Distribution of luminescent Vibrio harveyi and their bacteriophages in a commercial shrimp hatchery in South India

Luminescent Vibrio harveyi is a natural microflora of marine and coastal water bodies and is associated with mortality of larval shrimp in penaeid shrimp hatcheries. It is also known that the bacteriophages occur virtually in all places where their hosts exist. In this study, distribution of luminescent V. harveyi and the bacteriophages affecting these hosts was examined in a commercial Penaeus monodon hatchery during three shrimp larval production cycles, including a cycle affected by luminescent bacterial (LB) disease outbreak

Nutritional, textural and quality attributes of white and dark muscles of little tuna (Euthynnus affinis)

205-211The proximate composition, fatty acid profile, texture, colour and freshness of white and dark muscles of little tuna (Euthynnus affinis) were investigated. The moisture content was higher in white muscle (75.52±0.13%) compared to that in dark muscle (74.85±0.10%). Both white and dark muscle had higher levels of protein, 23.12± 0.13% and 23.15± 0.02%, respectively. Analysis of fatty acid profile by gas chromatography showed that the dark muscle had high levels of eicosapentaenoie acid (C20:5) and docosahexaenoic acid (C22:6) compared to white muscle. Texture profile analysis showed that dark muscle had higher values for hardness (3.74±0.15kgF), whereas adhesiveness, cohesiveness, springiness and chewiness values were greater for white muscle. Colour analysis revealed dark muscle had lower L* value than that of white muscle. The total volatile base nitrogen, tri - methyl amine, texture profile analysis and histamine contents were higher in dark muscle. Overall nutritional quality of dark muscle was superior to that of white muscle

A Nonluminescent and Highly Virulent Vibrio harveyi Strain Is Associated with “Bacterial White Tail Disease” of Litopenaeus vannamei Shrimp

Recurrent outbreaks of a disease in pond-cultured juvenile and subadult Litopenaeus vannamei shrimp in several districts in China remain an important problem in recent years. The disease was characterized by “white tail” and generally accompanied by mass mortalities. Based on data from the microscopical analyses, PCR detection and 16S rRNA sequencing, a new Vibrio harveyi strain (designated as strain HLB0905) was identified as the etiologic pathogen. The bacterial isolation and challenge tests demonstrated that the HLB0905 strain was nonluminescent but highly virulent. It could cause mass mortality in affected shrimp during a short time period with a low dose of infection. Meanwhile, the histopathological and electron microscopical analysis both showed that the HLB0905 strain could cause severe fiber cell damages and striated muscle necrosis by accumulating in the tail muscle of L. vannamei shrimp, which led the affected shrimp to exhibit white or opaque lesions in the tail. The typical sign was closely similar to that caused by infectious myonecrosis (IMN), white tail disease (WTD) or penaeid white tail disease (PWTD). To differentiate from such diseases as with a sign of “white tail” but of non-bacterial origin, the present disease was named as “bacterial white tail disease (BWTD)”. Present study revealed that, just like IMN and WTD, BWTD could also cause mass mortalities in pond-cultured shrimp. These results suggested that some bacterial strains are changing themselves from secondary to primary pathogens by enhancing their virulence in current shrimp aquaculture system

Phage Therapy and Photodynamic Therapy: Low Environmental Impact Approaches to Inactivate Microorganisms in Fish Farming Plants

Owing to the increasing importance of aquaculture to compensate for the progressive worldwide reduction of natural fish and to the fact that several fish farming plants often suffer from heavy financial losses due to the development of infections caused by microbial pathogens, including multidrug resistant bacteria, more environmentally-friendly strategies to control fish infections are urgently needed to make the aquaculture industry more sustainable. The aim of this review is to briefly present the typical fish farming diseases and their threats and discuss the present state of chemotherapy to inactivate microorganisms in fish farming plants as well as to examine the new environmentally friendly approaches to control fish infection namely phage therapy and photodynamic antimicrobial therapy

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Not AvailableLuminescent Vibrio harveyi has been reported to be one of the major causes of mass mortality of larval stages in penaeid shrimp hatcheries throughout the world. Therefore, understanding the virulence mechanism of V. harveyi and identifying traits has been our quest to detect pathogenic strains in shrimp aquaculture ecosystem. In this study pulsed field gel electrophoresis (PFGE)was used for differentiating V. harveyi isolates recovered from shrimp larvae affected by luminescent bacterial disease in hatcheries and water samples from various sources within the hatcheries. Forty two of the 400 V. harveyi isolates recovered from shrimp hatcheries over a period of two years were used in this study. Cluster analysis of PFGE profiles of 32 V. harveyi isolates in conjunction with virulence factors revealed that the isolates from disease episode were grouped in Cluster II. Further, the isolates in the cluster were all sucrose fermentative and had LD50 value in the order of 103 cfu ml-1 and ranged from 1.17 x 103 cfu ml-1 to 3.16 x 103 cfu ml-1. However, the clustering pattern could not be associated with LD50 values based on in vivo pathogenicity experiment. An interesting observation was that majority of the isolates capable of producing siderophores were clustered in IA (11 of 13) although 10 of the 16 isolates in cluster IB also produced siderophores. Six of 13 isolates in cluster IA and 7 of 16 isolates in cluster IB produced extracellular proteins (ECP) and this property was not found to be associated with any of the clustering pattern. This study could not show definite relationship between pulsotypes and virulence of V. harveyi. However, PFGE typing cluster analysis could help in differentiating isolates from disease episodes and normal shrimp seed production cycle. Further, the study has also revealed that sucrose fermenting trait seems to be animportant phenotypic trait indicative of virulence of V. harveyi in shrimp hatchery ecosystems.Not Availabl

Degenerate primed randomly amplified polymorphic DNA (DP-RAPD) fingerprinting of bacteriophages of<i>Vibrio harveyi</i>from shrimp hatcheries in Southern India

AbstractVibrio harveyiis a significant pathogen of shrimp. Seventy-six bacteriophages infecting luminescentV. harveyiwere isolated from a total of 194 water samples drawn from various sources of shrimp hatcheries located in South East coast and Andaman island of India. Degenerate primed randomly amplified polymorphic DNA (DP- RAPD) fingerprinting of these bacteriophages was carried out to determine their genetic relatedness. Similarity matrix based on Dice coefficient followed by construction of dendrogram by unweighted pair group method with arithmetic averages (UPGMA) revealed 12 major clusters. One phage was randomly selected from each of these major clusters for transmission electron microscopic observations. Eleven of them had an icosahedral head (46-115 nm) with a long non-contractile tail (132-329 nm), belonging to theSiphoviridaefamily and two phages had a short tail (15-27 nm), belonging to the familyPodoviridae. The phylogenetic analysis of the phages using DP-RAPD fingerprinting correlated to some extent to the phenotypic nature of the host specifically with regard to sucrose fermentation and source of isolation. However, phages specifically infectingV. harveyiand those belonging to different families did not cluster together in the DP-PCR cluster analysis. Hence, the genetic diversity of phages infecting same host with respect to phenotypic difference was revealed by the DP-RAPD applied in this study.</jats:p

A One-Step Method for the Growth of Ga2O3-Nanorod-Based White-Light-Emitting Phosphors

A one-step synthesis of Ga2O3 nanorods by heating molten gallium in ambient air at high temperatures is presented. The high-temperature synthesis creates oxygen vacancies and incorporates nitrogen from the environment. The oxygen vacancy in Ga2O3 is responsible for the emission in the blue-green region, while nitrogen in Ga2O3 is responsible for red emission

Detection of Escherichia fergusonii - an emerging pathogen harbouring drug resistant genes from seafood samples of Tamil Nadu, India

363-370Escherichia fergusonii harbouring drug resistant genes was isolated from seafood samples of Tamil Nadu, India while attempting to isolate Escherichia coli. Isolation of STEC was done by enrichment and plating on MacConkey agar MUG and sorbitol negative colonies were confirmed by IMViC test and by an automated system (Vitek-2 compact, BioMerieux, France). Antibiotic sensitivity test was performed by disc diffusion method and by PCR for antibiotic resistance genes. A total of 302 presumptive E. coli was isolated, of which 126 isolates were confirmed as E. coli. Few isolates could not ferment sorbitol and produce β-glucuronidase, and these were confirmed as presumptive E. coli O157:H7. However, two isolates were positive for adonitol and therefore confirmed as E. fergusonii (E011 and E060). The two isolates were sorbitol and lactose negative and adonitol, amygdalin and cellobiose positive. The isolates could not produce the enzyme β-glucuronidase. The isolates were then confirmed as E. fergusonii by gene specific PCR assay and 16S rDNA sequencing. ESBL studies showed that both the isolates harbour blaTEM. Presence of drug resistance and ESBL in E. fergusonii isolated from seafood samples is a matter of public health concern, as the resistance could enter the food chain and hinder the effectiveness of drugs used for treatment. To the best of our knowledge, this is the first report on the occurrence of E. fergusonii harbouring drug resistance genes from seafood samples of Tamil Nadu, India