A large spatial survey of colistin-resistant gene mcr-1-carrying E. coli in rivers across Taiwan

Ching Hao Teng, Pin Chieh Wu, Sen Lin Tang, Yi Chen Chen, Ming Fang Cheng, Ping Chih Huang, Wen Chien Ko, Jiun Ling Wang

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


Background: Colistin is one of the last-line antimicrobial agents against life-threatening infections. The distribution of the colistin resistance gene mcr-1 has been reported worldwide. However, most studies have focused on the distribution of mcr-1-positive bacteria in humans, animals, food, and sewage; few have focused on their distribution in natural environments. Method: We conducted a large spatial survey of mcr-1-positive Escherichia coli at 119 sites in 48 rivers, covering the entire island of Taiwan. We investigated the relationship between the livestock or poultry density in the surveyed riverine area and the number of mcr-1-positive E. coli in the river water. We then sequenced and characterized the isolated mcr-1-positive plasmids. Results: Seven mcr-1 positive E. coli were isolated from 5.9% of the sampling sites. The mcr-1-positive sites correlated with high chicken and pig stocking densities but not human population density or other river parameters. Four of the mcr-1-positive E. coli strains harbored epidemic IncX4 plasmids, and three of them exhibited identical sequences with a size of 33,309 bp. One of the plasmids contained identical 33,309 bp sequences but carried an additional 5711-bp transposon (Tn3 family). To our knowledge, this is the first demonstration that mcr-1-carrying IncX4 plasmids can contain an insertion of such transposons. All mcr-1-positive isolates belonged to phylogenetic group A and harbored few known virulence genes. Conclusion: This study showed a positive relationship between the number of mcr-1-positive sites and high livestock and poultry density. The sequencing analyses indicated that the epidemic plasmid in the mcr-1 isolates circulates not only in humans, animals, and food but also in the associated environments or natural habitats in Taiwan, suggesting that the surveillance of antibiotics-resistance genes for livestock or poultry farm quality control should include their associated environments.

Original languageEnglish
Article number722
Issue number4
Publication statusPublished - 2021 Apr

All Science Journal Classification (ASJC) codes

  • Microbiology
  • Microbiology (medical)
  • Virology


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