Tania Suarez-Yana¹ | Zulma Rojas¹ | Marília Salgado-Caxito² | Carmen Torres³ | Julio Benavides⁴

1. Program in Conservation Medicine, Facultad de Ciencias de la Vida, Universidad Andres Bello, Santiago, Chile; Centro de Investigación para la Sustentabilidad, Facultad de Ciencias de la Vida, Universidad Andrés Bello, Santiago, Chile; 2. School of Veterinary Medicine, Pontificia Universidad Católica de Chile, Santiago, Chile; Millennium Initiative for Collaborative Research on Bacterial Resistance (MICROB-R), Santiago, Chile; 3. Área Bioquímica y Biología Molecular, Universidad de La Rioja, Logroño, Spain; 4. Infectious diseases and vectors: ecology, genetics, evolution and control Group, French National Research Institute for Sustainable Development, Montpellier, France; Centro de Investigación para la Sustentabilidad, Facultad de Ciencias de la Vida, Universidad Andrés Bello, Santiago, Chile; Millennium Initiative for Collaborative Research on Bacterial Resistance (MICROB-R), Santiago, Chile.

Ponente: Tania Suarez-Yana, taniasuarezy@gmail.com

Seabirds have been reported as carriers of antimicrobial-resistant bacteria like extended-spectrum β-lactamase-producing (ESBL) Enterobacteriaceae, found in a wide range of habitats including central Chile. However, the temporal dynamics of ESBL- Enterobacteriaceae carried by seabirds remains poorly understood. The Kelp gull (Larus dominicanus) is a synanthropic resident species from the Humboldt Current Ecosystem with seasonal reproduction, so it is an ideal sentinel species to track the temporal dynamics of ESBL-Enterobacteriaceae in this ecosystem. We performed a longitudinal study between 2020 and 2022, collecting 352 faecal samples of Kelp gulls along the coastline of Algarrobo, Chile. We report preliminary results on the prevalence of ESBL-Enterobacteriacae from three summer seasons (2020, 2021, 2022) and one winter season (2021). Faecal samples were screened 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. We compared the prevalence of ESBL-Enterobacteriaceae isolates among the four sampling periods and between summer and winter using Chi-Square test. Our results showed that L. dominicanus had a high prevalence of ESBL-Enterobacteriaceae across years and seasons (summer: 58.2% in 2020, 50% in 2021 and 44.3% in 2022, winter: 67% in 2021). Although most prevalence rates were high, there was a statistically significant result among all sampling periods (p<0.01). However, there was no statistical difference in the prevalence between summer and winter (p>0.05). These preliminary results suggest that L. dominicanus can sustain the carriage of ESBL-Enterobacteriaceae over time, with a high prevalence independently of the season. Thus, this study suggests that ESBL-Enterobacteriaceae circulates among seabirds with synanthropic behaviour but changes in human contact (higher in summer and likely lower during the COVID lockdown) did not significantly affect its circulation. These findings call for a better understanding of the origin and drivers of antimicrobial resistance circulation among wild birds.