Abstract: Objective To investigate the role of spd1672 gene in the infection process of Streptococcus pneumoniae. Methods BALB/
c mice were intraperitoneally infected by a spd1672 knockout strain and a D39 wild-type strain of S. pneumoniae, and the
survival time of mice and blood bacterial counts were recorded. The adhesion and invasion ability of S. pneumoniae strains
were assessed in A549 cells. Bactericidal assays were carried out to determine the resistance of spd1672 knockout strains and
D39 wild strains, and the serum levels of inflammatory cytokines were detected in the infected mice. Results The mice infected
with spd1672 knockout strains showed a significantly longer median survival time, a higher survival rate, and a lower blood
bacterial load than the wild strain-infected mice (P<0.05). Having a similar cell adhesion ability to the wild-type strain (P>0.05),
the spd1672 knockout strain showed significantly lower cell invasion ability than the wild-type strain (P<0.05). The spd1672
knockout strain also had a reduced resistance to whole blood cells, and thw mice infected with spd1672 knockout strain exhibit
lower levels of serum inflammatory cytokines than those infected with the wild-type strain. Conclusion Spd1672 gene is
importantly related to the virulence of S. pneumoniae and plays important roles in modulating bacterial invasion, resistance to
whole blood cells and proinflammatory responses.