Purpose: The purpose of this study was to longitudinally follow the antimicrobial susceptibility patterns of Enterococcus species throughout an environment shared by dairy cattle and a transient population of Branta canadensis (Canada goose).
Methods: Approximately 5 g of feces were collected over a one year period from dairy cattle (n=275) and Canadian geese (n=242). Additionally, n=220 10g soil samples were collected from defined pasture plots representing areas where both cattle and geese mingled. Selective culture methods were used to isolate Enterococcus, and antimicrobial susceptibility was determined using broth microdilution (Vitek, BioMerieux, Marcy l'Etoile). Interpretations were based on CLSI guidelines.
Results: Enterococcus species from cattle (n=152), geese (n=195), and soil (n=152) were tested for susceptibility. The predominant species recovered was E. hirae (35%), followed by E. faecium (25%) and E. casseliflavus (18%). Approximately 94% of Enterococcus isolates were resistant to at least one antimicrobial. Multidrug resistant Enterococcus (≥ 3 antimicrobials) were obtained from 49%, 49%, and 47% of soil, geese, and cattle samples, respectively. The predominant MDR pattern of E. faecium (51%; n=88 isolates) was to clindamycin, enrofloxacin, marbofloxacin, and trimethoprim/sulfamethoxazole, and was observed in all sample types.
Significance: The presence of multidrug resistant Enterococcus sharing similar susceptibility patterns could be demonstrated in migratory geese, associated cattle and their shared soil environment. This suggests that migratory geese play a role in the dissemination of antimicrobial resistant bacteria.