Increased prevalence of antibiotic-resistant E. coli in gulls sampled in Southcentral Alaska is associated with urban environments

Abstract

Background

Antibiotic-resistant bacteria pose challenges to healthcare delivery systems globally; however, limited information is available regarding the prevalence and spread of such bacteria in the environment. The aim of this study was to compare the prevalence of antibiotic-resistant bacteria in large-bodied gulls (Larus spp.) at urban and remote locations in Southcentral Alaska to gain inference into the association between antibiotic resistance in wildlife and anthropogenically influenced habitats.

Methods

Escherichia coli was cultured (n=115 isolates) from fecal samples of gulls (n=160) collected from a remote location, Middleton Island, and a more urban setting on the Kenai Peninsula.

Results

Screening of E. coli from fecal samples collected from glaucous-winged gulls (Larus glaucescens) at Middleton Island revealed 8% of isolates were resistant to one or more antibiotics and 2% of the isolates were resistant to three or more antibiotics. In contrast, 55% of E. coli isolates derived from fecal samples collected from large-bodied gulls (i.e. glaucous, herring [Larus argentatus], and potentially hybrid gulls) on the Kenai Peninsula were resistant to one or more antibiotics and 22% were resistant to three or more antibiotics. In addition, total of 16% of the gull samples from locations on the Kenai Peninsula harbored extended-spectrum cephalosporin-resistant E. coli isolates (extended-spectrum beta-lactamases [ESBL] and plasmid-encoded AmpC [pAmpC]), in contrast to Middleton Island where no ESBL- or pAmpC-producing isolates were detected.

Conclusion

Our findings indicate that increased prevalence of antibiotic resistance is associated with urban environments in Southcentral Alaska and presumably influenced by anthropogenic impacts. Further investigation is warranted to assess how migratory birds may maintain and spread antimicrobial-resistant bacteria of relevance to human and animal health.

• ESBL
• pAmpC
• antimicrobial resistance
• anthropogenic
• gull

Acknowledgements

We appreciate field help provided by Brianna Williams and Morgan Walker and laboratory support provided by Jenny Isaksson, Badrul Hasan, and Henrik Reutherborg. We appreciate manuscript reviews provided by Christina Ahlstrom and John Pearce. We are grateful to John Reed for assistance with the preparation of Fig. 1. We thank Scott Hatch for logistical support while sampling on Middleton Island. This work was funded, in part, by the US Geological Survey through the Contaminants Biology Program of the Environmental Health Mission Area. None of the authors have any financial interests or conflict of interest with this article. Any use of trade names is for descriptive purposes only and does not imply endorsement by the US government.