Edwardsiella piscicida

Edwardsiella piscicida
Scientific classification Edit this classification
Domain: Bacteria
Kingdom: Pseudomonadati
Phylum: Pseudomonadota
Class: Gammaproteobacteria
Order: Enterobacterales
Family: Hafniaceae
Genus: Edwardsiella
Species:
E. piscicida
Binomial name
Edwardsiella piscicida
Abayneh et al., 2013

Edwardsiella piscicida is a species of gram-negative, rod-shaped bacterium from the order Enterobacterales. This species is a prominent bacterial pathogen in freshwater and marine fish. E. piscida is responsible for a significant amount of economic loss in aquaculture worldwide. Before its recognition as a separate species in 2013, many E. piscida isolates were misidentified as Edwardsiella tarda.

Taxonomy

The genus Edwardsiella was first described 1960s with two independent groups isolating the bacterium from snakes[1] and a patient with gastroenteritis.[2] The genus was validly established in 1965 with the description of Edwardsiella tarda.[3] Additional species including E. horshinae and E. ictaluri were later described from reptiles, birds, and catfish.

Edwardsiella piscicida was formally described as a novel species in 2013 after genetic and phylogentic studies demonstrated that many fish-pathogenic isolates previously identified as Edwardsiella tarda represented a distinct clade.[4] The species is now recognized as one of the five members of the genus alongside E. anguillarum, E. ictaluri, E. tarda, and E. horshinae.[5]

Phenotypic characteristics

Morphology and growth characteristics

Edwardsiella piscicida is a facultatively anaerobic, gram-negative rod that is usually motile.[6] Colonies are generally small, circular, smooth and white to grayish-white in appearance, resembling other members of its genus.[7][8]

The bacterium grows on a variety of routine laboratory media including tryptic soy agar, brain heart infusion agar, Mueller-Hinton agar, and marine agar.[6]

Biochemical characteristics

E. piscicida is an oxidase-negative, rod-shaped bacterium that is usually motile.[6] Similar to many other Edwardsiella species, E. piscicida is able to breakdown tryptophan to produce indole and is typically positive for lysine and ornithine decarboxylase activity. E. piscicida is generally considered hydrogen sulfide positive, although some strains reportedly produce little to no hydrogen sulfide.[7][8]

This species ferments glucose, mannose, and maltose.[6]

The fatty acid profile of E. piscicida is composed primarily of saturated, unsaturated, and cyclopropane fatty acids, with major components including tetrecanoic acid, hexadecanoic acid, and lactobacillic acid analogues.[6]

Virulence factors

Secretion systems

The type III secretion system (T3SS) and type VI secretion system (T6SS) are major virulence factors in Edwardsiella piscicida. The T3SS functions as a needle-like secretion apparatus that injects effector proteins directly into host cells, allowing the bacterium to manipulate host signalling pathways, evade immune defense, and promote intracellular survival.[9] Mutations affecting T3SS-associated effector proteins have been shown to reduce intracellular replication and attenuate virulence in fish infection models. The T6SS also contributes to pathogenicity as mutations in T6SS-associated effector proteins have been shown to reduce virulence in zebrafish and turbot models.[10] Additionally, the T6SS is thought to contribute to interbacterial competition and adaptation within aquatic environments.

Extracellular products

E. piscicida secretes several extracellular products that are proposed to play a role in virulence. The species also produces hemolysins to breakdown host red blood cells to access iron. Hemolysins have been shown experimentally in E. tarda to be essential for fish invasion.[11] Other extracellular proteins produced include amylase, protease, and lecithinase.[8]

Adhesion factors

E. piscicida produces an invasin (Inv1) and several adhesins (FliC, FlgD) on the cell surface.[6] Contact and adhesion factors are believed to play a role in forming biofilms. However, the ability to form biofilms does not appear to be essential for E. piscicida in the fish as virulent strains are unable to form biofilms under experimental conditions.[12]

Aquaculture

Edwardsiella piscicida is considered a major bacterial pathogen in global aquaculture and causes the disease known as Edwardsiellosis.[6] Surveys on catfish farms in thee southern United States found that Edwardsiella sp. were the third leading bacterial cause of mortality, after Aeromonas hydrophilia and columnaris.[13]

This bacterium has been isolated from numerous fish species including, whitefish (Coregonus lavaretus),[12] Nile tilapia (Oreochromis niloticus),[7] spotted sea bass (Lateolabrax maculatus),[8] and burrundi.

Pathogenesis

E. piscicida acts as an opportunistic pathogen, with disease outbreaks commonly occurring under conditions of aquatic environmental stress, such as higher water temperatures, water pollution, or poor water quality.[14] Misuse of antibiotics is also a potential risk factor.

Damaged intestinal mucosa are considered a major portal of entry.[15] E. piscicida utilizes actin condensation for entry into epithelial cells.[16] This species is capable of intracellular survival within epithelial cells and macrophages. Following host entry, E. piscicida can disseminate systemically and infect multiple organs.

Signs and symptoms

Fish infected with edwardsielliosis commonly present with skin discoloration, ulcerative lesions, ascites, and exophthalmia.[6] Septicemia and hemorrhaging may also occur. Internal lesions may include granulomas, necrosis of the liver and kidney, and abscesses.

Treatment

Edwardsiella piscicida is generally susceptible to antibiotics commonly used to treat edwardsiellosis, including trimethoprim/sulfamethoxazole, florfenicol, oxytetracycline, and enrofloxacin.[17] Acquired resistance to trimethoprim, oxytetracycline, and moxifloxacin have been reported.[7]

Phage therapy is being explored as a possible alternative to antibiotics. The bacteriophage EPP-1 has been shown to effectively inhibit E. piscicida growth and improve survival outcomes in zebrafish.[18]

Prevention

Vaccines are a validated, cost-effective preventative measure that can be taken against bacterial infections. An adjuvanted formalin-killed vaccine was developed that showed 90-100% relative percent survival.[19] Live attenuated vaccines generated through disrupting secretion systems or regulatory genes have also been shown to be effective at preventing E. piscicida infection in experimental infection models.[20] However, they are unlikely to be suitable for aquaculture due to environmental concerns.

References

  1. ↑ SAKAZAKI, RIICHI (1967). "Studies on the Asakusa Group of Enterobacteriaceae (Edwardsiella Tarda)". Japanese Journal of Medical Science and Biology. 20 (3): 205–212. doi:10.7883/yoken1952.20.205. ISSN 0021-5112. PMID 5299172.
  2. ↑ King, Benjamin M.; Adler, David L. (1964-02-01). "A Previously Undescribed Group of Enterobacteriaceae". American Journal of Clinical Pathology. 41 (2_ts): 230–232. doi:10.1093/ajcp/41.2_ts.230. ISSN 0002-9173.
  3. ↑ Ewing, W. H.; Mcwhorter, A. C.; Escobar, M. R.; Lubin, A. H. (1965-01-01). "Edwardsiella, a new genus of Enterobacteriaceae based on a new species, E. tarda". International Bulletin of Bacteriological Nomenclature and Taxonomy. 15 (1): 33–38. doi:10.1099/00207713-15-1-33. ISSN 0020-7713.
  4. ↑ Abayneh, T.; Colquhoun, D. J.; Sørum, H. (2013). "Edwardsiella piscicida sp. nov., a novel species pathogenic to fish". Journal of Applied Microbiology. 114 (3): 644–654. Bibcode:2013JApMb.114..644A. doi:10.1111/jam.12080. ISSN 1365-2672. PMID 23167785.
  5. ↑ Leung, Ka Yin; Wang, Qiyao; Yang, Zhiyun; Siame, Bupe A. (2019). "Edwardsiella piscicida: A versatile emerging pathogen of fish". Virulence. 10 (1): 555–567. doi:10.1080/21505594.2019.1621648. ISSN 2150-5608. PMC 6592360. PMID 31122125.
  6. 1 2 3 4 5 6 7 8 Buján, N.; Toranzo, Alicia E.; Magariños, B. (2018-10-16). "Edwardsiella piscicida: a significant bacterial pathogen of cultured fish". Diseases of Aquatic Organisms. 131 (1): 59–71. Bibcode:2018DisAO.131...59B. doi:10.3354/dao03281. ISSN 0177-5103. PMID 30324915.
  7. 1 2 3 4 Charoenwai, Onanong; Dong, Ha Thanh; Nguyen, Vuong Viet; Chatchaiphan, Satid; Senapin, Saengchan; Piamsomboon, Patharapol (2026-03-30). "Recovery of Edwardsiella tarda and Edwardsiella piscicida in freshwater fishes and assessment of their pathogenicity in Nile tilapia (Oreochromis niloticus)". Aquaculture. 615 743671. Bibcode:2026Aquac.61543671C. doi:10.1016/j.aquaculture.2026.743671. ISSN 0044-8486.
  8. 1 2 3 4 Hu, Jianmei; Wang, Baotun; Feng, Juan; Liu, Chun; Jiang, Biao; Li, Wei; Lin, Li; Su, Youlu (2022-02-01). "Edwardsiella piscicida, a pathogenic bacterium newly detected in spotted sea bass Lateolabrax maculatus in China". Aquaculture Reports. 22 100973. Bibcode:2022AqRep..2200973H. doi:10.1016/j.aqrep.2021.100973. ISSN 2352-5134.
  9. ↑ Han, Yu; Wei, Lifan; Xiao, Jingfan; Zhang, Yuanxing; Wang, Qiyao; Zhou, Mian (2020-07-01). "Identification and study of InV as an inverse autotransporter family representative in Edwardsiella piscicida". Archives of Microbiology. 202 (5): 1107–1116. Bibcode:2020ArMic.202.1107H. doi:10.1007/s00203-019-01804-y. ISSN 1432-072X. PMC 7223825. PMID 32052095.
  10. ↑ Cui, Shilei; Xiao, Jingfan; Wang, Qiyao; Zhang, Yuanxing (2016-09-01). "H-NS binding to evpB and evpC and repressing T6SS expression in fish pathogen Edwardsiella piscicida". Archives of Microbiology. 198 (7): 653–661. Bibcode:2016ArMic.198..653C. doi:10.1007/s00203-016-1226-4. ISSN 1432-072X. PMID 27125651.
  11. ↑ Wang, Xin; Wang, Qiyao; Xiao, Jingfan; Liu, Qin; Wu, Haizhen; Zhang, Yuanxing (2010-12-01). "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 Immunology. 29 (6): 1082–1091. doi:10.1016/j.fsi.2010.08.025. ISSN 1050-4648. PMID 20832475.
  12. 1 2 Shafiei, Shafigh; Viljamaa-Dirks, Satu; Sundell, Krister; Heinikainen, Sirpa; Abayneh, Takele; Wiklund, Tom (2016-03-01). "Recovery of Edwardsiella piscicida from farmed whitefish, Coregonus lavaretus (L.), in Finland". Aquaculture. 454: 19–26. Bibcode:2016Aquac.454...19S. doi:10.1016/j.aquaculture.2015.12.011. ISSN 0044-8486.
  13. ↑ Abdelrahman, Hisham A.; Hemstreet, William G.; Roy, Luke A.; Hanson, Terrill R.; Beck, Benjamin H.; Kelly, Anita M. (2023-03-15). "Epidemiology and economic impact of disease-related losses on commercial catfish farms: A seven-year case study from Alabama, USA". Aquaculture. 566 739206. Bibcode:2023Aquac.56639206A. doi:10.1016/j.aquaculture.2022.739206. ISSN 0044-8486.
  14. ↑ Roh, HyeongJin (2022). "A genome-wide association study of the occurrence of genetic variations in Edwardsiella piscicida , Vibrio harveyi , and Streptococcus parauberis under stressed environments". Journal of Fish Diseases. 45 (9): 1373–1388. Bibcode:2022JFDis..45.1373R. doi:10.1111/jfd.13668. ISSN 0140-7775. PMC 9541752. PMID 35735095.
  15. ↑ Lin, Changyi; Jiang, Biao; Huang, Weimin; Wu, Wenhao; Zhang, Jiahao; Su, Youlu (2025-06-30). "Environmental adaptability, virulence, and immune evasion mechanisms of Edwardsiella piscicida in the largemouth bass (Micropterus salmoides)". Aquaculture. 604 742505. Bibcode:2025Aquac.60442505L. doi:10.1016/j.aquaculture.2025.742505. ISSN 0044-8486.
  16. ↑ Ling, S. H. M.; Wang, X. H.; Xie, L.; Lim, T. M.; Leung, K. Y. (2000-01-01). "Use of green fluorescent protein (GFP) to study the invasion pathways of Edwardsiella tarda in in vivo and in vitro fish models". Microbiology. 146 (1): 7–19. doi:10.1099/00221287-146-1-7. ISSN 1350-0872. PMID 10658647.
  17. ↑ Kim, Ahran; Lim, Yunjin; Kim, Nameun; Luan Nguyen, Thanh; Roh, Heyong Jin; Park, Chan-Il; Han, Hyun-Ja; Jung, Sung-Hee; Cho, Mi-Young; Kim, Do-Hyung; Smith, Peter (2018). "A Comparison of Genotypic and Phenotypic Methods for Analyzing the Susceptibility to Sulfamethoxazole and Trimethoprim in Edwardsiella piscicida". Microbial Drug Resistance (Larchmont, N.Y.). 24 (8): 1226–1235. doi:10.1089/mdr.2017.0137. ISSN 1931-8448. PMID 29437540.
  18. ↑ Han, Ganghua; Huang, Ting; Liu, Xinchun; Liu, Ruyin (2024-04-24). "Bacteriophage EPP-1, a potential antibiotic alternative for controlling edwardsiellosis caused by Edwardsiella piscicida while mitigating drug-resistant gene dissemination". Scientific Reports. 14 (1): 9399. Bibcode:2024NatSR..14.9399H. doi:10.1038/s41598-024-60214-3. ISSN 2045-2322. PMC 11043334. PMID 38658654.{{cite journal}}: CS1 maint: unflagged free DOI (link)
  19. ↑ CASTRO, N; TORANZO, A; NUNEZ, S; MAGARINOS, B (2008). "Development of an effective Edwardsiella tarda vaccine for cultured turbot (Scophthalmus maximus)". Fish & Shellfish Immunology. 25 (3): 208–212. Bibcode:2008FSI....25..208C. doi:10.1016/j.fsi.2008.05.008. ISSN 1050-4648. PMID 18602276.
  20. ↑ Xiao, J.; Chen, T.; Wang, Q.; Liu, Q.; Wang, X.; Lv, Y.; Wu, H.; Zhang, Y. (2011). "Search for live attenuated vaccine candidate against edwardsiellosis by mutating virulence-related genes of fish pathogen Edwardsiella tarda: Live attenuated vaccine of Edw. tarda". Letters in Applied Microbiology. 53 (4): 430–437. doi:10.1111/j.1472-765X.2011.03126.x. PMID 21777261.
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