AUTHOR=Xiang Yungai , Liu Zengyuan , Yu Guo , Song Yuxia , Li Yan , Geng Xujing , Ma Liying , Guo Junqing , Tan Li , Chen Pengju 

TITLE=Genetic characteristic of coexisting of mcr-1 and blaNDM-5 in Escherichia coli isolates from lesion-bearing animal organs

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1116413

DOI=10.3389/fmicb.2023.1116413

ISSN=1664-302X

ABSTRACT=<p>The coexistence of <italic>mcr-1</italic> and <italic>bla</italic><sub>NDM-5</sub> in the plasmid of <italic>Escherichia coli</italic> has been widely reported and such strains have been mainly isolated from animal and human feces. However, few reports have focused on the genetic diversity of <italic>mcr-1</italic>-carrying chromosomes and <italic>bla</italic><sub>NDM-5</sub>-carrying plasmids in <italic>E. coli</italic> isolates from lesion-bearing animal organs. This study investigated the genetic characteristics of chromosome-mediated <italic>mcr-1</italic> and plasmid-mediated <italic>bla</italic><sub>NDM-5</sub> in <italic>E. coli</italic> isolated from lesion-bearing animal organs. Nine <italic>mcr-1</italic>- and <italic>bla</italic><sub>NDM-5</sub>-positive <italic>E. coli</italic> strains (MNPECs) showed extensive drug resistance (XDR). The predominant clonal complexes (CC) mainly belonged to CC156, CC10, and CC165 from the 56 MNEPCs (including nine strains in this study) retrieved from the literature. These strains were widely distributed in China, and originated from pig fecal samples, human stool/urine samples as well as intestinal contents of chicken. Two transconjugants harboring <italic>bla</italic><sub>NDM-5</sub> gene were also successfully obtained from two donors (J-8 and N-14) and this transfer increased the MIC for meropenem by 256 times. However, conjugative transfer of <italic>mcr-1</italic> gene failed. Both J-8 and N-14 strains contained point mutations associated with quinolone resistance and more than three types of AMR genes, including the <italic>mcr-1</italic> gene on the chromosome and the <italic>bla</italic><sub>NDM-5</sub> gene on the IncX3-type plasmid. The genetic structure of <italic>mcr-1</italic> located on the chromosome was an intact Tn<italic>6330</italic>, and <italic>bla</italic><sub>NDM-5</sub>-carrying IncX3-type plasmid was IS<italic>Ab125</italic>-IS<italic>5</italic>-<italic>bla</italic><sub>NDM-5</sub>-<italic>bleO</italic>-<italic>trpF</italic>-<italic>tat</italic>-<italic>cutA</italic>-IS<italic>26</italic> gene cassette. Moreover, differences between chromosomes included additional partial sequence of phage integrated into host genome and the different genes associated with <italic>O</italic>-antigen synthesis.</p>