Antibiotic Resistant Bacteria Acquired by Wild Birds in Urban Settings and Dispersed via Migration
USGS Studies Environmental Pathways of Antimicrobial Resistant Bacteria
U.S. Geological Survey (USGS) scientists have developed a model that demonstrates how migratory wild birds in urban areas can acquire bacteria that are resistant to antibiotics, including those used in clinics, and potentially disperse these bacteria between continents via migration.
Antimicrobial resistant (AMR) bacteria have been a concern for human and animal health, with an increasing number of clinical infections no longer responding to once-standard treatments. In addition, the use of antibiotics as growth promoters in livestock has been associated with increased antibiotic resistance in poultry, swine, and cattle. The environmental pathways of AMR bacteria are not well understood in part owing to the complexities of AMR spread and low levels of environmental surveillance. Previous research determined that gulls, especially those inhabiting landfills, sometimes acquire AMR bacteria; however, unanswered questions remain about AMR bacteria dispersal in different environments and its relevance, if any, to human health.
Researchers are beginning to address these questions through a series of coordinated studies. Researchers chose to begin by studying migratory gull populations in Alaska, an area with discrete populated areas and little livestock, thus providing somewhat well-defined human inputs. Researchers focused on identifying individual Escherichia coli (E. coli) from the gull feces, and then determined if the E. coli contained antimicrobial resistant genes by testing for resistance to 18 antibiotics and analyzing the bacterial deoxyribonucleic acid (DNA). A model was then developed using information on AMR bacteria and animal tracking to understand the potential for dispersal through migratory movements.
Results indicate that gulls acquire AMR bacteria at urban areas with human inputs (such as landfills) and that birds potentially disperse these bacteria across and between continents along their migratory pathways. Screening of E. coli found within the fecal samples indicated resistance to a wide variety of antibiotics including colistin and carbapenems, which are important antibiotics used for treating multidrug-resistant infections in humans.
Interspecies transmission of clinically important AMR bacteria has been demonstrated among humans, domestic animals, and wildlife in other situations such as backyard production of agricultural animals. In this series of studies, the results indicated migratory birds can acquire and disperse AMR bacteria—some of which are clinically relevant—along their migratory pathways; however, the occurrence and frequency of transmission between wildlife and humans are still unknown.
Findings from these studies help to refine our understanding of the environmental pathways through which AMR bacteria are spread, as well as the potential for wildlife to serve as sentinels for understanding the burden of AMR bacteria in human populations. Logical next steps may include comparison of AMR bacteria among geographic locations throughout migratory pathways, instituting systematic data collection to allow for comparisons among sites, genomic comparisons of AMR bacteria derived from human clinical cases and wild birds from the same geographic region and time period, and assessing the effect of different waste management practices on the availability of AMR bacteria to wild birds.
These studies were supported by the USGS Ecosystems Mission Area's Environmental Health Program (Contaminant Biology and Toxic Substances Hydrology), and Species Management Program; The U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services; Region Kalmar County, Sweden and Linköping University; the Swedish Research Council (grant number 2018-03841); and European Union’s Horizon 2020 – Research and Innovation Framework Programme (grant number 727922, Delta-Flu).
U.S. Geological Survey (USGS) scientists have developed a model that demonstrates how migratory wild birds in urban areas can acquire bacteria that are resistant to antibiotics, including those used in clinics, and potentially disperse these bacteria between continents via migration.
Antimicrobial resistant (AMR) bacteria have been a concern for human and animal health, with an increasing number of clinical infections no longer responding to once-standard treatments. In addition, the use of antibiotics as growth promoters in livestock has been associated with increased antibiotic resistance in poultry, swine, and cattle. The environmental pathways of AMR bacteria are not well understood in part owing to the complexities of AMR spread and low levels of environmental surveillance. Previous research determined that gulls, especially those inhabiting landfills, sometimes acquire AMR bacteria; however, unanswered questions remain about AMR bacteria dispersal in different environments and its relevance, if any, to human health.
Researchers are beginning to address these questions through a series of coordinated studies. Researchers chose to begin by studying migratory gull populations in Alaska, an area with discrete populated areas and little livestock, thus providing somewhat well-defined human inputs. Researchers focused on identifying individual Escherichia coli (E. coli) from the gull feces, and then determined if the E. coli contained antimicrobial resistant genes by testing for resistance to 18 antibiotics and analyzing the bacterial deoxyribonucleic acid (DNA). A model was then developed using information on AMR bacteria and animal tracking to understand the potential for dispersal through migratory movements.
Results indicate that gulls acquire AMR bacteria at urban areas with human inputs (such as landfills) and that birds potentially disperse these bacteria across and between continents along their migratory pathways. Screening of E. coli found within the fecal samples indicated resistance to a wide variety of antibiotics including colistin and carbapenems, which are important antibiotics used for treating multidrug-resistant infections in humans.
Interspecies transmission of clinically important AMR bacteria has been demonstrated among humans, domestic animals, and wildlife in other situations such as backyard production of agricultural animals. In this series of studies, the results indicated migratory birds can acquire and disperse AMR bacteria—some of which are clinically relevant—along their migratory pathways; however, the occurrence and frequency of transmission between wildlife and humans are still unknown.
Findings from these studies help to refine our understanding of the environmental pathways through which AMR bacteria are spread, as well as the potential for wildlife to serve as sentinels for understanding the burden of AMR bacteria in human populations. Logical next steps may include comparison of AMR bacteria among geographic locations throughout migratory pathways, instituting systematic data collection to allow for comparisons among sites, genomic comparisons of AMR bacteria derived from human clinical cases and wild birds from the same geographic region and time period, and assessing the effect of different waste management practices on the availability of AMR bacteria to wild birds.
These studies were supported by the USGS Ecosystems Mission Area's Environmental Health Program (Contaminant Biology and Toxic Substances Hydrology), and Species Management Program; The U.S. Department of Agriculture, Animal and Plant Health Inspection Service, Wildlife Services; Region Kalmar County, Sweden and Linköping University; the Swedish Research Council (grant number 2018-03841); and European Union’s Horizon 2020 – Research and Innovation Framework Programme (grant number 727922, Delta-Flu).