Genetic Features of Plasmid- and Chromosome-Mediated mcr-1 in Escherichia coli Isolates From Animal Organs With Lesions

Zengyuan Liu; Yingqiu Liu; Wei Xi; Shuangshi Liu; Jia Liu; Hailong Mu; Beibei Chen; Hao He; Yunpeng Fan; Wuren Ma; Weimin Zhang; Mingzhe Fu; Juan Wang; Xiaoping Song

doi:10.3389/fmicb.2021.707332

Genetic Features of Plasmid- and Chromosome-Mediated mcr-1 in Escherichia coli Isolates From Animal Organs With Lesions

Front Microbiol. 2021 Aug 5:12:707332. doi: 10.3389/fmicb.2021.707332. eCollection 2021.

Authors

Zengyuan Liu¹, Yingqiu Liu¹, Wei Xi², Shuangshi Liu¹, Jia Liu¹, Hailong Mu¹, Beibei Chen¹, Hao He¹, Yunpeng Fan¹, Wuren Ma¹, Weimin Zhang¹, Mingzhe Fu¹, Juan Wang¹, Xiaoping Song¹

Affiliations

¹ College of Veterinary Medicine, Northwest A&F University, Yangling, China.
² Qingdao Adverse Drug Reaction Monitoring Center, China Qingdao Institute for Food and Drug Control, Qingdao, China.

Abstract

The genomic context of the mcr-1 gene in Escherichia coli from animal feces has been widely reported. However, less is known about the mcr-1-carrying plasmid characteristics and other functional regions of Escherichia coli isolates from animal organs with lesions. The present study investigated the antimicrobial resistance, population structure, and genetic features of mcr-1-positive Escherichia coli strains isolated from animal organs with lesions. The antimicrobial susceptibility testing indicated that 24 mcr-1-positive Escherichia coli isolates were resistant to at least three or all antimicrobial categories. MLST analysis suggested that the dominant clone complexes (CC) were mainly CC156, CC448, and CC10. In addition, ST10596, a newly discovered sequence type in swine, failed to be classified. Meanwhile, the mcr-1 gene located on the different plasmids was successfully transferred to the recipients, and whole-genome sequencing indicated the mcr-1 gene was embedded in mcr-1-pap2 cassette but not flanked by ISApl1. The mcr-1 gene is located on the chromosome and embedded in Tn6330. Furthermore, NDM-5 was found on the IncX3-type plasmid of J-8. The virB6 and traI gene of type IV secretion system (T4SS) were truncated by IS2 and IS100 and located on the IncX4- and the IncHI2/HI2A/N-type plasmids, respectively. The multidrug-resistant (MDR) region of IncHI2/HI2A/N-type plasmids contained two class 1 integrons (In0, In640) and four composite transposons (Tn4352, Tn6010, cn_4692_IS26, cn_6354_IS26). Overall, 24 mcr-1-positive Escherichia coli isolates in our study showed MDR, or even extensively drug resistant (XDR), and exhibited population diversity. The T4SS gene truncation by the insertion sequence may affect the efficiency of plasmid conjugative transfer. Furthermore, the class 1 integrons and composite transposons in the MDR region of IncHI2/HI2A/n-type plasmid contributed to the multireplicon plasmid formation, the acquisition, and transfer of antimicrobial resistance genes (ARGs).

Keywords: Escherichia coli; T4SS; integrons and transposons; mcr-1; sequence type.