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Diseases of Aquatic Organisms

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DAO 57:1-9 (2003)  -  doi:10.3354/dao057001

Isolation and characterization of novel Helicobacter spp. from the gastric mucosa of harp seals Phoca groenlandica

Claudia G. Harper1, Shilu Xu1, Arlin B. Rogers1, Yan Feng1, Zeli Shen1, Nancy S. Taylor1, Floyd E. Dewhirst2,3, Bruce J. Paster2,3, Melissa Miller4, Jenifer Hurley5, James G. Fox1,*

1Division of Comparative Medicine, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Building 16, Room 825C, Cambridge, Massachusetts 02139, USA
2Department of Molecular Genetics, Forsyth Institute, Boston, Massachusetts 02115, USA
3Department of Oral and Developmental Biology, Harvard School of Dental Medicine, Boston, Massachusetts 02115, USA
4Department of Fish and Game and University of California Davis, Marine Wildlife Veterinary Care and Research Center, Santa Cruz, California 95060, USA
5California State University, Moss Landing Marine Laboratory, Moss Landing, California 95039, USA
*Corresponding author. Email:

ABSTRACT: Since the recent discovery of Helicobacter cetorum in cetaceans and its role in the development of gastritis, speculation has existed as to whether pinnipeds have Helicobacter spp. associated gastritis and peptic ulcer disease. The gastric mucosa of 4 stranded harp seals Phoca groenlandica from the Massachusetts coastline were assessed for Helicobacter spp. by culture and PCR. We cultured 2 novel Helicobacter spp. from the pyloric antrum of 1 of the 4 harp seals studied, and identified these by PCR in 2 of the 4 seals. Both gram-negative bacterial isolates were catalase- and oxidase-positive. However, a fusiform helicobacter with flexispira morphology was urease-positive, and a spiral-shaped helicobacter was urease-negative. Slender, spiral and fusiform-shaped bacteria were detected in the gastric mucosa by the Warthin-Starry stain. Histopathologic analysis revealed mild diffuse lymphoplasmacytic gastritis within the superficial mucosa of the pyloric antrum of both infected seals. The 2 bacterial isolates were classified by 16S rRNA analysis; they clustered with other enteric helicobacters and represent 2 novel Helicobacter spp. The urease-negative bacterial isolate clustered with H. canis and the urease-positive isolate clustered with an isolate from a sea lion and isolates from sea otters. This cluster of pinniped isolates has 97% similarity to a number of Helicobacter species, but appears to be most closely related to other helicobacters with flexispira morphology. These findings suggest that the novel Helicobacter spp. may play a role in the etiopathogenesis of gastrointestinal diseases in pinnipeds. To our knowledge, this represents the first isolation and characterization of a novel Helicobacter spp. from pinnipeds.

KEY WORDS: Harp seal · Pinniped · Helicobacter infection · Gastritis · Cryptosporidium

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