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Journal of Clinical Microbiology, November 2004, p. 5286-5297, Vol. 42, No. 11
0095-1137/04/$08.00+0 DOI: 10.1128/JCM.42.11.5286-5297.2004
Copyright © 2004, American Society for Microbiology. All Rights Reserved.
James B. Stanton,3,
Corrie C. Brown,3
Gregory J. Tsongalis,4
A. Brian West,5 and
Salvatore Frasca Jr.1*
Department of Pathobiology and Veterinary Science, University of Connecticut, Storrs, Connecticut,1 Electron Microscopy Laboratory, Department of Pathology, The University of Texas Medical Branch, Galveston, Texas,2 Department of Pathology, College of Veterinary Medicine, University of Georgia, Athens, Georgia,3 Department of Pathology, Dartmouth-Hitchcock Medical Center, Lebanon, New Hampshire,4 Department of Pathology, New York University Medical Center, New York, New York5
Received 16 March 2004/ Returned for modification 27 May 2004/ Accepted 5 July 2004
To characterize intracellular gram-negative bacteria associated with epitheliocystis in farmed Atlantic salmon (Salmo salar), gills with proliferative lesions were collected for histopathology, conventional transmission and immunoelectron microscopy, in situ hybridization, and DNA extraction during epitheliocystis outbreaks in Ireland and Norway in 1999 and 2000, respectively, and compared by ultrastructure and immunoreactivity to nonproliferative gills from Ireland archived in 1995. Genomic DNA from proliferative gills was used to amplify 16S ribosomal DNA (rDNA) for molecular phylogenetic analyses. Epitheliocystis inclusions from proliferative gills possessed variably elongate reticulate bodies, examples of binary fission, and vacuolated and nonvacuolated intermediate bodies, whereas inclusions in nonproliferative gills had typical chlamydial developmental stages plus distinctive head-and-tail cells. Immunogold processing using anti-chlamydial lipopolysaccharide antibody labeled reticulate bodies from proliferative and nonproliferative gills. 16S rDNA amplified directly from Irish (1999) and Norwegian (2000) gill samples demonstrated 99% nucleotide identity, and riboprobes transcribed from cloned near-full-length 16S rDNA amplicons from Norwegian gills hybridized with inclusions in proliferative lesions from Irish (1999) and Norwegian (2000) sections. A 1,487-bp consensus 16S rRNA gene sequence representing the chlamydia-like bacterium (CLB) from proliferative gills had the highest percent nucleotide identity with endosymbionts of Acanthamoeba spp. (order Chlamydiales). Molecular phylogenetic relationships inferred from 16S rRNA gene sequences using distance and parsimony indicated that the CLB from proliferative gills branched with members of the order Chlamydiales. "Candidatus Piscichlamydia salmonis" is proposed for the CLB associated with epitheliocystis from proliferative gills of Atlantic salmon, which exhibits developmental stages different from those identified in nonproliferative gills.
Present address: Department of Veterinary Pathobiology, Texas A&M University, College Station, Texas.
Present address: Department of Veterinary Microbiology and Pathology, Washington State University, Pullman, Washington.
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