SwineHealth News for January 6, 2023
The use of MLST typing is allowing diagnosticians to differentiate between virulent and non-virulent strains of Streptococcus suis at a genetic level.
Diagnosticians have typically used serotyping to categorise Strep suis isolates according to the protective capsule that surrounds the organism but, with the popularization of genetic sequencing, it's possible to obtain the whole genome, opening the door to the identification of markers specially associated with virulence.
Dr. Matheus Costa, an Assistant Professor with the Western College of Veterinary Medicine and an Adjunct Professor at Utrecht University, says within a serotype we have multiple MLST types but not all of them will cause disease in pigs.
Clip-Dr. Matheus Costa-Western College of Veterinary Medicine:
With the advent and popularization of sequencing, we can now obtain the whole genome of an isolate and whole genome sequence will open the door for the further identification of markers that are associated with virulent stains.
So, what does that mean?
It means that we can look for specific genetic sequences only associated with Strep suis that cause disease.
So, the first step beyond serotyping is called MLST.
MLST is actually a genetic characterization, so we're looking on the genome of Strep suis and saying is the genome related or does it resemble another virulent Strep suis or not?
Within a serotype, for example serotype 2, we have multiple different MLST types and not all of them can cause disease in pigs.
We can have a serotype 2 and expose or infect pigs with a serotype 2 and those pigs do not develop any kind of disease and some other serotypes 2 can actually induce very severe disease and the difference between those two isolates is actually a genetic difference that is identified by MLST.
Dr. Costa says MLST is providing us with a higher resolution look at strep suis and we can use that to differentiate between virulent and avirulent or commensal strains.
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