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NO49 - 1 (2014)

herapeutic Effect of Fosfomycin against Edwardsiellosis in Red Sea Bream Pagrus major

Azumi Yamashita1*, Akihiko Takechi1, Shusaku Takagi1 and Ayano Sato2
1Fisheries Research Center, Ehime Research Institute of Agriculture, Forestry and Fisheries, Ehime 798-0104, Japan
2Research Institute for Animal Science in Biochemistry and Toxicology, Kanagawa 252-0132, Japan

(Received September 26, 2013)

ABSTRACT―Therapeutic effect of fosfomycin (FOM) was studied in red sea bream experimentally and naturally infected with Edwardsiella tarda. Minimum inhibitory concentration of FOM against 67 strains of E. tarda isolated from red sea bream cultured in Ehime Prefecture ranged from 1 to 4 mmg/mL, and no strains resistant to FOM were observed. In experimental infections, the mortality decreased with the increase in FOM dosage, and a remarkable therapeutic effect of FOM was demonstrated by oral administration at a dose of 40-80 mg/kg body weight/day for 6 days. In field trials, FOM was administered to high and low mortality cases of red sea bream naturally infected with E. tarda orally for consecutive 6 days at a dosage of 40 mg/kg/day. Cumulative mortalities of the FOM-medicated groups were significantly lower than those of the non-medicated groups in both cases. In medicated groups, the administration of FOM was more efficient in the lower mortality case. These results indicate that FOM administration is effective against edwardsiellosis in red sea bream and the treatment in early stages of infection is important to obtain a favorable outcome.
Key words: fosfomycin, Edwardsiella tarda, Pagrus major, oral administration, therapeutic effect

A Novel Disorder of Cultured Juvenile Greater Amberjack Seriola dumerili Characterized by Renomegaly and Splenomegaly

Shinpei Wada1*, Osamu Kurata1, Hitoshi Hatakeyama2, Azumi Yamashita3, Shusaku Takagi3, Toyohiko Nishizawa4 and Hiroshi Yokoyama5
1Laboratory of Aquatic Medicine, Nippon Veterinary and Life Science University, Tokyo 180-8602, Japan
2Laboratory of Comparative Cellular Biology, Nippon Veterinary and Life Science University, Tokyo 180-8602, Japan
3Fisheries Research Center, Ehime Research Institute of Agriculture, Forestry and Fisheries, Ehime 798-0104, Japan
4Department of Aqualife Medicine, Chonnam National University, Yeosu 550-749, Republic of Korea
5Graduate School of Agricultural and Life Sciences, The University of Tokyo, Tokyo 113-8657, Japan

(Received October 23, 2013)

ABSTRACT―In 2008, several episodes of mortality were recorded in cultured populations of juvenile greater amberjack reared in the southwest region of Japan. Diseased fish had asymmetrical abdominal distention and pale gills. The head kidney, trunk kidney, and spleen of every fish that was examined was enlarged and discolored. The results of all microbiological and molecular biological assays of tissues taken from diseased fish were negative for major known pathogens. Histopathologically, the disease was characterized by proliferative interstitial nephritis and proliferative splenitis associated with minute, round structures within the cytoplasm of proliferating mono-nucleated cells. Transmission trial using the enlarged trunk kidney from a naturally infected fish successfully reproduced the disease. The results indicate that this disease is caused by an infectious microorganism, and the most likely etiological agent is the minute, round structures which are probably a hitherto unknown eukaryotic microorganism.
Key words: novel disorder, Seriola dumerili, amberjack, renomegaly, splenomegaly

First Isolation and Characterization of Tenacibaculum soleae from Sea Bass Dicentrarchus labrax

Nuria Castro*, Sabela Balboa, Soledad Núñez, Alicia E. Toranzo and Beatriz Magariños
Department of Microbiology and Parasitology, Faculty of Biology-CIBUS & Institut of Aquaculture University of Santiago de Compostela, Santiago de Compostela, 15782, Spain

(Received November 22, 2013)

ABSTRACTTenacibaculum soleae is a recently described pathogen that has been reported as the causative agent of considerable losses in sole cultures in Spain. This report documents the first case of T. soleae as an etiological agent of tenacibaculosis in farmed sea bass Dicentrarchus labrax. Its identification was performed employing phenotypical, serological and molecular methods. Although the sea bass isolates were homogeneous from a biochemical, chemotaxonomic and molecular point of view, they belonged to a serological group different from the type strain CECT7292, which can be of great importance in the development of future vaccines and other methods of disease prevention in sea bass industry. Virulence assays with a representative isolate confirmed the pathogenic potential for sea bass. The disease was experimentally reproduced by prolonged bath, while no mortalities could be recorded by intraperitoneal injection. The results presented here show that T. soleae must be taken into account as an important pathogen in the marine aquaculture industry.
Key words: Tenacibaculum soleae, Dicentrarchus labrax, fish pathogen, aquaculture, virulence

Efficacy of Chemotherapeutics against Experimentally Infected Ayu Plecoglossus altivelis with Edwardsiella ictaluri

Yasuhiko Kawato1,3, Yasuo Yamada1, Takahiro Nagai2, Ebtsam Sayed Hassan1,4 and Toshihiro Nakai1*
1Graduate School of Biosphere Science, Hiroshima University, Hiroshima 739-8528, Japan
2Fisheries and Marine Technology Center, Hiroshima Prefectural Technology Research Institute, Hiroshima 737-1207, Japan
3National Research Institute of Aquaculture, Fisheries Research Agency, Mie 516-0193, Japan
4Faculty of Veterinary Medicine, Assiut University, Assiut 71526, Egypt

(Received November 1, 2013)

ABSTRACT―Anti-bacterial activity of six approved drugs for ayu Plecoglossus altivelis, i.e. florfenicol (FFC), oxolinic acid (OXA), sulfisozole sodium (SIZ), sulfamonomethoxine, ormetoprim (OMP) and sulfamonomethoxine-ormetoprim combination, was examined against four Edwardsiella ictaluri strains. Of these drugs, FFC, OXA and OMP inhibited bacterial growth with MIC lower than 1 mg/mL. When chemotherapeutic efficacy of FFC, OXA and SIZ was examined against experimentally E. ictaluri-infected ayu, FFC and OXA strongly reduced mortality of fish. Although SIZ was slightly effective, survivors from the SIZ-treated group showed high carrier rates for E. ictaluri, suggesting that FFC and OXA are candidates in treating E. ictaluri infection of ayu.
Key words: Edwardsiella ictaluri, Plecoglossus altivelis, Chemotherapeutics, MIC

A Rapid Agglutinating Antibody-detection Method for the Diagnosis of Streptococcus dysgalactiae Infection in Farmed Fish Using Recombinant Surface Immunogenic Protein (rSd-Sip) -coated Latex Beads

Issei Nishiki1, Takayuki Minami2, Toshiaki Itami3 and Terutoyo Yoshida3*
1Interdisciplinary Graduate School of Agriculture and Engineering, University of Miyazaki, Miyazaki 889-2192, Japan
2Miyazaki Prefectural Fisheries Experimental Station, Miyazaki 889-2162, Japan
3Faculty of Agriculture, University of Miyazaki, Miyazaki 889-2192, Japan

(Received December 16, 2013)

ABSTRACT―To develop a rapid diagnosis method for Lancefield group C Streptococcus dysgalactiae (GCSD) infection, latex beads were coated with recombinant S. dysgalactiae surface immunogenic protein (rSd-Sip). The usefulness of the beads for slide agglutination tests with fish sera was examined. The beads were agglutinated with GCSD-infected sera collected from farmed amberjack Seriola dumerili. However, the beads were not agglutinated with non-infected sera or immunized sera collected from fish vaccinated with Lactococcus garvieae and Streptococcus iniae. The results demonstrate that the slide agglutination test using rSd-Sip-coated latex beads is an easy, rapid, and effective method for agglutinating antibody-detection in GCSD-infected fish.
Key words: Streptococcus dysgalactiae, Seriola dumerili, serodiagnosis, latex agglutination test, surface immunogenic protein