Assessment of commercial and wild birds as potential vectors of antibiotic resistant Escherichia coli and Enterococcus species.

Abstract

Due to zoonotic infections resulting from antibiotic resistant (ABR) bacteria, the presence of ABR bacteria in birds is a human health concern. The aim of this study was to assess if commercial free-range ducks, wild sacred ibis, and raptors are potential vectors of ABR E. coli and Enterococcus species. Thirty phenotypically and genotypically confirmed E. coli and Enterococcus spp. strains isolated from each bird’s faeces were analysed using the EUCAST disk diffusion method employing twelve (E. coli) and eight (Enterococcus spp.) appropriate antibiotics representing clinically important classes. β-Lactamase activity in isolates showing resistance to at least one of the tested β-lactam antibiotics was assessed using the nitrocefin spot test. Over 70% of E. coli isolates (47% from ducks; 73% from sacred ibis; 93% from raptors) were resistant to at least one of the twelve antibiotics tested, with resistance observed for penicillins, cephalosporins, aminoglycosides, and fluoroquinolones, but not for carbapenems, monobactams and tetracyclines. Additionally, two isolates each from sacred ibis’ and raptor faecal samples were classified as multidrug-resistant. Over 25% of Enterococcus spp. isolates (0% from ducks; 33% from sacred ibis; 47% from raptors) were resistant to at least one of the eight antibiotics tested. Resistance was observed for penicillins, carbapenems, glycopeptide/lipopeptides, and oxazolidinone, but not for aminoglycosides, tetracyclines, and fluoroquinolones. While the resistance level in E. coli isolates from commercial duck faeces was lower than in those from wild sacred ibis and raptors, none of the Enterococcus spp. isolates from duck displayed resistance to any of the tested antibiotics. β-Lactamase activity was detected in nine E. coli isolates from sacred ibis and raptors faeces and further confirmed using UV-Vis spectrometry. Therefore, commercial, and wild birds in KwaZulu-Natal, South Africa, carry ABR bacteria and may act as a source and vector for the dispersal and transfer of these antibiotic resistant bacteria.