Güney Çin’de Hastalıklı ve Sağlıklı Domuzlarda Streptococcus suis’in Antimikrobiyal Direnci, Serotipleri ve Genetik Çeşitliliği

In the study, the characteristics of 81 Streptococcus suis isolates recovered from healthy and diseased pigs in Southern China were analyzed. These isolates showed differential resistance rates of over 40% to 22 and over 80% to 11 antibiotics out of 42 tested drugs. These isolates belonged to 6 serotypes (2, 3, 7, 9, 19, and 28), 9.9% of which were characterised as non-typable (NT), and were classified into 15 sequence types (STs), 8 of which were new (ST812-ST815, ST821-823, and ST832). Additionally, 6 virulence-associated gene patterns (VAGPs) and 10 random amplified polymorphic DNA (RAPD) patterns were found among the 81 strains. Among the 4 genotyping methods used in this study, multilocus sequence typing (MLST) provided the highest resolution for identification of S. suis strains. Significant differences in STs, RAPD patterns, and VAGPs were observed between strains isolated from healthy pigs and those isolated from diseased pigs. This study did not find any statistically significant correlations between antimicrobial resistance and serotypes, STs, RAPD patterns, VAGPs, or strain sources. Serotype 2 strains were predominant (44.4%) in the study and all of these strains showed the molecular characteristics of highly pathogenic strains in VAGP, GDH sequence types, and MLST. Our results showed that S. suis strains in Southern China are continually evolving, and therefore increased surveillance of S. suis in piggeries must be considered.