The Surreptitious Survival of The Emerging Pathogen Staphylococcus lugdunensis in Macrophages Enhances S. aureus Infection

Staphylococcus lugdunensis is an opportunistic pathogen that can cause invasive infections suggesting an ability to circumvent host immunity. S. lugdunensis was shown to resist killing and persist within macrophages and acetylation of its peptidoglycan is important for this survival. This was consistent in vivo, as S. lugdunensis resides inside Kupffer cells for at least 16 hours post-infection in mice. Despite its capability for survival, S. lugdunensis is unable to replicate within phagolysosomes. Inhibiting phagolysosomal effectors allows S. lugdunensis to initiate replication, after which the bacteria escape phagosomal containment. Moreover, intracellular S. lugdunensis augments the growth S. aureus during co-infection. Eight hours following secondary infection of S. lugdunensis-infected mice with S. aureus, the S. aureus burden in the liver is amplified 10-fold above mice infected with S. aureus alone. I have shown that the macrophage represents an undescribed reservoir for viable S. lugdunensis that can potentiate the virulence of S. aureus