Serotype distribution and production of muramidase-released protein, extracellular factor and suilysin by field strains of Streptococcus suis isolated in the United States.
Streptococcus suis is an important swine pathogen and a zoonotic agent. Differences in virulence have been noted among the 33 described serotypes, serotype 2 being considered the most virulent. In this study, we aimed at assessing the serotype distribution and the production of virulence-associated markers by strains recovered from diseased pigs in the United States (U.S.). Results showed that among the 100 strains evaluated, serotype 3 (20% of the isolates) and serotype 2 (17%) were the most prevalent. We then investigated the presence in these isolates of the genes sly, epf and mrp, encoding the virulence-associated markers suilysin (SLY), extracellular factor (EF) and muramidase-released (MRP) protein, respectively. The effective production of the markers by the strains was also verified. Results showed that the presence of the gene did not always correlate with actual expression of the respective protein. In the case of MRP, this was due, in most cases, to frameshift mutations at the 5' end of the gene resulting in premature stop codons. The most prevalent phenotypes among U.S. strains were MRP(+)EF(-)SLY(-) (40%) and MRP(-)EF(-)SLY(+) (35%). Serotype distribution greatly differed from that reported in several European countries, as did the production of virulence markers, particularly for serotype 2. On the other hand, our results for the U.S. S. suis isolates are similar to those reported for Canadian strains, suggesting a common status in North America.
Fittipaldi
Nahuel
N
Groupe de Recherche sur les Maladies Infectieuses du Porc and Centre de Recherche en Infectiologie Porcine, Faculté de médecine vétérinaire, Université de Montréal, St-Hyacinthe, Qc J2S 7C6, Canada.
Fuller
Troy E
TE
Teel
Janet F
JF
Wilson
Thomas L
TL
Wolfram
Thaddeus J
TJ
Lowery
David E
DE
Gottschalk
Marcelo
M
D000818:Animals; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D006460:Hemolysin Proteins / Q000235:genetics / Q000378:metabolism; D009113:Muramidase / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D012703:Serotyping; D013290:Streptococcal Infections / Q000382:microbiology / Q000662:veterinary*; D017011:Streptococcus suis / Q000145:classification* / Q000235:genetics / Q000472:pathogenicity*; D034421:Sus scrofa; D013553:Swine Diseases / Q000382:microbiology*; D014481:United States; D014774:Virulence; D037521:Virulence Factors / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D006460:Hemolysin Proteins; D037521:Virulence Factors; C104760:suilysin; D009113:Muramidase