Glycosyl hydrolase contributes to the pathogenicity of Streptococcus suis type 2

Abstract:

[Background] Streptococcus suis serotype 2 (SS2) is a significant zoonotic pathogen responsible for severe infections in pigs and humans, resulting in pneumonia, septic shock, and even death. [Objective] Despite the diverse virulence factors identified, the underlying pathogenic mechanism of SS2 remains unclear. Therefore, it is urgent to search for new virulence factors or virulence-related genes for elucidating the pathogenic mechanism. [Methods] An insertion mutant with significantly attenuated pathogenicity in Galleria mellonella larvae was selected from the Tn917 transposon insertion mutant library of SS2, and its mutated gene was identified as B9H01_RS10315, which encoded a glycosyl hydrolase (ghA). An isogenic deletion mutant of ghA (∆ghA) and its complementary strain (C∆ghA) were constructed, and the growth and pathogenicity of the mutants were determined to reveal the pathogenic role of ghA. [Results] Compared with the wild type, ∆ghA displayed a growth defect, a 25% decrease in mortality of Galleria mellonella larvae within 24 h, a reduction of about 50% in adhesion to epithelial cells, a decrease of about 35% in survival in whole blood, and increases of about 100% and 200% in phagocytosis by phagocytes at 10:1 and 50:1 infection ratios, respectively. [Conclusion] The glycosyl hydrolase GhA promotes the growth and participates in the pathogenic process of SS2 by promoting the adhesion, improving the survival in blood, and resisting phagocytosis.

Key words:Streptococcus suis;pathogenicity;virulence gene;glycosyl hydrolase