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  • MDPI AG  (15)
  • Giri, Sib Sankar  (15)
  • English  (15)
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  • MDPI AG  (15)
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  • English  (15)
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  • 1
    Online Resource
    Online Resource
    Identification and Genome Analysis of Vibrio coralliilyticus Causing Mortality of Pacific Oyster (Crassostrea gigas) Larvae
    MDPI AG ; 2020
    In:  Pathogens Vol. 9, No. 3 ( 2020-03-11), p. 206-
    Details
    In: Pathogens, MDPI AG, Vol. 9, No. 3 ( 2020-03-11), p. 206-
    Abstract: Vibrio coralliilyticus is known as a coral pathogen that also infects marine bivalve larvae worldwide. It is considered to be one of the major constraints in artificial marine bivalve seed production as it causes mortality. In this study, we first isolated and characterized a high virulent of V. coralliilyticus designated as SNUTY-1 that was the cause of Pacific oyster larvae mortality in Korea. In the pathogenicity test, exposure to 2.14 × 105 CFU/mL for 24 h caused mortality to 88.65 ± 2.4% of the tested healthy Pacific oyster larvae. SNUTY-1 showed anti-microbial resistance to β-lactams, such as penicillins, cephalosporins, and carbapenems. We sequenced and assembled the complete genome of SNUTY-1 (5,842,676 bp), consisting of two chromosomes (Chr I and Chr II) and two plasmids (pSNUTY1 and pSNUTY2). The COG functional analysis confirmed that Chr I had more genes associated with basic cellular functions in comparison to Chr II. The results of the phylogenetic trees based on OrthoANI values indicated that the SNUTY-1 was closely related to V. coralliilyticus strains. SNUTY-1 had a unique plasmid (pSNUTY2), which could mean that the Korean isolate is different from other sequenced V. coralliilyticus strains from different geographical origins. Toxic proteins such as cytolysin/hemolysin and extracellular metalloprotease genes were encoded on Chr I and Chr II of SNUTY-1. These data facilitate the control of V. coralliilyticus infections in aquaculture by providing valuable insights into the biodiversity of this organism and valuable information for the study of virulence factors.
    Type of Medium: Online Resource
    ISSN: 2076-0817
    URL: Article
    DOI: 10.3390/pathogens9030206
    Language: English
    Publisher: MDPI AG
    Publication Date: 2020
    detail.hit.zdb_id: 2695572-6
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  • 2
    Online Resource
    Online Resource
    Genetic Characterization and Pathological Analysis of a Novel Bacterial Pathogen, Pseudomonas tructae, in Rainbow Trout (Oncorhynchus mykiss)
    MDPI AG ; 2019
    In:  Microorganisms Vol. 7, No. 10 ( 2019-10-10), p. 432-
    Details
    In: Microorganisms, MDPI AG, Vol. 7, No. 10 ( 2019-10-10), p. 432-
    Abstract: Pseudomonas species are one of the most prevalent bacterial species globally distributed in forest soil, river water, and human or animal skin. Some species are pathogens or opportunistic pathogens in hospitalized patients, animals, and plants. Various Pseudomonas species, including Pseudomonas putida, P. plecoglossicida, P. aeruginosa, and P. fluorescens, are known fish pathogens; P. fluorescens and P. putida cause severe losses in rainbow trout farming. Therefore, we investigated and isolated the pathogen that is responsible for mortality in a rainbow trout farm in Korea. The isolated bacterium was a strain of P. tructae, which was recently classified in the P. putida group. We performed taxonomical analysis of the bacteria in our previous study. In this study, we investigated the pathogenicity and clinical symptoms of P. tructae and analyzed its genomic characteristics. The pathogenicity of the strain was tested via challenge experiments in healthy rainbow trout and histopathologic analysis of the infected fish. Genome sequence was analyzed to identify the bacterial genes that are involved in antibiotic resistance and virulence. This is the first study reporting P. tructae as an emerging pathogen that is responsible for mortality in rainbow trout fisheries and providing the genome sequence of P. tructae.
    Type of Medium: Online Resource
    ISSN: 2076-2607
    URL: Article
    DOI: 10.3390/microorganisms7100432
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2720891-6
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  • 3
    Online Resource
    Online Resource
    Emergence of Rickettsial Infection in Rainbow Trout (Oncorhynchus mykiss) Fry Displaying the Appearance of Red Mark Syndrome in Korea
    MDPI AG ; 2019
    In:  Microorganisms Vol. 7, No. 9 ( 2019-08-29), p. 302-
    Details
    In: Microorganisms, MDPI AG, Vol. 7, No. 9 ( 2019-08-29), p. 302-
    Abstract: Red mark syndrome (RMS) is a fish disease caused by the infection of Rickettsial agents, especially affecting rainbow trout (Oncorhynchus mykiss). The disease is prevalent in many countries in Europe (France, Switzerland, Italy, and Slovenia), South America (Chile), North America (USA), and even Asia (Japan). However, it has not been reported in Korean aquaculture. In February 2019, rainbow trout presenting red spot lesions with swollen features on the lateral side of their body were observed at a hatchery in Korea. Fishes showing those clinical signs were fry weighing 25 ± 5 g. Moreover, the fish showing the red spot lesions were found dead, which suggests an outbreak of a mortality-causing disease. The symptoms were similar to those of RMS, and we identified the presence of Rickettsia-like organisms associated with this disease using polymerase chain reaction (PCR), sequencing, histopathologic examination, and transmission electron microscopy. The distinct features of this infection, compared to that in previous reports, were that RMS occurred in small-sized fish and accompanied mortality. Additionally, the presence of the Rickettsia agent was accompanied with outbreak of the disease. Therefore, this is the first report of RMS outbreak in rainbow trout fisheries in Korea.
    Type of Medium: Online Resource
    ISSN: 2076-2607
    URL: Article
    DOI: 10.3390/microorganisms7090302
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2720891-6
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  • 4
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    Online Resource
    Staphylococcus xylosus Infection in Rainbow Trout (Oncorhynchus mykiss) As a Primary Pathogenic Cause of Eye Protrusion and Mortality
    MDPI AG ; 2019
    In:  Microorganisms Vol. 7, No. 9 ( 2019-09-07), p. 330-
    Details
    In: Microorganisms, MDPI AG, Vol. 7, No. 9 ( 2019-09-07), p. 330-
    Abstract: Staphylococcal infections are extensively investigated in humans owing to the resistance of staphylococci to diverse antibiotics commonly used in hospitals. The resistance mechanism of methicillin-resistant Staphylococcus aureus has garnered the interest of researchers due to its risk to the global public health. Furthermore, the zoonotic potential of staphylococci has led to increased interest in their transmission mechanism via food, livestock, as well as domestic and wild animals. Although fish are globally consumed, there are only few studies on the potential threat of staphylococcal infection in aquatic animals. In this study, we present the first description of Staphylococcus xylosus infection and its pathogenicity in rainbow trout, which resulted in fish mortality and economic losses in trout fisheries. We focused on the pathogenic role of the bacterium and its influence on rainbow trout based on the clinical symptoms in the eyes. Staphylococcus xylosus infection induced exophthalmia and disrupted the primary immune barrier, which increased the possibility of other secondary bacterial infections in fish under poor conditions, resulting in continuous mortality.
    Type of Medium: Online Resource
    ISSN: 2076-2607
    URL: Article
    DOI: 10.3390/microorganisms7090330
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2720891-6
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  • 5
    Online Resource
    Online Resource
    Genome and Phylogenetic Analysis of Infectious Hematopoietic Necrosis Virus Strain SNU1 Isolated in Korea
    MDPI AG ; 2019
    In:  Pathogens Vol. 8, No. 4 ( 2019-10-21), p. 200-
    Details
    In: Pathogens, MDPI AG, Vol. 8, No. 4 ( 2019-10-21), p. 200-
    Abstract: Infectious hematopoietic necrosis virus (IHNV), one of the most important pathogenic fish viruses, affects trout fisheries and causes considerable economic losses. Currently, in Korea, more studies on IHNV infection are being reported. However, relatively less data is available on Korean isolates than on those from other countries. Few studies have focused on gene sequence analyses of IHNV glycoprotein (G) gene and almost none have focused on other gene fragments. Therefore, considering the dearth of adequate phylogenetic and genomic studies on Korean IHNV strains because of the lack of data, our study aimed to provide sufficient relevant data by sequencing the complete genome of the IHNV strain SNU1, which was recently isolated from a Korean rainbow trout farm. Moreover, we focused on expanding the perspectives on the phylogenesis of IHNV isolates from Korea and other Asian countries. IHNV was isolated from pooled hematopoietic tissue samples using Epithelioma papulosum cyprinid (EPC) cells, and phylogenetic analysis and genome study were conducted using complete G, N, and nonvirion (NV) gene sequences. Our main achievements were the development of a phylogenetic analytical method based on the NV gene and complete genome sequence analysis of the IHNV strain SNU1, which was compared with other Asian isolate sequences.
    Type of Medium: Online Resource
    ISSN: 2076-0817
    URL: Article
    DOI: 10.3390/pathogens8040200
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
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  • 6
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    Online Resource
    Janthinobacterium lividum as An Emerging Pathogenic Bacterium Affecting Rainbow Trout (Oncorhynchus mykiss) Fisheries in Korea
    MDPI AG ; 2019
    In:  Pathogens Vol. 8, No. 3 ( 2019-09-11), p. 146-
    Details
    In: Pathogens, MDPI AG, Vol. 8, No. 3 ( 2019-09-11), p. 146-
    Abstract: Janthinobacterium spp. are normally considered non-pathogenic, and few pathogenesis-related studies have been reported. Here, we report the first isolation of Janthinobacterium lividum in Korea as a pathogenic bacterium infecting rainbow trout. Mass mortality was observed at one rainbow trout hatchery, and dead fish were necropsied. Gram-negative, nonmotile, rod-shaped bacteria that grew on Cytophaga agar were isolated. A specific violet pigmentation was observed after 7 days of cultivation, and the species were characterized on the basis of the analysis of the 16S rRNA gene. Because no research has focused so far on the pathogenicity of these bacteria, our study was directed to their pathogenic role based on infection-induced histopathology. Examination of stained tissue sections revealed severe renal bacteraemia and tubule degeneration. Other tissue sections, including sections from the liver and the spleen, were relatively clear. The measured half-maximal lethal dose (LD50) was approximately 3 × 105 colony-forming units/fish, suggesting that this bacterium may be an opportunistic pathogen in rainbow trout fisheries. Since the bacterium commonly dwells in soil and most water for rainbow trout fisheries in Korea is supplied from ground water, the bacteria may naturally flow into the aquatic environment. Therefore, recognition of any pathogenic role of J. lividum is important for the prevention of disease in aquaculture.
    Type of Medium: Online Resource
    ISSN: 2076-0817
    URL: Article
    DOI: 10.3390/pathogens8030146
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
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  • 7
    Online Resource
    Online Resource
    A Case of Mortality Caused by Aeromonas hydrophila in Wild-Caught Red-Eyed Crocodile Skinks (Tribolonotus gracilis)
    MDPI AG ; 2019
    In:  Veterinary Sciences Vol. 7, No. 1 ( 2019-12-29), p. 4-
    Details
    In: Veterinary Sciences, MDPI AG, Vol. 7, No. 1 ( 2019-12-29), p. 4-
    Abstract: Aeromonas hydrophila, a Gram-negative bacterium commonly found in aquatic environments, is pathogenic to amphibians, reptiles, and mammals. In human medicine, the clinical symptoms of aeromonad infection include not only gastroenteritis but also extraintestinal infections, such as wounds, cellulitis, and septicemia, in immunocompromised and immunocompetent individuals. In this study, ten red-eyed crocodile skinks (Tribolonotus gracilis) that shared the same space were found dead 7 days after being shipped from Indonesia. The necropsy revealed A. hydrophila to be the causative agent, and the isolates were susceptible to most antibiotics, based on an antimicrobial susceptibility test. Seven virulence factors (act, ast, alt, aerA, fla, gcaT, and ahyB) considered to be associated with virulence were detected by PCR. Microscopic examination revealed several necrotic lesions and melano-macrophage centers in the tissue slides. Reptiles caught in the wild for trade experience captivity stress. Furthermore, in the winter, reptiles are easily exposed to the cold atmosphere. These stresses can negatively impact the immunity of these ectotherms, making them vulnerable to A. hydrophila infections. Therefore, to avoid such opportunistic infections and mortality following exposure to severe stress, medical care is recommended. The studies of alternatives, such as bacteriophage and bacteriocin, are needed for a preventive application.
    Type of Medium: Online Resource
    ISSN: 2306-7381
    URL: Article
    DOI: 10.3390/vetsci7010004
    Language: English
    Publisher: MDPI AG
    Publication Date: 2019
    detail.hit.zdb_id: 2768971-2
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  • 8
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    Online Resource
    Phage Cocktail in Combination with Kasugamycin as a Potential Treatment for Fire Blight Caused by Erwinia amylovora
    MDPI AG ; 2022
    In:  Antibiotics Vol. 11, No. 11 ( 2022-11-06), p. 1566-
    Details
    In: Antibiotics, MDPI AG, Vol. 11, No. 11 ( 2022-11-06), p. 1566-
    Abstract: Recently, there has been an increasing number of blight disease reports associated with Erwinia amylovora and Erwinia pyrifoliae in South Korea. Current management protocols that have been conducted with antibiotics have faced resistance problems and the outbreak has not decreased. Because of this concern, the present study aimed to provide an alternative method to control the invasive fire blight outbreak in the nation using bacteriophages (phages) in combination with an antibiotic agent (kasugamycin). Among 54 phage isolates, we selected five phages, pEa_SNUABM_27, 31, 32, 47, and 48, based on their bacteriolytic efficacy. Although only phage pEa_SNUABM_27 showed host specificity for E. amylovora, all five phages presented complementary lytic potential that improved the host infectivity coverage of each phage All the phages in the cocktail solution could lyse phage-resistant strains. These strains had a decreased tolerance to the antibiotic kasugamycin, and a synergistic effect of phages and antibiotics was demonstrated both in vitro and on immature wound-infected apples. It is noteworthy that the antibacterial effect of the phage cocktail or phage cocktail-sub-minimal inhibitory concentration (MIC) of kasugamycin was significantly higher than the kasugamycin at the MIC. The selected phages were experimentally stable under environmental factors such as thermal or pH stress. Genomic analysis revealed these are novel Erwinia-infecting phages, and did not encode antibiotic-, virulence-, or lysogenic phage-related genes. In conclusion, we suggest the potential of the phage cocktail and kasugamycin combination as an effective strategy that would minimize the use of antibiotics, which are being excessively used in order to control fire blight pathogens.
    Type of Medium: Online Resource
    ISSN: 2079-6382
    URL: Article
    DOI: 10.3390/antibiotics11111566
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2681345-2
    SSG: 15,3
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  • 9
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    Online Resource
    The Opportunistic Pathogen Chryseobacterium balustinum WLT: Pathogenicity and Antibiotic Resistance
    MDPI AG ; 2022
    In:  Fishes Vol. 7, No. 1 ( 2022-01-23), p. 26-
    Details
    In: Fishes, MDPI AG, Vol. 7, No. 1 ( 2022-01-23), p. 26-
    Abstract: This study aimed to re-evaluate the pathogenic characteristics of Chryseobacterium balustinum, generally known as a food spoilage bacterium. We observed mass mortality in a rainbow trout farm in Jeonbuk province, Republic of Korea. Fewer studies have reported on rainbow trout mortality or infections in Korea than in other countries; among these, few studies have reported cases of Chryseobacterium infections. Sequencing analysis revealed that this bacterium is closely related (99.24%) to Chryseobacterium balustinum. Bacterial identification assays, including the API test, sequencing, and phylogenetic analysis, found the 24 isolates to be C. balustinum. The strain showed multiple resistance to 18 of 25 antibiotics tested. Primary clinical symptoms of its infection are damage to the fins, necrosis, and cytoplasmic vacuolation in hepatocytes. The pathogenicity of the strain was determined following Koch’s postulates and the challenge test. The present results suggest that C. balustinum WLT can be considered a multidrug-resistant zoonotic pathogen responsible for mortality and economic losses.
    Type of Medium: Online Resource
    ISSN: 2410-3888
    URL: Article
    DOI: 10.3390/fishes7010026
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2932929-2
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  • 10
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    Prolongation of Fate of Bacteriophages In Vivo by Polylactic-Co-Glycolic-Acid/Alginate-Composite Encapsulation
    MDPI AG ; 2022
    In:  Antibiotics Vol. 11, No. 9 ( 2022-09-17), p. 1264-
    Details
    In: Antibiotics, MDPI AG, Vol. 11, No. 9 ( 2022-09-17), p. 1264-
    Abstract: With concern growing over antibiotics resistance, the use of bacteriophages to combat resistant bacteria has been suggested as an alternative strategy with which to enable the selective control of targeted pathogens. One major challenge that restrains the therapeutic application of bacteriophages as antibacterial agents is their short lifespan, which limits their antibacterial effect in vivo. Here, we developed a polylactic-co-glycolic acid (PLGA)/alginate-composite microsphere for increasing the lifespan of bacteriophages in vivo. The alginate matrix in PLGA microspheres encapsulated the bacteriophages and protected them against destabilization by an organic solvent. Encapsulated bacteriophages were detected in the tissue for 28 days post-administration, while the bacteriophages administered without advanced encapsulation survived in vivo for only 3–5 days. The bacteriophages with extended fate showed prophylaxis against the bacterial pathogens for 28 days post-administration. This enhanced prophylaxis is presumed to have originated from the diminished immune response against these encapsulated bacteriophages because of their controlled release. Collectively, composite encapsulation has prophylactic potential against bacterial pathogens that threaten food safety and public health.
    Type of Medium: Online Resource
    ISSN: 2079-6382
    URL: Article
    DOI: 10.3390/antibiotics11091264
    Language: English
    Publisher: MDPI AG
    Publication Date: 2022
    detail.hit.zdb_id: 2681345-2
    SSG: 15,3
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