What question did this study set out to answer?

This research aims to understand the role of gulls as reservoirs and vectors of multidrug-resistant Escherichia coli in Atlantic Canada.

April 23, 2026

Gulls as Reservoirs and Vectors of High-Risk, Multidrug-Resistant Escherichia coli in Atlantic Canada: Emergence of CMY-2-Producing ST648

Key Points

This research aims to understand the role of gulls as reservoirs and vectors of multidrug-resistant Escherichia coli in Atlantic Canada.
Characterized fecal samples from gulls in Nova Scotia for resistance types.
Analyzed resistance genes and plasmid content of isolates.
Examined phylogroups and sequence types of Escherichia coli strains.
Isolated 34 cefotaxime-resistant E. coli strains including 29 ESBL and 5 AmpC producers.
Detected multiple resistance genes, revealing high virulence potential in isolates.
Found high replicon burden, indicating extensive plasmid carriage among resistant strains.

Abstract

Gulls (Larus spp.) are key reservoirs and vectors of antimicrobial resistance (AMR). We characterized extended-spectrum β-lactamase (ESBL) and plasmid-mediated AmpCproducing Escherichia coli from Great Black-backed (Larus marinus) and American Herring (Larus smithsonianus) gulls in Nova Scotia, Canada. From 100 fecal samples, 34 cefotaxime-resistant isolates were recovered: 29 ESBL and 5 AmpC producers. Detected, and blaCMY-2 + blaTEM-1C (n = 1).. Additional resistance genes conferred resistance to sulfonamides (sul2/sul3), trimethoprim (dfrA14/dfrA17), tetracyclines (tet(A)/tet(B)), aminoglycosides, chloramphenicol (floR), macrolides (mph(A)), lincosamides (lnu(F)), and quinolones (qnrS), complemented by chromosomal mutations in gyrA, parC, and parE. The isolates represented phylogroups A (n=10), B1 (n=18), and D (n=6), and high-risk sequence types including ST155 (n=12), ST744 (n=7), ST224 (n=4), and ST648 (n=3). Plasmid analysis revealed a high replicon burden (≥3 in 70.6% of isolates), primarily IncFIB (70.6%), Col (58.8%), and IncI (50.0%). Key virulence factors detected were fimH (97.1%), lpfA (73.5%), fyuA (47.1%), and iss (38.2%). These results demonstrate that synanthropic gulls in Atlantic Canada carry multidrug-resistant ESBL/AmpC E. coli from globally significant clones, underscoring their role in the dissemination of antimicrobial resistance within a One Health context.

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