Regulatory effects on virulence and phage susceptibility revealed by sdiA mutation in Klebsiella pneumoniae

The results demonstrate that <i>sdiA</i> deficiency increases susceptibility to phage infection and human serum resistance, and promotes biofilm maturation and cell filamentation, although no effect on virulence was observed <i>in vivo</i> in the <i>Galleria mellonella</i> infection model. On the other hand, C6-HSL promoted <i>sdiA</i>-dependent biofilm maturation, capsule production and serum resistance while reducing virulence against <i>G. mellonella</i> in the absence of <i>sdiA</i>. The addition of C6-HSL did not affect phage susceptibility. The results of this study demonstrate that AHLs and SdiA exert a dual influence on virulence phenotypes, operating both independently and hierarchically. These findings provide new insights into the virulence of <i>K. pneumoniae</i> and its regulation by SdiA.