Sentinel or Disperser? The Role of White Storks (Ciconia ciconia) in the Spread of Antibiotic Resistant Bacteria

Antimicrobial resistance (AMR) represents a serious problem affecting human, animal and ecosystem health. This study evaluated the potential role of white storks as AMR dispersers between two locations frequently used for foraging and resting. Through a whole year, 346 samples (318 feces/ 28 water) were collected in two landfills (225 fecal samples) and two wetlands (93 fecal/ 28 water samples) with a previous tracking that confirmed continuous storks movements between foraging (landfill) and nighttime roosting (wetlands) locations. All samples were seeded in selective media with antibiotics for the isolation of antibiotic resistant bacteria. A total of 313 isolates from 35 different bacterial species were obtained, with an AMR prevalence of 43.1% in fecal samples from landfills, 7.5% in fecal samples from wetlands and 21.4% in water from wetlands. Multidrug resistant bacteria were only found in fecal samples (19.6% landfills/ 4.3% wetlands) and Extended-spectrum beta-lactamase producing-bacteria was found exclusively in fecal samples from landfills with a marked presence during the fall migration stork’s migration period. Despite subtle circumstantial evidence of dispersion between one landfill and its paired wetland and a possible link with migratory movements, the marked differences in prevalence and resistance phenotypes found in each location did not allow establishing a clear dispersal activity by storks.