Distribution of SSU0757 in S. suis Selected S. suis strains were tested for the presence of the subtilisin-encoding gene (SSU0757): S428 (serotype 1), 31533 (serotype 2), 89-999 (serotype 2), S735 (serotype 2), 90-1330 (serotype 2), 65 (serotype 2), 89-4223 (serotype GANT61 research buy 2), 2651 (serotype 1/2), 4961 (serotype 3), Amy12C (serotype 5), 1078212 (untypeable), and 1079277 (untypeable). Except for strains 90-1330, 65 and 89-4223, which were isolated from healthy pigs, all

other isolates were from diseased pigs. Cell lysates were prepared from bacterial colonies recovered from agar plates. The presence of the gene was determined by PCR using the SUB163 (5′-GTCAGCGAATCAGCCTCAGAAAGTCCCGTT-3′) and SUB4436R (5′-CTTCATCTTTTTTGTCAGTGGCAGTATTTG-3′) primers. Growth studies The generation times of S. suis wild-type strain P1/7 and the proteinase-deficient mutants were determined by inoculating erythromycin-free THB with late-log phase cultures and monitoring growth at OD660. Generation times were calculated from the growth curves. Susceptibility to whole blood Venous blood samples were collected from the antecubital vein of a human volunteer using the Vacutainer™ system and sterile endotoxin-free blood collection tubes containing 150 IU of sodium heparin (Becton Dickinson,

Franklin Lakes, NJ, USA). Informed consent was obtained from the donor prior to the experiment. The protocol was approved by the Université Laval ethics committee. S. Selleck Cisplatin suis (wild-type parent strain and mutants) were cultivated to the early stationary growth phase at 37°C. The cells were harvested by centrifugation at 11,000 g for 10 min, suspended in RPMI-1640 medium to an

OD660 of 0.1, and diluted 1:100 in RPMI-1640 medium. Whole blood (1 ml) was mixed with pig serum anti-S. suis (300 μl) and S. suis cells (100 μl). Anti-S. suis serum was prepared in pigs by injecting whole bacterial cells as previously described [17]. The mixtures were incubated for 4 h at 37°C with occasional gentle shaking. Infected whole blood cultures were harvested at 0 and 4 h. Diflunisal The first time point (0 h) was considered as the 100% viability control. Infected whole blood samples were 10-fold serially diluted (10-1 to 10-4) in PBS and plated on Todd-Hewitt agar plates. After a 24-h incubation at 37°C, the number of colony selleckchem forming units (cfu) was determined. The experiments were carried out in duplicate. Experimental infections in mice Thirty-nine female six-week-old CD1 mice (Charles River Laboratories, Saint-Constant, QC, Canada) were acclimatized to a 12 h light/dark cycle and were given rodent chow and water ad libitum. On the day of the experiment, the mice (11 per group) were infected by i.p. injection of 1 ml of either S. suis wild-type strain P1/7 or the Tn917 mutants deficient in proteinase activity at a concentration of 7 × 107 CFU/ml in THB. Six control mice were inoculated with the vehicle solution (sterile THB) alone. The CD1 mouse has proven to be an excellent model of S.