title: Molecular identification of a bronopol tolerant strain of Saprolegnia australis causing egg and fry mortality in farmed brown trout, Salmo trutta.
abstract: Some species of the genus Saprolegnia, such as Saprolegnia diclina and Saprolegnia ferax are responsible for devastating infections on salmonid eggs. Members of this group cause saprolegniasis, a disease resulting in considerable economic losses in aquaculture. Although both S. diclina and S. ferax have received much attention, the role of other Saprolegnia species in infecting fish eggs is less known. For this purpose, we have investigated the aetiology of chronic egg mortality events occurring in farmed brown trout, Salmo trutta. A total of 48 isolates were obtained from eggs with signs of infection as well as from water samples. A molecular analysis based on nrDNA internal transcribed spacer (ITS) operational taxonomic units indicated that the majority of the isolates correspond to Saprolegnia australis. All isolates of S. australis exhibited the same random amplified polymorphic DNA (RAPD) band patterns suggesting that a single strain is implicated in egg infections. The isolates followed Koch postulates using trout eggs and fry. Under standard concentrations of bronopol commonly used in farms, these isolates could grow, but not sporulate. However, both growth and sporulation were recovered when treatment was removed. This study shows that S. australis can infect and kill salmon eggs, and helps in defining oomycetes core pathogens.
authors.affiliation: Department of Mycology, Real Jardín Botánico CSIC, Plaza Murillo 2, 28014 Madrid, Spain.
authors.forename: Svetlana
authors.initials: S
authors.lastname: Rezinciuc
authors.affiliation: Department of Mycology, Real Jardín Botánico CSIC, Plaza Murillo 2, 28014 Madrid, Spain.
authors.forename: Jose-Vladimir
authors.initials: JV
authors.lastname: Sandoval-Sierra
authors.affiliation: Department of Mycology, Real Jardín Botánico CSIC, Plaza Murillo 2, 28014 Madrid, Spain. Electronic address: dieguez@rjb.csic.es.
authors.forename: Javier
authors.initials: J
authors.lastname: Diéguez-Uribeondo
mesh_terms: D000818:Animals; D000890:Anti-Infective Agents / Q000494:pharmacology*; D016000:Cluster Analysis; D021903:DNA, Ribosomal Spacer / Q000737:chemistry / Q000235:genetics; D004361:Drug Tolerance; D005393:Fish Diseases / Q000469:parasitology; D007239:Infections / Q000469:parasitology / Q000662:veterinary; D008969:Molecular Sequence Data; D010802:Phylogeny; D011409:Propylene Glycols / Q000494:pharmacology*; D019105:Random Amplified Polymorphic DNA Technique; D012487:Salmonidae / Q000469:parasitology*; D044762:Saprolegnia / Q000145:classification* / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D017422:Sequence Analysis, DNA; D015053:Zygote / Q000469:parasitology
chemical_list: D000890:Anti-Infective Agents; D021903:DNA, Ribosomal Spacer; D011409:Propylene Glycols; C006827:bronopol
keywords: Aquaculture; ITS nrDNA; Oomycetes; Pathogen; RAPD