Variability of faecal microbiota and antibiotic resistance genes in flocks of migratory gulls and comparison with the surrounding environment

• Published in: Environmental pollution (1987) 2024-10, Vol.359, p.124563, Article 124563
• Main Authors: Jarma, Dayana, Sacristán-Soriano, Oriol, Borrego, Carles M., Hortas, Francisco, Peralta-Sánchez, Juan M., Balcázar, José L., Green, Andy J., Alonso, Esteban, Sánchez-Melsió, Alexandre, Sánchez, Marta I.
• Format: Article
• Language: English
• Subjects: antibiotic resistance; Antibiotic resistance genes; Faecal microbiota; feces; habitat preferences; habitats; landfills; Larus fuscus; Lesser black-backed gull; microorganisms; migratory behavior; Mobile genetic elements; Movement ecology; pollution; soil; Spatial variation; wastes; wetlands; wild birds
• ISSN: 0269-7491; 1873-6424; 1873-6424
• DOI: 10.1016/j.envpol.2024.124563

Gulls commonly rely on human-generated waste as their primary food source, contributing to the spread of antibiotic-resistant bacteria and their resistance genes, both locally and globally. Our understanding of this process remains incomplete, particularly in relation to its potential interaction with surrounding soil and water. We studied the lesser black-backed gull, Larus fuscus, as a model to examine the spatial variation of faecal bacterial communities, antibiotic resistance genes (ARGs), and mobile genetic elements (MGEs) and its relationship with the surrounding water and soil. We conducted sampling campaigns within a connectivity network of different flocks of gulls moving across functional units (FUs), each of which represents a module of highly interconnected patches of habitats used for roosting and feeding. The FUs vary in habitat use, with some gulls using more polluted sites (notably landfills), while others prefer more natural environments (e.g., wetlands or beaches). Faecal bacterial communities in gulls from flocks that visit and spend more time in landfills exhibited higher richness and diversity. The faecal microbiota showed a high compositional overlap with bacterial communities in soil. The overlap was greater when compared to landfill (11%) than to wetland soils (6%), and much lower when compared to bacterial communities in surrounding water (2% and 1% for landfill and wetland water, respectively). The relative abundance of ARGs and MGEs were similar between FUs, with variations observed only for specific families of ARGs and MGEs. When exploring the faecal carriage of ARGs and MGEs in bird faeces relative to soil and water compartments, gull faeces were enriched in ARGs classified as High-Risk. Our results shed light on the complex dynamics of antibiotic resistance spread in wild bird populations, providing insights into the interactions among gull movement and feeding behavior, habitat characteristics, and the dissemination of antibiotic resistance determinants across environmental reservoirs. [Display omitted] •Different flocks of gulls harbor distinct bacterial communities in their faeces.•Faecal microbiota exhibit a high degree of compositional overlap with soil.•ARGs and MGEs in faeces of gulls are similar between different flocks.•Gull faeces are enriched in ARGs compared to soil and water reservoirs.