Streptococcus suis infection: An emerging/reemerging challenge of bacterial infectious diseases?

Feng, Youjun; Zhang, Huimin; Wu, Zuowei; Wang, Shihua; Cao, Min; Hu, Dan; Wang, Changjun

Streptococcosis is regarded as a leading infectious disease in the swine industry, that clinically features with meningitis, septicemia, or arthritis and annually results in significant economic loss worldwide. 1 Streptococcus suis (S. suis) that was initially reported in 1954 2 has been demonstrated as an etiological agent for this kind of frequently-occurring bacterial infection. 1, 3 Indeed, S. suis, a complex population consisting of heterogeneous strains, 4 can be classified into 35 serotypes (1-34, 1/2) based on the differentiation of capsule antigens. 1, 3 Based on the varied virulence of these bacteria, they may be categorized into highlypathogenic, weakly-pathogenic (hypo-virulent), and nonpathogenic (avirulent) strains. 1 Generally, serotype 2 of S. suis (SS2) is considered to be the most virulent, and is frequently isolated from clinically-diseased piglets. 1 In fact, serotype 9 of S. suis is also one of the most important serotypes in several countries.