Experimental infection of specific pathogen free piglets with French strains of Streptococcus suis capsular type 2

A standardized model of Streptococcus suis type 2 infection in specific-pat hogen-free piglets, housed in high-security barns, was used to compare the virulence of 3 French field strains of S, suis serotype 2 isolated from ton sils of a healthy pig (strain 65) or from diseased pigs (meningitis, strain 166', or septicemia, strain 24). In one of the 2 trials, 7-week-old pigs, in 3 groups of 8, were inoculated intravenously with 2 x 10(8) colony-formi ng units of S. suis type 2. In each group, 1 uninfected animal was a sentin el. Eight animals were also used as negative control group. The experiment was repeated under similar conditions with strains 65 and 166'. Virulence d iffered markedly among these S. suis strains when clinical signs, zootechni cal performances, lesions, and bacteriological data were analyzed. Strain 6 5 did not induce clinical signs in inoculated pigs. III contrast, pigs infe cted with the other 2 strains exhibited clinical signs and typical lesions of S. suis type 2 infections. Differences in virulence were also observed b etween the 2 virulent strains. Sentinel animals exhibited the same manifest ations as those recorded in inoculated piglets. Results were similar in the second trial, indicating that under the present experimental conditions, r esults were reproducible. The standardized conditions described in this stu dy could be a useful tool to further study about the S. suis infection.