Scientific article
OA Policy
English

Enterococcus faecalis persists and replicates intracellularly within neutrophils

Published inInfection and immunity, vol. 94, no. 1, e00364-25
Publication date2026-01-13
First online date2025-12-16
Abstract

Chronic wound infection is a major global public health issue, with Enterococcus faecalis among the most commonly isolated pathogens from such wounds. Neutrophils are short-lived immune cells critical for host defense, yet E. faecalis -neutrophil interactions are poorly understood. Here, we show that instead of eliminating E. faecalis , neutrophils provide a niche for intracellular persistence and replication, potentially prolonging infection and inflammation at the wound site. In murine wound beds and ex vivo wound cells, intracellular E. faecalis was detected in recruited neutrophils at 24 h post-infection (h p.i). Unexpectedly, extended infection did not induce neutrophil death. Rather, E. faecalis infection significantly prolonged the life spans of both murine and human neutrophils in vitro compared to uninfected controls. Quantification of intracellular CFU revealed that E. faecalis were phagocytosed regardless of opsonization and persisted intracellularly up to 24 h p.i. This finding was confirmed via transmission electron microscopy and confocal microscopy. Blinded quantification and fluorescent D-amino acid staining, which marks newly synthesized bacterial peptidoglycan, revealed active replication within murine neutrophils between 6 and 18 h p.i., followed by a predominately persistent phase between 18 and 24 h p.i. Infected murine neutrophils remained immunologically active, secreting pro-inflammatory and chemoattractant cytokines. These findings highlight an underappreciated intracellular lifestyle for E. faecalis that may contribute to its ability to persist in chronic wounds and contribute to biofilm-associated infections.

Keywords
  • Enterococcus faecalis
  • Host-pathogen
  • Neutrophils
  • Wound infection
  • Enterococcus faecalis / physiology
  • Enterococcus faecalis / growth & development
  • Enterococcus faecalis / immunology
  • Neutrophils / microbiology
  • Neutrophils / immunology
  • Animals
  • Humans
  • Mice
  • Gram-Positive Bacterial Infections / microbiology
  • Gram-Positive Bacterial Infections / immunology
  • Mice, Inbred C57BL
  • Phagocytosis
  • Wound Infection / microbiology
  • Wound Infection / immunology
Funding
  • the Singapore Ministry of Education [MOE2019-T2-2-089]
  • Singapore Centre for Environmental Life Sciences Engineering [SF-06]
Citation (ISO format)
STOCKS, Claudia J et al. Enterococcus faecalis persists and replicates intracellularly within neutrophils. In: Infection and immunity, 2026, vol. 94, n° 1, p. e00364–25. doi: 10.1128/iai.00364-25
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Identifiers
Additional URL for this publicationhttps://journals.asm.org/doi/10.1128/iai.00364-25
Journal ISSN0019-9567
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