Comprehensive Understanding of the Plasmid-Mediated Colistin Resistance Gene mcr-1 in Aquatic Environments

Abstract

The emergence of plasmid-mediated colistin resistance gene mcr-1 has attracted global attention and raised serious concerns about its possible cross-environment dissemination. However, the systematic exploration of mcr-1 both by monitoring and genetic dissection in aquatic environments has not been conducted. This study addresses the gap related to the occurrence and distribution of mcr-1 in watersheds, eastern China. The results showed an abundance of mcr-1 gene in four watersheds, and the highest level of mcr-1 reached 1.8 × 10 9 gene copies per liter of water. Furthermore, the transfer frequencies of the plasmids in isolated Escherichia coli were 2.76 × 10 −6 −6.11 × 10 −4 within genera and minimal inhibitory concentrations of polymyxin resistance were 8−16 mg/L for transconjugants. Mass spectrometry data allowed visualization of the function of mcr-1 expression, rendering bacterial resistance to colistin. The genetic details of six mcr-1-harboring plasmids in E. coli isolates of aquatic origin were obtained by single-molecule real-time sequencing. These plasmids were closely associated with E. coli strains of pig and human origin, supporting the concept of mcr-1 dissemination across natural environments, livestock farms, and humans. In conclusion, this study provides the first glimpse of the profile of mcr-1-harboring plasmids and their genetic environment in aquatic ecosystems.

Genetic relatedness of multidrug resistant Escherichia coli isolated from humans, chickens and poultry environments

“…Evidence shows that the IncX4 plasmids harbouring mcr-1 genes have been recovered from human and animal E. coli isolates however, our study recovered these plasmids from the poultry environment [43]. Another study conducted in China also detected PMCR genes -mcr 1 in E. coli isolates sourced from the aquatic environment [44] however, the mcr 3.1 gene was detected in a human Salmonella case in the US [45]. This further buttresses that mcr gene has spread across multiple pathogens.…”

Association of the colistin resistance gene mcr‐1 with faecal pollution in water environments in Hanoi, Vietnam

“…Our results indicated that mcr-1 was also prevalent in urban districts. The concentrations of mcr-1 in four samples collected from three rivers ranged from 8Á0 9 10 4 to 1Á3 9 10 7 copies per litre, which was within the range (approximately 10 3 -10 9 copies per litre) of mcr-1 in Haihe River (Yang et al 2017), Yangtze River (Wang et al 2019), and rivers in Zhejiang (Zhu et al 2020) in China. Although the drinking water source (Duong River) exhibited the lowest concentration, Day River and Nhue River were highly polluted by mcr-1 at levels of 3Á0 9 10 6 -1Á3 9 10 7 copies per litre.…”

“…The correlation between mcr-1/16S rRNA gene and intI1/16S rRNA gene was also statistically significant (r = 0Á61, P < 0Á05) (Table S2). In aquatic environments in China, a significant correlation between mcr-1 and intI1 contamination was also reported (Zhu et al 2020). In addition to mcr-1, the levels of three different ARGs (tetA, sul1, and ere(A)) were measured (Fig.…”

“…The rapid spread of mcr-1 associated with humans and animals has been observed globally (von Wintersdorff et al 2016;Al-Tawfiq et al 2017;Wang et al 2018). Some studies demonstrated that mcr-1 was also prevalent in rivers (Tuo et al 2018;Zhu et al 2020) and domestic wastewater (Lekunberri et al 2017;Hayashi et al 2019;Vu and Kasuga 2020), indicating that the water environment is a potential reservoir of this gene.…”

Genetic relatedness of multidrug resistant Escherichia coli isolated from humans, chickens and poultry environments

“…Evidence shows that the IncX4 plasmids harbouring mcr-1 genes have been detected in human and animal E. coli isolates however, our study recovered these plasmids from the poultry environment [ 43 ]. Another study conducted in China also detected PMCR genes— mcr 1 in E. coli isolates sourced from the aquatic environment [ 44 ] however, the mcr 3.1 gene was detected in a human Salmonella case in the US [ 45 ]. This further buttresses that mcr gene has spread across multiple pathogens.…”