d -Alanylation of Lipoteichoic Acid Contributes to the Virulence of Streptococcus suis

Abstract

ABSTRACT We generated by allelic replacement a Δ dltA mutant of a virulent Streptococcus suis serotype 2 field strain and evaluated the contribution of lipoteichoic acid (LTA) d -alanylation to the virulence traits of this swine pathogen and zoonotic agent. The absence of LTA d -alanylation resulted in increased susceptibility to the action of cationic antimicrobial peptides. In addition, and in contrast to the wild-type strain, the Δ dltA mutant was efficiently killed by porcine neutrophils and showed diminished adherence to and invasion of porcine brain microvascular endothelial cells. Finally, the Δ dltA mutant was attenuated in both the CD1 mouse and porcine models of infection, probably reflecting a decreased ability to escape immune clearance mechanisms and an impaired capacity to move across host barriers. The results of this study suggest that LTA d -alanylation is an important factor in S. suis virulence.