title: Prevalence of extended-spectrum cephalosporin-resistant Escherichia coli in a farrowing farm: ST1121 clone harboring IncHI2 plasmid contributes to the dissemination of bla CMY-2.
abstract: During a regular monitoring of antimicrobial resistance in a farrowing farm in Southern China, 117 Escherichia coli 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 bla CMY-2/bla CTX-M genes in the sow isolates (34.2%) was also significantly higher than that of the piglet isolates (13.6%; p < 0.05). The bla CMY-2 gene had a relatively high prevalence (11.1%) in the E. coli isolates. MLST and PFGE analysis revealed the clonal spread of ST1121 E. coli in most (7/13) of the bla CMY-2-positive isolates. An indistinguishable IncHI2 plasmid harboring bla CMY-2 was also identified in each of the seven ST1121 E. coli isolates. Complete sequence analysis of this IncHI2 plasmid (pEC5207) revealed that pEC5207 may have originated through recombination of an IncHI2 plasmid with a bla CMY-2-carrying IncA/C plasmid like pCFSAN007427_01. In addition to bla CMY-2, pEC5207 also carried other resistance determinants for aminoglycosides (aacA7), sulfonamides (sul1), 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 bla CMY-2-positive isolates under the selective pressure of heavy metals, cephalosporins, and other antimicrobials. In conclusion, clonal spread of an ST1121 type E. coli strain harboring an IncHI2 plasmid contributed to the dissemination of bla CMY-2 in a farrowing farm in Southern China. We also have determined the first complete sequence analysis of a bla CMY-2-carrying IncHI2 plasmid.
authors.affiliation: National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, South China Agricultural University Guangzhou, China ; College of Veterinary Medicine, South China Agricultural University Guangzhou, China.
authors.forename: Hui
authors.initials: H
authors.lastname: Deng
authors.affiliation: College of Animal Science and Technology, Guangxi University Nanning, China.
authors.forename: Hong-Bin
authors.initials: HB
authors.lastname: Si
authors.affiliation: National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, South China Agricultural University Guangzhou, China ; College of Veterinary Medicine, South China Agricultural University Guangzhou, China.
authors.forename: Shu-Yi
authors.initials: SY
authors.lastname: Zeng
authors.affiliation: National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, South China Agricultural University Guangzhou, China ; College of Veterinary Medicine, South China Agricultural University Guangzhou, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Sun
authors.affiliation: National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, South China Agricultural University Guangzhou, China ; College of Veterinary Medicine, South China Agricultural University Guangzhou, China.
authors.forename: Liang-Xing
authors.initials: LX
authors.lastname: Fang
authors.affiliation: National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, South China Agricultural University Guangzhou, China ; College of Veterinary Medicine, South China Agricultural University Guangzhou, China.
authors.forename: Run-Shi
authors.initials: RS
authors.lastname: Yang
authors.affiliation: National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, South China Agricultural University Guangzhou, China ; College of Veterinary Medicine, South China Agricultural University Guangzhou, China ; Jiangsu Co-Innovation Centre for Prevention and Control of Important Animal Infectious Diseases and Zoonoses Yangzhou, China.
authors.forename: Ya-Hong
authors.initials: YH
authors.lastname: Liu
authors.affiliation: National Risk Assessment Laboratory for Antimicrobial Resistance of Animal Original Bacteria, South China Agricultural University Guangzhou, China ; College of Veterinary Medicine, South China Agricultural University Guangzhou, China.
authors.forename: Xiao-Ping
authors.initials: XP
authors.lastname: Liao
keywords: Escherichia coli; IncHI2 plasmid; blaCMY-2; clonal spread; farrowing farm