Detection of mcr-1-positive Escherichia coli in slaughterhouse wastewater collected from Dawen river

Abstract

Background: Low levels of mcr-1 were detected in Escherichia coli from wastewater samples across the world; hence, further monitoring and management of accumulation of mcr-1-positive bacteria in wastewater are urgently recommended. Objectives: In this study, we have reported the detection of E. coli strains carrying the colistin resistance gene mcr-1 in slaughterhouse wastewater discharged into Dawen river. Methods: Twenty samples were collected aseptically and subjected to polymerase chain reaction (PCR) analysis, multilocus sequence typing and antibiotic resistance tests. Conjugation tests were also performed. Results: The screening results showed a positive rate of 20% (4/20), which suggested that the mcr-1 gene had polluted the environment of the river. The mcr-1 gene had successfully transferred from the donor to recipient cells, which showed the possibility of horizontal transfer of mcr-1 and subsequently, the formation of multidrug resistant bacteria in the river. Conclusions: Our findings demonstrated a high occurrence of colistin-resistant E. coli carrying the mcr-1 gene on transferrable plasmids in slaughterhouses and indicated their dissemination into river. Large-scale cross-border cooperation would be required for the effective control of the spread of antibiotic-resistant bacteria.