Characterization and experimental infection of Flexibacter maritimus (Wakabayashi et al. 1986) in hatcheries of post-larvae of Litopenaeus vannamei Boone, 1931

Abstract

A preliminary study to characterize filamentous bacteria, whose presence is related to high mortality of Litopenaeus vannamei larvae cultured in Santa Catarina State, Brazil, is reported. The extract of infected larvae was diluted in different concentrations, cultured in marine agar (Difco TM , Marine Agar 2216) and incubated at 30 °C for 48 hours. The biochemical characterization included hydrolytic reactions of starch, gelatin and tyrosine, growth in TCBS agar, growth in 0 and 37‰ salinity, pigment production in tyrosine agar, production of H 2 S, nitrate reduction, congo red reaction, oxidase and catalase. The isolated bacteria belong to the species Flexibacter maritimus, Gram-negative bacilli of 0.4-0.5 µm width and 15 µm length. Experiments were carried out on pathogenicity of F. maritimus in post-larvae of L. vannamei. Survival and symptoms in L. vannamei post-larvae 24 hours after inoculation with F. maritimus and its growth in marine agar were evaluated. Mortality was detected around 92,5% as well as symptoms like melanized lesions in several parts of body, discolouration of gills, bad formation of appendages and of the last abdominal segment, low motility and feeding reduction. The experimental infection results suggested that isolated bacteria of the genus Flexibacter are pathogenic to the shrimp Litopenaeus vannamei post-larvae. Keywords: Litopenaeus vannamei, hatchery, Flexibacter maritimus, experimental infection. Caracterização e infecção experimental de Flexibacter maritimus em pós-larvas de Litopenaeus vannamei ResumoNeste trabalho, relata-se um estudo preliminar para caracterizar bactérias filamentosas associadas a elevadas mortalidades de larvas e pós-larvas cultivadas no Estado de Santa Catarina, Brasil. Um extrato de larvas infectadas foi diluído em diferentes concentrações, cultivado em Agar Marine (Difco TM , Marine Agar 2216) e incubado a 30° C por 48 horas. A caracterização bioquímica inclui reações de amido, gelatina e tirosesine, crescimento em Agar TCBS,crescimento a 0 e 37‰ de salinidade, produção de pigmentos em Agar Tirosine, produção de H 2 S, redução de nitrato, reação vermelho congo, oxidase e catalase. A bactéria isolada apresentou características de Flexibacter maritimus, um bacilo Gram negativo de 0,4-0,5 µm de largura e 15 µm de comprimento. Os experimentos foram realizados sobre a patogenicidade de F. Maritimus, em pós-larvas de L. vannamei. Foram avaliados a sobrevivência e os sintomas das pós-larvas 24 horas após a inoculação com F. Maritimus, além do seu crescimento em Agar Marine. Foram encontradas mortalidades de 92,5% e sintomas próprios da enfermidade, tais como lesões melanizadas em várias partes do corpo, descoloração das brânquias e diminuição da motilidade e da alimentação. Com base nos resultados da infecção experimental, pode se concluir que a bactéria isolada do gênero Flexibacter é patogênica para pós-larvas de L. vannamei.Palavras-chave: Litopenaeus vannamei, pós-larvas, Flexibacter maritimus, infecção experimental. Mouriño, JLP. et al.

Pathological Findings of Tenacibaculum maritimus Infection in Black Damselfish, Neoglyphieodon melas and Picasso Triggerfish, Rhinecanthus assasi in Red Sea, Egypt

“…T. maritimum was re-isolated in pure culture from the experimentally infected fish. A higher percentage of mortality (92.5%) was observed in shrimp, Litopenaeus vannamei post-larvae after bath challenge with 1.2 x 10 8 colony forming unit Ml -1 [27]. However, mortalities were 80-100% and 20-40% in juvenile Japanese flounder Paralichthys olivaceus after a bath challenge with 10 7.9 and 10 6.9 colony forming unit /mL, respectively [28].…”

Effect of combined use ofBacillusand molasses on microbial communities in shrimp cultural enclosure systems

“…Among these, Flexibacter sp. (2‐1) was found in Groups A and B, was the dominant phylum in Group A, and is a known pathogen causing shrimp disease (Mouriño, Vinatea, Buglione‐Neto, Ramirez, Vieira, Pedrotti, Martins, Derner, Aguilar & Beltrame ). Paracoccus sp.…”

Experimental infection with different bacterial strains in larvae and juvenile Litopenaeus vannamei reared in Santa Catarina State, Brazil

“…The larval quality was observed by swimming activity homogeneous stage, lipid contents and hepatopancreas color relative to diet, cromathophorus color, the presence of food in the intestines, necrosis, cannibalism, deformities, epibionts, fouling, luminous appearance (suggesting bacterial contamination) determined by a protocol for larval quality FM-03/PO-4/LCM (FAO, 2004) and slightly modified by Mouriño et al (2008a).…”

“…In six of these aquaria the animals were injected with 25 μL sterile saline solution containing 1 x 10 7 CFU Vibrio alginolyticus 1 mL -1 (the strain that caused the highest mortality in larvae) in the first segment of the abdomen with the aid of a 1 mL syringe (MOURIÑO et al, 2008b). In the other six aquaria, the shrimps received 25 μL saline solution (control group).…”

“…On the other hand, the disadvantage of the ZEAH system is the low control of water quality, phytoplankton density, metabolism and community composition compared to other systems (HARGREAVES, 2006). In the aquatic environment the microorganism population normally consists of non-pathogenic bacteria, as well as obligatory and opportunist organisms (SCHULZE et al, 2006). This equilibrium can be broken due to inadequate handling that favors pathogenic bacteria reproduction (KARUNASAGAR et al, 1994).…”