ESBL-E. coli prevalence in seabirds from the Southeast Pacific Coast. Effects of Season, Host Species and Origin of Antimicrobial Resistance in seabirds from the Southeast Pacific Coast

Antimicrobial resistance (AMR) is a global public threat given the rapid emergence and spread of antimicrobial resistance bacteria and genes. Seabirds have been reported as carriers of extended-spectrum beta-lactamase-(ESBL) producing Escherichia coli (ESBL-EC) which is of public health concern and found in a wide range of habitats including central Chile. Different foraging habits and reproductive cycles in seabirds could impact their AMR prevalence. In the Humboldt Current Large Marine Ecosystem in Chile, climate variation occurs over the year and is home to the resident, migratory, and native seabirds, making it an adequate environment to explore AMR variability by host species. We aim to estimate the prevalence of ESBL-EC of Larus dominicanus, Larus pipixcan, and Pelecanus thagus during a two-year period (2021-2023). We collected faecal samples and screened them for ESBL-Enterobacteriaceae using McConkey media supplemented with cefotaxime 2mg/L and incubated overnight at 37°C. Lactose-positive colonies compatible with Enterobacteriaceae were purified. Escherichia coli was confirmed by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry. ESBL production was tested using the double-disk diffusion method. We compared the prevalence of ESBL-EC among the host species during summer season using a Generalized Linear Model.