Abstract:

A total of 132 strains of Streptococcus suis (S. suis) were isolated from 398 submaxillary lymphonodi samples
collected from pig slaughterhouses and 140 pork samples collected from farmers’ markets in Chongqing. The average
contamination rate of S. suis in the total samples was 24.5% (132/538). In addition, the S. suis contamination rates of
submaxillary lymphonodi and pork were 26.7% (106/398) and 18.6% (26/140), respectively. The serotype-specific PCR
assays were used to identify the serotypes and the detection rates of serotype 1, 2, 7, and 9 were 3.16% (17/538), 3.16%
(17/538), 6.88% (37/538) and 1.67% (9/538) in samples, respectively. The drug resistance of 18 isolates was evaluated
by K-B method. The results exhibited that these isolates were strongly tolerant to aminoglycosides, tetracyclines and
sulfonamides, but sensitive to penicillins and cephalosporins. Infection experiments in mice were conducted to determine the
virulence of 15 of the isolates. It was shown that these isolates were pathogenic differently to mice. The results of this study
indicated that much attention should be paid to multi-serotype S. suis contamination of pig carcass and pork in quarantine.

Key words: Streptococcus suis, pork, serotype, drug resistance, pathogenicity