Genetic divergence between the fish pathogens

Dec 05, 2013
Electronic micrograph of E. Tarda (now E. piscicida) LTB4 strain after negative staining Credit: Lan et al.

Edwardsiella tarda is a bacterium that can infect a number of animal species and also humans. Edwardsiellosis is one of the most serious systemic bacterial diseases in fish, resulting in substantial losses in the fish farming industry all over the world.

Takele Abayneh Tefera has developed effective molecular tools for the identification and characterization of different of Edwardsiella. He developed a new TaqMan real-time and conventional PCR analysis for this purpose and then evaluated it in relation to the Loop Mediated Isothermal Amplification (LAMP) analysis. For the first time, he also used the Multi-locus Sequence Analysis (MLSA) for the typing and characterization of E. tarda, isolated from different sources. This is a useful tool for detecting sources of infection and for understanding the epidemiological relationship between isolates from the environment, fish, livestock and humans.

The MLSA analysis showed that there exist geographic and host-specific genotypes of the E. tarda. Bacterial strains from fish were found to be only distantly related to E. tarda type strain and other strains from humans. Furthermore, genetic and phenotypic analyses also confirmed a genetic divergence between these strains of bacteria.

The findings of this study indicate that the fish pathogenic strain has been wrongly classified as E. tarda. Phenotypic characterization by means of a number of biochemical tests and pathogenity studies on zebra fish identified phenotypic markers which also differentiate fish from the reference bacterium.

Based on genetic and phenotypic differences, Tefera and his colleagues have proposed that fish pathogenic Edwardsiella strains previously classified as Edwardsiella tarda should now be classified as a : Edwardsiella piscicida. The new species has now been approved and incorporated into prokaryotic nomenclature.

Tefera's work also led to the introduction of a new Multi-locus Variable Number Tandem Repeat Analysis (MLVA) for the further typing of different isolates of the new species of bacteria Edwardsiella piscicida. Employing this method proved to be more sensitive than the MLSA-analysis when it came to investigating outbreaks of E. piscicida.

Takele Abayneh Tefera defended his doctoral research on 26th November 2013 at the Norwegian School of Veterinary Science with a thesis entitled: "Fish pathogenic Edwardsiella tarda: Evaluation of molecular identification methods and characterization of a novel species."

Explore further: MRSA strain in humans originally came from cattle, research says

add to favorites email to friend print save as pdf

Related Stories

Mycobacteriosis in fish

Jan 15, 2013

Mycobacteriosis in fish is a disease that is difficult to detect and therefore often underdiagnosed. For the same reason, information about the effects of this disease on the fish farming industry has been ...

New models predict where E. coli strains will thrive

Nov 18, 2013

Bioengineers at the University of California, San Diego have used the genomic sequences of 55 E. coli strains to reconstruct the metabolic repertoire for each strain. Surprisingly, these reconstructions do an excellent job of ...

Recommended for you

Citizen scientists match research tool when counting sharks

5 hours ago

Shark data collected by citizen scientists may be as reliable as data collected using automated tools, according to results published April 23, 2014, in the open access journal PLOS ONE by Gabriel Vianna from The University of Wes ...

Researchers detail newly discovered deer migration

12 hours ago

A team of researchers including University of Wyoming scientists has documented the longest migration of mule deer ever recorded, the latest development in an initiative to understand and conserve ungulate ...

How Australia got the hump with one million feral camels

13 hours ago

A new study by a University of Exeter researcher has shed light on how an estimated one million-strong population of wild camels thriving in Australia's remote outback have become reviled as pests and culled ...

Former Iron Curtain still barrier for deer

19 hours ago

The Iron Curtain was traced by an electrified barbed-wire fence that isolated the communist world from the West. It was an impenetrable Cold War barrier—and for some inhabitants of the Czech Republic it ...

Humpback protections downgrade clears way for pipeline

Apr 22, 2014

Environmentalist activists on Tuesday decried Canada's downgrading of humpback whale protections, suggesting the decision was fast-tracked to clear a major hurdle to constructing a pipeline to the Pacific ...

Maine baby lobster decline could end high catches

Apr 22, 2014

Scientists say the number of baby lobsters settling off the rocky coast of Maine continues to steadily decline—possibly foreshadowing an end to the recent record catches that have boosted New England's lobster fishery.

User comments : 0

More news stories