bla_NDM-1-producing multidrug-resistant Escherichia coli isolated from a companion dog in China

This study characterised a bla_NDM-1-producing Escherichia coli isolate from a companion dog.

The E. coli strain was isolated from a surveillance study of carbapenem-resistant Gram-negative bacteria from companion animals in the Animal Teaching Hospital of China Agricultural University (Beijing, China) in 2013. Species identification was performed using an API 20E system and matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF/MS). Minimum inhibitory concentrations (MICs) of various antimicrobial agents were determined by agar dilution. Multilocus sequence typing (MLST) was performed and various carbapenemase genes, including bla_NDM, bla_IMP, bla_VIM, bla_SME, bla_IMI, bla_KPC, bla_GES, bla_SPM, bla_GIM, bla_NMC, bla_DIM, bla_SIM, bla_OXA-23, bla_OXA-24, bla_OXA-48, bla_OXA-51 and bla_OXA-58 were screened by PCR. S1 nuclease pulsed-field gel electrophoresis (S1-PFGE) and Southern blotting as well as a modified random primer walking strategy were performed to analyse the location and genetic environment of bla_NDM-1.

An E. coli isolate belonging to ST167 was found to be positive for the bla_NDM-1 gene and exhibited resistance to β-lactams, tetracycline, gentamicin, fosfomycin and ciprofloxacin. The bla_NDM-1 gene in this strain was located on an ca. 150-kb plasmid and the flanking sequences of the bla_NDM-1-carrying region (a common gene cluster, ΔISAba125-bla_NDM-1-ble-trpF-ΔdsbC) exhibited >99% identity to the corresponding regions of bla_CTX-M-15-harboring plasmids in nosocomial E. coli ST131 isolates.

This is the first report of bla_NDM-1-producing ST167 E. coli in a companion dog. Companion animals harbouring carbapenemase-producing isolates are an upcoming public health threat and it is worthy paying attention to the emergence of carbapenem resistance in companion animals.