Antimicrobial Susceptibility of Bacterial Isolates from Sea Otters: One Health
American Association of Zoo Veterinarians Conference 2010

David A. Jessup1, DVM, MPVM, DACZM; Deborah Brownstein1, BS; Melissa A. Miller1, MS, DVM, PhD; Barbara A. Byrne2, DVM, PhD; Spencer Jang3; Michael J. Murray4, DVM

1Marine Wildlife Veterinary Care and Research Center, California Department of Fish and Game, Santa Cruz, CA, USA; 2Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California-Davis, Davis, CA, USA; 3William R. Pritchard Teaching Hospital, School of Veterinary Medicine, University of California-Davis, Davis, CA, USA; 4Monterey Bay Aquarium, Monterey, CA, USA

Read the Spanish translation: Susceptiblidad Antimicrobiana de Aislados Bacterianos de Nutrias Marinas: Una Salud


Despite decades of legal protection, southern sea otter (Enhydra lutris nereis) population recovery has been hindered by high mortality, including deaths of prime-aged adult animals. Up to 50% of sea otter mortality has been attributed to intoxications and infection by bacteria and parasites.3,7 Potentially pathogenic enteric bacteria appear to be more prevalent along urbanized coastlines and near river mouths, suggesting that land-sea pathogen spread may be an important component of exposure to some bacterial species (Miller et al. 2010).5 Some aspects of sea otter biology may make them especially vulnerable to infection by bacterial contaminants in polluted runoff. They feed near shore, often within or adjacent to coastal surface water plumes,4,5 may rest and forage in sheltered embayments near human population centers,2 display intraspecific aggression that often culminates in soft tissue trauma and sustained stress, and they consume large amounts of filter-feeding invertebrate prey that can bioconcentrate pathogens, including bacteria6.

Antibiotics are an important therapeutic tool for management of bacterial infections in stranded sea otters and for prevention of infection following invasive procedures in free-ranging otters. In the current study, susceptibility to commonly used antibiotics was determined for 126 isolates of 15 bacterial species or groups, from necropsied, live-stranded, and apparently healthy wild sea otters examined between 1998 and 2005. These isolates included both gram-positive and gram-negative strains of known pathogens, opportunistic pathogens, and environmental flora, including bacterial species with proven zoonotic potential.

Sea otters are a superb marine sentinel species whose site fidelity and other characteristics allow identification of local sources of pollution that can affect the health of humans, domestic animals and other wildlife.1 Results of this study point to potential sources of zoonotic infections in near shore waters heavily used for recreation and should help optimize selection of appropriate antibiotics for treatment of bacterial infections of sea otters, other marine species and humans in contact with them. Minimal evidence of antimicrobial resistance and no strains with unusual or clinically significant multiple-drug resistance patterns were identified in this study. An increasing body of evidence suggest that recovery of sea otter populations in California may be dependent on mitigating a number of types and sources of pollution, including bacterial pathogens, and that they provide an excellent example of how the “One Health” concept may help bring about positive changes.

Literature Cited

1.  Jessup, D.A., M. Miller, J. Ames, M. Harris, P. Conrad C. Kreuder and J.A.K. Mazet. 2004. The southern sea otter (Enhydra lutris nereis) as a sentinel of marine ecosystem health. Ecol Health. 1:239–245.

2.  Jessup, D., M. Miller, C. Kreuder-Johnson, P. Conrad, T. Tinker, J. Estes, and J. Mazet. 2007. Sea otters in a dirty ocean. J Am Vet Med Assoc. 231:11;1648–1652.

3.  Kreuder, C., M.A. Miller, D.A. Jessup, L.J. Lowenstine, M.D. Harris, J.A. Ames, T.E. Carpenter, P.A. Conrad and J.A.K. Mazet. 2003. Patterns of mortality in southern sea otters (Enhydra lutris nereis) from 1998–2001. J Wildl Dis. 39:495–509.

4.  Miller, M.A., I. Gardener, C. Kreuder, D. Paradies, K. Worcester, D. Jessup, E. Dodd, M. Harris, J. Ames, A. Packham, and P. Conrad. 2002. Coastal freshwater runoff is a risk factor for Toxoplasma gondii infection of southern sea otters (Enhydra lutris nereis). Int J Parasit. 32:997–1006.

5.  Miller M., B.A. Byrne, S.S. Jang, E.M. Dodd, E. Dorfmeier, M.D. Harris, J. Ames, D. Paradies, K. Worcester, D.A. Jessup, and W.A. Miller. 2010. Enteric bacterial pathogen detection in southern sea otters (Enhydra lutris nereis) is associated with coastal urbanization and freshwater runoff. Vet Res. 41:01.

6.  Miller W.A., M.A. Miller, I.A. Gardner, E.R. Atwill, B.A. Byrne, S. Jang, M. Harris, J. Ames, D. Jessup, D. Paradies, K. Worcester, A. Melli, and P. Conrad. 2006. Salmonella spp., Vibrio spp., Clostridium perfringens and Plesiomonas shigelloides in freshwater and marine invertebrates from coastal California ecosystems. Microb Ecol. 52:198–206.

7.  Thomas, N.J., and R.A. Cole. 1996. The risk of disease and threats to the wild population. Endangered Species Update. 13:23–27.


Speaker Information
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David A. Jessup, DVM, MPVM, DACZM
Marine Wildlife Veterinary Care and Research Center
California Department of Fish and Game
Santa Cruz, CA, USA

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