Molecular characterization of Streptococcus suis strains by 16S–23S intergenic spacer polymerase chain reaction and restriction fragment length polymorphism analysis |
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| Authors: | Corinne Marois Laëtitia Le Devendec Marcelo Gottschalk and Marylne Kobisch |
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| Affiliation: | Agence Fran?aise de Sécurité Sanitaire des Aliments, Unité de Mycoplasmologie-Bactériologie, BP53, 22440 Ploufragan, France. c.marois@ploufragan.afssa.fr |
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| Abstract: | We developed a new molecular method of typing Streptococcus suis based on polymerase chain reaction (PCR) amplification of a large fragment of rRNA genes, including a part of the 16S and 23S genes and the 16S-23S intergenic spacer region (ISR), followed by restriction fragment length polymorphism (RFLP) analysis with RsaI or MboII endonuclease. The 16S-23S ISRs of 5 S. suis isolates were sequenced and compared. Size and sequence polymorphisms were observed between the S735 reference strain and the 4 wild-type strains. The genetic relationships between 138 independent S. suis strains belonging to various serotypes, isolated from swine or human cases, were determined. The discriminatory power of the method was > 0.95, the threshold value for interpreting typing results with confidence (0.954 with RsaI and 0.984 with RsaI plus MboII). The in vitro reproducibility was 100%. The strains isolated from humans were less genetically diverse than the strains isolated from pigs. For the first time, 2 molecular patterns (R6, M9) were significantly associated with S. suis serotype 2 strains. This genetic tool could be valuable in distinguishing individual isolates of S. suis during epidemiologic investigations. |
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