Genomic Characterization of Two Escherichia fergusonii Isolates Harboring mcr-1 Gene From Farm Environment.

The prevalence and transmission of mobile colistin resistance (mcr) genes have led to a severe threat to humans and animals. Escherichia fergusonii is an emerging pathogen which is closely related to a variety of diseases. However, the report of mcr genes harboring E. fergusonii is still rare. One study in Brazil reported the E. fergusonii isolates with IncHI2-type plasmids harboring mcr-1. A Chinese study reported two strains carrying mcr-1 gene with the same plasmid type IncI2. Here, we identified two strains of E. fergusonii carrying mcr-1 gene from farm environments with IncX4-type and IncI2-type plasmids, respectively. To our best knowledge, this is the first report about mcr-1 gene located on IncX4-type plasmid in E. fergusonii. We investigate the resistance mechanism of colistin-resistant Escherichia fergusonii strains 6S41-1 and 5ZF15-2-1 and elucidate the genetic context of plasmids carrying mcr-1 genes. In addition, we also investigated chromosomal mutations mediated colistin resistance in these two strains. Species identification was performed using MALDI-TOF MS and 16S rRNA gene sequencing. The detection of mcr-1 gene was determined by PCR and Sanger sequencing. S1-pulsed-field gel electrophoresis (PFGE), Southern blotting, antimicrobial susceptibility testing, conjugation experiments, complete genome sequencing, and core genome analysis were conducted to investigate the characteristics of isolates harboring mcr-1. The mcr-1 genes on two strains were both plasmids encoded and the typical IS26-parA-mcr-1-pap2 cassette was identified in p6S41-1 while a nikA-nikB-mcr-1 locus sites on the conjugative plasmid p5ZF15-2-1. In addition, Core genome analysis reveals that E. fergusonii 6S41-1 and 5ZF15-2-1 have close genetic relationships. The mcr-1 gene is located on conjugative IncI2-type plasmid p5ZF15-2-1, which provides support for its further transmission. In addition, there's the possibility of mcr-1 spreading to humans through farm environments and thereby threatening public health. Therefore, continuous monitoring and investigations of mcr-1 among Enterobacteriaceae in farm environments are necessary to control the spread.

Liu R ，Xu H ，Guo X ，Liu S ，Qiao J ，Ge H ，Zheng B ，Gou J ... -  《Frontiers in Cellular and Infection Microbiology》

Prevalence and Genomic Characteristics of mcr-Positive Escherichia coli Strains Isolated from Humans, Pigs, and Foods in China.

Lu X ，Zhang P ，Du P ，Zhang X ，Wang J ，Yang Y ，Sun H ，Wang Z ，Cui S ，Li R ，Bai L ... -  《Microbiology Spectrum》

Antimicrobial resistance and molecular epidemiological analysis of Escherichia fergusonii harboring the mcr gene in pigs and broiler chickens in Okinawa, Japan.

Kakita T ，Shigemura H ，Fukuda A ，Katamune C ，Nidaira M ，Kudeken T ，Kyan H ... -  《-》

Emergence of Incl2 plasmid-mediated colistin resistance in avian Escherichia fergusonii.

Escherichia fergusonii, an opportunistic zoonotic pathogen, has a greatly increased importance in public health with the discovery of cephalosporin- and colistin-resistant strains. The IncHI2 plasmid carrying mcr-1 has been reported in E. fergusonii, but the other types of plasmids carrying mcr-1 have never been reported. In this study, 268 samples of cecal contents or anal swabs were collected from slaughterhouses and farms in two cities in Zhejiang, China, where 54 E. fergusonii strains (18.88%) were isolated between 2020 and 2021. To our knowledge, this is the first report of the isolation of E. fergusonii in meat ducks (slaughterhouse). The minimum inhibitory concentration (MIC) of isolates was determined by the broth microdilution method, in which it was determined that the tetracycline resistance rate was the highest (83.33%) and the multidrug-resistance (MDR) rate was 75.93%. A total of four strains of colistin-resistant E. fergusonii were found and identified as mcr-1-positive by PCR. Importantly, these strains could transfer the mcr-1 gene to strain E. coli J53 by conjugation. Genome sequencing revealed that the mcr-1 genes of the above four strains were all located on the Incl2 plasmid, and the mobile element ISApl1 upstream of mcr-1 was missing. Moreover, the plasmid pEF45-4 (61 140 bp) harboring mcr-1 in strain EF20JDJ4045 was revealed by Oxford Nanopore Technology, showing high homology with the previously reported in E. coli. Taken together, the high antimicrobial resistance (AMR) rate of E. fergusonii may herald a novel reservoir of AMR genes and IncI2 plasmid may be an important factor affecting mcr-1 transfer in poultry.

Lin J ，Tang B ，Zheng X ，Chang J ，Ma J ，He Y ，Yang H ，Wu Y ... -  《-》

Detection of mcr-1 Plasmids in Enterobacteriaceae Isolates From Human Specimens: Comparison With Those in Escherichia coli Isolates From Livestock in Korea.

The emerging mobile colistin resistance gene, mcr-1, is an ongoing worldwide concern and an evaluation of clinical isolates harboring this gene is required in Korea. We investigated mcr-1-possessing Enterobacteriaceae among Enterobacteriaceae strains isolated in Korea, and compared the genetic details of the plasmids with those in Escherichia coli isolates from livestock. Among 9,396 Enterobacteriaceae clinical isolates collected between 2010 and 2015, 1,347 (14.3%) strains were resistant to colistin and those were screened for mcr-1 by PCR. Colistin minimum inhibitory concentrations (MICs) were determined by microdilution, and conjugal transfer of the mcr-1-harboring plasmids was assessed by direct mating. Whole genomes of three mcr-1-positive Enterobacteriaceae clinical isolates and 11 livestock-origin mcr-1-positive E. coli isolates were sequenced. Two E. coli and one Enterobacter aerogenes clinical isolates carried carried IncI2 plasmids harboring mcr-1, which conferred colistin resistance (E. coli MIC, 4 mg/L; E. aerogenes MIC, 32 mg/L). The strains possessed the complete conjugal machinery except for E. aerogenes harboring a truncated prepilin peptidase. The E. coli plasmid transferred more efficiently to E. coli than to Klebsiella pneumoniae or Enterobacter cloacae recipients. Among the three bacterial hosts, the colistin MIC was the highest for E. coli owing to the higher mcr-1-plasmid copy number and mcr-1 expression levels. Ten mcr-1-positive chicken-origin E. coli strains also possessed mcr-1-harboring IncI2 plasmids closely related to that in the clinical E. aerogenes isolate, and the remaining one porcine-origin E. coli possessed an mcr-1-harboring IncX4 plasmid. mcr-1-harboring IncI2 plasmids were identified in clinical Enterobacteriaceae isolates. These plasmids were closely associated with those in chicken-origin E. coli strains in Korea, supporting the concept of mcr-1 dissemination between humans and livestock.

Yoon EJ ，Hong JS ，Yang JW ，Lee KJ ，Lee H ，Jeong SH ... -  《-》