Widespread distribution of mcr-1-bearing bacteria in the ecosystem, 2015 to 2016

Area of Science:

• Microbiology
• Genetics
• Public Health

Background:

• The emergence of antimicrobial resistance (AMR) poses a significant global health threat.
• Mobile colistin resistance (mcr) genes, particularly mcr-1, are critical as they confer resistance to last-resort antibiotics.
• Understanding the prevalence and transmission of mcr-1 across different ecological niches is crucial for effective control strategies.

Purpose of the Study:

• To survey the prevalence of the mcr-1 gene in various environmental, food, animal, and human samples.
• To identify the bacterial species and genetic elements (plasmids) involved in mcr-1 dissemination.
• To assess the potential for mcr-1 transmission across different ecological niches.

Main Methods:

• Development and application of a novel in-house method for detecting mcr-1.
• Sampling across diverse ecological niches: food (n=1,371), animal feces (n=480), human feces (n=150), and water (n=34).
• Identification of bacterial species and characterization of plasmids carrying the mcr-1 gene.

Main Results:

• mcr-1 was frequently detected in water (71%), animal feces (51%), and food products (36%).
• Stable carriage of mcr-1 was observed in 28% of surveyed human subjects.
• Escherichia coli was the dominant Enterobacteriaceae species carrying mcr-1, with the gene found on chromosomes and plasmids, including conjugative plasmids of ~33 kb and ~60 kb mediating transmission.

Conclusions:

• The widespread presence of mcr-1 in various ecological niches, including humans, highlights a significant public health concern.
• Conjugative plasmids serve as key vectors for mcr-1 transmission.
• Continued vigilance, robust antibiotic stewardship, and the development of novel antimicrobials are imperative to combat the spread of colistin resistance.