compared with the isolates from piglets, the isolates from sows exhibited higher resistance rates to the tested cephalosporins. Correspondingly, the total detection rate of the <italic>bla</italic><sub>CMY-2</sub>/<italic>bla</italic><sub>CTX-M</sub> genes in the sow isolates (34.2%) was also significantly higher than that of the piglet isolates (13.6%; <italic>p</italic> &lt; 0.05). The <italic>bla</italic><sub>CMY-2</sub> gene had a relatively high prevalence (11.1%) in the <italic>E. coli</italic> isolates. MLST and PFGE analysis revealed the clonal spread of ST1121 <italic>E. coli</italic> in most (7/13) of the <italic>bla</italic><sub>CMY-2</sub>-positive isolates. An indistinguishable IncHI2 plasmid harboring <italic>bla</italic><sub>CMY-2</sub> was also identified in each of the seven ST1121 <italic>E. coli</italic> isolates. Complete sequence analysis of this IncHI2 plasmid (pEC5207) revealed that pEC5207 may have originated through recombination of an IncHI2 plasmid with a <italic>bla</italic><sub>CMY-2</sub>-carrying IncA/C plasmid like pCFSAN007427_01. In addition to <italic>bla</italic><sub>CMY-2</sub>, pEC5207 also carried other resistance determinants for aminoglycosides (<italic>aacA7</italic>), sulfonamides (<italic>sul1</italic>), as well as heavy metals ions, such as Cu and Ag. The susceptibility testing showed that the pEC5207 can mediate both antibiotic and heavy metal resistance. This highlights the role of pEC5207 in co-selection of <italic>bla</italic><sub>CMY-2</sub>-positive isolates under the selective pressure of heavy metals, cephalosporins, and other antimicrobials. In conclusion, clonal spread of an ST1121 type <italic>E. coli</italic> strain harboring an IncHI2 plasmid contributed to the dissemination of <italic>bla</italic><sub>CMY-2</sub> in a farrowing farm in Southern China. We also have determined the first complete sequence analysis of a <italic>bla</italic><sub>CMY-2</sub>-carrying IncHI2 plasmid.</p>