Outbreaks of mass mortality among cultured tiger prawns (Penaeus monodon) with white spotted syndrome (WSS) in the carapace occurred in the summer of 1994 in I-Lan, Taiwan. A swarming strain Val was isolated from hemolymph of the moribund prawns with tryptic soy agar (TSA, supplemented with 1% NaCl, Oxoid) and/or thiosulfate citrate bile salt sucrose (TCBS, Difco) agar. This strain was characterized and identified to be Vibrio alginolyticus. The strain was susceptible to antibiotics such as chloramphenicol, ciprofloxacin, doxycycline hydrochloride, nalidixic acid, oxolic acid, and oxytetracycline while resistant to ampicillin, novobiocin, penicillin G, sulfisoxazole, and sulfonamide. The bacteria and their extracellular products (ECP) were lethal to both tiger prawns (P. monodon) and kuruma prawns (P. japonicus) with LD50 values of 1.13 x 10(5), 2.46 x 10(5) CFU/g, and 0.23, 0.63 micrograms protein/g prawn body weight, respectively.

An outbreak of serious mortality among the cultured groupers Epinephelus coioides, characterized by a swollen intestine containing yellow fluid, occurred in the summer of 1993 in Taiwan. A motile strain EmI82KL was isolated from the intestinal yellow fluid of the moribund groupers with tryptic soy agar supplemented with 2% NaCl and/or thiosulfate citrate bile salt sucrose agar. This strain was characterized and identified as Vibrio carchariae and was susceptible to chloramphenicol, doxycycline-HCl, nalidixic acid, oxolinic acid, oxytetracycline, and sulfonamide while resistant to ampicillin and penicillin G. In addition, the strain was neither auto-agglutinating nor hemagglutinating, but it was hemolytic against erythrocytes from sheep, rabbit, tilapia, and grouper. The bacteria could be reisolated from kidney, liver, and the transparent yellow fluid of swollen intestine of moribund groupers after bacterial challenge and re-identified as the same species. The LD50 value was 2.53 x 10(7) colony forming units/g grouper body weight.

Outbreaks of serious mortality among cultured kuruma prawns (Penaeus japonicus) with white spotted syndrome in the carapace occurred in the summer of 1993 in I-Lan, Taiwan. A swarming bacterium, strain Swy, was isolated from the hepatopancreas of the moribund prawns using tryptic soy agar supplemented with 1% NaCl and/or thiosulphate citrate bile salt sucrose agar. This strain was characterized and identified as Vibrio alginolyticus on the basis of a number of biochemical tests. The Swy strain was virulent to both kuruma prawns (P. japonicus) and tiger prawns (P. monodon) with LD50 values of 4.43 x 10(4) and 1.57 x 10(5) cfu g body weight-1, respectively.

. 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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