Characterization of NDM-5-producing <i>Enterobacteriaceae</i> isolates from retail grass carp (<i>Ctenopharyngodon idella</i>) and evidence of <i>bla</i><sub>NDM-5</sub>-bearing IncHI2 plasmid transfer between ducks and fish
Luchao Lv, 华南农业大学兽医学院、农业农村部人畜共患病重点实验室、国家兽医微生物耐药性风险评估实验室、广东省兽药研制与安全评价重点实验室, 广东 广州 510642, 中国, Yaoyao Lu, Xun Gao, Wan-Yun He, Ming-Yi Gao, Kaibin Mo, Jian–Hua Liu, 岭南现代农业科学与技术广东省实验室, 广东 广州 510642, 中国
Abstract
We aimed to characterize NDM-5-producing <i>Enterobacteriaceae</i> from aquatic products in Guangzhou, China. A total of 196 intestinal samples of grass carp collected in 2019 were screened for carbapenemase genes. Characterization of <i>bla</i><sub>NDM-5</sub> positive isolates and plasmids was determined by antimicrobial susceptibility testing, conjugation experiments, Illumina HiSeq, and Nanopore sequencing. One <i>Citrobacter freundii</i> and six <i>Escherichia coli</i> strains recovered from seven intestinal samples were verified as <i>bla</i><sub>NDM-5</sub> carriers (3.57%, 7/196). The<i> bla</i><sub>NDM-5</sub> genes were located on the IncX3 (<i>n</i>=5), IncHI2 (<i>n</i>=1), or IncHI2-IncF (<i>n</i>=1) plasmids. All <i>bla</i><sub>NDM-5</sub>-bearing plasmids were transferred by conjugation at frequencies of ~10<sup>−4</sup>–10<sup>−6</sup>. Based on sequence analysis, the IncHI2 plasmid pHNBYF33-1 was similar to other <i>bla</i><sub>NDM-5</sub>-carrying IncHI2 plasmids deposited in GenBank from Guangdong ducks. In all IncHI2 plasmids, <i>bla</i><sub>NDM-5</sub> was embedded in a novel transposon, Tn<i>7051</i> (IS<i>3000</i>-ΔIS<i>Aba125</i>-IS<i>5</i>-ΔIS<i>Aba125</i>-<i>bla</i><sub>NDM-5</sub>-<i>ble</i><sub>MBL</sub>-<i>trpF</i>-<i>tat</i>-∆<i>dct</i>-IS<i>26</i>-∆<i>umuD</i>-∆IS<i>Kox3</i>-IS<i>3000</i>), which was identical to the genetic structure surrounding <i>bla</i><sub>NDM-5</sub> found in some IncX3 plasmids. The IncHI2-IncF hybrid plasmid pHNTH9F11-1 was formed by homologous recombination of the<i> bla</i><sub>NDM-5</sub>-carrying IncHI2 plasmid and a heavy-metal-resistant IncF plasmid through ∆Tn<i>1721</i>. To the best of our knowledge, this is the first report on the characterization of <i>bla</i><sub>NDM-5</sub>-bearing plasmids in fish in China. The IncHI2 plasmid pHNBYF33-1 may be transmitted from ducks, considering the common duck-fish freshwater aquaculture system in Guangdong. Tn<i>7051</i> is likely responsible for the transfer of <i>bla</i><sub>NDM-5</sub> from IncX3 to IncHI2 plasmids in <i>Enterobacteriaceae</i>, resulting in the expansion of transmission vectors of <i>bla</i><sub>NDM-5</sub>.