Antimicrobial resistance phenotypes in urban wildlife: white storks (Ciconia ciconia) admitted at a wildlife rehabilitation center as sentinels of environmental contamination

Antimicrobial resistance (AMR) has been described as a significant threat to public and animal health. Regarding the One Health strategy to assess and face AMR, including wildlife in those studies becomes essential. In this context, urban birds such as white storks (Ciconia ciconia) are considered great sentinels of environmental pollution and serve as bridges between cities and the natural environment. This study aimed to evaluate AMR in Escherichia coli isolated from 44 white storks admitted to a wildlife rehabilitation center in central Spain. To this end, 44 isolates were submitted to two antimicrobial susceptibility tests: disk diffusion and broth microdilution with VITEK®2 Compact 15. The disk diffusion method showed 72.7% AMR and 43.8% multidrug resistance (MDR), while VITEK® confirmed 93.2% and 90.2%, respectively. Moreover, 70.5% of the isolates tested positive for extended-spectrum beta-lactamases (ESBLs). Indeed, penicillins and third- and fourth-generation cephalosporins were the antimicrobial classes with the highest resistance rates. Amikacin was the only antimicrobial to which all isolates were susceptible. Among the individual variables analyzed, white storks collected near landfills exhibited E. coli strains resistant to a significantly higher number of antimicrobials than those located farther away. The proportion of AMR and MDR reported in the present study supports the worldwide upward trend of AMR detection.