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Title: Characterization of a Neochlamydia-like bacterium associated with epitheliocystis in cultured Arctic charr Salvelinus alpinus

Author
item DRAGHI, II, ANDREW - STUDENT-UNIV. CONNECTICUT
item Bebak, Julie
item POPOV,, VSEVOLOD - UNIV. TEXAS MED. BRANCH
item NOBLE, ALICIA - FRESHWATER INSTITUTE
item GEARY, STEVEN - UNIV. OF CONNECTICUT
item WEST, A. BRIAN - UNIV. OF CONNECTICUT
item BYRNE, PHILIP - FISH. & OCEANS CANADA
item FRASCA, JR., SALVATORE - UNIV. OF CONNECTICUT

Submitted to: Diseases of Aquatic Organisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/28/2006
Publication Date: 6/7/2007
Citation: Draghi, Ii, A., Bebak, J.A., Popov,, V.L., Noble, A.C., Geary, S.J., West, A., Byrne, P., Frasca, Jr., S. 2007. Characterization of a Neochlamydia-like bacterium associated with epitheliocystis in cultured Arctic charr Salvelinus alpinus. Diseases of Aquatic Organisms. 76:27-38.

Interpretive Summary: The gill disease, epitheliocystis, has limited production of Arctic char (Salvelinus alpinus). To characterize a bacterium associated with epitheliocystis in cultured char, gills were sampled for histopathologic and ultrastructural examination, and molecular assay, during outbreaks of epitheliocystis at the Freshwater Institute (Shepherdstown, WV) in April and May 2002. Results indicated, with a high degree of confidence, that the bacterium was a Neochlamydia species in the Order Chlamydiales. This is the first molecular characterization of a chlamydia associated with epitheliocystis in Arctic char and the fourth Neochlamydia spp. sequence to be associated with epitheliocystis. Presence of a clinical neochlamydial sequence, first identified from a cat, in Arctic char suggests a possible mammalian and piscine host range for some environmental chlamydiae.

Technical Abstract: Infections of branchial epithelium by intracellular gram-negative bacteria, termed epitheliocystis, have limited culture of Arctic char (Salvelinus alpinus). To characterize a bacterium associated with epitheliocystis in cultured char, gills were sampled for histopathologic examination, conventional and immunoelectron microscopy, in situ hybridization, 16S ribosomal DNA (rDNA) amplification, sequence analysis and phylogenetic inference. Sampling was conducted at the Freshwater Institute (Shepherdstown, WV) during outbreaks of epitheliocystis in April and May 2002. Granular, basophilic, cytoplasmic inclusions in char gill were shown to stain with Macchiavello, Lendrum’s phloxine-tartrazine and Gimenez histochemical techniques. Ultrastructurally, inclusions were membrane-bound and contained round to elongate reticulate bodies that were immunoreactive to an antibody against chlamydial lipopolysaccharide, suggesting the presence of similar epitopes. DNA extracted from gills supported amplification of the most polymorphic and phylogenetically relevant region of the 16S rRNA gene, which had 97 to 100% identity with several uncultured clinical Neochlamydia spp. (Order Chlamydiales) clones WB13 (AY225593.1) and WB258 (AY225594.1). Sequence-specific riboprobes localized to inclusions during in situ hybridization experiments. Taxonomic affiliation was inferred by distance- and parsimony-based phylogenetic analyses of the 16S sequence, which branched with Neochlamydia hartmannellae in the Order Chlamydiales with high confidence. This is the first molecular characterization of a chlamydia associated with epitheliocystis in Arctic char and the fourth Neochlamydia spp. sequence to be associated with epitheliocystis. Presence of a clinical neochlamydial sequence, first identified from a cat, in Arctic char suggests a possible mammalian and piscine host range for some environmental chlamydiae.