Yellow legged gulls (Larus michahellis): the bridge between human and environmental carbapenemase-producing Enterobacteriaceae?

Wildlife is frequently reported as a host of antimicrobial resistant bacteria (AMR), often reflecting anthropogenic contamination. Among them, carbapenemase-producing Enterobacteriaceae (CPE) are one of the most worrying for human health. This study investigated the carriage of CPE in yellow-legged gull chicks ( Larus michahellis ) from a breeding colony of southern France, where CPE have already been detected, and compared these bacterial strains with isolates from humans hospitalized in Montpellier University Hospital, France. Cloacal swabs from 112 chicks revealed a high CPE carriage rate (12 isolates carried by 10 gulls; 8.9%). Detected species included Escherichia coli (n = 3), Citrobacter portucalensis (n = 1) and members of Enterobacter cloacae complex (n = 8). Whole-genome sequencing revealed that 8/12 isolates produced IMI-type carbapenemases (IMI-4 and NMC-A) inserted within EcloIMEX integrative elements, and 4/12 produced OXA-48 located in IncL plasmids. Human and avian CPE isolates did not have common sequences types, although they harbored identical resistance structures (EcloIMEX-1). Some OXA-48-producing E. coli isolates belonged to high-risk human-associated genotypes (ST10, ST648), confirming the potential AMR transmission to gulls via anthropic activities. Conversely, the predominance of IMI-type carbapenemases, typically associated with aquatic environments and rare in clinical settings, suggests that gulls may also carry multidrug resistant bacteria of environmental origin. Positioned at the interface between aquatic ecosystems and human-impacted areas, gulls could contribute to the dissemination of these pathogens beyond their primary reservoirs. These findings highlight the need to integrate wildlife into One Health surveillance frameworks, not only as indicators of anthropogenic AMR but also as potential sentinels of emerging resistance threats. • High CPE carriage (8.9%) detected in yellow-legged gull chicks in southern France. • Avian carriage of high-risk human-associated lineages of E. coli (ST10, ST648) • IMI carbapenemases variants identified in wildlife for the first time (NmcA, IMI-4). • Environmental reservoir of IMI on the Mediterranean coast, amplified by gulls