A niche-specific role for ArlRS enables Staphylococcus aureus growth within Kupffer cells

Abstract

Staphylococcus aureus bloodstream infections cause severe morbidity and mortality despite antibiotic therapy. We previously identified Kupffer cells (KCs) as the primary hepatic macrophages that rapidly clear circulating S. aureus, yet a subset of bacteria survives intracellularly and seeds systemic infection. Here, using spinning-disk intravital and super-resolution microscopy, we show that bacterial two-component system (TCS) signaling is required for intracellular replication within KCs in vivo. A global mutant lacking all non-essential TCSs failed to form intracellular microcolonies, and targeted analysis identified the ArlRS system as specifically required for KC replication. {Delta}arlRS bacteria remained as single non-replicating organisms within KCs, exhibited reduced dissemination and kidney abscess formation, and showed attenuated virulence with improved host survival. Complementation with arlRS restored the wildtype phenotype. Notably, the intracellular replication defect was not observed in primary or cultured macrophages, indicating that ArlRS-dependent replication is highly niche-specific and not reproduced by conventional in vitro models. Furthermore, restricting the KC reservoir with vancomycin treatment after infection further reduced renal infection by {Delta}arlRS bacteria. These findings identify ArlRS as a critical regulator of intracellular replication within KCs and establish the KC intracellular reservoir as a key driver of S. aureus pathogenesis and a potential therapeutic target during bloodstream infection.

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BibTeX RIS

BibTeX

@misc{hommes2026nichespecific,
  title = {{A niche-specific role for ArlRS enables Staphylococcus aureus growth within Kupffer cells}},
  author = {J. W. Hommes and L. M. Orthner and F. van der Wal and R. S. W. Flannagan and R. Shim and L. Samaniego Barron and M. Dao and I. Lasa and A. R. Horswill and B. G. J. Surewaard},
  howpublished = {bioRxiv},
  year = {2026},
  month = oct,
  doi = {10.64898/2026.10.07.757369},
  url = {https://www.biorxiv.org/content/10.64898/2026.10.07.757369v1},
  note = {CC BY},
}

RIS

TY  - UNPB
TI  - A niche-specific role for ArlRS enables Staphylococcus aureus growth within Kupffer cells
AU  - J. W. Hommes
AU  - L. M. Orthner
AU  - F. van der Wal
AU  - R. S. W. Flannagan
AU  - R. Shim
AU  - L. Samaniego Barron
AU  - M. Dao
AU  - I. Lasa
AU  - A. R. Horswill
AU  - B. G. J. Surewaard
PY  - 2026
DA  - 2026/10/07
PB  - bioRxiv
DO  - 10.64898/2026.10.07.757369
UR  - https://www.biorxiv.org/content/10.64898/2026.10.07.757369v1
AB  - Staphylococcus aureus bloodstream infections cause severe morbidity and mortality despite antibiotic therapy. We previously identified Kupffer cells (KCs) as the primary hepatic macrophages that rapidly clear circulating S. aureus, yet a subset of bacteria survives intracellularly and seeds systemic infection. Here, using spinning-disk intravital and super-resolution microscopy, we show that bacterial two-component system (TCS) signaling is required for intracellular replication within KCs in vivo. A global mutant lacking all non-essential TCSs failed to form intracellular microcolonies, and targeted analysis identified the ArlRS system as specifically required for KC replication. {Delta}arlRS bacteria remained as single non-replicating organisms within KCs, exhibited reduced dissemination and kidney abscess formation, and showed attenuated virulence with improved host survival. Complementation with arlRS restored the wildtype phenotype. Notably, the intracellular replication defect was not observed in primary or cultured macrophages, indicating that ArlRS-dependent replication is highly niche-specific and not reproduced by conventional in vitro models. Furthermore, restricting the KC reservoir with vancomycin treatment after infection further reduced renal infection by {Delta}arlRS bacteria. These findings identify ArlRS as a critical regulator of intracellular replication within KCs and establish the KC intracellular reservoir as a key driver of S. aureus pathogenesis and a potential therapeutic target during bloodstream infection.
ER  -

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