Publication details

Genetic variety of plasmid mediated colistin resistance in Gram-negative bacteria from raw meat products



Year of publication 2019
Type Appeared in Conference without Proceedings
Description Currently, there are multiple variants of mcr-mediated colistin resistance in Gram-negative bacteria from different sources around the whole world. The most prevalent gene in Enterobacteriaceae mcr-1 has been located on several types of plasmids. This study was focused on plasmid characteristics of Enterobacteriaceae isolates with mcr-1 gene and one Aeromonas spp. isolate carrying both mcr-3 and mcr-7-like genes obtained from retailed raw meat products. Altogether, 17 colistin resistant isolates carrying mcr genes originated from 12 meat samples (turkey, rabbit and quail meat). Twelve Escherichia coli isolates carrying mcr-1 gene were isolated from turkey meat and liver from the Czech Republic (n=3), Poland (n=5), Germany (n=3) and Brazil (n=1). Two Klebsiella pneumoniae carrying mcr-1 originated from turkey meat and liver from the Czech Republic (n=1) and Brazil (n=1). One isolate of E. coli with mcr-1 and one Citrobacter braakii isolate with mcr-1 were obtained from the same rabbit meat sample from China. Aeromonas spp. with mcr-3 and mcr-7-like genes was isolated from quail meat sample from France. The sequencing was performed using Illumina MiSeq and Oxford Nanopore MinION platform and the whole sequences of plasmids carrying mcr genes were obtained by hybrid assembly. The content of plasmid sequences was analysed using ResFinder and PlasmidFinder, the annotation of genes was done by Prokka (Galaxy Version 1.13). The comparison of plasmid sequences was done using BLAST Ring Image Generator (BRIG). The hybrid assembly of the genomes showed three plasmid types (IncX4, IncHI2 and IncI2) carrying the mcr-1 gene in tested isolates. The most prevalent plasmid type carrying mcr-1 was IncX4 detected in E. coli (n=8) and K. pneumoniae (n=2) isolated from meat products of different origin (Czech Republic, Poland, Germany, Brazil). The size of IncX4 varied between ~33 to ~34 kb with two exceptions of ~38 kb and ~188 kb large plasmids. The IncX4 plasmids with size ~33 to ~34 kb did not carry any other antimicrobial resistance genes except for mcr-1 gene. Four E. coli isolates from turkey meat of Polish origin had localized mcr-1 on plasmid type IncHI2 which varied in their size (between ~153 kb to 284 kb) and carried other resistance genes. The isolates of E. coli and C. braakii from one rabbit meat sample from China carried mcr-1 gene on IncI2 plasmid (~60 kb). The comparison of both IncI2 plasmids showed their high identity. Similarly, in case of E. coli and K. pneumoniae isolates obtained from one meat sample, the IncX4 plasmids carrying mcr-1 gene were almost identical. These results support a transmission capability of these plasmids among different species of Enterobacteriaceae. On the other hand, the mcr-3.8 and mcr-7-like genes in colistin resistant Aeromonas spp. were found to be located in the chromosome and the isolate did not contain any plasmids. The mcr-7-like gene was found twice in the chromosome and had 86% and 82% identity, respectively, with the mcr-7.1 gene described in the NCBI database. These results are consistent with the estimated origin of mcr-3 and mcr-7 genes from Aeromonas species. The results of this study indicate a possible spread of plasmid mediated colistin resistance via raw meat market between bacteria of different genus. IncX4 plasmids carrying mcr-1 gene were found to be conserved among species of Enterobacteriaceae isolated from raw meat products of different origin. While the most of tested IncX4 and IncI2 plasmids had similar size and carried only mcr-1, the tested IncHI2 plasmids carrying mcr-1 gene were diverse in size and in the content of resistance genes. The presence of mcr-3 and mcr-7-like genes on plasmids in colistin resistant Aeromonas spp. isolate was not confirmed.

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