Details of a Researcher - NISHIKI Issei

Papers - NISHIKI Issei

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Characterization and Epidemiological Study of Newly Emerging Lactococcus garvieae Serotype III in Farmed Fish in Japan

Araki Kaho, Nishiki Issei, Yoshida Terutoyo

魚病研究 59 ( 4 ) 119 - 126 2024.12

Language：English Publishing type：Research paper (scientific journal) Publisher：日本魚病学会

Lactococcus garvieae serotype III, a newly emerging pathogen that causes lactococcal infection, has been detected in fish farms since 2021. This pathogen has caused severe damage to the striped jack Pseudocaranx dentex and greater amberjack Seriola dumerili. This study collected strains from various fish species on farms between 2021 and 2023 and conducted an epidemiological and characterization study of L. garvieae serotype III using biochemical characterization tests, agglutinating titers against diagnostic antisera, biased sinusoidal field gel electrophoresis (BSFGE), and drug susceptibility tests. Capsule-like structures were found on the cell surfaces of L. garvieae serotype III strains, and strains showed similar characteristics except for the reaction of acidification ribose in biochemical characterization test using the API 20 STREP system. All strains were agglutinated with antiserum raised against L. garvieae serotype III and lower or non-agglutinated with antiserum raised against L. garvieae serotype I. BSFGE analysis identified three types of electrophoretic pattern: A, B, and C. BSFGE types A and B spread to fish farms in 2021, while type C found in 2022. All strains analyzed in this study were thought to be resistant to lincomycin but not to erythromycin.

DOI： 10.3147/jsfp.59.119

CiNii Research

Development of a Discriminating Method for Pathogenic Bacteria that Cause Lactococcal Infections in Marine Fish Farms in Japan

Araki Kaho, Mouri Ayaka, Minami Takayuki, Nishiki Issei, Yoshida Terutoyo

Fish Pathology 59 ( 2 ) 63 - 70 2024.6

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japanese Society of Fish Pathology

Pathogenic bacteria that cause lactococcal infections in marine aquaculture in Japan are currently classified into three types based on serotype and genetic characterization: Lactococcus garvieae type I, L. formosensis (formerly, L. garvieae type II), and L. garvieae type III. Although a slide agglutination test with rabbit antiserum is used to discriminate these three types, its accuracy is insufficient for clinical diagnosis owing to the existence of isolates that show agglutination with more than one diagnostic antiserum. Furthermore, a previously developed PCR assay was not able to distinguish L. garvieae type I from L. garvieae type III, a newly emerging pathogen. In this study, primers specific to each type were designed and applied in a newly developed multiplex PCR assay to discriminate these three types of lactococcal pathogens isolated from diseased fish. Amplification products with the expected sizes of 262, 1,007, and 500 bp could be obtained for L. garvieae type I, L. formosensis, and L. garvieae type III, respectively. Amplification products could not be obtained from isolates of Lactococcus spp. from non-marine fish species. These results show that the multiplex PCR assay can discriminate these three pathogens that cause lactococcal infections in fish farms.

DOI： 10.3147/jsfp.59.63

CiNii Research

Pathogenicity of Lactococcus garvieae serotype III against yellowtail Seriola quinqueradiata and striped jack Pseudocaranx dentex

Fish Pathology 59 ( 1 ) 33 - 35 2024.3

Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japanese Society of Fish Pathology

DOI： 10.3147/jsfp.59.33

CiNii Research

Emerging New Serotype Lactococcus garvieae Infection in Farmed Marine Fish in Japan Reviewed

Minami Takayuki, Yoshida Terutoyo, Nishiki Issei

Fish Pathology 58 ( 4 ) 146 - 152 2023.12

Authorship：Corresponding author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japanese Society of Fish Pathology

Mortalities due to Lactococcus garvieae-like infection have been observed in farmed greater amberjack Seriola dumerili previously immunized with a commercial L. garvieae vaccine containing serotype I and II strains in Miyazaki Prefecture since August 2021. The isolates from diseased fish were not agglutinated by the anti-serotype I and II sera, and showed genetic similarity to L. garvieae serotype I in multi-locus sequence (16S rRNA gene, pheS, recA, rpoA and rpoB) analysis. The pathogenicity of isolates was confirmed by intraperitoneal injection in greater amberjack, and the lethal dose fifty was less than 1.6 × 103 CFU/FISH. In a vaccine trial, greater amberjack, which had been immunized with formalin-killed cells (FKC) prepared from both serotype I and II strains, was not effectively protected against an isolate from this study, whereas those immunized with FKC prepared using the isolate were effectively protected against the infection with an isolate exhibiting the same antigenicity. Based on these findings, we propose a new serotype: serotype III, which is not agglutinated with both anti-serotype I and II serum and not protected against a serotype I and serotype II-combined vaccine.

DOI： 10.3147/jsfp.58.146

CiNii Research

Isolation and Complete Genome Sequencing of NS-I, a Lytic Bacteriophage Infecting Fish Pathogenic Strains of Nocardia seriolae

Muhammad Akmal, Kaho Araki, Issei Nishiki, Terutoyo Yoshida

PHAGE 4 ( 4 ) 151 - 158 2023.12

Publishing type：Research paper (scientific journal) Publisher：Mary Ann Liebert Inc

DOI： 10.1089/phage.2023.0019

CiNii Research

Resistance and genomic characterization of a plasmid pkh2101 harbouring erm(B) isolated from emerging fish pathogen Lactococcus garvieae serotype II in Japan. Reviewed

Akmal M, Akatsuka M, Nishiki I, Yoshida T

Journal of fish diseases 46 ( 8 ) 841 - 848 2023.8

Language：English Publishing type：Research paper (scientific journal) Publisher：Wiley

<jats:title>Abstract</jats:title><jats:p>The emergence of antibiotic‐resistant pathogenic strains of <jats:italic>Lactococcus garvieae</jats:italic> serotype II isolated from fish in Japan has become a growing concern in recent years. The data on drug susceptibility and its associated resistance mechanism are limited. Therefore, the present study was conducted to determine the minimum inhibitory concentrations (MICs) of chemotherapeutic agents against 98 pathogenic strains of emerging <jats:italic>Lactococcus garvieae</jats:italic> serotype II isolated from fish from six different prefectures in Japan from 2018 to 2021. The tested strains were resistant to erythromycin, lincomycin and tiamulin. PCR amplification revealed the presence of <jats:italic>erm</jats:italic>(B) in all erythromycin‐resistant strains, while a conjugation experiment confirmed that these strains carried <jats:italic>erm</jats:italic>(B) that could be transferred to recipient <jats:italic>Enterococcus faecalis</jats:italic> OG1RF with frequencies from 10<jats:sup>−4</jats:sup> to 10<jats:sup>−6</jats:sup> per donor cells. Nucleotide sequencing of the representative isolated plasmid pkh2101 from an erythromycin‐resistant strain showed that it was a 26,850 bp molecule with an average GC content of 33.49%, comprising 31 CDSs, 13 of which remained without any functional annotation. Comparative genomic analysis suggested that pkh2101 shared the highest similarity (97.57% identity) with the plasmid pAMbeta1, which was previously isolated clinically from <jats:italic>Enterococcus faecalis</jats:italic> DS‐5. This study provides potential evidence that the plasmid harbouring <jats:italic>erm</jats:italic>(B) could be a source of antibiotic resistance transmission in emerging <jats:italic>L. garvieae</jats:italic> infection in aquaculture.</jats:p>

DOI： 10.1111/jfd.13793

PubMed

CiNii Research

A Single Point Mutation in the lsa(D) Variant in Fish Pathogenic Lactococcus garvieae Serotype I Which Affects Lincomycin and Related Antibiotics Resistance Reviewed

Fish Pathology 58 ( 2 ) 48 - 59 2023.6

Language：English Publishing type：Research paper (scientific journal) Publisher：The Japanese Society of Fish Pathology

DOI： 10.3147/jsfp.58.48

CiNii Research

Vibrio anguillarum J-O-1 Type Infection in Farmed Greater Amberjack Seriola dumerili Reviewed

Minami Takayuki, Tawara Yusei, Hirokawa Yusuke, Nishiki Issei

Fish Pathology 57 ( 4 ) 131 - 135 2023.1

Authorship：Corresponding author Language：Japanese Publishing type：Research paper (scientific journal) Publisher：The Japanese Society of Fish Pathology

Mortalities were observed in farmed greater amberjack Seriola dumerili immunized with a commercial Vibrio anguillarum serotype J-O-3 vaccine. Symptoms of infection included extruded eye, opacity of cornea, exfoliation of head epithelium and operculum redding. Bacteria isolated from infected fish were identified as V. anguillarum serotype J-O-1 based on APE20E, anti V. anguillarum J-O-1 serum, species-specific multiplex PCR assays, and 16S rRNA sequence analysis. Experimental infection revealed that the isolate was pathogenic to greater amberjack. In a vaccine trial, mortality of fish immunized with formalin-killed cells (FKC) of the isolate was significantly lower than that of control fish, suggesting that FKC of the isolate prevents greater amberjack from V. anguillarum serotype J-O-1 infection.

DOI： 10.3147/jsfp.57.131

CiNii Research

Complete Genome Sequence of Lactococcus garvieae MS210922A, Isolated from Farmed Greater Amberjack (Seriola dumerili) in Japan. Reviewed

Akmal M, Yoshida T, Nishiki I

Microbiology resource announcements 11 ( 12 ) e0089022 2022.12

Language：English Publishing type：Research paper (scientific journal) Publisher：American Society for Microbiology

<jats:p>
Here, we report the complete genome sequence of a potentially new serotype,
<jats:named-content content-type="genus-species">Lactococcus garvieae</jats:named-content>
strain MS210922A, isolated from greater amberjack. It is nonreactive to serotype I or II antisera. The complete genome comprises 2,007,159 bp, including 1,929 coding, 16 rRNA, and 58 tRNA genes, with 38.9% G+C content.
</jats:p>

DOI： 10.1128/mra.00890-22

PubMed

CiNii Research

Complete genome sequence of a novel lytic bacteriophage, PLG-II, specific for Lactococcus garvieae serotype II strains that are pathogenic to fish. Reviewed

Akmal M, Nishiki I, Zrelovs N, Yoshida T

Archives of virology 167 ( 11 ) 2331 - 2335 2022.11

Language：English Publishing type：Research paper (scientific journal)

DOI： 10.1007/s00705-022-05568-7

PubMed

Characterization of lsa(D), a Novel Gene Responsible for Resistance to Lincosamides, Streptogramins A, and Pleuromutilins in Fish Pathogenic Lactococcus garvieae Serotype II.

Shi YZ, Yoshida T, Fujiwara A, Nishiki I

Microbial drug resistance (Larchmont, N.Y.) 27 ( 3 ) 301 - 310 2021.3

Language：English Publishing type：Research paper (scientific journal) Publisher：Mary Ann Liebert Inc

Aims: Fish pathogenic Lactococcus garvieae serotype II has been isolated from cultured fish species in Japan. This study aimed to investigate the molecular mechanisms of lincomycin (LCM)-resistant ...

DOI： 10.1089/mdr.2020.0218

PubMed

CiNii Research

Characterization of lsa(D), a Novel Gene Responsible for Resistance to Lincosamides, Streptogramins A, and Pleuromutilins in Fish Pathogenic Lactococcus garvieae Serotype II Reviewed

Shi, Y.-Z., Yoshida, T., Fujiwara, A., Nishiki, I.

Microbial Drug Resistance 2021