Experimental Research on β-toxin of Staphylococcus aureus promotes breaking the blood-brain barrier in mice

Abstract

Objective To investigate the role of β-toxin (Hlb) in the penetration of Staphylococcus aureus (S. aureus) through blood-brain barrier (BBB). Methods The high Hlb-producing strain of S. aureus MW2 was screened by streaking on blood agar plate, and its effect on the permeability of hCMEC/D3 simulated BBB cell model was verified. Bioinformatics analysis was used to screen the strains with complete hlb gene, and then the hlb knockout strain was constructed with homologous recombination. The hemolytic activities of strains of interest were verified by streaking on blood agar plate. The permeability of different strains of S. aureus was compared in BBB cell model. A hematogenous meningitis/brain microabscess model was generated by injection of the wild-type or the hlb-deletion strain individually into CD1 mice through tail vain, and the bacterial load in the brain tissue was determined in 72 h after infection. Results The Hlb high-producing strain of MW2 (Hyper-β) led to increased permeability of the BBB model cells than the wild-type strain. The NCTC8325-4, COL, and RN4220 strains had intact hlb gene without phage insertion. The NCTC8325-4Δhlb strain was successfully constructed, and the lack of β-hemolysis of the mutant was verified by blood agar plate. A reduced permeability of NCTC8325-4Δhlb on the BBB cell model was observed in comparison to that of the wild-type strain. The bacterial load of NCTC8325-4Δhlb strain in the brain tissue of the mouse hematogenous meningitis/brain microabscess model was obviously lower than that of the wild-type strain. Conclusion β-toxin from S. aureus promotes the bacteria destroying BBB.

Keywords

• staphylococcus aureus
• β-toxin
• blood-brain barrier
• hematogenous meningitis/brain microabscess model
• blood-brain barrier cell model