Isolation of Strains of Enterococcus faecalis from the Feces of Wild Birds and Their Drug Resistance Test Results

Abstract

In this study, we isolated strains of Enterococcus faecalis from a total of 113 feces from 11 wild bird species in order to comprehend the distribution of antimicrobial resistance in the natural environment of Japan, and to survey the actual roles of wild birds as reservoirs of resistant bacteria. We also examined the rate of isolation in each bird species, and performed microbial sensitivity tests using the Kirby-Bauer method. E. faecalis strains were isolated from a total of 36 feces from 6 bird species: the Oriental great reed warbler (Acrocephalus orientalis), Japanese bush warbler (Horornis diphone), bull-headed shrike (Lanius bucephalus), Siberian rubythroat (Calliope calliope), black-faced bunting (Emberiza spodocephala) and reed bunting (Emberiza schoeniclus). However, E. faecalis strains were not isolated from 5 bird species: the Oriental greenfinch (Chloris sinica), tree sparrow (Passer montanus), great tit (Parus minor), rustic bunting (Emberiza rustica) and cinnamon sparrow (Passer rutilans). In microbial sensitivity tests using three strains from each bird species, a total of 74 strains were examined. Moderate resistances to erythromycin, teicoplanin and vancomycin were found, and the rates of isolation of resistant strains were 24.3%, 12.2% and 8.1%, respectively. There were no resistant strains in reed bunting and Siberian rubythroat. Some strains were found to have multi-resistance to multiple drugs. These results reflect the strict controls of sewage and livestock excrement by legislation in Japan, and the policy of reviewing the usage of antimicrobial drugs. Surveys of wild birds should be regularly undertaken, including species of wild birds not only in this study, and with a larger survey area.