. Outbreaks of mass mortality among cultured small abalone Haliotis diversicolor supertexta with withering syndrome occurred in May and September 1998 in Kao-Hsiung, Taiwan. Bacterial strains CH-1 and B4 were isolated from the haemolymph of the moribund small abalone using tryptic soy agar supplemented with 3% NaCl and/or thiosulphate citrate bile salt sucrose agar. These two strains were characterized and identi®ed as Vibrio parahaemolyticus on the basis of various biochemical tests. The B4 strain and its extracellular products were virulent to small abalone with LD 50 values of 1Á6 Â 10 5 colony-forming units and 7Á58 mg protein g À1 body weight, respectively.
. 1999. The role of an extracellular cysteine protease, produced by pathogenic luminous Vibrio harveyi strain 820514 originally isolated from diseased tiger prawn (Penaeus monodon), in the disease process in the prawns was studied. The protease was lethal to P. monodon with an LD 50 value of 0·3 mg protein g −1 prawn. The lethal toxicity of the extracellular products (ECP) of the bacterium was neutralized by pre-incubation of the ECP with rabbit antiserum to the cysteine protease. Pre-incubation of ECP with CuCl 2 (an inhibitor of cysteine protease) also inhibited toxicity. This suggests that cysteine protease is the major toxin produced by the bacterium. The present protease is the first toxic cysteine protease to be found in Vibrio species.
Summary An outbreak of serious mortality among the cultured red drum Sciaenops ocellatus (L.) characterized by a swollen intestine containing transparent yellow fluid (ascites and gastroenteritis) occurred in July 2000 in Taiwan. A motile strain Rd 0700 was isolated from head kidney and/or the intestinal yellow fluid on tryptone soya agar (TSA) supplemented with 2% (w/v) NaCl and/or thiosulfate citrate bile salt (TCBS) sucrose agar plates. Applying biochemical characteristics, this strain was characterized and identified as Vibrio harveyi (V. carchariae). The bacteria could be re‐isolated from kidney, liver, and the transparent yellow fluid of swollen intestine of fish after bacterial challenge. The LD50 values of the organism and its extracellular products (ECP) were 2.9×107 colony forming units (CFU) and 3.85 μg protein g−1 fish body weight, respectively. All moribund/dead fish exhibited gastroenteritis except those killed within 12 h. This is a first report showing that intraperitoneal (i.p.) injection of the ECP from V. carchariae is lethal to red drum and can reproduce gastroenteritis in the fish.
. The effects of both crude extracellular products (ECP) and a partially purified protease of Vibrio alginolyticus on the plasma components of kuruma prawn (Penaeus japonicus) and tiger prawn (P. monodon) were studied using crossed immunoelectrophoresis (CIE). A component of the plasma, tentatively identified as coagulogen, apparently disappeared after incubation with the ECP, while the amount of a component tentatively identified as haemocyanin decreased. The coagulogen and an unknown component (component 1) in the penaeid plasma showed an increased migration rate after incubation with a partially purified 33 kDa protease of the bacterium. In contrast, incubation with protease had no detectable effect on the amount of haemocyanin. These events may significantly contribute to the pathogenicity of Vibrio alginolyticus in penaeids.
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