An epidemic of mass mortality of abalone (Haliotis diversicolor supertexta) postlarvae aged 40 days or less has existed across south coast of China since the second half of 2002. Among 20 bacterial strains isolated from diseased abalone postlarvae on 2216E marine agar plates during an outbreak of postlarval disease in August 2005, a predominant strain (designated strain 20) was demonstrated to be virulent to postlarvae with an LD50 value of 1.0-105 colony forming units (CFU ml 1) on day 4, while the other 19 strains were either avirulent (16 strains) or weakly virulent (3 strains). The same bacterium could be re-isolated from postlarvae after bacterial challenge using 2216E marine agar plates. Preliminary toxicity tests of ECPs of strain 20 revealed that at 2.77 mg protein ml 1, crude ECPs completely liquefied postlarvae within 24 h, leaving only shells. API 20E analysis identified strain 20 as Klebsiella oxytoca. 16S and ITS rDNA sequencing and phylogenetic analyses further confirmed this identification. Antibiotic susceptibility tests showed that strain 20 exhibited 94% of susceptibility to 16 various antibiotics tested and only showed resistance to streptomycin. Results of this work demonstrated that K. oxytoca is also linked to this epidemic in Fujian, China. This is considered to be the first report regarding K. oxytoca involved in the mass mortality of postlarval abalone in south China and the world.

Outbreaks of mass mortality among cultured postlarvae of abalone Haliotis diversicolor supertexta aged between 7 and 30 days occurred since 2002 on the south coast of China. Among 24 bacterial strains isolated from diseased abalone postlarvae on 2216E Marine and TCBS agar plates during an outbreak in July 2003, 23 were avirulent whilst a predominant strain (designated as strain 2) was highly virulent to postlarvae with an LD50 value under 1.0×103 colony forming units (CFU) ml−1. All the moribund/dead postlarvae exhibited the same gross symptoms as that observed in natural outbreaks. The same bacteria could be re-isolated from postlarvae after bacterial challenge using 2216E Marine and TCBS agar plates. API analysis identified it to be Vibrio parahaemolyticus with 99% confidence. 16S and ITS rDNA sequencing analysis also revealed it to be highly homologous with Vibrio parahaemolyticus. Kanagawa reaction and PCR amplification of TDH gene on strain 2 proved to be negative. Antibiotic susceptibility tests showed that strain 2 exhibited 56.25% of susceptibility to chemotherapeutic agents tested, and was resistant to penicillin G, amikacin, trimethoprim–sulfamethoxazole, tetracycline, ciprofloxacin, novobiocin and neomycin. Results in this study reveal that V. parahaemolyticus strain 2 is an infectious agent to abalone postlarvae in South China.

Outbreaks of serious mortality among cultured abalone postlarvae have occurred across Southern China since July 2002. Five motile bacterial strains were isolated from diseased abalone postlarvae on tryptic soy agar supplemented with 1% NaCl (TSA1) and/ or thiosulphate citrate bile salt (TCBS) sucrose agar plates during an outbreak in August 2003 in Shanwei, Guangdong province. All isolates were characterized and identi¢ed asVibrio alginolyticus on the basis of biochemical characteristics and comparisonswiththose of the reference strainV. alginolyticus ATCC 17749. Strain 19 (a representative of ¢ve similar isolates) was virulent to abalone postlarvae with an LD50 value of 1.00 104 colony-forming unitsmL 1. All abalone postlarvae exhibited the same signs as in natural outbreaks.The same bacterium could be re-isolated from abalone postlarvae after bacterial challenge usingTSA1andTCBS plates. The results reveal thatV. alginolyticus is an infectious agent of abalone postlarvae.

噬菌蛭弧菌具有裂解病原菌的特殊功效，可以用作生物净化因子。本实验从海洋环境中分离到4 株Bh04系列蛭弧菌(Bh04-4, Bh04-41a, Bh04-A+ 和 Bh04-1f)。以41株弧菌为蛭弧菌的宿主菌，本文研究了蛭弧菌对海产品中常见弧菌的裂解消除能力，以探索其对由弧菌所引起的食物中毒等流行性传染疾病的预防效果。实验结果表明，41株弧菌中共有36菌株可被4株蛭弧菌(Bh04-4, Bh04-41a, Bh04-A+和Bh04-1f)中的任一株所裂解，占总试验菌株的87.8%；对副溶血弧菌、非01 非0139 群霍乱弧菌、溶藻胶弧菌这三种常见致病弧菌的裂解率分别达88.9%、83.3%、81.8%。本研究结果揭示了蛭弧菌作为生物消除剂在由弧菌所引起的食物中毒等流行性传染疾病的防治方面有潜在应用价值。