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Reference image of a coho salmon with SRS.
Reference image of a coho salmon with SRS.

Two breakthroughs that should help the salmonid industry tackle Piscirickettsiosis (SRS) while reducing the use of antibiotics have been reported by ADL Diagnostic Chile.

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The research company has been studying Piscirickettsia salmonis, the disease that causes Piscirickettsiosis (SRS) for more than a decade. Recently, company researchers reported in the scientific journal Genome Announcements that they had finished the first complete genome sequence of an oxytetracycline-resistant P. salmonis isolate – a breakthrough that will help improve antibiotic treatments and, in particular, reduce their use.

The study was conducted by the company’s Bioinformatics Unit, using data generated by two types of chemical sequencing. The methodology was applied to a DNA sample from isolate AY3800B, which was recovered from Atlantic salmon during an outbreak of Piscirickettsiosis that occurred in Aysén in 2013.

ADL commented that, according to additional analyses, the plasmid appears to have originated from a similar element found in Edwardsiella tarda, another fish pathogen. However, resistance to tetracyclines could perhaps derive from interaction with Aeromonas salmonicida. If confirmed, this would be the first report of horizontal transfer of genes by P. salmonis.

Detection

The firm has also successfully developed a detection test, called Atbplex, which will help to predict the efficacy of various antibiotics on P. salmonis, without having to isolate the bacteria – saving time and guiding the application of antibiotics for the management of SRS outbreaks. The molecular antibiogram will be commercially available in version 3.0 from March 1.

The general manager of the company, Patricio Bustos, confirmed that Atbplex incorporates the detection of isolates resistant to oxytetracycline, and to date, results have been relevant in the early detection of resistant cases, so as to avoid the application of this antibiotic either orally or by injection, and thus reduce by mortality, while optimizing and rationalizing the use of antibiotics.

Watch the Atbplex video at https://www.youtube.com/watch?v=1yjNjPvSWzg.

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