Multi-resistant Enterobacteriaceae in Yellow-legged Gull. Multi-resistant Enterobacteriaceae

Over the past decade, growing evidence has underlined the common carriage of antimicrobial resistant bacteria (AMR) by various wild species, which calls for a better understanding of the dynamics of these bacteria in this compartment. Until today, most studies that focus on AMR in wildlife have analyzed samples collected on an ad hoc basis with little information on the individuals that carry them. In this case, we studied AMR carriage in a Yellow-legged Gull (Larus michahellis) colony in Southern France. We chose this anthropophilic bird as a model since AMR carriage has frequently been observed in this species. Our goal was to investigate the spatio-temporal dynamics of AMR within the colony through three sampling sessions during which the location of the sampled nests and chicks were recorded. Our results confirm the common carriage of AMR that is of clinical importance in this population, including several CTX-M- as well as CMY-2-producing Escherichia coli and Proteus mirabilis, respectively. Using the Comprehensive Antibiotic Resistance Database (CARD), we draw attention to a very wide range of resistance genes carried by the bacterial strains we isolated from gulls. Moreover, we observe a significant increase of AMR carriage over time from hatching to fledging in chicks. Finally, we underline that AMR carriage is not spatially structured in the colony, probably due to the frequent exchanges existing between chicks combined with shared sources of food used by parents. Our study highlights the complexity of AMR carriage patterns in a wild species, notably underlining temporal heterogeneity. Now that the carriage of AMR by wildlife has been well-established, our study calls for more research on the dynamics of AMR in this compartment. Such research could help to design protocols that effectively use some species as environmental sentinels. Further research is also needed to assess the public health risk associated with AMR carriage by these birds.