Vibrio ichthyoenteri sp. nov., a Pathogen of Japanese Flounder (Paralichthys olivaceus) Larvae

Abstract

Seven similar strains which were pathogens of Japanese flounder (Paralichthys olivaceus) larvae with opaque intestines had characteristics of the genus Vibrio. These strains were divided into two genomic species (species 1 containing six strains, and species 2 containing one strain) on the basis of the results of DNA-DNA hybridization experiments in which the membrane filter method was used, and these two species could be differentiated from each other by the following characteristics: acid production from D-galactose and utilization of D-glucuronate and P-hydroxybutyrate. Strain F-2, the type strain of species 1, exhibited levels of DNA relatedness with 29 previously described Vibrio species of 5 to 18%. The flounder isolates belonging to species 1 were also differentiated from the previously described Vibrio species phenotypically by the following characteristics: they were nitrate reduction positive; each cell had a single polar flagellum; they did not produce arginine dihydrolase, chitinase, gelatinase, and lipase; they did not utilize D-cellobiose and citrate; and they did not grow at 35°C. The G+C contents of the DNAs of four species 1 strains were 43 to 44 mol%. The name Vibrio ichthyoenteri sp. nov. is proposed for genomic species 1. The type strain of K ichthyoenteri is strain F-2 (= IF0 15847). Species 2 was also considered a new genomic species, but a species name is not proposed in this paper because only one strain is available and the phenotypic variability of the species is not known.Since 1971, a bacterial disease characterized by opaque intestines or intestinal necrosis and high rates of mortality has occurred often in larval Japanese flounder (Paralichthys olivaceus) reared at marine hatcheries in Japan (13). 0. Murata (12) isolated the causative agent of the disease, a vibrio, from affected flounder larvae between 1971 and 1973 in Wakayama Prefecture, but the strains isolated by Murata have been lost. Between 1986 and 1988 we isolated the causative agent of the disease mainly in Hiroshima Prefecture. On the basis of its morphological, biochemical, physiological, pathological, and serological characteristics, this flounder pathogen, which was tentatively designated Vibrio species INFL (intestinal necrosis of flounder larvae), was thought to be a new species (11). The disease caused by Wbrio species INFL is a very unusual fish disease because a local (intestinal) infection develops only in larval fish (14). In this study we determined the taxonomic position of this flounder pathogen and propose the name Vibrio ichthyoenteri sp. nov. for it. MATERIALS AND METHODSBacterial strains. The strains which we used are listed in Table 1. The seven strains belonging to the INFL group were isolated from the guts of diseased Japanese flounder larvae reared in prefectures in western Japan. These strains were isolated and subcultured on ZoBell 2216e agar plates (1) at 25°C and were maintained in semisolid ZoBell 2216e medium containing 0.55% agar at 20°C: they were subcultured every 6 months. Aged and filtered...

Carriage of potentially fish-pathogenic bacteria in Sparus aurata cultured in Mediterranean fish farms

“…Although V. ichthyoenteri was originally described as pathogenic for Japanese flounder larvae (Ishimaru et al 1996), our isolates were very infrequent in fish with clinical signs, and were clearly associated with asymptomatic individuals during the whole year. Whether these facts could be related to a protective or beneficial role against infection by other bacteria, as suggested for other Vibrio spp.…”

“…This allowed the identification of the isolates at the genus and, in most cases, at the species level. The tentative identification of Vibrio ichthyoenteri, the only species not included in the previous references, was accomplished according to Ishimaru et al (1996).…”

“…This allowed the identification of the isolates at the genus and, in most cases, at the species level. The tentative identification of Vibrio ichthyoenteri, the only species not included in the previous references, was accomplished according to Ishimaru et al (1996).Conservation: All strains were maintained in semisolid marine agar tubes, as stab cultures at room temperature in the dark. Long-term conservation was achieved by suspending cells grown on MA plates in marine broth supplemented with 20% glycerol and then freezing the suspensions at -80°C.…”

Vibrio ruber sp. nov., a red, facultatively anaerobic, marine bacterium isolated from sea water

“…They are closely associated with many kinds of marine organisms, from plankton to fish (Cerdà-Cuéllar et al, 1997;MacDonald et al, 1986;Nair et al, 1988;Onarheim et al, 1994;Simidu et al, 1969Simidu et al, , 1971Sochard et al, 1979). Some species are found as symbionts in specialized luminous organs of marine fish and invertebrates (Lee & Ruby, 1994;Leisman et al, 1980;Reichelt et al, 1977;Ruby & Asato, 1993;Ruby & Morin, 1978), whereas many other species are pathogens of humans or marine animals (Blake et al, 1980;Borrego et al, 1996;Egidius et al, 1986;Hada et al, 1984;Ishimaru et al, 1996;Schiewe et al, 1981). These halophilic, facultatively anaerobic, Gram-negative rods are known to include both nitrogen-fixers and denitrifiers (Guerinot & Colwell, 1985;Guerinot et al, 1982;Shieh & Lin, 1992Shieh & Liu, 1996;Shieh & Yang, 1997;Shieh et al, 1989), though the definitions given in Bergey's Manual of Systematic Bacteriology in 1984 indicated that these bacteria include neither nitrogen-fixers nor denitrifiers Baumann & Schubert, 1984;.…”

Infectious necrotizing enteritis and mortality caused by Vibrio carchariae in summer flounder Paralichthys dentatus during intensive culture

“…Nodavirus causing viral nervous necrosis was described as the cause of high mortality in cultured Japanese flounder larvae (Nguyen et al 1994). An atypical strain of Aeromonas salmonicida has been associated with ulcerative skin disease in wild-caught and cultured adult flounder (Wiklund (Levin et al 1972), cultured turbot Scophthalmus maxjmus (Lupiani et al 1989, Grisez et al 1996 and cultured Japanese flounder larvae (Ishimaru et al 1996).…”