A selective and differential medium for Vibrio harveyi.

A new medium, termed Vibrio harveyi agar, has been developed for the isolation and enumeration of V. harveyi. It is possible to differentiate V. harveyi colonies from the colonies of strains representing 15 other Vibrio species with this medium. This medium has been shown to inhibit the growth of two strains of marine Pseudomonas spp. and two strains of marine Flavobacterium spp. but to allow the growth of Photobacterium strains. Colonies displaying typical V. harveyi morphology were isolated from the larval rearing water of a commercial prawn hatchery with V. harveyi agar as a primary isolation medium and were positively identified, by conventional tests, as V. harveyi. This agar displays great potential as a primary isolation medium and offers significant advantages over thiosulfate-citrate-bile salts-sucrose agar as a medium for differentiating V. harveyi from other marine and estuarine Vibrio species.     

Differential detection of vibrios pathogenic to shrimp by multiplex PCR

The research was focused on the multiplex polymerase chain reaction (PCR) differential detection of shrimp pathogens Vibrio harveyi, Vibrio campbellii and isolates from a variant strain of Vibrio (referred to as Philippine Vibrio isolates in this study) exhibiting characteristics distinct from these two species. Sequence alignment of the hemolysin gene from type strains Vibrio harveyi (NBRC 15634) and Vibrio campbellii (NBRC 15631), as well as 10 variant Philippine Vibrio isolates, was performed in order to design a set of hemolysin-targeted primers for the specific detection of the Philippine Vibrio isolates. Primer PNhemo amplified a 320-bp hemolysin gene fragment of the Philippine Vibrio isolates in PCR using 65 degrees C annealing temperature, but did not amplify the target gene fragment in type strains V. harveyi and V. campbellii. Another new primer (VcatoxR) targeting the toxR gene was designed for the specific detection of type strain V. campbellii under stringent 65 degrees C annealing temperature. PCR using VcatoxR primer resulted in the specific amplification of a 245-bp V. campbellii toxR fragment. The simultaneous use of three primer sets in PCR, including PNhemo and VcatoxR (the two new primers designed in this study), and a primer VhtoxR (previously reported for the specific detection of V. harveyi), resulted in differential profiles with 390-bp, 245-bp, and 320-bp amplicons for V. harveyi, V. campbellii, and variant Philippine Vibrio isolates, respectively. Presence of all three types of Vibrio shrimp pathogens in the sample could be detected with a multiplex PCR profile containing all the expected size amplicons.     

Description of a bacteriocinogenic plasmid in Beneckea harveyi.

A total of 795 strains of marine Vibrio species and Beneckea harveyi, a luminescent marine bacterium, were isolated from various sources in the area of Galveston Island, Tex., and screened for the production of bacteriocin-like substances. More than 8% of the Vibrio isolates produced low-molecular-weight (dialyzable) substances, which were lethal to a test strain of V. parahaemolyticus. Approximately 5% of the B. harveyi isolates produced higher-molecular-weight (nondialyzable) substances which were lethal to a test strain of B. harveyi. One of the B. harveyi strains (strain SY) produced a nondialyzable substance which was lethal to two of 39 strains of B. harveyi. The substance showed no activity toward 17 test strains drawn from the Vibrionaceae and Enterobacteriaceae. Strain SY showed no sensitivity to its own lethal agent and was shown by agarose gel electrophoresis and electron microscopy to harbor a single plasmid of 38 x 10(6) daltons. Variants of strain SY lacking the plasmid were produced by growth in the presence of the antibiotic novobiocin. These variants lacked both the ability to produce the lethal substance and the ability to survive in its presence. The lethal agent produced by strain SY is the first bacteriocin reported in marine bacteria. The term "harveyicin" is proposed to name this lethal substance.     

PCR detection of hemolysin (vhh) gene in Vibrio harveyi

The Vibrio harveyi hemolysin gene (vhh), which encodes for a virulence factor involved in pathogenicity to fish and shellfish species, may be targeted for species detection or strain differentiation. Primers designed for this gene were used in detection studies of V. harveyi strains from various hosts. One primer set among four tested, could amplify the expected gene fragment in PCR using templates from all 11 V. harveyi strains studied. Detection of the presence of the hemolysin gene could therefore serve as a suitable detection marker of Vibrio harveyi isolates potentially pathogenic to fish and shrimps.     

Cross-species induction of luminescence in the quorum-sensing bacterium Vibrio harveyi.

Different species of bacteria were tested for production of extracellular autoinducer-like activities that could stimulate the expression of the luminescence genes in Vibrio harveyi. Several species of bacteria, including the pathogens Vibrio cholerae and Vibrio parahaemolyticus, were found to produce such activities. Possible physiological roles for the two V. harveyi detection-response systems and their joint regulation are discussed.     

Quorum sensing-disrupting brominated furanones protect the gnotobiotic brine shrimp Artemia franciscana from pathogenic Vibrio harveyi, Vibrio campbellii, and Vibrio parahaemolyticus isolates

Autoinducer 2 (AI-2) quorum sensing was shown before to regulate the virulence of Vibrio harveyi towards the brine shrimp Artemia franciscana. In this study, several different pathogenic V. harveyi, Vibrio campbellii, and Vibrio parahaemolyticus isolates were shown to produce AI-2. Furthermore, disruption of AI-2 quorum sensing by a natural and a synthetic brominated furanone protected gnotobiotic Artemia from the pathogenic isolates in in vivo challenge tests.     

Inhibitory effects of Bacillus probionts on growth and toxin production of Vibrio harveyi pathogens of shrimp

Aim:  To investigate the effects of Bacillus subtilis , Bacillus licheniformis and Bacillus megaterium in terms of toxin and growth of pathogenic Vibrio harveyi .
Methods and Results:  Three Bacillus probionts were isolated from probiotic BZT aquaculture and identified using a 16S rDNA sequence. Growth inhibition assay showed that supernatants from the 24-h culture of three Bacillus species were able to inhibit the growth of V. harveyi (LMG 4044); B. subtilis was the most effective based on the well diffusion method. Results of a liquid culture model showed that B. subtilis was also widely effective in inhibiting three strains of V. harveyi (isolated from Thailand, the Philippines and LMG 4044), and that both B. licheniformis and B. megaterium inhibit the growth of V. harveyi isolated from the Philippines. Moreover, a haemolytic activity assay demonstrated that V. harveyi (IFO 15634) was significantly decreased by the addition of B. licheniformis or B. megaterium supernatant.
Conclusions:  Bacillus subtilis inhibited Vibrio growth, and both B. licheniformis and B. megaterium suppressed haemolytic activity in Vibrio .
Significance and Impact of the Study:  The cell-free supernatants produced by Bacillus probionts inhibit Vibrio disease, and Bacillus probionts might have an influence on Vibrio cell-to-cell communications.     

Comparison of Vibrio harveyi strains isolated from shrimp farms and from culture collection in terms of toxicity and antibiotic resistance

Vibrio harveyi strains isolated from shrimp farms (wild strains) were compared with those from culture collections in terms of minimum inhibitory concentration (MIC) and toxicity. Wild strains had higher MIC values for four antibiotics (kanamycin, carbenicillin, oxytetracycline and ampicillin) and also showed higher toxicity compared with culture collection strains. Vibrio harveyi with the lowest antibacterial resistance was chosen to test if a gradual increase in antibiotic concentration and frequent subculture would enhance its antibiotic resistance. Results showed that V. harveyi was able to develop resistance to oxytetracycline. The MIC value was 250 times higher compared with the MIC before subculturing. Moreover, the V. harveyi strain developed slightly higher toxicity. Therefore, it is possible that there is a relationship between antibiotic resistance and toxicity in V. harveyi.     

Separation of bacterial luciferase from oxidoreductases by affinity chromatography

The NADH-dependent and NADPH-dependent oxidoreductase activities associated with bacterial luciferase in Vibrio (Beneckea) harveyi can simultaneously be removed from purified luciferase through a Blue Sepharose CL-6B column. The result achieved with this one-step affinity chromatography is similar to that obtained with two sequential "reverse-affinity" chromatographies.     

大黄鱼病原哈维氏弧菌单克隆抗体的制备及其应用

用甲醛灭活哈维氏弧菌（Vibrio harveyi）GYC1108-1制备免疫原免疫8周龄雌性BALB/c小鼠,利用淋巴细胞杂交瘤技术,用间接酶联免疫吸附试验（ELISA）对杂交瘤进行筛选,阳性克隆经2－3次亚克隆后,共获得5株针对GYC1108-1的单克隆抗体。选取1B7制备小鼠腹水抗体,其细胞上清及腹水效价分别为1∶3200和1∶32000。同样用灭活的哈维氏弧菌免疫新西兰大白兔,5次免疫后颈动脉采血,离心取血清,并用饱和硫酸铵法进行纯化,制备了兔抗哈维氏弧菌多克隆抗体,其ELISA效价为1∶51200。利用1B7单克隆抗体和兔抗哈维氏弧菌多克隆抗体以及山羊抗小鼠HRP酶标二抗,建立了检测哈维氏弧菌的三抗体夹心酶联免疫吸附试验（TAS-ELISA）方法。该方法对哈维氏弧菌的最小检出浓度为1×104个/mL。用该TAS-ELISA方法检测大黄鱼（Pseudosciaena crocea）样品,54尾患病大黄鱼中有45尾检出哈维氏弧菌,而14尾健康大黄鱼都没有检出哈维氏弧菌。由此可见,本试验建立的TAS-ELISA方法,可以用于患病大黄鱼哈维氏弧菌的快速诊断。     

Amplification and sequence analysis of the full length toxR gene in Vibrio harveyi

This study was focused on obtaining the complete gene sequence of the toxR gene in V. harveyi by using toxR-targeted PCR to amplify 5' and 3' regions flanking the 576-bp Vibrio harveyi (NBRC 15634) toxR gene fragment previously amplified using degenerate PCR. To obtain the 5' flanking sequences, a forward PCR primer (VhtoxRpv) was designed based on known sequences upstream of toxR in V. parahaemolyticus and V. vulnificus. The reverse primer (VctoxR2R) was based on the sequence of the 576-bp Vibrio harveyi toxR fragment. The resulting 750-bp amplicon was sequenced, providing the 5' sequences of the V. harveyi (NBRC 15634) toxR gene. The 3' flanking region was amplified using a primer pair toxRS1 and toxRS2 based on V. parahaemolyticus and V. vulnificus toxR and toxS, resulting in a 900-bp amplicon that contained the remaining 3' sequences of the V. harveyi NBRC 15634 toxR. This paper reports, for the first time, a complete 882-bp nucleotide sequence for toxR in Vibrio harveyi. Sequence analysis and alignment revealed that the complete toxR gene in V. harveyi shares 87% sequence similarity with toxR of V. parahaemolyticus, 84% similarity with V. fluvialis, 83% with V. vulnificus and partial sequence of V. campbellii. The phylogenetic trees revealed wider divergence in toxR compared to 16S rRNA genes, so that V. harveyi could easily be distinguished from V. campbellii and V. parahaemolyticus.     

Study on the relationship of protease production and luminescence in Vibrio harveyi

AIMS: To demonstrate that Vibrio harveyi produces various types of toxins and how the production of those toxins is related with luminescence. METHODS AND RESULTS: Luminescence and toxicity of eight V. harveyi were evaluated. We demonstrated that all V. harveyi emitting luminescence were isolated from marine organisms and also showed that they were highly pathogenic when compared with culture collection V. harveyi based on cytotoxic assay test. On the contrary, V. harveyi isolated from shrimp farm showed no luminescence but showed high pathogenicity based on toxicity test. The effect of protease inhibitors on pathogenicity and luminescence was also investigated. We demonstrated that light emission of pathogenic V. harveyi remarkably decreased after addition of protease inhibitor. Furthermore, extracellular proteins from cell-free culture supernatant of luminescent and nonluminescent V. harveyi were compared using SDS-PAGE analysis. Results showed that there were differences in molecular weight and amount of proteins. CONCLUSIONS: Vibrio harveyi parasiting marine organisms have both luminescence and pathogenicity. Based on this study, luminescence and protease toxin activity in V. harveyi are related. Moreover, this paper clarified that V. harveyi produces various types of toxins. SIGNIFICANCE AND IMPACT OF THE STUDY: The current study demonstrated that V. harveyi produces two kinds of toxins, haemolysin and protease toxin. It may be clear roots of V. harveyi toxin.     

Identification of Vibrio harveyi using PCR amplification of the toxR gene

AIMS: The aim of this study was to develop an effective method for the identification of Vibrio harveyi based on using the toxR gene as a taxonomic marker. METHODS AND RESULTS: Primers for the toxR gene were designed for specificity to V. harveyi, and incorporated in a polymerase chain reaction (PCR). The results of the PCR, which took <5 h from DNA extraction to amplification, revealed positive amplification of the toxR gene fragment in 20 V. harveyi isolates including type strains, whereas DNA from 23 other Vibrionaceae type strains and 13 Vibrio parahaemolyticus strains were negative. The detection limit of the PCR was 4.0 x 10(3) cells ml(-1). In addition, the technique enabled the recognition of V. harveyi from diseased fish. CONCLUSIONS: The PCR was specific and sensitive, enabling the identification of V. harveyi within 5 h. SIGNIFICANCE AND IMPACT OF THE STUDY: The PCR allowed the rapid and sensitive detection of V. harveyi.     

Shrimps survive white spot syndrome virus challenge following treatment with Vibrio bacterin

Taking an innovative approach, a vaccination study using five bacterial strains viz. Vibrio campbelli (B60), V. alginolyticus (B73), V. parahaemolyticus-like (B79), V. parahaemolyticus (R8) and V. harveyi (RG203) was conducted in Penaeus monodon against white spot syndrome virus (WSSV) infection, considered as one of the serious pathogens of shrimps. Oral challenge with shrimps infected with WSSV showed a relative percentage survival of 5 and 47% in the P. monodon juveniles vaccinated with V. parahaemolyticus and V. harveyi, respectively. Results showed that there is a possibility of specifically immunising the shrimps against WSSV using bacterin prepared out of Vibrio harveyi isolates taken from shrimps infected with WSSV. Also, there was a level of protection attained by the shrimps due to immunisation with Vibrio strains.     

Experimental bacteriophage-mediated virulence in strains of Vibrio harveyi

Vibriosis is a major disease problem in prawn aquaculture. Until now there has been no clear explanation why some strains of Vibrio are pathogenic, while others are not. This study demonstrated that the presence of the bacteriophage V. harveyi myovirus like (VHML) may confer virulence to V. harveyi Strain 642. This was demonstrated by infecting na?ve avirulent V. harveyi Strains 12, 20, 45 and 645 with the bacteriophage and converting them into virulent strains. The previously na?ve strains of Vibrio infected with Bacteriophage VHML from V. harveyi Strain 642 demonstrated up-regulation of haemolysin, up-regulation of protein excretion, additional proteins which were recognised as toxic proteins from Strain 642 by monoclonal antibodies specific to the exotoxin sub-units, and a significant increase in mortality of larval Penaeus monodon. It was concluded that Bacteriophage VHML conferred virulence to V. harveyi Strains 12, 20, 45 and 645 and that Bacteriophage VHML either fully or partly confers virulence in V. harveyi Strain 642.     

16S ribosomal DNA sequencing confirms the synonymy of Vibrio harveyi and V. carchariae

Seventeen bacterial strains previously identified as Vibrio harveyi (Baumann et al. 1981) or V. carchariae (Grimes et al. 1984) and the type strains of V. harveyi, V. carchariae and V. campbellii were analyzed by 16S ribosomal DNA (rDNA) sequencing. Four clusters were identified in a phylogenetic analysis performed by comparing a 746 base pair fragment of the 16S rDNA and previously published sequences of other closely related Vibrio species. The type strains of V. harveyi and V. carchariae and about half of the strains identified as V. harveyi or V. carchariae formed a single, well-supported cluster designed as 'bona fide' V. harveyi/carchariae. A second more heterogeneous cluster included most other strains and the V. campbellii type strain. Two remaining strains are shown to be more closely related to V. rumoiensis and V. mediterranei. 16S rDNA sequencing has confirmed the homogeneity and synonymy of V. harveyi and V. carchariae. Analysis of API20E biochemical profiles revealed that they are insufficient by themselves to differentiate V. harveyi and V. campbellii strains. 16S rDNA sequencing, however, can be used in conjunction with biochemical techniques to provide a reliable method of distinguishing V. harveyi from other closely related species.     

Production of monoclonal antibodies for detection of Vibrio harveyi

Monoclonal antibodies (MAbs) against Vibrio harveyi were produced from mice immunized with heat-killed and SDS-mercaptoethanol-treated highly virulent V. harveyi 639. Fifteen MAbs were selected and sorted into 6 groups according to their specificity to various proteins of apparent molecular weight ranging from 8 to 49 kDa. Some antibodies were used for detection of V. harveyi at concentrations as low as 10(4) CFU ml(-1) using immunodot blots. Most of the selected MAbs did not show cross-reactivity to other Vibrio species and other gram-negative bacteria tested. Only 1 MAb (VH39-4E) showed slight cross-reactivity to Aeromonas hydrophila. Another MAb (VH24-8H) bound lightly to V. harveyi 1526 but strongly to V. harveyi 639, allowing rapid differentiation. Two of the MAb groups were used to localize V. harveyi in tissues of infected black tiger shrimp Penaeus monodon by immunohistochemistry. This study demonstrates the versatility of a highly specific immunological tool for the detection of V. harveyi in aquaculture and opens the way for further development of convenient test kits.