Genomic Characterization of mcr-1-carrying Salmonella enterica Serovar 4,[5],12:i:- ST 34 Clone Isolated From Pigs in China

Abstract

Salmonella enterica serovar 4,[5],12:i:-, so-called Typhimurium monophasic variant, has become one of the most frequently isolated serovars both in humans and in animals all over the world. The increasing prevalence of mcr-1-carrying Salmonella poses significant global health concerns. However, the potential role of Salmonella 4,[5],12:i:-in mcr-1 gene migration through the food chain to the human remains obscure. Here, we investigated 337 Salmonella isolates from apparently healthy finishing pigs, which is rarely studied, obtained from pig farms and slaughterhouses in China. The mcr-1 gene was found in four colistin-resistant S. enterica 4,[5],12:i:-isolates. Notably, all four isolates belonged to sequence type 34 (ST34) with multidrug resistance phenotype. Further genomic sequencing and antimicrobial resistance characterization confirmed that mcr was responsible for the colistin resistance, and the conjugation assay demonstrated that three of four isolates carried mcr-1 in IncHI2 plasmid. Importantly, mcr-1 and class-1 integron were found to co-localize in two strains with IncHI2 plasmid. By collecting all the mcr-1-carrying Typhimurium and monophasic variant strains across the food chain (farm animals, animal-origin food, and humans), our phylogenomic analysis of available 66 genomes, including four strains in this study, demonstrated an independent phylogenetic cluster of all eight Chinese swine-originated isolates and one human isolate. Together, this study provides direct evidence for clonal and pork-borne transmission of mcr-1 by Salmonella 4,[5],12:i:-ST34 in China and highlighted a domestication pathway by acquisition of additional antimicrobial resistance determinants in Chinese ST34 isolates.

Molecular Epidemiology of mcr-1, blaKPC-2, and blaNDM-1 Harboring Clinically Isolated Escherichia coli from Pakistan

“… 54 The dissemination of mcr-1 in extra-intestinal pathogenic and avian pathogenic E. coli in samples of human origin suggests food chain transmission of mcr-1 . 55 …”

WITHDRAWN: Discovery of mcr-1 Harboring Incl2 Plasmids from Clinical Isolates of Multiclonal E. Coli prevalent in Pakistan.

“…ST117 belongs to avian pathogenic E. coli lineage and may form a reservoir for human extraintestinal pathogenic E coli and antimicrobial resistance [33]. The detection of mcr-1 in avian pathogenic and extraintestinal pathogenic E. coli in human clinical isolates is threatening because it supports the statement of mcr-1 transmission via the food chain [34].…”

Characterization of Salmonella Resistome and Plasmidome in Pork Production System in Jiangsu, China

“…The genomic DNA of 105 samples was done as according to pervious study ( 23 – 25 ) using a commercial genomic DNA isolation kit (Tiangen, China). Then, the whole genome sequencing was performed by next-generation sequencing using BGI BGISEQ-500 Platform.…”