Identification of ‘Candidatus Piscichlamydia salmonis’ in Arctic charr Salvelinus alpinus during a survey of charr production facilities in North America

Abstract

Arctic charr Salvelinus alpinus production facilities, nonproduction water sources and effluents in the United States and Canada were sampled to determine if chlamydiae associated with epitheliocystis were present in water and were associated with inclusions of epitheliocystis in gill tissue. Gills from 607 fish from 13 sites were processed for histopathologic examination and DNA extraction. Water was collected from 21 locations for DNA testing. Eighteen fish from one location had inclusions of epitheliocystis with proliferative and inflammatory gill lesions. Inclusions were stained using the Gimenez technique and, at the ultrastructural level, consisted of intracytoplasmic membrane-bound vacuoles containing reticulate and intermediate bodies in a fibrillar matrix. PCR using Order Chlamydiales-specific primers performed on DNA extracts from 12 of 13 infected fish yielded amplicons that were identical to (GQ302988) or differed at one base from (GQ302987) the 16S ribosomal RNA gene signature sequence of 'Candidatus Piscichlamydia salmonis', which is the chlamydia that was previously identified in epitheliocystis inclusions of farmed Atlantic salmon. In situ hybridization using a ~1.5 kb riboprobe corresponding to the 'Candidatus Piscichlamydia salmonis' 16S rRNA genetic sequence (AY462244) confirmed its presence within Arctic charr gill inclusions. DNA isolated from water samples was tested by Chlamydiales-specific PCR and yielded 54 partial 16S rRNA genetic sequences spanning the signature region; however, no 16S rRNA genetic sequences associated with epitheliocystis were identified. This is the first report of 'Candidatus Piscichlamydia salmonis' associated with epitheliocystis in Arctic charr, the first identification of 'Candidatus Piscichlamydia salmonis' from a freshwater production location, and the first reported occurrence in North America.

Molecular Characterization of “Candidatus Similichlamydia latridicola” gen. nov., sp. nov. (Chlamydiales: “Candidatus Parilichlamydiaceae”), a Novel Chlamydia-Like Epitheliocystis Agent in the Striped Trumpeter, Latris lineata (Forster)

“…Epithelial hyperplasia, epithelial lifting along the lamellae, and lamellar fusion in the striped trumpeter were observed, although the filling of the interlamellar spaces was not as severe as that in previous reports. This differs from the nearly complete filling of the interlamellar spaces reported in both the largemouth bass (28) and the Arctic charr (15,27), which resulted in a severely compromised respiratory system. Striped trumpeter fish were recently reported to be affected by epitheliocystis (6).…”

“…Epitheliocystis is now known to affect Ͼ80 different species of fish (7,10), and intriguingly, from all of these reports, it appears that the host responses considered to be severe or as having a hyperinfection are all from farmed fish (14)(15)(16)(27)(28)(29)(30)(31)(32). Molecular diagnostics confirmed that this CLO, from both cultured and wild sources, is a member of the order Chlamydiales, based on the Ͼ80% sequence similarity to other species in the order (18).…”

“…Piscichlamydia salmonis" from the Atlantic salmon (accession no. AY462244 [25] and EU326495 [26]) and the Arctic charr (GQ302987 [27]). …”

Microbial and pathological findings in farmed Atlantic salmon Salmo salar with proliferative gill inflammation

“…These results confirm a recent report that 'Ca. P. salmonis' is not restricted to seawater (Draghi et al 2010). No conclusions can be made at this stage regarding the possible contribution of freshwater infections of either 'Ca.…”

Molecular Characterization of “Candidatus Parilichlamydia carangidicola,” a Novel Chlamydia-Like Epitheliocystis Agent in Yellowtail Kingfish, Seriola lalandi (Valenciennes), and the Proposal of a New Family, “Candidatus Parilichlamydiaceae” fam. nov. (Order Chlamydiales)

“…This agrees with previous reports for the molecular description of "Ca. Piscichlamydia salmonis" in Atlantic salmon (24,47) and Neochlamydia-like bacteria in Arctic charr (14).…”