Christina is a Geneticist for the Alaska Science Center.
Professional Experience
2017 - Present Geneticist, USGS Alaska Science Center, Anchorage, Alaska
2015 - 2017 Consultant Epidemiologist & Data Analyst, Epi-interactive, Wellington, New Zealand
2017 Molecular Epidemiology Consultant, Food and Agriculture Organisation, Rome, Italy
2016 Molecular Epidemiology Consultant, Food and Agriculture Organisation, Rome, Italy
2005 - 2008 Seasonal Research Assistant, Quality Milk Production Services, Cornell University, Ithaca, NY
Education and Certifications
Ph.D. 2015 University of Calgary, Calgary, Alberta, Canada Veterinary Medical Sciences
M.S. 2011 Colorado State University, Fort Collins, CO Animal Science
B.S. 2008 University at Buffalo, Buffalo, NY Biology
Science and Products
Avian Influenza Research
Antibiotic Resistant Bacteria Acquired by Wild Birds in Urban Settings and Dispersed via Migration
Antibiotic Resistant Bacteria in Migratory Birds
Antimicrobial Resistance Testing and qPCR Detection of Antimicrobial Resistance Genes in Surface Water and Gull (Larus spp.) Feces on the Kenai Peninsula, Alaska, 2021
Tracking Data for Three Large-bodied Gull Species and Hybrids (Larus spp.)
Data for Continental-Scale Dispersal of Antimicrobial Resistant Bacteria by Alaska Landfill-Foraging Gulls
Sampling, Antimicrobial Resistance Testing, and Genomic Typing of Carbapenemase Producing E. coli in Gulls (Larus spp.) in Alaska, 2016
Sampling, antimicrobial resistance testing, and genomic typing of E. coli in gulls (Larus spp.) on the Kenai Peninsula, Alaska, 2016
Sampling and Resistance and Genomic Typing of Cephalosporin-resistant E. coli in Gulls (Larus spp.) and Bald Eagles (Haliaeetus leucocephalus) in Southcentral Alaska, 2016
Environmental antimicrobial resistance gene detection from wild bird habitats using two methods: A commercially available culture-independent qPCR assay and culture of indicator bacteria followed by whole-genome sequencing
Exchange of carbapenem-resistant Escherichia coli Sequence Type 38 intercontinentally and among wild bird, human, and environmental niches
Antibiotic resistance in free-ranging wildlife
Maintenance and dissemination of avian-origin influenza A virus within the northern Atlantic Flyway of North America
Genomically diverse carbapenem resistant Enterobacteriaceae from wild birds provide insight into global patterns of spatiotemporal dissemination
Genomic comparison of carbapenem-resistant Enterobacteriaceae from humans and gulls in Alaska
Evidence for continental-scale dispersal of antimicrobial resistant bacteria by landfill-foraging gulls
Comparative genomics and genomic epidemiology of mycobacterium avium subsp. paratuberculosis strains
Validation of a screening method for the detection of colistin-resistant E. coli containing mcr-1 in feral swine feces
Gulls as sources of environmental contamination by colistin-resistant bacteria
Antibiotic resistant bacteria in wildlife: Perspectives on trends, acquisitions and dissemination, data gaps, and future directions
Early emergence of mcr-1-positive Enterobacteriaceae in gulls from Spain and Portugal
Non-USGS Publications**
**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.
Science and Products
- Science
Avian Influenza Research
Since 2006, the USGS Alaska Science Center has been part of the State and Federal interagency team for the detection and response to highly pathogenic (HPAI) viruses in North America. Avian influenza or "bird flu" is a viral disease that primarily infects domestic poultry and wild birds. Avian influenza viruses are naturally occurring in wild birds such as ducks, geese, swans, and gulls. These...Antibiotic Resistant Bacteria Acquired by Wild Birds in Urban Settings and Dispersed via Migration
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.Antibiotic Resistant Bacteria in Migratory Birds
Migratory birds, and particularly those using habitats close to human settlements, may be infected with antibiotic resistant bacteria. The USGS is working with public health professionals to understand the role of birds in the maintenance and dispersal of antibiotic resistant bacteria. Additionally, the USGS is investigating how antibiotic resistant bacteria in birds may relate to public and... - Data
Antimicrobial Resistance Testing and qPCR Detection of Antimicrobial Resistance Genes in Surface Water and Gull (Larus spp.) Feces on the Kenai Peninsula, Alaska, 2021
This data set includes information on collections of surface water and fecal samples from wild gulls (Larus spp.) at two locations on the Kenai Peninsula, Alaska, USA. Samples were screened for Escherichia coli (E. coli) and Klebsiella pneumoniae (K. pneumoniae) and tested for resistance to multiple antibiotics.Tracking Data for Three Large-bodied Gull Species and Hybrids (Larus spp.)
This metadata document describes the data contained in the "processedData" folder of this data package. This data package contains all data collected by the Argos System from 6 satellite transmitters attached to Glaucous-winged gulls on Middleton Island and 42 Argos-linked GPS satellite transmitters attached to three species of large-bodied gulls (genus Larus) and hybrids thereof, captured at landData for Continental-Scale Dispersal of Antimicrobial Resistant Bacteria by Alaska Landfill-Foraging Gulls
This data set includes information on collections of fecal samples from wild gulls (Larus spp.) at seven locations in Alaska, USA. Samples were screened for Escherichia coli (E. coli) and tested for resistance to multiple antibiotics.Sampling, Antimicrobial Resistance Testing, and Genomic Typing of Carbapenemase Producing E. coli in Gulls (Larus spp.) in Alaska, 2016
This data set includes information on collections of fecal samples from wild gulls (Larus spp.) at seven locations in Alaska, USA. Samples were screened for carbapenemase producing Escherichia coli (E. coli) and tested for resistance to multiple antibiotics.Sampling, antimicrobial resistance testing, and genomic typing of E. coli in gulls (Larus spp.) on the Kenai Peninsula, Alaska, 2016
This data set includes information on collections of fecal or cloacal samples from wild gulls (Larus spp.) at four locations on the Kenai Peninsula, Alaska, USA. Samples were also collected from sockeye salmon harvested as part of the personal-use fisheries on the Kenai and Kasilof Rivers. Samples were screened for Escherichia coli (E. coli) and tested for resistance to multiple antibiotics.Sampling and Resistance and Genomic Typing of Cephalosporin-resistant E. coli in Gulls (Larus spp.) and Bald Eagles (Haliaeetus leucocephalus) in Southcentral Alaska, 2016
This data set includes information on collections of fecal or cloacal samples from wild birds at a location in Alaska, USA. Samples were screened for Escherichia coli (E. coli) and tested for resistance to multiple antibiotics. - Multimedia
- Publications
Filter Total Items: 15
Environmental antimicrobial resistance gene detection from wild bird habitats using two methods: A commercially available culture-independent qPCR assay and culture of indicator bacteria followed by whole-genome sequencing
ObjectivesA variety of methods have been developed to detect antimicrobial resistance (AMR) in different environments to better understand the evolution and dissemination of this public health threat. Comparisons of results generated using different AMR detection methods, such as quantitative PCR (qPCR) and whole-genome sequencing (WGS), are often imperfect, and few studies have analysed samples iAuthorsChristina Ahlstrom, Laura Celeste Scott, Hanna Woksepp, Jonas Bonnedahl, Andrew M. RameyExchange of carbapenem-resistant Escherichia coli Sequence Type 38 intercontinentally and among wild bird, human, and environmental niches
Carbapenem-resistant Enterobacteriaceae (CRE) are a global threat to human health and are increasingly being isolated from nonclinical settings. OXA-48-producing Escherichia coli sequence type 38 (ST38) is the most frequently reported CRE type in wild birds and has been detected in gulls or storks in North America, Europe, Asia, and Africa. The epidemiology and evolution of CRE in wildlife and humAuthorsChristina Ahlstrom, Hanna Woksepp, Linus Sandegren, Andrew M. Ramey, Jonas BonnedahlAntibiotic resistance in free-ranging wildlife
In this chapter, we provide an overview of antimicrobial resistant (AMR) bacteria in wildlife through the presentation of general trends of occurrence among both captive and free-ranging wild animal populations, discussion of importance to human health and wildlife conservation, and identification of priority areas for future research and monitoring efforts. Once most commonly identified in humanAuthorsAndrew M. Ramey, Christina AhlstromMaintenance and dissemination of avian-origin influenza A virus within the northern Atlantic Flyway of North America
Wild waterbirds, the natural reservoirs for avian influenza viruses, undergo migratory movements each year, connecting breeding and wintering grounds within broad corridors known as flyways. In a continental or global view, the study of virus movements within and across flyways is important to understanding virus diversity, evolution, and movement. From 2015 to 2017, we sampled waterfowl from breeAuthorsDiann Prosser, Jiani Chen, Christina Ahlstrom, Andrew B. Reeves, Rebecca L. Poulson, Jeffery D. Sullivan, Daniel McAuley, Carl R. Callahan, Peter C. McGowan, Justin Bahl, David E. Stallknecht, Andrew M. RameyGenomically diverse carbapenem resistant Enterobacteriaceae from wild birds provide insight into global patterns of spatiotemporal dissemination
Carbapenem resistant Enterobacteriaceae (CRE) are a threat to public health globally, yet the role of the environment in the epidemiology of CRE remains elusive. Given that wild birds can acquire CRE, likely from foraging in anthropogenically impacted areas, and may aid in the maintenance and dissemination of CRE in the environment, a spatiotemporal comparison of isolates from different regions anAuthorsChristina Ahlstrom, Hanna Woksepp, Linus Sandegren, Mashkoor Mohsin, Badrul Hasan, Denys Muzyka, Jorge Hernandez, Filip Aguirre, Atalay Tok, Jan Söderman, Bjorn Olsen, Andrew M. Ramey, Jonas BonnedahlGenomic comparison of carbapenem-resistant Enterobacteriaceae from humans and gulls in Alaska
ObjectivesWildlife may harbor clinically important antimicrobial resistant (AMR) bacteria, but the role of wildlife in the epidemiology of AMR bacterial infections in humans is largely unknown. In this study, we aimed to assess dissemination of theblaKPC carbapenemase gene among humans and gulls in Alaska.MethodsWe performed whole genome sequencing to determine the genetic context ofblaKPC in bactAuthorsChristina Ahlstrom, Anna Frick, Catherine Pongratz, Kimberly Spink, Catherine Xavier, Jonas Bonnedahl, Andrew M. RameyEvidence for continental-scale dispersal of antimicrobial resistant bacteria by landfill-foraging gulls
Anthropogenic inputs into the environment may serve as sources of antimicrobial resistant bacteria and alter the ecology and population dynamics of synanthropic wild animals by providing supplemental forage. In this study, we used a combination of phenotypic and genomic approaches to characterize antimicrobial resistant indicator bacteria, animal telemetry to describe host movement patterns, and aAuthorsChristina Ahlstrom, Mariëlle L. van Toor, Hanna Woksepp, Jeffrey C Chandler, John Reed, Andrew B. Reeves, Jonas Waldenström, Alan B. Franklin, David C. Douglas, Jonas Bonnedahl, Andrew M. RameyComparative genomics and genomic epidemiology of mycobacterium avium subsp. paratuberculosis strains
Two phenotypically distinct strains of Mycobacterium avium subsp. paratuberculosis (MAP) were recognized in the 1930s but it was not until the introduction of restriction endonuclease analysis (REA) in the mid-1980s that these two strains, MAP-C and MAP-S, could be distinguished genetically. Since then, a plethora of molecular typing techniques has been applied to MAP isolates (reviewed by Li et aAuthorsKaren Stevenson, Christina AhlstromValidation of a screening method for the detection of colistin-resistant E. coli containing mcr-1 in feral swine feces
A method was developed and validated for the detection of colistin-resistant Escherichia coli containing mcr-1 in the feces of feral swine. Following optimization of an enrichment method using EC broth supplemented with colistin (1 µg/mL) and vancomycin (8 µg/mL), aliquots derived from 100 feral swine fecal samples were spiked with of one of five different mcr-1 positive E. coli strains (between 1AuthorsJeffrey C Chandler, Alan B. Franklin, Sarah N. Bevins, Kevin T Bentler, Jonas Bonnedahl, Christina Ahlstrom, Bledar Bisha, Susan A. ShrinerGulls as sources of environmental contamination by colistin-resistant bacteria
In 2015, the mcr-1 gene was discovered in Escherichia coli in domestic swine in China that conferred resistance to colistin, an antibiotic of last resort used in treating multi-drug resistant bacterial infections in humans. Since then, mcr-1 was found in other human and animal populations, including wild gulls. Because gulls could disseminate the mcr-1 gene, we conducted an experiment to assess whAuthorsAlan B. Franklin, Andrew M. Ramey, Kevin T Bentler, Nicole L Barret, Loredana M McCurdy, Christina Ahlstrom, Jonas Bonnedahl, Susan A. Shriner, Jeffrey C ChandlerAntibiotic resistant bacteria in wildlife: Perspectives on trends, acquisitions and dissemination, data gaps, and future directions
The proliferation of antibiotic resistant bacteria in the environment has potential negative economic and health consequences. Thus, previous investigations have targeted wild animals to understand the occurrence of antibiotic resistance in diverse environmental sources. In this critical review and synthesis, we summarize important concepts learned through the sampling of wildlife for antibioticAuthorsAndrew M. Ramey, Christina AhlstromEarly emergence of mcr-1-positive Enterobacteriaceae in gulls from Spain and Portugal
We tested extended‐spectrum β‐lactamase producing bacteria from wild gulls (Larusspp.) sampled in 2009 for the presence of mcr‐1. We report the detection of mcr‐1 and describe genome characteristics of four Escherichia coli and one Klebsiella pneumoniaeisolate from Spain and Portugal that also exhibited colistin resistance. Results represent the earliest evidence for colistin‐resistant bacteria inAuthorsChristina Ahlstrom, Andrew M. Ramey, Hanna Woksepp, Jonas BonnedahlNon-USGS Publications**
Muellner, U., G. Fournie, P. Muellner, C. A. Ahlstrom, and D. U. Pfeiffer. 2018. Epidemix - an Interactive Multi-Model Application for Teaching and Visualizing Infectious Disease Transmission. Epidemics 23:49-54. doi:10.1016/j.epidem.2017.12.003.Ahlstrom, C. A., P. Muellner, G. Lammers, M. Jones, S. Octavia, R. Lan, and J. Heller. 2017. Shiga-toxin producing E. coli O157 shedding dynamics in an Australian beef herd. Frontiers in Veterinary Science 4:200. doi:10.3389/fvets.2017.00200.Ahlstrom, C. A., C. S. Manuel, H. C. Den Bakker, M. Wiedmann, and K. K. Nightingale. 2017. Molecular Ecology of Listeria spp., Salmonella, Escherichia coli O157:H7, and non-O157 Shiga Toxin Producing Escherichia coli in Pristine Natural Environments in Northern Colorado. Journal of Applied Microbiology. doi:10.1111/jam.13657.Ahlstrom, C. A., P. Muellner, S. Spencer, S. Hong, A. Saupe, A. Rovira, C. Hedberg, A. Perez, and J. Alvarez. 2017. Inferring source attribution from a multi-year multi-source dataset of Salmonella in Minnesota. Zoonoses and Public Health 64(8):589-598. doi:10.1111/zph.12351.Bauman, C. A., A. Jones-Bitton, C. A. Ahlstrom, L. Mutharia, J. De Buck, J. Jansen, D. F. Kelton, and P. Menzies. 2017. Identification of Mycobacterium avium ssp. paratuberculosis strains isolated from dairy goats and dairy sheep in Ontario, Canada. Canadian Journal of Veterinary Research 81(4):304-307.Hong, S., A. Rovira, P. Davies, C. A. Ahlstrom, P. Muellner, A. Rendahl, K. Olsen, J. B. Bender, S. Wells, A. Perez, and J. Alvarez. 2016. Serotypes and antimicrobial resistance in Salmonella enterica recovered from clinical samples from cattle and swine in Minnesota, 2006 to 2015. International Journal of Parasitology: Parasites and Wildlife 11(12):e0168016. doi:10.1371/journal.pone.0168016.Muellner, P., U. Muellner, M. C. Gates, T. Pearce, C. A. Ahlstrom, D. O'Neill, D. Brodbelt, and N. J. Cave. 2016. Evidence in Practice – A Pilot Study Leveraging Companion Animal and Equine Health Data from Primary Care Veterinary Clinics in New Zealand. Frontiers in Veterinary Science 3:116. doi:10.3389/fvets.2016.00116.Davidson, F., C. A. Ahlstrom, J. De Buck, H. G. Whitney, and K. Tahlan. 2016. Examination of Mycobacterium avium subspecies paratuberculosis mixed genotype infections in dairy animals using a whole genome sequencing approach. PeerJ 4:e2793. doi:10.7717/peerj.2793.Ahlstrom, C. A., H. W. Barkema, and J. De Buck. 2016. Relative frequency of 4 major strain types of Mycobacterium avium ssp. paratuberculosis in Canadian dairy herds using a novel single nucleotide polymorphism-based polymerase chain reaction. Journal of Dairy Science 99(10):8297-8303. doi:10.3168/jds.2016-11397.Ahlstrom, C. A., H. W. Barkema, K. Stevenson, R. N. Zadoks, R. Biek, R. Kao, H. Trewby, D. Haupstein, D. F. Kelton, G. Fecteau, O. Labrecque, G. P. Keefe, S. L. B. McKenna, K. Tahlan, and J. De Buck. 2016. Genome-wide diversity and phylogeography of Mycobacterium avium subsp. paratuberculosis in Canadian dairy cattle. PLoS One 11:e0149017. doi:10.1371/journal.pone.0149017.Ahlstrom, C. A., H. W. Barkema, K. Stevenson, R. N. Zadoks, R. Biek, R. Kao, H. Trewby, S. Hendrick, D. Haupstein, D. F. Kelton, G. Fecteau, O. Labrecque, G. P. Keefe, S. L. B. McKenna, and J. De Buck. 2015. Limitations of variable number of tandem repeat typing identified through whole genome sequencing of Mycobacterium avium subsp. paratuberculosis on a national and herd level. BMC Genomics 16:161. doi:10.1186/s12864-015-1387-6.Den Bakker, H. C., S. Warchocki, E. M. Wright, A. F. Allred, C. A. Ahlstrom, C. S. Manuel, M. J. Stasiewicz, A. Burrell, S. Roof, L. Strawn, E. D. Fortes, K. K. Nightingale, D. Kephart, and M. Wiedmann. 2014. Listeria floridensis sp. nov., Listeria aquatica sp. nov., Listeria cornellensis sp. nov., Listeria riparia sp. nov., and Listeria grandensis sp. nov., from agricultural and natural environments. International Journal of Systematic and Evolutionary Microbiology 64:1882-1889. doi:10.1099/ijs.0.052720-0.Ahlstrom, C. A., H. W. Barkema, and J. De Buck. 2014. Improved Short-Sequence-Repeat Genotyping of Mycobacterium avium subsp. paratuberculosis by Using Matrix-Assisted Laser Desorption Ionization—Time of Flight Mass Spectrometry. Applied and Environmental Microbiology 80:534-539. doi:10.1128/AEM.03212-13.Zadoks, R. N., H. M. Griffiths, M. A. Munoz, C. A. Ahlstrom, G. J. Bennett, E. Thomas, and Y. H. Schukken. 2011. Sources of Klebsiella and Raoultella species on dairy farms: be careful where you walk. Journal of Dairy Science 94(2):1045-1051. doi:10.3168/jds.2010-3603.Munoz, M. A., G. J. Bennett, C. A. Ahlstrom, H. M. Griffiths, Y. H. Schukken, and R. N. Zadoks. 2008. Cleanliness Scores as Indicator of Klebsiella Exposure in Dairy Cows. Journal of Dairy Science 91(10):3908-3916. doi:10.3168/jds.2008-1090.Munoz, M. A., C. A. Ahlstrom, B. J. Rauch, and R. N. Zadoks. 2006. Fecal Shedding of Klebsiella pneumoniae by Dairy Cows. Journal of Dairy Science 89(9):3425-3430. doi:10.3168/jds.S0022-0302(06)72379-7.Muellner, P., D. Hodges, C. A. Ahlstrom, M. Newman, R. Davidson, D. U. Pfeiffer, J. Marshall, and C. Morley. 2018. Creating a framework for the prioritization of biosecurity risks to the New Zealand dairy industry. Transboundary and Emerging Diseases 65(4):1067-1077. doi:10.1111/tbed.12848.**Disclaimer: The views expressed in Non-USGS publications are those of the author and do not represent the views of the USGS, Department of the Interior, or the U.S. Government.