SREL Reprint #3377

Patterns of multi-antibiotic-resistant Escherichia coli from streams with no history of antimicrobial inputs

J. V. McArthur1, D. E. Fletcher1, R. Cary Tuckfield2, and C. Baker-Austin3

1Savannah River Ecology Laboratory, University of Georgia, Drawer E, Aiken, SC 29802, USA
2Ecostatys, LLC, Aiken, SC, USA
3Centre for Environment, Fisheries and Aquaculture Science, Weymouth, Dorset, UK

Abstract: A growing body of evidence suggests that contaminated environments may harbor a greater proportion of antibiotic-resistant microorganisms than unpolluted reference sites. Here, we report the screening of 427 Escherichia coli strains isolated from 11 locations on nine streams draining the US Department of Energy’s Savannah River Site against a panel of five antibiotics. Streams were chosen to capture a wide range of watersheds from minimally disturbed to highly impacted. Overall, higher levels of resistance were found in waterborne E. coli that also generally exhibited low spatial variability. However, 3 of 11 locations also demonstrated elevated resistance levels in sediments. Two of these occurred in highly disturbed tributaries with no obvious sources of antimicrobials. To further investigate these patterns, we screened a subset of isolates obtained from three streams against 23 antibiotics or antibiotic combinations. A large proportion of these isolates (>40 %) demonstrated resistance to 10 or more antimicrobials, suggesting that environmental multi-antibiotic resistance may be prevalent in this bacterial commensal. Only 4 of 87 viable isolates were tested susceptible to all 23 antibiotics and combinations. Among these multi-antibioticresistant isolates, several demonstrated resistance to all structural classes of antimicrobial agents tested, including frontline antibiotics such as gatifloxacin and ciprofloxacin.

Keywords: E. coli; Antibiotic resistance; Industrial activity

SREL Reprint #3377

McArthur, J. V., D. E. Fletcher, R. C. Tuckfield, and C. Baker-Austin. 2016. Patterns of multi-antibiotic-resistant Escherichia coli from streams with no history of antimicrobial inputs. Microbial Ecology 72(4): 840-850.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).