Interview with the author: Antimicrobial resistance in gull populations

Antimicrobial resistance is an increasing concern worldwide, but our knowledge of how multi-drug resistant bacteria get around in wildlife populations is relatively poor. In their recent paper, Ahlstrom et al. triangulate results from multiple approaches to help address this important issue in gulls in Alaska. Christina Ahlstrom from the USGS  Alaska Science Center gives us an insider take on their really interesting work..

What led to your interest in this topic / what was the motivation for this study? 

It has been speculated that birds could potentially transport antimicrobial resistant bacteria via their local movements and long distance migration, however there has been little direct research to investigate this. We previously detected antimicrobial resistant E. coli in gulls at a local Alaska landfill and at the mouth of a nearby river where Alaska residents harvest sockeye salmon during the summer. Therefore, we sought to investigate whether there was evidence for dissemination of antimicrobial resistant bacteria by gulls at these two locations and other nearby sites.

Image credit: Andrew Ramey, USGS

What difficulties did you run into along the way? 

In order to assess dispersal of antimicrobial resistant bacteria, we had to first understand movement patterns of birds. However, capturing gulls is no easy feat! To catch birds, we hand tied ~2,000 nooses made of fishing line attached to mats,  camouflaged them with plastic grocery bags, baited them with chips and fish guts, and spent long days in the landfill waiting for wary gulls to land on our “noose carpets”. The elation of finally capturing and successfully tagging a gull overpowered the discomfort of the bites and scratches received while attaching a satellite transmitter.

What is the biggest or most surprising finding from this study? 

We found multidrug resistant bacteria in many samples collected from gulls in Alaska, a state with relatively little intensive agriculture. I think this finding is surprising, since many people associate antimicrobial resistance with this sector. It was also noteworthy that, although we found extensive evidence for dispersal of antibiotic resistant bacteria between the landfill and the mouth of a nearby river, we found much less evidence for dispersal between these sites and an area further upstream. This finding was congruent with few detected gull movements between this upriver site and the landfill or river mouth and highlights the strength of using multiple research approaches.

Moving forward, what are the next steps for this research? 

We are interested in exploring if gulls may disperse antibiotic resistant bacteria via long distance migratory movements. Many of the gulls that we marked in southcentral Alaska migrated to the Pacific Northwest and California. Other birds that we marked as part of ongoing research migrated to East Asia. We hypothesize that there may be differences in antimicrobial resistant bacteria harbored by gulls that have different migratory tendencies. We aim to investigate if there are indeed differences and whether they could be related to different areas that gulls inhabit during the annual cycle.

What would your message be for students about to start their first research projects in this topic? 

Start small and then build up to investigate larger research questions. The epidemiology of antimicrobial resistance is extremely complex. I found it was helpful to first explore what was happening in a single system and then work up from there. We analyzed antimicrobial resistant bacteria from wild birds at a single site, followed by a similar analyses at multiple nearby sites (this study), and our future research will explore similarities/differences at locations across Alaska. This approach has allowed us to fine-tune our analytical methods and hone in on the most relevant research questions.

What have you learned about science over the course of this project? 

Science is so diverse, but different disciplines can be surprisingly complementary. When I first became interested in molecular epidemiology, I never imagined I would someday use satellite telemetry to quantify wild bird movements. Collaborating with experts in other fields and combining information from diverse scientific disciplines is a powerful (and fun!) way to approach a research question. 

Describe the significance of this research for the general scientific community in one sentence.

Antimicrobial resistance is not confined to hospitals nor to agricultural areas, but can be found in, and dispersed by, landfill-foraging gulls in Alaska.

Describe the significance of this research for your scientific community in one sentence.

Wildlife and the environment are important, yet often overlooked, components of the One Health triad – investigating these ecosystems can enhance our understanding of the epidemiology of antimicrobial resistant bacteria.

Find the paper here: Ahlstrom, CA, Bonnedahl, J, Woksepp, H, et al. Satellite tracking of gulls and genomic characterization of faecal bacteria reveals environmentally mediated acquisition and dispersal of antimicrobial‐resistant Escherichia coli on the Kenai Peninsula, Alaska. Mol Ecol. 2019; 28: 2531– 2545.