U.S. Department of Agriculture: Animal and Plant Health Inspection Service



Alan B. Franklin http://orcid.org/0000-0001-9491-795X

Christina A. Ahlstrom http://orcid.org/0000-0001-5414-8076

Date of this Version



Scientific Reports (2020) 10:4408

doi 10.1038/s41598-020-61318-2


This article is licensed under a Creative Commons Attribution 4.0 International License


In 2015, the mcr-1 gene was discovered in Escherichia coli in domestic swine in China that conferred resistance to colistin, an antibiotic of last resort used in treating multi-drug resistant bacterial infections in humans. Since then, mcr-1 was found in other human and animal populations, including wild gulls. Because gulls could disseminate the mcr-1 gene, we conducted an experiment to assess whether gulls are readily colonized with mcr-1 positive E. coli, their shedding patterns, transmission among conspecifics, and environmental deposition. Shedding of mcr-1 E. coli by small gull flocks followed a lognormal curve and gulls shed one strain >101 log10 CFU/g in their feces for 16.4 days, which persisted in the environment for 29.3 days. Because gulls are mobile and can shed antimicrobial-resistant bacteria for extended periods, gulls may facilitate transmission of mcr-1 positive E. coli to humans and livestock through fecal contamination of water, public areas and agricultural operations.