- Open Access
Pathogenesis of and strategies for preventing Edwardsiella tarda infection in fish
Veterinary Research volume 43, Article number: 67 (2012)
Edwardsiella tarda is one of the serious fish pathogens, infecting both cultured and wild fish species. Research on edwardsiellosis has revealed that E. tarda has a broad host range and geographic distribution, and contains important virulence factors that enhance bacterial survival and pathogenesis in hosts. Although recent progress in edwardsiellosis research has enabled the development of numerous, highly effective vaccine candidates, these efforts have not been translated into a commercialized vaccine. The present review aims to provide an overview of the identification, pathology, diagnosis and virulence factors of E. tarda in fish, and describe recent strategies for developing vaccines against edwardsiellosis. The hope is that this presentation will be useful not only from the standpoint of understanding the pathogenesis of E. tarda, but also from the perspective of facilitating the development of effective vaccines.
Table of contents
Identification and classification
Pathology and diagnosis
Edwardsiellosis, caused by Edwardsiella tarda, has been reported worldwide in economically important fish species, including Japanese eel (Anguilla japonica), red sea bream (Pagrus major), yellowtail (Seriola quinqueradiata), channel catfish (Ictalurus punctatus), and turbot (Scophthalmus maximus) [1–4]. This infection also leads to serious economic losses in the aquaculture of olive flounder (Japanese flounder; Paralichthys olivaceus), the most important fish species in South Korean aquaculture, with production valued at 489.7 billion Korean Won (40 922 MT), which corresponds to 56.5% of total fisheries production in 2010 [5–7].
Recent studies on vaccine development have applied a variety of antigen-preparation methods; however, commercial vaccines are not yet available. In addition, numerous studies have reported on virulence factors of E. tarda and immune responses of hosts. In the present study, the pathogenicities of E. tarda in fish that can be exploited to elicit effective protection strategies against edwardsiellosis will be discussed.
2. Identification and classification
The genus Edwardsiella is composed of three species, E. tarda, E. ictaluri, and E. hoshinae[8–10]. Fish are usually infected with E. tarda or E. ictaluri, whereas E. hoshinae infection is usually reported in reptiles and birds . Panangala et al.  suggested that biochemical tests can differentiate E. tarda from E. ictaluri among bacteria isolated from freshwater fish based on the positive reaction of E. tarda in tests of indole production, methyl red reduction and hydrogen sulfide generation. In protein profiling of bacterial isolates using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and Western blotting, the authors also demonstrated that E. ictaluri is more homogenously distributed than E. tarda.
E. tarda was originally isolated from cultured Japanese eel (Anguilla japonica) in Japan in 1962 . Subsequent findings for the bacterium were reported from snakes in Japan  and from human feces in the USA; the bacterium was designated E. tarda by Ewing et al. . Although there was a move to change the epithet tarda to anguillimortiferum since it had been initially reported as Paracolobactrum anguillimortiferum, the bacterium is commonly named E. tarda because P. anguillimortiferum was not registered and the original culture was lost [6, 15].
E. tarda is a Gram-negative, short, rod–shaped, facultative anaerobic bacterium that measures about 2–3 μm in length and 1 μm in diameter . It is usually motile, but isolates from red sea bream and yellowtail are non-motile . This bacterium can survive at 0–4% sodium chloride, pH 4.0–10.0, and 14–45°C . The biochemical characteristics of E. tarda are catalase positive, cytochrome oxidase negative, production of indole and hydrogen sulfide, fermentation of glucose, and reduction of nitrate to nitrite . However, several variations of biochemical tests have been found for ornithine decarboxylase, citrate utilization, hydrogen sulfide production, and fermentation of mannitol and arabinose. These discrepancies allow division into two groups: wild type and biogroup 1 [8, 9, 18]. The characteristics of wild-type E. tarda are negative for arabinose, mannitol and sucrose production, and positive for hydrogen sulfide production; the characteristics of biogroup 1 are the opposite.
Park et al.  demonstrated that E. tarda can be divided into four serotypes, A, B, C and D, using O-antigen extracts of 445 isolates from infected eel, water, and sediments. They suggested that 72% of isolates belonged to serotype A, the most virulent group based on experimental challenge tests, whereas a subsequent study of E. tarda isolated from olive flounder revealed that all isolates were serotype A . Another study established an E. tarda serotyping scheme comprising 61 O groups and 45 H antigens that is preferable for international applications .
Several important findings suggest that intra- and/or inter-specific variability exists among E. tarda strains. E. tarda isolated from humans could be differentiated from isolates from fish by RAPD (random amplified polymorphic DNA) analysis , and E. tarda isolated from freshwater fish or pond sediments showed diverse and/or homogeneous characteristics in plasmid profiling, ERIC-PCR (enterobacterial repetitive intergenic consensus-polymerase chain reaction), SDS-PAGE, and RFLP (restriction fragment length polymorphism) analyses of 16S rDNA [12, 23, 24]. In addition, Western blot profiles of LPS (lipopolysaccharides) from E. tarda strains isolated from turbot and other fish revealed that only isolates from turbot were recognized by rabbit sera raised against the isolate from turbot . Biochemical tests, protein profiling, LPS profiling, and RAPD analysis showed that E. tarda strains from olive flounder have highly homogeneous phenotypic and genotypic characteristics compared to isolates from Japanese eel (unpublished data).
Since the first report of E. tarda infection in Japanese eel , E. tarda has been isolated from numerous marine and freshwater fishes, including barramundi (Lates calcarifer) , channel catfish , largemouth bass (Micropterus salmoides) , mullet (Mugil cephalus) , crimson sea bream (Evynnis japonica) , tilapia (Tilapia nilotica) , chinook salmon (Oncorhynchus tshawytscha) , red sea bream , yellow tail , olive flounder , common carp (Cyprinus carpio) , European sea bass (Dicentrarchus labrax) , turbot , Asian catfish (Claris batrachus) , brook trout (Salvelinus fontinalis) , Indian major carp (Catla catla) , rohu (Labeo rohita) , European eel (Anguilla anguilla) , and Far Eastern catfish (Silurus asotus) . In addition, isolation of E. tarda has been reported in invertebrates , amphibians , reptiles [13, 26], birds [27, 41, 42] and mammals, including humans, cattle, swine, dogs, and Weddell seals (Leptonychotes weddellii) [8, 41–45]. These numerous reports indicate that E. tarda has a wide geographical distribution, even in Antarctica , and is an important pathogen in terms of public health, since it can progress as an epizootic and zoonotic bacterium .
4. Pathology and diagnosis
Edwardsiellosis in fish usually occurs under imbalanced environmental conditions, such as high water temperature, poor water quality, and high organic content . Fish infected with E. tarda show abnormal swimming behavior, including spiral movement and floating near the water surface [3, 46]. Although clinical signs vary after onset, fish infected with E. tarda show loss of pigmentation, exophthalmia, opacity of the eyes, swelling of the abdominal surface, petechial hemorrhage in fin and skin, and rectal hernia (Figure 1) [6, 35, 46]. Internally, watery and bloody ascites in the abdominal space and congested liver, spleen, and kidney are found [46, 47]. Histopathological characteristics of edwardsiellosis in fish are suppurative interstitial nephritis, suppurative hepatitis, and purulent inflammation in the spleen [6, 46–48]. Abscesses of various sizes, bacterial colonization, and infiltration of neutrophils and macrophages are found in the liver, spleen, and kidney [6, 47, 48]. Some remarkable pathological features have also been demonstrated in fish, such as dorsolateral petechial hemorrhage and abscesses in cutaneous lesions of channel catfish [3, 49]; hyperplasia, necrosis and inflammation in lateral line canals of striped bass ; and necrosis and aggregation of bacteria-laden macrophages in red sea bream . However, the symptoms and pathological changes in fish are similar to those of other bacterial infections, including Aeromonas hydrophila, Vibrio anguillarum and Pseudomonas anguilliseptica; thus, other molecular or biochemical methods are recommended for diagnosis of E. tarda infection .
E. tarda is usually identified based on its unique biochemical characteristics after isolation on brain-heart infusion agar or tryptone soya agar from infected fish. Several studies have suggested that serological techniques are useful for diagnosis of E. tarda infection, including agglutination tests, enzyme linked immunosorbent assays (ELISA), and fluorescent antibody techniques [3, 31, 37]. Recently, PCR-based methods have been reported for accurate, sensitive, and differential diagnosis. Real-time PCR has been used to analyze the blood of oyster toadfish (Opsanus tau) infected with E. tarda, and the loop-mediated isothermal amplification (LAMP) method is able to detect E. tarda in infected tissue samples and pond water . Chang et al.  developed a multiplex nested PCR for four important fish pathogens in subtropical Asia that can simultaneously detect A. hydrophila, E. tarda, Photobacterium damselae and Streptococcus iniae from pure colonies and tissue homogenates. In addition, a primer set, evaluated using 53 E. tarda strains isolated from various sources and 18 representative strains of related and unrelated bacterial species, was shown capable of detecting two cells from pure culture and 3 × 102 cells in seeded turbot tissues .
5. Virulence factors
E. tarda survive in their host by utilizing several important substances and abilities that serve as virulence factors in the host (Figure 2). A study using green fluorescent protein (GFP) showed that both avirulent and virulent E. tarda are able to adhere to, invade, and replicate in the carp epithelial papilloma (EPC) cell line using host microfilaments and protein tyrosine kinase . Histopathological and infection kinetics studies using GFP revealed that the gill, gastrointestinal tract, and body surface of blue gourami (Trichogaster trichopterus) are the sites of entry of the virulent strain .
Type ІІІ secretion system (T3SS) and type VІ secretion system (T6SS) play important roles in adherence, penetration, survival, and replication of E. tarda in epithelial cells and phagocytes (Table 1). The T6SS of E. tarda comprises 16 genes, and 13 of the encoded proteins are involved in the secretion of EvpP (E. tarda virulence protein) . Three proteins (EvpP, EvpI and EvpC) are secreted into the extracellular milieu, and the secretion of EvpC and EvpI are required for the secretion of EvpP . The putative ATPase, EvpO, contains a Walker A motif, which possibly interacts with EvpA, EvpL, and EvpN . T3SS is a multi-protein complex that is essential for host and pathogen interaction. The central component of T3SS is a needle complex, which is structurally similar to bacterial flagella, that spans the bacterial inner and outer membrane . This needle can connect to the host cell membrane via the tip complex through the translocon, which can allow the delivery of bacterial effector proteins from an ATPase dependent manner . In E. tarda, T3SS proteins include the E. tarda secretion system apparatus (EsaB and EsaN), effectors (EseB, EseC and EseD), chaperones (EscA, EscB and EscC), and regulators (EsrA, EsrB and EsrC) [60–62]. Proteomic studies have revealed that EseB, EseC and EseD are the major ECP, and mutations of these genes in E. tarda reduces virulence compared to parental E. tarda.
Several reports found that motility-related proteins, such as flagellin and autotransport adhesin AIDA, a fimbrial adhesin-like protein, are important for attachment and penetration into the epithelial cells of hosts [63–65]. An E. tarda mutant containing a deletion of the eth A gene (hemolysin gene locus from E. tarda), regulated by the two-component system EsrA-EsrB and nucleid protein HhaEt, shows reduced capacity to internalize into EPC cells . Interestingly, a recent study showed that the qseB and qseC two-component system of E. tarda inhibits flagella biosynthesis and motility, and induces the expression of the T3SS after invasion into host cells . These findings indicate that E. tarda is capable of modulating the expression of genes involved in adjusting to environmental changes, such as adaptation to intracellular living.
Indeed, E. tarda is able to survive and adapt to various host environmental conditions, including host hormonal change, temperature, pH, salinity, and variations in several important nutritional elements, such as iron, phosphate, and Mg2+[64–74]. The qseB and qseC two-component system, an important virulence regulator that contributes to intracellular replication and systemic infection, are able to regulate flagella motility and the intracellular expression of T3SS elements EseB and EsaC in response to eukaryotic hormone-like signals, such as epinephrine and norepinephrine . The PhoP-PhoQ two-component system of E. tarda is able to sense changes in temperature and Mg2+ concentration and control the T3SS and T6SS via activation of esrB. This study showed that a conformational change in PhoQ over a temperature range of 23–37°C and at low Mg2+ concentration causes PhoQ autophosphorylation and subsequent activation of PhoP, which promotes expression of esrB and leads to secretion of virulent proteins, whereas below 20°C or above 37°C, no such conformational change in PhoQ takes place and the production of virulence proteins is decreased. Similarly, on the basis of observations of mutants containing an insertion of the pstSCAB-phoU operon, which is part of the phosphate regulon, Srinivasa Rao et al.  suggested that natural conditions of low inorganic phosphate in phagocytic and epithelial cells might stimulate virulent genes to promote survival and replication within the host. In another study, a high concentration of NaCl (3%) was shown to induce hemagglutination activity, which correlated with the expression of fimbrial major subunit (FimA), a 19.3 kDa protein; moreover, E. tarda enriched for this fimbrial protein showed higher virulence in challenge experiments compared to E. tarda raised in 0% NaCl broth .
The ability of bacteria to acquire iron acquisition using the bacterial iron chelator, siderophore, is essential for the survival and replication of bacteria [64, 73]. A natural mutant with lower siderophore production and a mutant with a gene encoding aryl sulfate sulfotransferase producing less siderophore showed significantly reduced virulence in E. tarda challenge experiments [72, 73]. Recently, an E. tarda deletion mutant lacking the T6SS component evpP, which encodes a consensus ferric uptake regulator (Fur) box, was shown to exhibit low virulence in vivo and in vitro . This finding might indicate that the EvpP protein in T6SS plays an important role in invasion mechanisms and thus may be a critical virulence factor.
It has been reported that E. tarda produces two kinds of hemolysin; one is a cell associated, iron-regulated hemolysin, encoded by eth A and eth B, that is secreted as an extracellular protein (ECP) under iron-regulated conditions , and the other is an extracellular hole-forming hemolysin distinct from EthA and EthB that is not regulated by iron [77–79]. A recent functional study demonstrated that EthA is critical for invasion in vivo and in vitro, and is regulated by the two-component system EsrA-EsrB and nucleid protein HhaEt. Other enzymes, including catalase, chondroitinase, dermatotoxin, protease, and collagenase, are also important for the pathogenesis of E. tarda[64, 74, 80, 81].
Several studies have indicated that E. tarda is able to survive and replicate in phagocytes, leading to systemic infections [82–86]. Virulent E. tarda opsonized with serum of blue gourami can replicate within phagocytes and fails to induce an oxidative burst, possibly providing a mechanism for avoiding phagocyte-mediated killing . A subsequent study revealed that the expression of the catalase (Kat B) gene of E. tarda is responsible for the resistance to H2O2 and phagocyte-mediated killing . Similarly, a comparison of the response of peritoneal macrophages from olive flounder to high- and low-virulence E. tarda demonstrated that only the highly virulent strain is able to resist reactive oxygen species generated by macrophages, and survive and replicate within macrophages . In a subsequent report, the authors of this latter study extended their results, demonstrating that virulent E. tarda elicit a significantly greater induction of nitric oxide and tumor necrosis factor (TNF)-α production by macrophages, actions that may account for the pathogenicity of E. tarda infection . In addition, a study of E. tarda septicemia revealed that E. tarda induces systemic immunosuppression through lymphocyte apoptosis, which suppresses systemic immune responses during the initial stage of septicemia .
The host also seems to possess immune mechanisms for avoiding or resisting the propagation of E. tarda. An examination of the pathogenicity of motile and non-motile E. tarda strains toward olive flounder, red sea bream, and yellow tail showed that all strains were virulent in the olive flounder and yellow tail, whereas only atypical strains showed mortality in the red sea bream . These findings might indicate that immune mechanisms involved in recognition of and resistances against E. tarda vary among hosts. In zebra fish (Danio rerio), experimental infection with E. tarda resulted in an acute elevation of the inflammatory cytokines, interleukin-1β (IL-1β) and TNF-α . Indian major carp challenged with E. tarda exhibited a significant induction of immune responses and expression of several immune related genes, including IL-1β, TNF-α, inducible nitric oxide synthase (iNOS), complement component C3, β2-microglobulin, CXCa, and C-type and G-type lysozyme . T. Aoki and colleagues surveyed over a thousand genes in olive flounder infected with E. tarda using microarray analyses, identifying 36 genes that were differentially expressed between susceptible and resistant olive flounder groups [89–91]. Notably, 3 days post challenge, MHC class I antigen processing- and presenting-related genes were highly expressed in resistant groups, but susceptible groups showed high expression of genes involved in innate immune responses .
Understanding the virulence factors of E. tarda may inform the development of protection strategies against edwardsiellosis in fish. Recent progress in analytical methods, such as genomics and proteomics, has revealed important virulence factors, including T3SS, T6SS, and two-component systems (Figure 2). Verjan et al. demonstrated seven antigenic proteins, which were identified as lipoproteins, periplasmic proteins, exported, and secreted proteins . Additional proteomic studies on outer membrane proteins (OMP), ECP, and outer membrane vesicles (OMV) may also contribute to the development of effective protection strategies against edwardsiellosis [60, 63, 65, 69, 93–98]. In addition, knowing the full genome sequence of E. tarda would enhance our understanding of the relationship between E. tarda and the host, and further the development of new prophylactic and therapeutic strategies for managing edwardsiellosis in fish .
A vaccine is by definition a biological preparation that improves immunity to a specific disease. The vaccine typically consists of several agents, such as weakened or killed forms of the microbe, its toxin or one of its surface proteins . Numerous antigen preparation methods have been used to develop effective vaccines against edwardsiellosis, including formalin killed cells (FKC), LPS, ECP, live attenuated E. tarda, avirulent E. tarda, ghost cells, OMP, recombinant proteins, recombinant protein-expressing cells, OMV, and DNA vaccines (Table 2). Several early studies noted that immunization of Japanese eel with FKC or LPS exerted protective effects after challenge with a virulent strain of E. tarda[101–103]. However, another study reported no protective effect of FKC and LPS against E. tarda infection , possibly indicating the diverse antigenicity of E. tarda species . Recent progress in vaccine preparation using diverse antigens has led to highly effective vaccines against E. tarda infection [106–122]. Several vaccine trials coupled with adjuvants have shown 100% relative survival, and most evaluated trials were shown to produce significant protective effects (Table 2). Interestingly, more than 75% of the studies published in China, Japan and South Korea during the last decade have focused on the protective effects of vaccines in olive flounder, providing an indication that edwardsiellosis in olive flounder is a serious problem in Far East Asia and highlighting the urgent need to develop an effective, commercializable vaccine. Thus, to improve the efficacy of the vaccine, comprehensive understanding of bacterial pathogenesis, including intracellular surviving, host cell mediated-immune responses, and comparative epidemiological investigation on E. tarda originating from different finfish species is necessary. These efforts will allow for the identification of host pathogen cross-talk, which will lead to the identification of valuable vaccine candidates, such as a cocktail bacterin vaccine originating from different fish species, mutant vaccine made by deleting different genes compared with previous studies and DNA vaccine combined with several important multiple antigen genes.
7. Concluding remarks
E. tarda is a versatile Gram-negative bacterium that exhibits a broad geographical distribution and host range, and causes significant economic losses to the aquaculture industry. Despite limitations in this emerging field, recent studies on various virulence factors of E. tarda have enhanced our understanding of the pathogenesis of E. tarda, which adhere to, invade, and replicate in host cells and modulate their own gene expression to survive and adapt in fish. In addition, immune studies on edwardsiellosis applying proteomic and genomic approaches suggest that hosts sense the bacterium, induce inflammatory responses, and synergistically direct innate and adaptive immune responses against E. tarda infection. Furthermore, numerous studies on edwardsiellosis have reported highly efficacious vaccines, efforts that will encourage the development of a novel vaccine for use in aquaculture.
Hoshina T: On a new bacterium, paracolobactrum anguillimortiferum n. sp. Bull Jpn Soc Sci Fish. 1962, 28: 162-164.
Yasunaga N, Ogawa S, Hatai K: Characteristics of the fish pathogen Edwardsiella isolated from several species of cultured marine fishes. Bull Nagasaki Prefect Inst Fish. 1982, 8: 57-65.
Meyer FP, Bullock GL: Edwardsiella tarda, a new pathogen of channel catfish (Ictalurus punctatus). Appl Microbiol. 1973, 25: 155-156.
Nougayrede PH, Vuillaume A, Vigneulle M, Faivre B, Luengo S, Delprat J: First isolation of Edwardsiella tarda from diseased turbot (Scophthalmus maximus) reared in a sea farm in the Bay of Biscay. Bull Eur Assoc Fish Pathol. 1994, 14: 128-129.
Statistics Korea (KOSTAT): Republic of Korea: 2010 Survey on the status of fish culture. 2011, http://kostat.go.kr/portal/english/news/1/8/index.board?bmode=download&bSeq=&aSeq=251088&ord=1 [consulted 23 April 2012]
Egusa S: Some bacterial diseases of freshwater fishes in Japan. Fish Pathol. 1976, 10: 103-114.
Bang JD, Chun SK, Park SI, Choi YJ: Studies on the biochemical and serological characteristics of Edwardsiella tarda isolated from cultured flounder, Paralichthys olivaceus. J Fish Pathol. 1992, 5: 29-35.
Ewing WH, McWhorter AC, Escobar MR, Lubin AH: Edwardsiella, a new genus of Enterobacteriaceae based on a new species, E. Tarda. Int J Syst Evol Microbiol. 1965, 15: 33-38.
Grimont PAD, Grimont F, Richard C, Sakazaki R: Edwardsiella hoshinae, a new species of Enterobacteriaceae. Curr Microbiol. 1980, 4: 347-351.
Hawke JP, Mcwhorter A, Steigerwalt AG, Brenner DONJ: Edwardsiella ictaluri sp. nov., the causative agent of enteric septicemia of catfish. Int J Syst Evol Microbiol. 1981, 31: 396-400.
Woo PTK, Bruno DW: Fish diseases and disorders. Volume 3: viral, bacterial and fungal infections. Edwardsiella septicaemias. Edited by: Evans JJ, Klesius PH, Plumb JA, Shoemaker CA. 2010, Wallingford: CABI International, 512-534. 2
Panangala VS, Shoemaker CA, McNulty ST, Arias CR, Klesius PH: Intra‐and interspecific phenotypic characteristics of fish‐pathogenic Edwardsiella ictaluri and E. tarda. Aquacult Res. 2006, 37: 49-60.
Sakazaki R: A proposed group of the family Enterobacteriaceae, the asakusa group. Int J Syst Evol Microbiol. 1965, 15: 45-47.
Sakazaki R, Tamura K: Priority of the specific epithet anguillimortiferum over the specific epithet tarda in the name of the organism presently known as Edwardsiella tarda. Int J Syst Bacteriol. 1975, 25: 219-220.
Farmer JJ, Brenner DONJ, Clark WA: Proposal to conserve the specific epithet tarda over the specific epithet anguillimortiferum in the name of the organism presently known as Edwardsiella tarda: request for an opinion. Int J Syst Evol Microbiol. 1976, 26: 293-294.
Matsuyama T, Kamaishi T, Ooseko N, Kurohara K, Iida T: Pathogenicity of motile and non-motile Edwardsiella tarda to some marine fish. Fish Pathol. 2005, 40: 133-136.
Ishihara S, Kusuda R: Growth and survival of Edwardsiella tarda bacteria in environmental water. Bull Jpn Soc Sci Fish. 1982, 48: 483-488.
Walton DT, Abbott SL, Janda JM: Sucrose-positive Edwardsiella tarda mimicking a biogroup 1 strain isolated from a patient with cholelithiasis. J Clin Microbiol. 1993, 31: 155-156.
Park S, Wakabayashi H, Watanabe Y: Serotype and virulence of Edwardsiella tarda isolated from eel and their environment. Fish Pathol. 1983, 18: 85-89.
Rashid MM, Honda K, Nakai T, Muroga K: An ecological study on Edwardsiella tarda in flounder farms. Fish Pathol. 1994, 29: 221-227.
Tamura K, Sakazaki R, McWhorter AC, Kosako Y: Edwardsiella tarda serotyping scheme for international use. J Clin Microbiol. 1988, 26: 2343-2346.
Nucci C, Da Silveira WD, da Silva Corrêa S, Nakazato G, Bando SY, Ribeiro MA, de Castro AF P: Microbiological comparative study of isolates of Edwardsiella tarda isolated in different countries from fish and humans. Vet Microbiol. 2002, 89: 29-39.
Maiti NK, Mandal A, Mohanty S, Mandal RN: Phenotypic and genetic characterization of Edwardsiella tarda isolated from pond sediments. Comp Immunol Microbiol Infect Dis. 2009, 32: 1-8.
Wei LS, Musa N: Phenotyping, genotyping and whole cell protein profiling of Edwardsiella tarda isolated from cultured and natural habitat freshwater fish. Am Eurasian J Agric Environ Sci. 2008, 3: 681-691.
Castro N, Toranzo AE, Barja JL, Nunez S, Magarinos B: Characterization of Edwardsiella tarda strains isolated from turbot, Psetta maxima (L.). J Fish Dis. 2006, 29: 541-547.
Iveson JB: Strontium chloride B and EE enrichment broth media for the isolation of Edwardsiella, Salmonella and Arizona species from tiger snakes. J Hyg (Lond). 1971, 69: 323-330.
White FH, Simpson CF, Williams LE: Isolation of Edwardsiella tarda from aquatic animal species and surface waters in Florida. J Wildl Dis. 1973, 9: 204-209.
Kusuda R, Toyoshima T, Iwamura Y, Sako H: Edwardsiella tarda from an epizootic of mullets (Mugil cephalus) in Okitsu Bay. Bull Jpn Soc Sci Fish. 1976, 42: 271-275.
Kusuda R, Itami T, Munekiyo M, Nakajima H: Characteristics of an Edwardsiella sp. from an epizootic of cultured crimson sea breams. Bull Jpn Soc Sci Fish. 1977, 43: 129-134.
Van Damme LR, Vandepitte J: Frequent isolation of Edwardsiella tarda and pleisiomonas shigelloides from healthy zairese freshwater fish: a possible source of sporadic diarrhea in the tropics. Appl Environ Microbiol. 1980, 39: 475-479.
Amandi A, Hiu SF, Rohovec JS, Fryer JL: Isolation and characterization of Edwardsiella tarda from fall chinook salmon (Oncorhynchus tshawytscha). Appl Environ Microbiol. 1982, 43: 1380-1384.
Nakatsugawa T: Edwardsiella tarda isolated from cultured young flounder. Fish Pathol. 1983, 18: 99-101.
Sae-Oui D, Muroga K, Nakai T: A case of Edwardsiella tarda infection in cultured colored carp Cyprinus carpio. Fish Pathol. 1984, 19: 197-199.
Blanch AR, Pinto RM, Jofre JT: Isolation and characterization of an Edwardsiella sp. strain, causative agent of mortalities in sea bass (Dicentrarchus labrax). Aquaculture. 1990, 88: 213-222.
Sahoo PK, Mukherjee SC, Sahoo SK: Aeromonas hydrophila versus Edwardsiella tarda: a pathoanatomical study in Clarias batrachus. J Aquacult. 1998, 6: 57-66.
Uhland FC, Hélie P, Higgins R: Infections of Edwardsiella tarda among brook trout in Quebec. J Aquat Anim Health. 2000, 12: 74-77.
Swain P, Nayak SK: Comparative sensitivity of different serological tests for seromonitoring and surveillance of Edwardsiella tarda infection of Indian major carps. Fish Shellfish Immunol. 2003, 15: 333-340.
Alcaide E, Herraiz S, Esteve C: Occurrence of Edwardsiella tarda in wild European eels Anguilla anguilla from Mediterranean Spain. Dis Aquat Organ. 2006, 73: 77-81.
Yu JH, Han JJ, Park KS, Park KH, Park SW: Edwardsiella tarda infection in Korean catfish, silurus asotus, in a Korean fish farm. Aquacult Res. 2009, 41: 19-26.
Wyatt LE, Nickelson RI, Vanderzant C: Edwardsiella tarda in freshwater catfish and their environment. Appl Environ Microbiol. 1979, 38: 710-714.
Van Damme LR, Vandepitte J: Isolation of Edwardsiella tarda and plesiomonas shigelloides from mammals and birds in Zaire. Rev Elev Med Vet Pays Trop. 1984, 37: 145-151.
Leotta GA, Piñeyro P, Serena S, Vigo GB: Prevalence of Edwardsiella tarda in Antarctic wildlife. Polar Biol. 2009, 32: 809-812.
Arambulo PV, Westerlund NC, Sarmiento RV: On the isolation of human enteric organisms from the bile of pigs and cattle. Acta Medica Philipp. 1968, 5: 84-86.
Mizunoe S, Yamasaki T, Tokimatsu I, Matsunaga N, Kushima H, Hashinaga K, Kadota JI: A case of empyema caused by Edwardsiella tarda. J Infect. 2006, 53: 255-258.
Tacal JV, Menez CF: The isolation of Edwardsiella tarda from a dog. Philipp J Vet Med. 1969, 7: 143-145.
Miyazaki T, Kaige N: Comparative histopathology of edwardsiellosis in fishes. Fish Pathol. 1985, 20: 219-227.
Miyazaki T, Egusa S: Histopathological studies of edwardsiellosis of the Japanese eel (Anguilla japonica), 1: suppurative interstitial nephritis form. Fish Pathol. 1976, 11: 33-43.
Miyazaki T, Egusa S: Histopathological studies of edwardsiellosis of the Japanese eel (Anguilla japonica), 2: suppurative hepatitis form. Fish Pathol. 1976, 11: 67-75.
Darwish A, Plumb JA, Newton JC: Histopathology and pathogenesis of experimental infection with Edwardsiella tarda in channel catfish. J Aquat Anim Health. 2000, 12: 255-266.
Herman RL, Bullock GL: Pathology caused by the bacterium Edwardsiella tarda in striped bass. Trans Am Fish Soc. 1986, 115: 232-235.
Nishibuchi M, Muroga K, Jo Y: pathogenic vibrio isolated from cultured eel. VI. Diagnostic tests for the disease due to the present bacterium. Fish Pathol. 1980, 14: 124-132.
Horenstein S, Smolowitz R, Uhlinger K, Roberts S: Diagnosis of Edwardsiella tarda infection in oyster toadfish (Opsanus tau) held at the Marine Resources Center. Biol Bull. 2004, 207: 171-
Savan R, Kono T, Itami T, Sakai M: Loop‐mediated isothermal amplification: an emerging technology for detection of fish and shellfish pathogens. J Fish Dis. 2005, 28: 573-581.
Chang CI, Wu CC, Cheng TC, Tsai JM, Lin KJ: Multiplex nested‐polymerase chain reaction for the simultaneous detection of Aeromonas hydrophila, Edwardsiella tarda, Photobacterium damselae and Streptococcus iniae, four important fish pathogens in subtropical Asia. Aquacult Res. 2009, 40: 1182-1190.
Castro N, Toranzo AE, Núñez S, Osorio CR, Magariños B: Evaluation of four polymerase chain reaction primer pairs for the detection of Edwardsiella tarda in turbot. Dis Aquat Organ. 2010, 90: 55-61.
Ling SHM, Wang XH, Xie L, Lim TM, Leung KY: Use of green fluorescent protein (GFP) to study the invasion pathways of Edwardsiella tarda in in vivo and in vitro fish models. Microbiology. 2000, 146: 7-19.
Ling SHM, Wang XH, Lim TM, Leung KY: Green fluorescent protein‐tagged Edwardsiella tarda reveals portal of entry in fish. FEMS Microbiol Lett. 2001, 194: 239-243.
Zheng J, Leung KY: Dissection of a type VI secretion system in Edwardsiella tarda. Mol Microbiol. 2007, 66: 1192-1206.
Zheng J, Tung SL, Leung KY: Regulation of a type III and a putative secretion system in Edwardsiella tarda by EsrC is under the control of a two-component system, EsrA-EsrB. Infect Immun. 2005, 73: 4127-4137.
Tan YP, Zheng J, Tung SL, Rosenshine I, Leung KY: Role of type III secretion in Edwardsiella tarda virulence. Microbiology. 2005, 151: 2301-2313.
Zheng J, Li N, Tan YP, Sivaraman J, Mok YK, Mo ZL, Leung KY: EscC is a chaperone for the Edwardsiella tarda type III secretion system putative translocon components EseB and EseD. Microbiology. 2007, 153: 1953-1962.
Wang B, Mo ZL, Xiao P, Li J, Zou YX, Hao B, Li GY: EseD, a putative T3SS translocon component of Edwardsiella tarda, contributes to virulence in fish and is a candidate for vaccine development. Mar Biotechnol (NY). 2010, 12: 678-685.
Tan YP, Lin Q, Wang XH, Joshi S, Hew CL, Leung KY: Comparative proteomic analysis of extracellular proteins of Edwardsiella tarda. Infect Immun. 2002, 70: 6475-6480.
Srinivasa Rao PS, Lim TM, Leung KY: Functional genomics approach to the identification of virulence genes involved in Edwardsiella tarda pathogenesis. Infect Immun. 2003, 71: 1343-1351.
Sakai T, Matsuyama T, Sano M, Iida T: Identification of novel putative virulence factors, adhesin AIDA and type VI secretion system, in atypical strains of fish pathogenic Edwardsiella tarda by genomic subtractive hybridization. Microbiol Immunol. 2009, 53: 131-139.
Wang X, Wang Q, Xiao J, Liu Q, Wu H, Zhang Y: Hemolysin EthA in Edwardsiella tarda is essential for fish invasion in vivo and in vitro and regulated by two-component system EsrA-EsrB and nucleoid protein HhaEt. Fish Shellfish Immunol. 2010, 29: 1082-1091.
Wang X, Wang Q, Yang M, Xiao J, Liu Q, Wu H, Zhang Y: QseBC controls flagellar motility, fimbrial hemagglutination and intracellular virulence in fish pathogen Edwardsiella tarda. Fish Shellfish Immunol. 2011, 30: 944-953.
Leung KY, Siame BA, Snowball H, Mok YK: Type VI secretion regulation: crosstalk and intracellular communication. Curr Opin Microbiol. 2011, 14: 9-15.
Srinivasa Rao PS, Yamada Y, Tan YP, Leung KY: Use of proteomics to identify novel virulence determinants that are required for Edwardsiella tarda pathogenesis. Mol Microbiol. 2004, 53: 573-586.
Chakraborty S, Li M, Chatterjee C, Sivaraman J, Leung KY, Mok YK: Temperature and Mg2+ sensing by a novel PhoP-PhoQ two-component system for regulation of virulence in Edwardsiella tarda. J Biol Chem. 2010, 285: 38876-38888.
Kokubo T, Iida T, Wakabayashi H: Production of siderophore by Edwardsiella tarda. Fish Pathol. 1990, 25: 237-241.
Mathew JA, Tan YP, Srinivasa Rao PS, Lim TM, Leung KY: Edwardsiella tarda mutants defective in siderophore production, motility, serum resistance and catalase activity. Microbiology. 2001, 147: 449-457.
Igarashi A, Iida T, Crosa JH: Iron-acquisition ability of Edwardsiella tarda with involvement in its virulence. Fish Pathol. 2002, 37: 53-58.
Wang X, Wang Q, Xiao J, Liu Q, Wu H, Xu L, Zhang Y: Edwardsiella tarda T6SS component evpP is regulated by esrB and iron, and plays essential roles in the invasion of fish. Fish Shellfish Immunol. 2009, 27: 469-477.
Yasunobu H, Arikawa Y, Fumtsuka-Uozumi K, Dombo M, Iida T, Mahmoud MM, Okuda J, Nakai T: Induction of Hemagglutinating activity of Edwardsiella tarda by sodium chloride. Fish Pathol. 2006, 41: 29-34.
Janda JM, Abbott SL: Expression of an iron-regulated hemolysin by Edwardsiella tarda. FEMS Microbiol Lett. 1993, 111: 275-280.
Chen JD, Lai SY, Huang SL: Molecular cloning, characterization, and sequencing of the hemolysin gene from Edwardsiella tarda. Arch Microbiol. 1996, 165: 9-17.
Hirono I, Tange N, Aoki T: Iron‐regulated haemolysin gene from Edwardsiella tarda. Mol Microbiol. 1997, 24: 851-856.
Strauss EJ, Ghori N, Falkow S: An Edwardsiella tarda strain containing a mutation in a gene with homology to shlB and hpmB is defective for entry into epithelial cells in culture. Infect Immun. 1997, 65: 3924-3932.
Ullah MA, Arai T: Exotoxic substances produced by Edwardsiella tarda. Fish Pathol. 1983, 18: 71-75.
Jiao X, Zhang M, Cheng S, Sun L: Analysis of Edwardsiella tarda DegP, a serine protease and a protective immunogen. Fish Shellfish Immunol. 2010, 28: 672-677.
Ainsworth JA, Dexiang C: Differences in the phagocytosis of four bacteria by channel catfish neutrophils. Dev Comp Immunol. 1990, 14: 201-209.
Srinivasa Rao PS, Lim TM, Leung KY: Opsonized virulent Edwardsiella tarda strains are able to adhere to and survive and replicate within fish phagocytes but fail to stimulate reactive oxygen intermediates. Infect Immun. 2001, 69: 5689-5697.
Ishibe K, Osatomi K, Hara K, Kanai K, Yamaguchi K, Oda T: Comparison of the responses of peritoneal macrophages from Japanese flounder (Paralichthys olivaceus) against high virulent and low virulent strains of Edwardsiella tarda. Fish Shellfish Immunol. 2008, 24: 243-251.
Ishibe K, Yamanishi T, Wang Y, Osatomi K, Hara K, Kanai K, Yamaguchi K, Oda T: Comparative analysis of the production of nitric oxide (NO) and tumor necrosis factor-[alpha](TNF-[alpha]) from macrophages exposed to high virulent and low virulent strains of Edwardsiella tarda. Fish Shellfish Immunol. 2009, 27: 386-389.
Pirarat N, Maita M, Endo M, Katagiri T: Lymphoid apoptosis in Edwardsiella tarda septicemia in tilapia, Oreochromis niloticus. Fish Shellfish Immunol. 2007, 22: 608-616.
Pressley ME, Phelan PE, Eckhard Witten P, Mellon MT, Kim CH: Pathogenesis and inflammatory response to Edwardsiella tarda infection in the zebrafish. Dev Comp Immunol. 2005, 29: 501-513.
Mohanty BR, Sahoo PK: Immune responses and expression profiles of some immune-related genes in Indian major carp, Labeo rohita to Edwardsiella tarda infection. Fish Shellfish Immunol. 2010, 28: 613-621.
Matsuyama T, Fujiwara A, Nakayasu C, Kamaishi T, Oseko N, Hirono I, Aoki T: Gene expression of leucocytes in vaccinated Japanese flounder (Paralichthys olivaceus) during the course of experimental infection with Edwardsiella tarda. Fish Shellfish Immunol. 2007, 22: 598-607.
Yasuike M, Takano T, Kondo H, Hirono I, Aoki T: Differential gene expression profiles in Japanese flounder (Paralichthys olivaceus) with different susceptibilities to edwardsiellosis. Fish Shellfish Immunol. 2010, 29: 747-752.
Aoki T, Hirono I, Kondo H, Hikima J, Jung TS: Microarray technology is an effective tool for identifying genes related to the aquacultural improvement of Japanese flounder, Paralichthys olivaceus. Comp Biochem Physiol Part D Genomics Proteomics. 2011, 6: 39-43.
Verjan N, Hirono I, Aoki T: Genetic loci of major antigenic protein genes of Edwardsiella tarda. Appl Environ Microbiol. 2005, 71: 5654-5658.
Park SB, Jang HB, Nho SW, Cha IS, Hikima J, Ohtani M, Aoki T, Jung TS: Outer Membrane Vesicles as a Candidate Vaccine against Edwardsiellosis. PLoS One. 2011, 6: e17629-
Lee DC, Kim DH, Park SI: Effects of extracellular products of Edwardsiella tarda on the innate immunity in olive flounder Paralichthys olivaceus. Fish Pathol. 2009, 45: 17-23.
Kumar G, Rathore G, Sengupta U, Singh V, Kapoor D, Lakra WS: Isolation and characterization of outer membrane proteins of Edwardsiella tarda and its application in immunoassays. Aquaculture. 2007, 272: 98-104.
Vinogradov E, Nossova L, Perry MB, Kay WW: Structural characterization of the O-polysaccharide antigen of Edwardsiella tarda MT 108. Carbohydr Res. 2005, 340: 85-90.
Tang X, Zhan W, Sheng X, Chi H: Immune response of Japanese flounder Paralichthys olivaceus to outer membrane protein of Edwardsiella tarda. Fish Shellfish Immunol. 2010, 28: 333-343.
Kumar G, Sharma P, Rathore G, Bisht D, Sengupta U: Proteomic analysis of outer membrane proteins of Edwardsiella tarda. J Appl Microbiol. 2010, 108: 2214-2221.
Wang Q, Yang M, Xiao J, Wu H, Wang X, Lv Y, Xu L, Zheng H, Wang S, Zhao G: Genome sequence of the versatile fish pathogen Edwardsiella tarda provides insights into its adaptation to broad host ranges and intracellular niches. PLoS One. 2009, 4: e7646-
Robinson A, Hudson MJ, Cranage MP: Vaccine potocols. Overview of Vaccines. Edited by: Ada G. 2003, Totowa: Humana Press, 1-17. 2
Salati F, Kawai K, Kusuda R: Immune response of eel to Edwardsiella tarda lipopolysaccharide. Fish Pathol. 1984, 19: 187-192.
Gutierrez MA, Miyazaki T: Responses of Japanese eels to oral challenge with Edwardsiella tarda after vaccination with formalin-killed cells or lipopolysaccharide of the bacterium. J Aquat Anim Health. 1994, 6: 110-117.
Salati F, Kusuda R: Vaccine preparations used for immunization of eel Anguilla japonica against Edwardsiella tarda infection. Bull Jpn Soc Sci Fish. 1985, 51: 1233-1237.
Mekuchi T, Kiyokawa T, Honda K, Nakai T, Muroga K: Vaccination trials in the Japanese flounder against edwardsiellosis. Fish Pathol. 1995, 30: 251-256.
Newman SG: Bacterial vaccines for fish. Annu Rev Fish Dis. 1993, 3: 145-185.
Dang W, Zhang M, Sun L: Edwardsiella tarda DnaJ is a virulence-associated molecular chaperone with immunoprotective potential. Fish Shellfish Immunol. 2011, 31: 182-188.
Maiti B, Shetty M, Shekar M, Karunasagar I, Karunasagar I: Recombinant outer membrane protein A (OmpA) of Edwardsiella tarda, a potential vaccine candidate for fish, common carp. Microbiol Res. 2011, 167: 1-7.
Choi SH, Kim KH: Generation of two auxotrophic genes knock-out Edwardsiella tarda and assessment of its potential as a combined vaccine in olive flounder (Paralichthys olivaceus). Fish Shellfish Immunol. 2011, 31: 58-65.
Sun Y, Liu CS, Sun L: Comparative study of the immune effect of an Edwardsiella tarda antigen in two forms: Subunit vaccine vs DNA vaccine. Vaccine. 2011, 29: 2051-2057.
Sun Y, Liu C, Sun L: Construction and analysis of the immune effect of an Edwardsiella tarda DNA vaccine encoding a D15-like surface antigen. Fish Shellfish Immunol. 2010, 30: 273-279.
Sun Y, Liu C, Sun L: Identification of an Edwardsiella tarda surface antigen and analysis of its immunoprotective potential as a purified recombinant subunit vaccine and a surface-anchored subunit vaccine expressed by a fish commensal strain. Vaccine. 2010, 28: 6603-6608.
Takano T, Matsuyama T, Oseko N, Sakai T, Kamaishi T, Nakayasu C, Sano M, Iida T: The efficacy of five avirulent Edwardsiella tarda strains in a live vaccine against Edwardsiellosis in Japanese flounder, Paralichthys olivaceus. Fish Shellfish Immunol. 2010, 29: 687-693.
Jiao X, Hu Y, Sun L: Dissection and localization of the immunostimulating domain of Edwardsiella tarda FliC. Vaccine. 2010, 28: 5635-5640.
Qin H, Jin X, Huang W, Liu Y: Production of an anti-idiotypic antibody single chain variable fragment vaccine against Edwardsiella tarda. Acta Biochim Biophys Sin (Shanghai). 2010, 42: 129-136.
Cheng S, Hu Y, Zhang M, Sun L: Analysis of the vaccine potential of a natural avirulent Edwardsiella tarda isolate. Vaccine. 2010, 28: 2716-2721.
Jiao X, Dang W, Hu Y, Sun L: Identification and immunoprotective analysis of an in vivo-induced Edwardsiella tarda antigen. Fish Shellfish Immunol. 2009, 27: 633-638.
Jiao X, Zhang M, Hu Y, Sun L: Construction and evaluation of DNA vaccines encoding Edwardsiella tarda antigens. Vaccine. 2009, 27: 5195-5202.
Hou JH, Zhang WW, Sun L: Immunoprotective analysis of two Edwardsiella tarda antigens. J Gen Appl Microbiol. 2009, 55: 57-61.
Lan MZ, Peng X, Xiang MY, Xia ZY, Bo W, Jie L, Li XY, Jun ZP: Construction and characterization of a live, attenuated esrB mutant of Edwardsiella tarda and its potential as a vaccine against the haemorrhagic septicaemia in turbot, Scophthamus maximus (L.). Fish Shellfish Immunol. 2007, 23: 521-530.
Kwon SR, Lee EH, Nam YK, Kim SK, Kim KH: Efficacy of oral immunization with Edwardsiella tarda ghosts against edwardsiellosis in olive flounder (Paralichthys olivaceus). Aquaculture. 2007, 269: 84-88.
Kwon SR, Nam YK, Kim SK, Kim KH: Protection of tilapia (Oreochromis mosambicus) from edwardsiellosis by vaccination with Edwardsiella tarda ghosts. Fish Shellfish Immunol. 2006, 20: 621-626.
Kawai K, Liu Y, Ohnishi K, Oshima S: A conserved 37 kDa outer membrane protein of Edwardsiella tarda is an effective vaccine candidate. Vaccine. 2004, 22: 3411-3418.
This work was supported by a grant from the World Class University Program (no. R32-10253) funded by the Ministry of Education, Science and Technology, of South Korea.
The authors declare that they have no competing interests.
SBP drafted the manuscript, tables, and figure. TA and TSJ critically evaluated and revised the manuscript for important intellectual content. All authors have read and approved the final manuscript.
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Park, S.B., Aoki, T. & Jung, T.S. Pathogenesis of and strategies for preventing Edwardsiella tarda infection in fish. Vet Res 43, 67 (2012) doi:10.1186/1297-9716-43-67
- Weddell Seal
- Outer Membrane Vesicle
- Lateral Line Canal
- Hydrogen Sulfide Production
- Anguilla Japonica