Comparison of susceptibility to antimicrobials of the enterococcal species isolated from pigeons (Columba livia).

Antimicrobial resistance profiles were assessed in Enterococcus faecium, Enterococcus faecalis, and Enterococcus columbae strains isolated from racing pigeons (Columba livia). E. columbae is the most prevalent enterococcal species in the intestines of pigeons. Acquired resistance against the antimicrobials bambermycin, vancomycin, monensin, narasin, virginiamycin (cross-resistant with quinupristin/dalfopristin), avilamycin (cross-resistant with evernimicin), and ampicillin was not seen. Only for the antimicrobials tetracycline and tylosin was a frequent occurrence of resistance found in all three enterococcal species tested. Resistance to the fluoroquinolone antimicrobial enrofloxacin was present in E. columbae. Bacitracin resistance was seen in the species E. faecalis and E. faecium but not in E. columbae. High-level streptomycin resistance was found in E. columbae and in one E. faecium strain, whereas high-level gentamicin resistance was mainly associated with E. faecalis. The differences noted between the different species illustrate the difficulties related to the choice of indicator bacteria for antimicrobial resistance in the intestinal flora.