Hindawi Publishing CorporationReview Article Comparative Pathogenomics of Bacteria Causing Infectious Diseases in Fish (original) (raw)
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Review Article Comparative Pathogenomics of Bacteria Causing Infectious Diseases in Fish
Fish living in the wild as well as reared in the aquaculture facilities are susceptible to infectious diseases caused by a phylogenetically diverse collection of bacterial pathogens. Control and treatment options using vaccines and drugs are either inadequate, inefficient, or impracticable. The classical approach in studying fish bacterial pathogens has been looking at individual or few virulence factors. Recently, genome sequencing of a number of bacterial fish pathogens has tremendously increased our understanding of the biology, host adaptation, and virulence factors of these important pathogens. This paper attempts to compile the scattered literature on genome sequence information of fish pathogenic bacteria published and available to date. The genome sequencing has uncovered several complex adaptive evolutionary strategies mediated by horizontal gene transfer, insertion sequence elements, mutations and prophage sequences operating in fish pathogens, and how their genomes evolved from generalist environmental strains to highly virulent obligatory pathogens. In addition, the comparative genomics has allowed the identification of unique pathogen-specific gene clusters. The paper focuses on the comparative analysis of the virulogenomes of important fish bacterial pathogens, and the genes involved in their evolutionary adaptation to different ecological niches. The paper also proposes some new directions on finding novel vaccine and chemotherapeutic targets in the genomes of bacterial pathogens of fish. * Unpublished. * * Coding sequences.
Over the last 15 years new approaches have been developed for the identification and study of the functions of genes and proteins involved in the virulence mechanisms of bacteria. Some of these approaches are based on the identification of genes required by the bacteria to survive and grow inside the host. Most of these techniques have recently been applied to bacterial fish pathogens successfully. Some of these techniques involve the " In vivo expression technology (IVET) " , which identifies specific promoters expressed in bacteria grown inside the fish body but not in conventional culture media; " Signature-tagged mutagenesis (STM) " , a useful tool for the screening of null mutants which show a decreased virulence capability in the host; and " Suppression Subtractive Hybridisation (SSH) " , a genome-wide technology, which enables the identification of genes present only in virulent strains of bacteria or the identification of genes expressed only inside the fish host. This paper reviews the application of these techniques to important pathogenic bacteria for the aquaculture field.
A review of molecular diagnoses of bacterial fish diseases
Aquaculture International, 2022
Egypt is the world's ninth-largest fish producer with a total production of 1.5 billion tons per year, and farmed fishes comprise almost 79.6% of the total production. Massive mortalities in market-sized farmed fish (freshwater and marine species) were documented all over fish farms in Egypt leading to serious economic losses. The poor biosecurity practices and awareness among smallholder fish farmers accompanied with a long period of temperature fluctuation may predispose farmed fish to be simultaneously coinfected with multiple pathogens. Moribund fishes usually exhibited various septicemic clinical signs and post-mortem lesions indicating that one or more septicemic bacterial pathogens were involved in these outbreak reports. Therefore, rapid and accurate identification of pathogens in the asymptomatic fish population is important for preventing the occurrence of infectious diseases and protecting consumers from seafoodborne illnesses. Molecular techniques provide sensitive, quick, and accurate data for identifying specific pathogens without the need for time-consuming traditional techniques. In addition, the development of cost-effective molecular techniques facilitates their wide implementation in routine clinical diagnostic approaches. Molecular diagnostic methods are useful for simultaneously identifying multiple bacterial pathogens that were challenging to recognize by commercial biochemical techniques. Genetic testing procedures could determine the genetic diversity between closely related strains at the subspecies level. Consequently, these techniques are required for the development of detecting methods for specific strains and for epidemiological investigations in bacterial diseases. This review documented a variety of molecular techniques, including amplification of nucleic acids, polymerase chain reaction (PCR), nested PCR, real-time PCR, multiplex PCR, loop-mediated isothermal amplification (LAMP), DNA microarrays, and nucleotide sequencing assays, that are commonly used to identify fish pathogens.
Putative Virulence gene-Fish Disease
The genome of Vibrio anguillarum strain H775-3 was partially determined by a random sequencing procedure. A total of 2300 clones, 2100 from a plasmid library and 200 from a cosmid library, were sequenced and subjected to homology search by the BLAST algorithm. The total length of the sequenced clones is 1.5 Mbp. The nucleotide sequences were classified into 17 broad functional categories. Forty putative virulence-related genes were identified, 36 of which are novel in V. anguillarum, including a repeat in toxin gene cluster, haemolysin genes, enterobactin gene, protease genes, lipopolysaccharide biosynthesis genes, capsule biosynthesis gene, flagellar genes and pilus genes.
Bacteriome Structure, Function, and Probiotics in Fish Larviculture: The Good, the Bad, and the Gaps
Annual Review of Animal Biosciences, 2021
Aquaculture is the fastest-growing sector in food production worldwide. For decades, research on animal physiology, nutrition, and behavior established the foundations of best practices in land-based fish rearing and disease control. Current DNA sequencing, bioinformatics, and data science technologies now allow deep investigations of host-associated microbiomes in a tractable fashion. Adequate use of these technologies can illuminate microbiome dynamics and aid the engineering of microbiome-based solutions to disease prevention in an unprecedented manner. This review examines molecular studies of bacterial diversity, function, and host immunitymodulation at early stages of fish development, where microbial infections cause important economic losses. We uncover host colonization and virulence factors within a synthetic assemblage of fish pathogens using high-end comparative genomics and address the use of probiotics and paraprobiotics as applicable disease-prevention strategies in f...
International Journal of Fisheries and Aquatic Studies, 2018
Clinically diseased Oreochromis niloticus, Claris gariepinus, and Mugil cephalus were collected from different localities at El-Riah El-Tawfiki and its tributaries (Qalyubia), Kafr El-Sheik and Ismailia governorates. The clinical picture and gross lesions were recorded. Isolation and identification of the bacterial pathogens using traditional and molecular methods were demonstrated. It was found that the diseased fishes were showing general septicemic signs as skin hemorrhages and ulcerations, uni-and bilateral exophthalmia, congested internal organs with significant mortalities. Additionally, the total prevalence of the retrieved bacterial isolates was (55.27%) among the species and it was 62.5, 45, and 32.5 % in O. niloticus, C. gariepinus, and M. cephalus respectively. Summer season displayed the highest prevalence in the examined fishes. Based on the phenotypic and biochemical characterization using API20E, the isolated bacteria were identified as Aeromonads (A.
Pathogenesis of gram-negative bacterial infections in warmwater fish
Annual Review of Fish Diseases, 1993
Knowledge concerning the pathogenesis of many bacterial diseases in fish is limited, especially in those diseases that occur in warmwater species. This limited knowledge base is due to the relative recent emergence of warmwater fish culture as a major industry in many parts of the world, and to the previous economic insignificance of warmwater aquaculture and the bacterial pathogens affecting warmwater species. This article is an overview of the important gram-negative pathogens of warmwater fish, including members of the genera Aeromonus, Edwurdsiella, Pasteurella, Pseudomonas, and Vibrio. The current knowledge of the pathogenesis of these organisms is emphasized, including: the source of the pathogen, its preferred site and method for attaching to and penetrating the host, its adaptations for surviving the host immune system, and its strategies for obtaining nutrients required for proliferation and growth. Although information for many of these pathogens is limited, the intent of this article is to provide a baseline for the development of future research projects. Increases in worldwide aquaculture production will result in a demand for knowledge about the pathogenesis of bacterial pathogens in warmwater fish, because of its importance in making health management decisions, in deciding on treatment regimens, and in the development of vaccines.
Prevalence and distribution of pathogenic bacteria found in fish and fishery products: A review
2020
Fishes are among one of the major sources of food for many counties globally and a vital source of protein. Fishes are known to be carriers and vectors of pathogenic bacteria that are of major concern to consumers and public health. Contamination of pathogenic bacteria can arise from the aquatic ecosystem via pollution from domestic, industrial and agricultural discharges, contamination from soil, and also from the processing and marketing environments. Pathogenic bacteria that are associated with fishes and their related products include Gram negative bacteria like Vibrio spp., Escherichia coli, Salmonella spp., Shigella spp., Staphylococcus aureus, Pseudomonas spp., Listeria monocytogenes, C. botulinum and C. perfringens dominating the micro-flora of fishes. Members of the Enterobacteriaceae family are among one of the most prevalent pathogenic bacteria isolated from fishes that pose serious health problems. Several parts of fishes including the skin/scales, flesh, intestines, and...