Stability and genetic insights of the co-existence of blaCTX-M-65, blaOXA-1, and mcr-1.1 harboring conjugative IncI2 plasmid isolated from a clinical extensively-drug resistant Escherichia coli ST744 in Shanghai

Abstract

BackgroundCo-existence of colistin, β-lactam and carbapenem in multidrug-resistant Enterobacteriaceae isolates poses a serious threat to public health. In this study, we investigated and characterized the co-occurrence of blaCTX-M-65, blaOXA-1, and mcr-1.1 strain isolated from a clinical extensively-drug-resistant Escherichia coli ST744 in Shanghai.MethodsAntimicrobial susceptibility test was carried out by agar dilution methods. Whole genome sequencing was conducted, and resistance genes, and sequence types of colistin in E. coli isolates were analyzed. Plasmid stability and amino acid mutations were assessed in E. coli isolates.ResultsA colistin resistant E. coli ST744, named ECPX221, was identified out of 145 fecal samples collected. The strain carries a 60,168 IncI2 plasmid with the mcr-1.1 gene. The strain also has blaCTX-M-65, blaOXA-1, dfrA14, qnrS1, cmlA5, arr2, ampC, aph(4)-Ia, sul1, and aadA5 resistance genes. The plasmid pECPX221 was capable of conjugation with an efficiency of 2.6 × 10−2. Notably, 45% of the transconjugants were determined as mcr-1.1-harboring in the colistin-free environment after 60 generation of passage. No mutations occurred in pmrB, mgrB, and phoPQ gene in the mcr-1.1-harboring transconjugants. Bioinformatic analysis indicated pECPX221 shared highly similar backbone with the previously reported mcr-1.1-harboring pAH62-1, pMFDS1339.1, pSCZE4, and p2018-10-2CC. Furthermore, sequencing and phylogenetic analyses revealed a similarity between other MCR-1-homolog proteins, indicating that ECPX221 was colistin resistant.ConclusionThe stable transferable mcr-1.1-harboring plasmid found in the E. coli ST744 strain indicated the high risk to disseminate the extensively-drug-resistance phenotype among Enterobacteriaceae.

First Report of Colistin-Resistant Escherichia coli Carrying mcr-1 IncI2(delta) and IncX4 Plasmids from Camels (Camelus dromedarius) in the Gulf Region

“…IncI2 plasmids have been identified in several mcr-1 cases on various hosts worldwide [ 32 ], while the IncX4 plasmid type has been recognized as the primary carrier of the mcr-1 gene in isolates from healthy individuals in China [ 33 ], as well as in Enterobacteriaceae isolates carrying carbapenem and mcr-1 resistance genes simultaneously from clinical patients in Thailand [ 34 ]. Our study identified the presence of mcr-1 genes on both IncI2 and IncX4 plasmids, which have been recently observed in E. coli isolates from food, livestock, and humans across various countries [ 35 , 36 ].…”

Genetic epidemiology and plasmid-mediated transmission of mcr-1 by Escherichia coli ST155 from wastewater of long-term care facilities

“…Our study suggests a lower prevalence (0.33%, 1/306) of mcr-1 in LTCF wastewater than that reported from other LTCFs in other countries such as Italy ( 31 ) and the Netherlands ( 18 ). Furthermore, the prevalence was also lower than E. coli strains isolated from human populations in Shanghai ( 25 , 32 , 33 ), and it was not as high as that found in E. coli isolated from hospitalized companion animals ( 34 ). Given that those E. coli strain carriers were only detected during the prevalence survey, most carriers remain undetected in Shanghai.…”