Construction and pathogenicity of mutant strain ATP binding cassette transporter SSU05_0948 of Streptococcus suis type 2

Abstract

Objective To construct the mutant strain ATP binding cassette transporter SSU05_0948 of Streptococcus suis type 2 and comprehensively study its pathogenicity, and to provide useful insights for understanding the mechanism that Streptococcus suis avoid host innate immunity. Methods The mutant strain 05ZYH33Δ0948 was constructed through homologous recombination technology. The differences between the mutant strain and the wild type strain were evaluated through bacterial adhesion, whole blood killing, mice meningitis assay, mice and piglets virulence assay. Chi-square test and t test were used. Results Successfully constructed the mutant strain 05ZYH33Δ0948. The adhesion results showed that the adhesion rate (0.663±0.047)% of the wild strain to A549 cell was significantly higher than that of the mutant (0.246±0.074)%, the difference was statistically significant (χ2=5.267, P=0.014); the adhesion rate (16.540±2.320)% of the wild strain to Hep2 cell was significantly higher than that of the mutant (1.970±0.320)%, the difference was statistically significant (χ2=0.014, P<0.01); the adhesion rate (5.497±0.174)% of the wild strain to Hep2 cell was significantly higher than that of the mutant (1.950±0.335)%, the difference was statistically significant (χ2=0.016, P<0.01). The killing rate (32.970±3.589)% of the wild strain in whole blood is no difference with the mutant (29.560±3.737)% (χ2=1.200, P=0.133). Piglets competitive infection showed that, the competitive index at 12 h, 24 h and 36 h were 0.046±0.003, 0.107±0.003, 0.064±0.001, respectively. 12 h and 24 h was significant differences(t=15.490, P=0.041), 24 h and 36 h was significant differences(t=5.660, P=0.047), 12 h and 36 h was no differences(t=1.445, P=0.285). Conclusions Streptococcus suis type 2 ABC transporter SSU05_0948 is a new adhesion factor and virulence factor of Streptococcus suistype 2, and also a new meningitis factor, which plays important roles in Streptococcus suis against host innate immunity. Key words: Meningitis; Streptococcus suis type 2; Gene knockout; ABC transporter