A taxonomic characterization was carried out on strains of the bacteria that cause the brown ring disease of clams. On the basis of their phenotypic and genotypic characteristics, these strains can be considered to constitute a new taxonomic unit, distinct from other Ebrio species. The guanine-plus-cytosine content of the strains ranged between 42.9 and 45.5 mol% (43.2 mol% for the proposed type strain). DNA-DNA hybridization studies showed 100% intragroup relatedness, but levels of genetic relatedness to the reference strains of different Ebrio species tested ranged between 15 and 58%. The strains have all the properties characteristic of the genus vibrio and can be clearly differentiated from other species of this genus by their growth at 4°C and their negative responses for growth at 30°C and in 6% NaCl, arginine dehydrolase, lysine decarboxylase, ornithine decarboxylase, and Voges-Proskauer reaction. The name yibrio tapetis is proposed for the new species; strain B1090 (CECT 4600) is the type strain.Since 1980, the genus Vibrio has been subject to an extensive taxonomic revision, and 15 new species have been described (12,22). At present, the genus Vibrio includes more than 35 species, most of which are of aquatic origin. Some of them have been demonstrated to be pathogenic for aquatic animals, including fish (Vibrio anguillarum, V. alginolyticus, K damsela, K Jischeri, K ordalii, K salmonicida, V. splendidus, and I/: vulniJicus) and shellfish (V. haweyi, K pelagtus, K splendidus, and

Lymphocystis disease is a geographically widespread disease affecting more than 150 different species of marine and freshwater fish. The disease, provoked by the iridovirus lymphocystis disease virus (LCDV), is characterized by the appearance of papillomalike lesions on the skin of affected animals that usually self-resolve over time. Development of the disease is usually associated with several environmental factors and, more frequently, with stress conditions provoked by the intensive culture conditions present in fish farms. In gilthead sea bream (Sparus aurata), an economically important cultured fish species in the Mediterranean area, a distinct LCDV has been identified but not yet completely characterized. We have used direct sequencing of the virome of lymphocystis lesions from affected S. aurata fish to obtain the complete genome of a new LCDV-Sa species that is the largest vertebrate iridovirus sequenced to date. Importantly, this approach allowed us to assemble the full-length circular genome sequence of two previously unknown viruses belonging to the papillomaviruses and polyomaviruses, termed Sparus aurata papillomavirus 1 (SaPV1) and Sparus aurata polyomavirus 1 (SaPyV1), respectively. Epidemiological surveys showed that lymphocystis disease was frequently associated with the concurrent appearance of one or both of the new viruses. SaPV1 has unique characteristics, such as an intron within the L1 gene, and as the first member of the Papillomaviridae family described in fish, provides evidence for a more ancient origin of this family than previously thought. IMPORTANCELymphocystis disease affects marine and freshwater fish species worldwide. It is characterized by the appearance of papillomalike lesions on the skin that contain heavily enlarged cells (lymphocysts). The causative agent is the lymphocystis disease virus (LCDV), a large icosahedral virus of the family Iridoviridae. In the Mediterranean area, the gilthead sea bream (Sparus aurata), an important farmed fish, is frequently affected. Using next-generation sequencing, we have identified within S. aurata lymphocystis lesions the concurrent presence of an additional LCDV species (LCDV-Sa) as well as two novel viruses. These are members of polyomavirus and papillomavirus families, and here we report them to be frequently associated with the presence of lymphocysts in affected fish. Because papillomaviruses have not been described in fish before, these findings support a more ancient origin of this virus family than previously thought and evolutionary implications are discussed. L ymphocystis is a widely distributed disease affecting over 150 different marine and freshwater fish species (1). It was initially described during the 19th century and is characterized by the appearance of papillomalike lesions on the skin and fins, which develop over prolonged periods of time ranging from weeks to months. Occasionally, lesions on internal organs have been described, but the condition is rarely life-threatening and the outgrowths usually self-r...

The in vivo and in vitro toxicity of bacterial cells and their extracellular products (ECPs) from 16 strains of Photobacterium damselae subsp. damselae isolated from 7 epizootic outbreaks were evaluated. On the basis of their 50% lethal dose (LD 50 ) values (about 1 × 10 5 CFU), these strains may be considered as moderately virulent. However, their ECPs were strongly lethal for redbanded seabream Pagrus auriga causing fish death within 2 h post-inoculation (protein concentration ranged between 2.1 and 6.41 µg g -1 fish). The bacterial ECPs tested exhibited several enzymatic activities, such as amylase, lipase, phospholipase, alkaline phosphatase, esterase-lipase, acid phosphatase, and β-glucosaminidase. These ECPs displayed a strong cytotoxic effect on 4 fish and 2 mammalian cell lines, although this activity disappeared when ECPs were heated at 100°C. The virulence of the strains tested could not be related to the hemolytic activity or to the production of the toxin damselysin. Therefore, another unknown type of toxin could play an important role in the virulence mechanisms of this bacterial pathogen.KEY WORDS: Toxicity · ECP · Photobacterium damselae subsp. damselae · Cultured marine fish Resale or republication not permitted without written consent of the publisherDis Aquat Org 92: [31][32][33][34][35][36][37][38][39][40] 2010 brane, has been described (Kreger 1984, Kothary & Kreger 1985, Kreger et al. 1987. In addition, a relationship between the degree of virulence and the hemolytic activity has been demonstrated in P. damselae subsp. damselae strains isolated from fish (Fouz et al. 1993). However, Cutter & Kreger (1990) found that not all the P. damselae subsp. damselae strains presented the damselysin gene (dly), but only those strains showing intense hemolytic activity. A further study demonstrated that the presence of this gene was not correlated to the virulence in mice and fish of 17 P. damselae subsp. damselae strains isolated from different sources (Osorio et al. 2000).The extracellular products (ECPs) are produced by bacterial pathogens to facilitate the uptake of nutrients from the surrounding environment, and/or for the successful penetration and survival of pathogens inside the host (Bakopoulos et al. 2003). However, the role of ECPs in the pathogenesis of Photobacterium damselae subsp. damselae in fish is poorly known, which is a considerable disadvantage for the development of vaccines and vaccine strategies, since it has been suggested that the ECP components are major antigenic compounds of several vaccine formulations (Collado et al. 2000, Bakopoulos et al. 2004.The aim of this study was to determine the toxicity of different Photobacterium damselae subsp. damselae strains isolated from cultured diseased fish. For this purpose, we performed in vivo and in vitro assays using bacterial cultures and their ECPs. In addition, the enzymatic activities of the ECPs and their cytotoxicity in fish and mammalian cell lines were compared. MATERIALS AND METHODSBacterial strains. In this...

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Brown Ring Disease (BRD) is a bacterial disease caused by Vibrio tapetis which affects cultured clams and causes heavy economic losses. In this study, 28 V. tapetis strains isolated from 5 different hosts were intraspecifically characterized by 3 different polymerase chain reaction-(PCR-) based typing methods: enterobacteria repetitive intergenic consensus (ERIC)-PCR, repetitive extragenic palindromic (REP)-PCR and randomly amplified polymorphic DNA (RAPD)-PCR. Cluster analysis of genetic profiles obtained from these molecular techniques clearly showed the existence of 3 genetic groups strongly correlated to the host origin. The first group was formed by 23 V. tapetis strains isolated from Manila clam Ruditapes philippinarum, 1 isolated from venus clam Venerupis aurea, and 1 isolated from common cockle Cerastoderma edule, all collected from France and Spain. The second group was formed by 2 strains isolated from carpet-shell clam R. decussatus cultured in the northwest of Spain. The third group was composed of 1 strain isolated from Atlantic halibut Hippoglossus hippoglossus from the UK. We concluded that the 3 typing methods based on PCR were useful for the intraspecific typing of V. tapetis strains, and that they can potentially be used as a fast and reliable tool for epidemiological studies in the future. KEY WORDS: Vibrio tapetis · RAPD · ERIC-PCR · REP-PCR · Typing Resale or republication not permitted without written consent of the publisherDis Aquat Org 69: [175][176][177][178][179][180][181][182][183] 2006 demonstrated some genetic variations among V. tapetis strains (Castro et al. 1997, Romalde et al. 2002, Chevalier et al. 2003.Repetitive element PCR is a group of techniques that generates DNA fingerprints which can be utilized for the discrimination of bacterial species and/or strains (Versalovic et al. 1991(Versalovic et al. , 1994. These methods involve the application of oligonucleotide primers based on families of short, highly conserved extragenic repetitive sequences, including the repetitive extragenic palindromic (REP) and the enterobacterial repetitive intergenic consensus (ERIC) sequences (Stern et al. 1984, Hulton et al. 1991. REP and ERIC sequences are present in species throughout the Enterobacteriaceae family (Versalovic et al. 1991, Bachellier et al. 1999. The use of appropriate outward-facing PCR primers directed at these repeated sequences generates multiple amplification products, which reflect distance polymorphisms between adjacent DNA repeats. PCR with primers based on ERIC and REP sequences has been successfully used to differentiate bacterial strains from diverse species (de Bruijn 1992, Bennasar et al. 2002, Bruant et al. 2003, Hahm et al. 2003.The RAPD assay is based on the use of short random sequence primers, 9 to 10 bases in length, which hybridize with sufficient affinity to chromosomal DNA sequences to render a pattern of bands that is used for fingerprinting bacterial strains (Welsh & McClelland 1990, Williams et al. 1990. A number of studies have reported...

Immunohistochemistry (IHC) and in situ hybridization (ISH) techniques have been used for the detection of lymphocystis disease virus (LCDV) in formalin-fixed, paraffin-embedded tissues from gilt-head seabream, Sparus aurata L. Diseased and recovered fish from the same population were analysed. IHC was performed with a polyclonal antibody against a 60-kDa viral protein. A specific digoxigenin-labelled probe, obtained by PCR amplification of a 270-bp fragment of the gene coding the LCDV major capsid protein, was used for ISH. LCDV was detected in skin dermis and gill lamellae, as well as in several internal organs such as the intestine, liver, spleen and kidney using both techniques. Fibroblasts, hepatocytes and macrophages seem to be target cells for virus replication. The presence of lymphocystis cells in the dermis of the skin and caudal fin, and necrotic changes in the epithelium of proximal renal tubules were the only histological alterations observed in fish showing signs of the disease.

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Two viruses were isolated from cultured sole, Solea senegalensis, and wild blackspot sea bream, Pagellus bogaraveo, and preliminarily characterized as lymphocystis disease viruses (LCDVs). Viral isolates were characterized by morphological, biochemical and biophysical properties. In addition, the susceptibility of four fish cell lines was also tested. LCDV isolates developed cytopathic effects on the SAF-1 cell line at 5 and 6 days post-infection and reached titres of 10(6) TCID50 mL(-1). The antigenic and structural protein analysis of the two new LCDV isolates showed identical profiles to that obtained for LCDV strain Leetown NFH (ATCC VR-342), used as a reference viral strain, and for an LCDV isolate collected from gilt-head sea bream, Sparus aurata, cultured in southern Spain. Molecular confirmation was performed by polymerase chain reaction. Specific primers for LCDV produced a 270-bp DNA fragment, the expected size for LCDV.