Low occurrence of multi-antimicrobial and heavy metal resistance in Salmonella enterica from wild birds in the United States |
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Authors: | Yezhi Fu Nkuchia M M'ikanatha Chris A Whitehouse Heather Tate Andrea Ottesen Jeffrey M Lorch David S Blehert Brenda Berlowski-Zier Edward G Dudley |
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Institution: | 1. Department of Food Science, The Pennsylvania State University, University Park, PA, 16802 USA;2. Pennsylvania Department of Health, Harrisburg, PA, 17120 USA;3. Center for Veterinary Medicine, U.S. Food and Drug Administration, Laurel, MD, 20708 USA;4. U.S. Geological Survey - National Wildlife Health Center, Madison, WI, 53711 USA |
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Abstract: | Wild birds are common reservoirs of Salmonella enterica. Wild birds carrying resistant S. enterica may pose a risk to public health as they can spread the resistant bacteria across large spatial scales within a short time. Here, we whole-genome sequenced 375 S. enterica strains from wild birds collected in 41 U.S. states during 1978–2019 to examine bacterial resistance to antibiotics and heavy metals. We found that Typhimurium was the dominant S. enterica serovar, accounting for 68.3% (256/375) of the bird isolates. Furthermore, the proportions of the isolates identified as multi-antimicrobial resistant (multi-AMR: resistant to at least three antimicrobial classes) or multi-heavy metal resistant (multi-HMR: resistant to at least three heavy metals) were both 1.87% (7/375). Interestingly, all the multi-resistant S. enterica (n = 12) were isolated from water birds or raptors; none of them was isolated from songbirds. Plasmid profiling demonstrated that 75% (9/12) of the multi-resistant strains carried resistance plasmids. Our study indicates that wild birds do not serve as important reservoirs of multi-resistant S. enterica strains. Nonetheless, continuous surveillance for bacterial resistance in wild birds is necessary because the multi-resistant isolates identified in this study also showed close genetic relatedness with those from humans and domestic animals. |
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