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Xu H, Zhu N, Chen Y, Yue H, Zhuo M, Wangkahart E, Liang Q, Wang R. Pathogenicity of Streptococcus iniae causing mass mortalities of yellow catfish ( Tachysurus fulvidraco) and its induced host immune response. Front Microbiol 2024; 15:1374688. [PMID: 38585696 PMCID: PMC10995319 DOI: 10.3389/fmicb.2024.1374688] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2024] [Accepted: 02/26/2024] [Indexed: 04/09/2024] Open
Abstract
The outbreak of mass mortality occurred in Tachysurus fulvidraco farm in Hubei province of China. The pathogenic strain of Streptococcus iniae (termed 2022SI08) was isolated and identified from diseased T. fulvidraco, based on morphological, physiological, and biochemical characteristics, as well as 16S rRNA gene sequence and phylogenetic analysis. Further, the whole genome of isolate S. iniae was sequenced and predicted to contain one single circular chromosome of 1,776,777 bp with a GC content of 37.14%. The genomic sequence analysis showed that 2022SI08 was positive for 204 virulent and 127 antibiotic resistant genes. The experimental challenge demonstrated the high pathogenicity of the retrieved isolate of S. iniae, with a median lethal dosage (LD50) 9.53 × 105 CFU/g. Histopathological examination indicated that the 2022SI08 strain could induce extensive tissue cell degeneration, necrosis, hemorrhage, and inflammation in the skin, gill, fin, spleen, liver, kidney, intestine, eye, and brain. Moreover, the innate immune enzyme activities in serum such as acid phosphatase and alkaline phosphatase were increased significantly at 24 and 48 h post infection (hpi) and then decreased at 168 hpi. The transcriptional profile of immune associated gene in T. fulvidraco following bacterial infection was detected at each point of time, and the results revealed clear transcriptional activation of those genes, which proving their reacting and regulatory role during the response of the host against S. iniae infection. The results revealed that S. iniae was an etiological agent in the mass mortalities of T. fulvidraco and this research will be conducive for increasing our understanding on pathogenesis and host defensive system in S. iniae invasion.
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Affiliation(s)
- Hongsen Xu
- Hubei Key Laboratory of Animal Nutrition and Feed Science, School of Animal Science and Nutritional Engineering, Wuhan Polytechnic University, Wuhan, China
| | - Nengbin Zhu
- Hubei Key Laboratory of Animal Nutrition and Feed Science, School of Animal Science and Nutritional Engineering, Wuhan Polytechnic University, Wuhan, China
| | - Yiling Chen
- Hubei Key Laboratory of Animal Nutrition and Feed Science, School of Animal Science and Nutritional Engineering, Wuhan Polytechnic University, Wuhan, China
| | - Huamei Yue
- Key Lab of Freshwater Biodiversity Conservation Ministry of Agriculture and Rural Affairs of China, Yangtze River Fisheries Research Institute, CAFS, Wuhan, China
| | - Meiqin Zhuo
- Hubei Key Laboratory of Animal Nutrition and Feed Science, School of Animal Science and Nutritional Engineering, Wuhan Polytechnic University, Wuhan, China
| | - Eakapol Wangkahart
- Laboratory of Fish Immunology and Nutrigenomics, Applied Animal and Aquatic Sciences Research Unit, Division of Fisheries, Faculty of Technology, Mahasarakham University, Mahasarakham, Thailand
| | - Qianrong Liang
- Zhejiang Fisheries Technical Extension Center, and Zhejiang Fisheries Test and Aquatic Disease Prevention Center, Hangzhou, China
| | - Rui Wang
- Hubei Key Laboratory of Animal Nutrition and Feed Science, School of Animal Science and Nutritional Engineering, Wuhan Polytechnic University, Wuhan, China
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2
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Varga JFA, Brunner SR, Cheng G, Min D, Aucoin MG, Doxey AC, Dixon B. Identification and characterization of a novel peptide from rainbow trout (Oncorhynchus mykiss) with antimicrobial activity against Streptococcus iniae. DEVELOPMENTAL AND COMPARATIVE IMMUNOLOGY 2022; 137:104518. [PMID: 36044968 DOI: 10.1016/j.dci.2022.104518] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/21/2022] [Revised: 08/11/2022] [Accepted: 08/23/2022] [Indexed: 06/15/2023]
Abstract
The overuse and misuse of antibiotics has led to the emergence of antibiotic-resistant bacterial species which remain a challenge to treat therapeutically. Novel and efficacious drugs are desperately needed to combat pathogens. One method to facilitate these discoveries is the use of in silico methods. Computational biology has the power to scan large data sets and screen for potential molecules with antibacterial function. In the current study, an in silico approach was used to identify an antimicrobial peptide (AMP) derived from rainbow trout von Willebrand Factor. The AMP was tested against a panel of aquatic bacterial pathogens and was found to possess antibacterial activity against Streptococcus iniae (S. iniae). Since S. iniae is a zoonotic pathogen, this may be useful in other species as well. The peptide was non-hemolytic and non-cytotoxic at the concentrations tested in rainbow trout cells. Pre-treatment of rainbow trout cells with the peptide did not result in an upregulation of immune genes but stimulating the rainbow trout macrophage/monocyte-like cell line, RTS11, with heat-killed S. iniae, did result in a significant upregulation of the tumor necrosis factor alpha (tnfa) gene. In this study, a new AMP has been identified but its expression, synthesis and role in vivo remains unknown. Nevertheless, the findings presented improve our understanding of fish gill and macrophage responses towards this important zoonotic pathogen.
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Affiliation(s)
- Joseph F A Varga
- Department of Biology, University of Waterloo, Waterloo, N2L 3G1, Canada
| | - Sascha R Brunner
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, 9747 AG Groningen, the Netherlands
| | - Grant Cheng
- Department of Biology, University of Waterloo, Waterloo, N2L 3G1, Canada
| | - Daniel Min
- Department of Biology, University of Waterloo, Waterloo, N2L 3G1, Canada; Department of Chemical Engineering, University of Waterloo, Waterloo, N2L 3G1, Canada
| | - Marc G Aucoin
- Department of Chemical Engineering, University of Waterloo, Waterloo, N2L 3G1, Canada
| | - Andrew C Doxey
- Department of Biology, University of Waterloo, Waterloo, N2L 3G1, Canada
| | - Brian Dixon
- Department of Biology, University of Waterloo, Waterloo, N2L 3G1, Canada.
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3
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Colussi S, Pastorino P, Mugetti D, Antuofermo E, Sciuto S, Esposito G, Polinas M, Tomasoni M, Burrai GP, Fernández-Garayzábal JF, Acutis PL, Pedron C, Prearo M. Isolation and Genetic Characterization of Streptococcus iniae Virulence Factors in Adriatic Sturgeon ( Acipenser naccarii). Microorganisms 2022; 10:883. [PMID: 35630328 PMCID: PMC9144172 DOI: 10.3390/microorganisms10050883] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2022] [Revised: 04/15/2022] [Accepted: 04/20/2022] [Indexed: 02/04/2023] Open
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.
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Affiliation(s)
- Silvia Colussi
- The Veterinary Medical Research Institute for Piemonte, Liguria and Valle d’Aosta, 10154 Turin, Italy; (S.C.); (S.S.); (G.E.); (M.T.); (P.L.A.); (M.P.)
| | - Paolo Pastorino
- The Veterinary Medical Research Institute for Piemonte, Liguria and Valle d’Aosta, 10154 Turin, Italy; (S.C.); (S.S.); (G.E.); (M.T.); (P.L.A.); (M.P.)
| | - Davide Mugetti
- The Veterinary Medical Research Institute for Piemonte, Liguria and Valle d’Aosta, 10154 Turin, Italy; (S.C.); (S.S.); (G.E.); (M.T.); (P.L.A.); (M.P.)
| | - Elisabetta Antuofermo
- Department of Veterinary Medicine, University of Sassari, 07100 Sassari, Italy; (E.A.); (M.P.); (G.P.B.)
| | - Simona Sciuto
- The Veterinary Medical Research Institute for Piemonte, Liguria and Valle d’Aosta, 10154 Turin, Italy; (S.C.); (S.S.); (G.E.); (M.T.); (P.L.A.); (M.P.)
| | - Giuseppe Esposito
- The Veterinary Medical Research Institute for Piemonte, Liguria and Valle d’Aosta, 10154 Turin, Italy; (S.C.); (S.S.); (G.E.); (M.T.); (P.L.A.); (M.P.)
| | - Marta Polinas
- Department of Veterinary Medicine, University of Sassari, 07100 Sassari, Italy; (E.A.); (M.P.); (G.P.B.)
| | - Mattia Tomasoni
- The Veterinary Medical Research Institute for Piemonte, Liguria and Valle d’Aosta, 10154 Turin, Italy; (S.C.); (S.S.); (G.E.); (M.T.); (P.L.A.); (M.P.)
| | - Giovanni Pietro Burrai
- Department of Veterinary Medicine, University of Sassari, 07100 Sassari, Italy; (E.A.); (M.P.); (G.P.B.)
| | | | - Pier Luigi Acutis
- The Veterinary Medical Research Institute for Piemonte, Liguria and Valle d’Aosta, 10154 Turin, Italy; (S.C.); (S.S.); (G.E.); (M.T.); (P.L.A.); (M.P.)
| | | | - Marino Prearo
- The Veterinary Medical Research Institute for Piemonte, Liguria and Valle d’Aosta, 10154 Turin, Italy; (S.C.); (S.S.); (G.E.); (M.T.); (P.L.A.); (M.P.)
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4
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Ghodsi Z, Kalbassi MR, Farzaneh P, Mobarez AM, Beemelmanns C, Amiri Moghaddam J. Immunomodulatory function of antimicrobial peptide EC-Hepcidin1 modulates the induction of inflammatory gene expression in primary cells of Caspian Trout (Salmo trutta caspius Kessler, 1877). FISH & SHELLFISH IMMUNOLOGY 2020; 104:55-61. [PMID: 32473358 DOI: 10.1016/j.fsi.2020.05.067] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/12/2020] [Revised: 05/08/2020] [Accepted: 05/25/2020] [Indexed: 06/11/2023]
Abstract
Hepcidins, a group of antimicrobial peptides (AMPs), play a key role in the innate immune system of fishes and act against different pathogens. In this study, antimicrobial and immune-inflammatory activity of a synthetic EC-hepcidin1, previously identified from orange-spotted grouper, were evaluated. EC-hepcidin1 showed weak activity against the zoonotic fish pathogen Streptococcus iniae (MIC 100 μg mL-1 and MBC 150 μg mL-1). To study the effect of AMPs in general, and EC-hepcidin1 in particular, a primary cell culture (SC) from the fin tissue of the Caspian Trout (Salmo trutta caspius) was established. The neutral Red method on SC cells revealed that EC-hepcidin1 has no or very low cytotoxic properties. Treatment of cells with either EC-hepcidin1 (150 μg mL-1) or fish pathogen Streptococcus iniae (MOI = 10) and a mixture of both resulted in the up-regulation of gene expression of MHC-UBA, IL-6, and TNFα indicating the modulatory function on inflammatory processes. These findings indicate that EC-hepcidin1 might act as a candidate for modulation of the innate immune system in S. iniae-based infection.
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Affiliation(s)
- Zohreh Ghodsi
- Department of Aquaculture, Marine Sciences Faculty, Tarbiat Modares University, Tehran, Iran
| | - Mohammad Reza Kalbassi
- Department of Aquaculture, Marine Sciences Faculty, Tarbiat Modares University, Tehran, Iran.
| | - Parvaneh Farzaneh
- Human and Animal Cell Bank, Iranian Biological Resource Center, ACECR, Tehran, Iran
| | - Ashraf Mohebati Mobarez
- Department of Bacteriology, Medical Sciences Faculty, Tarbiat Modares University, Tehran, Iran
| | - Christine Beemelmanns
- Leibniz Institute for Natural Product Research and Infection Biology e.V. Hans-Knöll-Institute (HKI), Jena, Germany
| | - Jamshid Amiri Moghaddam
- Leibniz Institute for Natural Product Research and Infection Biology e.V. Hans-Knöll-Institute (HKI), Jena, Germany.
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5
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Identification of some main Streptococcus iniae associated proteins: relationship. Vet Res Commun 2017; 41:85-95. [DOI: 10.1007/s11259-017-9675-z] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2016] [Accepted: 01/08/2017] [Indexed: 10/20/2022]
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6
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Herath HMLPB, Elvitigala DAS, Godahewa GI, Umasuthan N, Whang I, Noh JK, Lee J. Molecular characterization and comparative expression analysis of two teleostean pro-inflammatory cytokines, IL-1β and IL-8, from Sebastes schlegeli. Gene 2015; 575:732-42. [PMID: 26449313 DOI: 10.1016/j.gene.2015.09.082] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2014] [Revised: 09/22/2015] [Accepted: 09/22/2015] [Indexed: 10/22/2022]
Abstract
Interleukin 1β (IL-1β) and interleukin 8 (IL-8) are two major pro-inflammatory cytokines which play a central role in initiation of inflammatory responses against bacterial- and viral-infections. IL-1β is a member of the interleukin 1 family proteins and IL-8 is classified as a CXC-chemokine. In the current study, putative IL-1β and IL-8 counterparts were identified from a black rockfish transcriptomic database and designated as RfIL-1β and RfIL-8. The RfIL-1β cDNA sequence consists of 1140 nucleotides with a 759bp open reading frame (ORF) which encodes a 252 amino acid (aa) protein, whereas the RfIL-8 cDNA sequence (898bp) harbors a 300bp ORF encoding a 99 aa protein. Furthermore, the RfIL-1β aa sequence contains an IL-1 super family-like domain and an N-terminal IL-1 super family propeptide, while the amino acid sequence of RfIL-8 consists of a typical chemokine-CXC domain. Analysis of sequenced BAC clones containing RfIL-1β and RfIL-8 showed each gene to contain 4 exons interrupted by 3 introns. Pairwise comparison and phylogeny analysis of these cytokine sequences clearly revealed their closer relationship with other corresponding members of teleosts compared to birds and mammals. Constitutive differences in RfIL-1β and RfIL-8 mRNA expression were detected in a tissue-specific manner with the highest expression of each mRNA in spleen tissue. Two immune challenge experiments were conducted with Streptococcus iniae and polyinosinic:polycytidylic acid (poly I:C; a viral double stranded RNA mimic), and transcripts were quantified in spleen and peripheral blood cells. Significantly increased RfIL-1β and RfIL8 transcript levels were detected with almost similar profile patterns, further suggesting a putative involvement of these pro-inflammatory cytokines in the rockfish immunity.
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Affiliation(s)
- H M L P B Herath
- Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea; Fish Vaccine Research Center, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea
| | - Don Anushka Sandaruwan Elvitigala
- Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea; Fish Vaccine Research Center, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea
| | - G I Godahewa
- Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea; Fish Vaccine Research Center, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea
| | - Navaneethaiyer Umasuthan
- Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea; Fish Vaccine Research Center, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea
| | - Ilson Whang
- Fish Vaccine Research Center, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea
| | - Jae Koo Noh
- Genetics & Breeding Research Center, National Fisheries Research & Development Institute, Geoje 656-842, Republic of Korea
| | - Jehee Lee
- Department of Marine Life Sciences, School of Marine Biomedical Sciences, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea; Fish Vaccine Research Center, Jeju National University, Jeju Self-Governing Province 690-756, Republic of Korea.
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7
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El Aamri F, Real F, Acosta F, Bravo J, Román L, Déniz S, Padilla D. Differential innate immune response of European seabass (Dicentrarchus labrax) against Streptococcus iniae. FISH & SHELLFISH IMMUNOLOGY 2015; 46:436-441. [PMID: 26099220 DOI: 10.1016/j.fsi.2015.05.054] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2015] [Revised: 05/19/2015] [Accepted: 05/24/2015] [Indexed: 06/04/2023]
Abstract
Streptococcus iniae is a Gram-positive bacteria that causes invasive infections with severe septicemia and meningitis, producing high economic losses in marine and continental aquaculture. Head kidney leukocytes of European sea bass (Dicentrarchus labrax) were used to measure the differential innate immune response upon infection with S. iniae. The complete inhibition in the production of intracellular superoxide radicals and total peroxidase content was observed in infected cells. This study also elucidates changes in the relative expression of some immune-related genes. Interleukin 1β, tumor necrosis factor-α and interleukin-6 reached a peak of expression at 4-8 h post-infection, subsequently decreasing significantly up to 48 h post-infection. However, interleukin-10 and Mx protein increased over time, reaching the pick of expression at 48 h post-infection, whereas caspase-3 showed down regulation until 48 h post-infection. The in vivo study of immune related genes show the same kinetics of mRNAs expression as in vitro experience. The proinflammatory cytokines mRNA transcription levels peaked at an earlier time in vivo than in vitro system. Our findings indicate that there is a direct relationship between the dissemination of bacteria and the resulting infection-associated inhibition of respiratory burst, apoptosis, and the pro- and anti-inflammatory gene expression profiles.
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Affiliation(s)
- F El Aamri
- University of Las Palmas de Gran Canaria, 35413 Arucas, Spain
| | - F Real
- University of Las Palmas de Gran Canaria, 35413 Arucas, Spain
| | - F Acosta
- University of Las Palmas de Gran Canaria, 35413 Arucas, Spain.
| | - J Bravo
- University of Las Palmas de Gran Canaria, 35413 Arucas, Spain
| | - L Román
- University of Las Palmas de Gran Canaria, 35413 Arucas, Spain
| | - S Déniz
- University of Las Palmas de Gran Canaria, 35413 Arucas, Spain
| | - D Padilla
- University of Las Palmas de Gran Canaria, 35413 Arucas, Spain
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El Aamri F, Remuzgo-Martínez S, Acosta F, Real F, Ramos-Vivas J, Icardo JM, Padilla D. Interactions of Streptococcus iniae with phagocytic cell line. Microbes Infect 2015; 17:258-65. [DOI: 10.1016/j.micinf.2014.06.006] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2013] [Revised: 05/20/2014] [Accepted: 06/06/2014] [Indexed: 10/25/2022]
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9
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Li MF, Zhang BC, Li J, Sun L. Sil: a Streptococcus iniae bacteriocin with dual role as an antimicrobial and an immunomodulator that inhibits innate immune response and promotes S. iniae infection. PLoS One 2014; 9:e96222. [PMID: 24781647 PMCID: PMC4004548 DOI: 10.1371/journal.pone.0096222] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Accepted: 04/04/2014] [Indexed: 11/18/2022] Open
Abstract
Streptococcus iniae is a Gram-positive bacterium and a severe pathogen to a wide range of economically important fish species. In addition, S. iniae is also a zoonotic pathogen and can cause serious infections in humans. In this study, we identified from a pathogenic S. iniae strain a putative bacteriocin, Sil, and examined its biological activity. Sil is composed of 101 amino acid residues and shares 35.6% overall sequence identity with the lactococcin 972 of Lactococcus lactis. Immunoblot analysis showed that Sil was secreted by S. iniae into the extracellular milieu. Purified recombinant Sil (rSil) exhibited a dose-dependent inhibitory effect on the growth of Bacillus subtilis but had no impact on the growths of other 16 Gram-positive bacteria and 10 Gram-negative bacteria representing 23 different bacterial species. Treatment of rSil by heating at 50°C abolished the activity of rSil. rSil bound to the surface of B. subtilis but induced no killing of the target cells. Cellular study revealed that rSil interacted with turbot (Scophthalmus maximus) head kidney monocytes and inhibited the innate immune response of the cells, which led to enhanced cellular infection of S. iniae. Antibody blocking of the extracellular Sil produced by S. iniae significantly attenuated the infectivity of S. iniae. Consistent with these in vitro observations, in vivo study showed that administration of turbot with rSil prior to S. iniae infection significantly increased bacterial dissemination and colonization in fish tissues. Taken together, these results indicate that Sil is a novel virulence-associated bacteriostatic and an immunoregulator that promotes S. iniae infection by impairing the immune defense of host fish.
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Affiliation(s)
- Mo-fei Li
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Bao-cun Zhang
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- University of Chinese Academy of Sciences, Beijing, China
| | - Jun Li
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- School of Biological Sciences, Lake Superior State University, Sault Ste Marie, Michigan, United States of America
| | - Li Sun
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Collaborative Innovation Center of Deep Sea Biology, Zhejiang University, Hangzhou, China
- * E-mail:
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10
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Zhang BC, Zhang J, Sun L. Streptococcus iniae SF1: complete genome sequence, proteomic profile, and immunoprotective antigens. PLoS One 2014; 9:e91324. [PMID: 24621602 PMCID: PMC3951389 DOI: 10.1371/journal.pone.0091324] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2013] [Accepted: 02/10/2014] [Indexed: 01/06/2023] Open
Abstract
Streptococcus iniae is a Gram-positive bacterium that is reckoned one of the most severe aquaculture pathogens. It has a broad host range among farmed marine and freshwater fish and can also cause zoonotic infection in humans. Here we report for the first time the complete genome sequence as well as the host factor-induced proteomic profile of a pathogenic S. iniae strain, SF1, a serotype I isolate from diseased fish. SF1 possesses a single chromosome of 2,149,844 base pairs, which contains 2,125 predicted protein coding sequences (CDS), 12 rRNA genes, and 45 tRNA genes. Among the protein-encoding CDS are genes involved in resource acquisition and utilization, signal sensing and transduction, carbohydrate metabolism, and defense against host immune response. Potential virulence genes include those encoding adhesins, autolysins, toxins, exoenzymes, and proteases. In addition, two putative prophages and a CRISPR-Cas system were found in the genome, the latter containing a CRISPR locus and four cas genes. Proteomic analysis detected 21 secreted proteins whose expressions were induced by host serum. Five of the serum-responsive proteins were subjected to immunoprotective analysis, which revealed that two of the proteins were highly protective against lethal S. iniae challenge when used as purified recombinant subunit vaccines. Taken together, these results provide an important molecular basis for future study of S. iniae in various aspects, in particular those related to pathogenesis and disease control.
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Affiliation(s)
- Bao-cun Zhang
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Graduate University of the Chinese Academy of Sciences, Beijing, China
| | - Jian Zhang
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Graduate University of the Chinese Academy of Sciences, Beijing, China
| | - Li Sun
- Key Laboratory of Experimental Marine Biology, Institute of Oceanology, Chinese Academy of Sciences, Qingdao, China
- Collaborative Innovation Center of Deep Sea Biology, Zhejiang University, Hangzhou, China
- * E-mail:
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11
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Abstract
Streptococcus iniae causes systemic infection characterized by meningitis and sepsis. Here, we report a larval zebrafish model of S. iniae infection. Injection of wild-type S. iniae into the otic vesicle induced a lethal infection by 24 h postinfection. In contrast, an S. iniae mutant deficient in polysaccharide capsule (cpsA mutant) was not lethal, with greater than 90% survival at 24 h postinfection. Live imaging demonstrated that both neutrophils and macrophages were recruited to localized otic infection with mutant and wild-type S. iniae and were able to phagocytose bacteria. Depletion of neutrophils and macrophages impaired host survival following infection with wild-type S. iniae and the cpsA mutant, suggesting that leukocytes are critical for host survival in the presence of both the wild-type and mutant bacteria. However, zebrafish larvae with impaired neutrophil function but normal macrophage function had increased susceptibility to wild-type bacteria but not the cpsA mutant. Taking these findings together, we have developed a larval zebrafish model of S. iniae infection and have found that although neutrophils are important for controlling infection with wild-type S. iniae, neutrophils are not necessary for host defense against the cpsA mutant.
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12
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Evolution of the capsular operon of Streptococcus iniae in response to vaccination. Appl Environ Microbiol 2012; 78:8219-26. [PMID: 23001668 DOI: 10.1128/aem.02216-12] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Streptococcus iniae causes severe septicemia and meningitis in farmed fish and is also occasionally zoonotic. Vaccination against S. iniae is problematic, with frequent breakdown of protection in vaccinated fish. The major protective antigens in S. iniae are the polysaccharides of the capsule, which are essential for virulence. Capsular biosynthesis is driven and regulated by a 21-kb operon comprising up to 20 genes. In a long-term study, we have sequenced the capsular operon of strains that have been used in autogenous vaccines across Australia and compared it with the capsular operon sequences of strains subsequently isolated from infected vaccinated fish. Intriguingly, strains isolated from vaccinated fish that subsequently become infected have coding mutations that are confined to a limited number of genes in the cps operon, with the remainder of the genes in the operon remaining stable. Mutations in strains in diseased vaccinated fish occur in key genes in the capsular operon that are associated with polysaccharide configuration (cpsG) and with regulation of biosynthesis (cpsD and cpsE). This, along with high ratios of nonsynonymous to synonymous mutations within the cps genes, suggests that immune response directed predominantly against capsular polysaccharide may be driving evolution in a very specific set of genes in the operon. From these data, it may be possible to design a simple polyvalent vaccine with a greater operational life span than the current monovalent killed bacterins.
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