Patterns of antibiotic resistance in Southeastern US raptors before and after rehabilitation

Antibiotic resistance is an increasing issue that affects human and animal health. Birds can serve as reservoirs of antibiotic resistant bacteria, which combined with their ability to fly, increases the risk of disseminating resistant bacteria. To assess antibiotic resistance patterns, bacteria were isolated from fecal samples collected from raptors, defined as birds of prey, admitted to a raptor rehabilitation center. A total of 389 isolates from the Enterobacteriaceae family were recovered from 61 raptors, and each isolate was subjected to phenotypic susceptibility tests for nine antibiotics. Resistant phenotypes were recorded, and the highest levels were observed when isolates were exposed to tetracycline (71/389 isolates; 18.3 %), ampicillin (35/389 isolates; 9.0 %), trimethoprim-sulfamethoxazole (21/389 isolates; 5.4 %), and trimethoprim (19/389 isolates; 4.9 %) via the disk diffusion method. Of the resistant isolates, 31.6 % displayed resistance to two or more antibiotics within the same isolate and 6.3 % displayed multidrug resistance; the greatest amount of multidrug resistance was observed in Escherichia coli and Enterobacter hormaechei isolates, some due to intrinsic resistance for En. hormaechei. Birds slated for release maintained similar antibiotic resistance profiles compared to intake. Conversely, non-releasable birds harbored different types of antibiotic resistance. Based on logistic regression for 374 isolates and a subset of isolates collected from the same bird at different timepoints, our study indicates that time influences phenotypic antibiotic resistance during rehabilitation. Antibiotic use, variety of food items, and bird health outcome also influence antibiotic resistance patterns, suggesting that this is a complex but relevant topic for study.