Katy Vaillancourt

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Streptococcus salivarius is a lactose- and galactose-positive bacterium that is phylogenetically closely related to Streptococcus thermophilus, a bacterium that metabolizes lactose but not galactose. In this paper, we report a comparative characterization of the S. salivarius and S. thermophilus gal-lac gene clusters. The clusters have the same organization(More)
Streptococcus suis is a major swine pathogen and zoonotic agent that mainly causes septicemia, meningitis, and endocarditis. It has recently been suggested that proteinases produced by S. suis (serotype 2) are potential virulence determinants. In the present study, we screened a S. suis mutant library created by the insertion of Tn917 transposon in order to(More)
The lactic acid bacterium Streptococcus thermophilus is widely used by the dairy industry for its ability to transform lactose, the primary sugar found in milk, into lactic acid. Unlike the phylogenetically related species Streptococcus salivarius, S. thermophilus is unable to metabolize and grow on galactose and thus releases substantial amounts of this(More)
Streptococcus suis is a major swine pathogen that is responsible for severe infections such as meningitis, endocarditis, and septicemia. S. suis is also recognized as a zoonotic agent and expresses several virulence factors. The recently identified subtilisin-like protease (SspA) of S. suis plays an important role in the pathogenicity of this bacterium in(More)
In gram-positive bacteria, the HPr protein of the phosphoenolpyruvate:sugar phosphotransferase system (PTS) can be phosphorylated on a histidine residue at position 15 (His(15)) by enzyme I (EI) of the PTS and on a serine residue at position 46 (Ser(46)) by an ATP-dependent protein kinase (His approximately P and Ser-P, respectively). We have isolated from(More)
In Streptococcus thermophilus, lactose is taken up by LacS, a transporter that comprises a membrane translocator domain and a hydrophilic regulatory domain homologous to the IIA proteins and protein domains of the phosphoenolpyruvate:sugar phosphotransferase system (PTS). The IIA domain of LacS (IIALacS) possesses a histidine residue that can be(More)
The oral bacterium Streptococcus salivarius takes up lactose via a transporter called LacS that shares 95% identity with the LacS from Streptococcus thermophilus, a phylogenetically closely related organism. S. thermophilus releases galactose into the medium during growth on lactose. Expulsion of galactose is mediated via LacS and stimulated by(More)
Streptococcus thermophilus is unable to metabolize the galactose moiety of lactose. In this paper, we show that a transformant of S. thermophilus SMQ-301 expressing Streptococcus salivarius galK and galM was able to grow on galactose and expelled at least twofold less galactose into the medium during growth on lactose.
Streptococcus suis serotype 2 is known to cause severe infections (meningitis, endocarditis, and septicemia) in pigs and is considered an emerging zoonotic agent. Antibiotics have long been used in the swine industry for disease treatment/prevention and growth promoters. This pattern of utilization resulted in the spread of antibiotic resistance in S. suis(More)
While Streptococcus suis serotype 2 is known to cause severe infections in pigs, it can also be isolated from the tonsils of healthy animals that do not develop infections. We hypothesized that S. suis strains in healthy carrier pigs may have the ability to produce bacteriocins, which may contribute to preventing infections by pathogenic S. suis strains.(More)