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Advances in Bacterial Fish and Shellfish Diseases in Aquaculture

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A special issue of Microorganisms (ISSN 2076-2607). This special issue belongs to the section "Environmental Microbiology".

Deadline for manuscript submissions: closed (30 April 2022) | Viewed by 17957

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Special Issue Editor

Dr. Miguel Balado

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Guest Editor

Instituto de Acuicultura, Universidade de Santiago de Compostela, Santiago, Spain
Interests: bacterial fish diseases; virulence factors; iron uptake mechanisms; novel therapeutic targets
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

Aquaculture of fish and shellfish has shown a significant worldwide expansion over recent decades. The increasing demand for marine and freshwater products associated with the growing world population has resulted in a decline in wild populations, making aquaculture a strategic sector for many countries. Unfortunately, its development has led to a higher incidence of disease caused by viruses and bacteria and, despite the efforts made, infectious outbreaks continue to occur. In that context, aquaculture that is safe for consumers, environmentally sustainable and economically viable must be developed from scientific knowledge.

A combination of the scrupulous handling of animals and the implementation of disease prevention strategies, such as vaccination programs, has been shown as the most efficient way to prevent infectious diseases, minimizing the use of antimicrobial drugs. However, the use of vaccines and antibiotics impose strong selection for resistance leading to the fast evolution of microbial pathogens that inhabit farms (e.g., by horizontal gene transfer). Thus, continuous efforts must be made to characterize the novel variants of relevant pathogens and potential emergent pathogens and, in turn, adjust prevention strategies.

In this Special Issue of Microorganisms, we invite you to send contributions focused on any biological aspect concerning some of the most important bacterial pathogens affecting cultured fish and shellfish. We will welcome manuscripts focused on any aspect related to diagnosis, treatment, vaccination and the development of prevention strategies, the infection process and host–pathogen interactions, the characterization of virulence factors, microbial ecology, and any other research related to infectious diseases affecting cultured aquatic animals.

Dr. Miguel Balado
Guest Editor

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Microorganisms is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2700 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

infection disease
bacterial pathogen
aquaculture
host–pathogen interaction
infection process
microbiota
virulence factor
diagnosis
disease prevention
vaccine
mollusk
fish
shellfish

Published Papers (7 papers)

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11 pages, 3234 KiB

Open AccessCommunication

Isolation and Genetic Characterization of Streptococcus iniae Virulence Factors in Adriatic Sturgeon (Acipenser naccarii)

by Silvia Colussi, Paolo Pastorino, Davide Mugetti, Elisabetta Antuofermo, Simona Sciuto, Giuseppe Esposito, Marta Polinas, Mattia Tomasoni, Giovanni Pietro Burrai, José Francisco Fernández-Garayzábal, Pier Luigi Acutis, Claudio Pedron and Marino Prearo

Microorganisms 2022, 10(5), 883; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms10050883 - 22 Apr 2022

Cited by 6 | Viewed by 1822

Abstract

The first case of infection of Streptococcus iniae in Adriatic sturgeon (Acipenser naccarii) was recently reported in a raceway system located in Northern Italy. A second episode of infection in sturgeons with absence of mortality and evident clinical signs, was registered in November 2020 in the same farm and is reported in this study. Histopathological changes observed in infected organs are described. The strains isolated in the two episodes were compared using molecular analysis based on PCR, phylogeny and virulence factors analysis. Not all the major virulence factors were detected for the two strains; in particular the strains 78697, isolated in November, lacks cpsD, compared to the strains 64844, isolated in September. Moreover, genetic variations were reported for lctO and pmg genes. These findings let us hypothesize a different virulence of the strains in accordance with clinical findings related to the sturgeons. Full article

(This article belongs to the Special Issue Advances in Bacterial Fish and Shellfish Diseases in Aquaculture)

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28 pages, 10540 KiB

Open AccessArticle

Epitheliocystis in Greater Amberjack: Evidence of a Novel Causative Agent, Pathology, Immune Response and Epidemiological Findings

by Maria Chiara Cascarano, Maja Ruetten, Lloyd Vaughan, Maria Ioanna Tsertou, Dimitra Georgopoulou, Kleoniki Keklikoglou, Nikos Papandroulakis and Pantelis Katharios

Microorganisms 2022, 10(3), 627; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms10030627 - 15 Mar 2022

Cited by 4 | Viewed by 2406

Abstract

Epitheliocystis is a fish gill disease caused by a broad range of intracellular bacteria infecting freshwater and marine fish worldwide. Here we report the occurrence and progression of epitheliocystis in greater amberjack reared in Crete (Greece). The disease appears to be caused mainly by a novel Betaproteobacteria belonging to the Candidatus Ichthyocystis genus with a second agent genetically similar to Ca. Parilichlamydia carangidicola coinfecting the gills in some cases. After a first detection of the disease in 2017, we investigated epitheliocystis in the following year’s cohort of greater amberjack juveniles (cohort 2018) transferred from inland tanks to the same cage farm in the open sea where the first outbreak was detected. This cohort was monitored for over a year together with stocks of gilthead seabream and meagre co-farmed in the same area. Our observations showed that epitheliocystis could be detected in greater amberjack gills as early as a month following the transfer to sea cages, with ionocytes at the base of the gill lamellae being initially infected. Cyst formation appears to trigger a proliferative response, leading to the fusion of lamellae, impairment of gill functions and subsequently to mortality. Lesions are characterized by infiltration of immune cells, indicating activation of the innate immune response. At later stages of the outbreak, cysts were no longer found in ionocytes but were observed in mucocytes at the trailing edge of the filament. Whole cysts appeared finally to be expelled from infected mucocytes directly into the water, which might constitute a novel means of dispersion of the infectious agents. Molecular screening indicates that meagre is not affected by this disease and confirms the presence of previously described epitheliocystis agents, Ca. Ichthyocystis sparus, Ca. Ichthyocystis hellenicum and Ca. Similichlamydia spp., in gilthead seabream. Prevalence data show that the bacteria persist in both gilthead seabream and greater amberjack cohorts after first infection. Full article

(This article belongs to the Special Issue Advances in Bacterial Fish and Shellfish Diseases in Aquaculture)

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9 pages, 858 KiB

Open AccessArticle

Susceptibility to Bismuth(III) of Aquaculture Bacterial Pathogens: Effectiveness of Bismuth–Deferiprone Therapy against Vibrio anguillarum Infection in Fish

by Miguel Balado, Diego Rey-Varela, Ana M. Albela and Manuel L. Lemos

Microorganisms 2021, 9(11), 2399; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms9112399 - 21 Nov 2021

Viewed by 1649

Abstract

Bismuth is a heavy metal with antibacterial properties that has a long history of medicinal use. The results reported here suggest that bismuth(III) (chelated with deferiprone) could be used in aquaculture systems to treat bacterial disease outbreaks, greatly reducing antibiotic use. We tested bismuth susceptibility in a collection of aquaculture bacterial pathogens. In the presence of bismuth concentrations ranging from 1.3 to 13 µM, most bacteria started showing a drastic decrease in their growth ability, although with high inter- and intraspecific variability. The minimal inhibitory concentrations of bismuth ranged from 13 to more than 780 µM, depending on bacterial species and strain. The results of in vivo assays suggest that low concentrations of bismuth could be especially effective to treat vibriosis caused by Vibrio anguillarum, since bismuth greatly reduced mortality in experimentally infected fish without any observable side effects. A bismuth therapy, alone or combined with other antimicrobials, could contribute to reduce the use of antibiotics in aquaculture. Full article

(This article belongs to the Special Issue Advances in Bacterial Fish and Shellfish Diseases in Aquaculture)

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21 pages, 4298 KiB

Open AccessArticle

Factors Driving Bacterial Microbiota of Eggs from Commercial Hatcheries of European Seabass and Gilthead Seabream

by Babak Najafpour, Patricia I. S. Pinto, Katerina A. Moutou, Adelino V. M. Canario and Deborah M. Power

Microorganisms 2021, 9(11), 2275; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms9112275 - 01 Nov 2021

Cited by 6 | Viewed by 2235

Abstract

A comprehensive understanding of how bacterial community abundance changes in fishes during their lifecycle and the role of the microbiota on health and production is still lacking. From this perspective, the egg bacterial communities of two commercially farmed species, the European seabass (Dicentrarchus labrax) and the gilthead seabream (Sparus aurata), from different aquaculture sites were compared, and the potential effect of broodstock water microbiota and disinfectants on the egg microbiota was evaluated. Moreover, 16S ribosomal RNA gene sequencing was used to profile the bacterial communities of the eggs and broodstock water from three commercial hatcheries. Proteobacteria were the most common and dominant phyla across the samples (49.7% on average). Vibrio sp. was the most highly represented genus (7.1%), followed by Glaciecola (4.8%), Pseudoalteromonas (4.4%), and Colwellia (4.2%), in eggs and water across the sites. Routinely used iodine-based disinfectants slightly reduced the eggs’ bacterial load but did not significantly change their composition. Site, species, and type of sample (eggs or water) drove the microbial community structure and influenced microbiome functional profiles. The egg and seawater microbiome composition differed in abundance but shared similar functional profiles. The strong impact of site and species on egg bacterial communities indicates that disease management needs to be site-specific and highlights the need for species- and site-specific optimization of disinfection protocols. Full article

(This article belongs to the Special Issue Advances in Bacterial Fish and Shellfish Diseases in Aquaculture)

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17 pages, 3913 KiB

Open AccessArticle

Isolation and Characterization of Vibrio kanaloae as a Major Pathogen Associated with Mass Mortalities of Ark Clam, Scapharca broughtonii, in Cold Season

by Bowen Huang, Xiang Zhang, Chongming Wang, Changming Bai, Chen Li, Chenghua Li and Lusheng Xin

Microorganisms 2021, 9(10), 2161; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms9102161 - 16 Oct 2021

Cited by 9 | Viewed by 2354

Abstract

High temperature is a risk factor for vibriosis outbreaks. Most vibrios are opportunistic pathogens that cause the mortality of aquatic animals at the vibrio optimal growth temperature (~25 °C), whereas a dominant Vibrio kanaloae strain SbA1-1 is isolated from natural diseased ark clams (Scapharca broughtonii) during cold seasons in this study. Consistent symptoms and histopathological features reappeared under an immersion infection with SbA1-1 performed at 15 °C. The pathogenicity difference of SbA1-1 was assessed under different temperatures (15 °C and 25 °C). The cumulative mortality rates of ark clams were significantly higher at the low temperature (15 °C) than at the high temperature (25 °C); up to 98% on 16th day post SbA1-1 infection. While the growth ratio of SbA1-1 was retarded at the low temperature, the hemolytic activity and siderophores productivity of SbA1-1 were increased. This study constitutes the first isolation of V. kanaloae from the natural diseased ark clams (S. broughtonii) in cold seasons and the exposition of the dissimilar pathogenicity of SbA1-1 at a different temperature. All the above indicates that V. kanaloae constitutes a threat to ark clam culture, especially in cold seasons. Full article

(This article belongs to the Special Issue Advances in Bacterial Fish and Shellfish Diseases in Aquaculture)

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36 pages, 6138 KiB

Open AccessArticle

A Novel Marine Pathogen Isolated from Wild Cunners (Tautogolabrus adspersus): Comparative Genomics and Transcriptome Profiling of Pseudomonas sp. Strain J380

by Navaneethaiyer Umasuthan, Katherinne Valderrama, Ignacio Vasquez, Cristopher Segovia, Ahmed Hossain, Trung Cao, Hajarooba Gnanagobal, Jennifer Monk, Danny Boyce and Javier Santander

Microorganisms 2021, 9(4), 812; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms9040812 - 12 Apr 2021

Cited by 9 | Viewed by 3366

Abstract

Cunner (Tautogolabrus adspersus) is a cleaner fish being considered for utilized in the North Atlantic salmon (Salmo salar) aquaculture industry to biocontrol sea lice infestations. However, bacterial diseases due to natural infections in wild cunners have yet to be described. This study reports the isolation of Pseudomonas sp. J380 from infected wild cunners and its phenotypic, genomic, and transcriptomic characterization. This Gram-negative motile rod-shaped bacterium showed a mesophilic (4–28 °C) and halotolerant growth. Under iron-limited conditions, Pseudomonas sp. J380 produced pyoverdine-type fluorescent siderophore. Koch’s postulates were verified in wild cunners by intraperitoneally (i.p.) injecting Pseudomonas sp. J380 at 4 × 10³, 4 × 10⁵, and 4 × 10⁷ colony forming units (CFU)/dose. Host-range and comparative virulence were also investigated in lumpfish and Atlantic salmon i.p. injected with ~10⁶ CFU/dose. Lumpfish were more susceptible compared to cunners, and Atlantic salmon was resistant to Pseudomonas sp. J380 infection. Cunner tissues were heavily colonized by Pseudomonas sp. J380 compared to lumpfish and Atlantic salmon suggesting that it might be an opportunistic pathogen in cunners. The genome of Pseudomonas sp. J380 was 6.26 megabases (Mb) with a guanine-cytosine (GC) content of 59.7%. Biochemical profiles, as well as comparative and phylogenomic analyses, suggested that Pseudomonas sp. J380 belongs to the P. fluorescens species complex. Transcriptome profiling under iron-limited vs. iron-enriched conditions identified 1159 differentially expressed genes (DEGs). Cellular metabolic processes, such as ribosomal and energy production, and protein synthesis, were impeded by iron limitation. In contrast, genes involved in environmental adaptation mechanisms including two-component systems, histidine catabolism, and redox balance were transcriptionally up-regulated. Furthermore, iron limitation triggered the differential expression of genes encoding proteins associated with iron homeostasis. As the first report on a bacterial infection in cunners, the current study provides an overview of a new marine pathogen, Pseudomonas sp. J380. Full article

(This article belongs to the Special Issue Advances in Bacterial Fish and Shellfish Diseases in Aquaculture)

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12 pages, 729 KiB

Open AccessBrief Report

The Analysis of Live-Attenuated Piscirickettsia salmonis Vaccine Reveals the Short-Term Upregulation of Innate and Adaptive Immune Genes in Atlantic Salmon (Salmo salar): An In Situ Open-Sea Cages Study

by Deborah Vargas, Eva Vallejos-Vidal, Sebastián Reyes-Cerpa, Aarón Oyarzún-Arrau, Claudio Acuña-Castillo, Mónica Imarai, Felipe E. Reyes-López and Ana María Sandino

Microorganisms 2021, 9(4), 703; https://0-doi-org.brum.beds.ac.uk/10.3390/microorganisms9040703 - 29 Mar 2021

Cited by 9 | Viewed by 2768

Abstract

Piscirickettsia salmonis, the etiological agent of the Salmon Rickettsial Septicemia (SRS), is one the most serious health problems for the Chilean salmon industry. Typical antimicrobial strategies used against P. salmonis include antibiotics and vaccines, but these applications have largely failed. A few years ago, the first attenuated-live vaccine against SRS (ALPHA JECT LiVac^® SRS vaccine) was released to the market. However, there is no data about the agents involved in the activation of the immune response induced under field conditions. Therefore, in this study we evaluated the expression profile of a set of gene markers related to innate and adaptive immunity in the context of a cellular response in Atlantic salmon (Salmo salar) reared under productive farm conditions and immunized with a live-attenuated vaccine against P. salmonis. We analyzed the expression at zero, 5-, 15- and 45-days post-vaccination (dpv). Our results reveal that the administration of the attenuated live SRS LiVac vaccine induces a short-term upregulation of the cellular-mediated immune response at 5 dpv modulated by the upregulation of ifnα, ifnγ, and the cd4 and cd8α T cell surface markers. In addition, we also registered the upregulation of il-10 and tgfβ. Altogether, the results suggest that a balanced activation of the immune response took place only at early times post-vaccination (5 dpv). The scope of this short-term upregulation of the cellular-mediated immune response against a natural outbreak in fish subjected to productive farm conditions deserves further research. Full article

(This article belongs to the Special Issue Advances in Bacterial Fish and Shellfish Diseases in Aquaculture)

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