Science Bite (3 minute oral presentation with PPT in live session and poster) - Students and ECRs only 14th Lorne Infection and Immunity 2024

Enterococcus faecalis exploit neutrophils as an intracellular niche for replication and persistence (#39)

Claudia J Stocks 1 , Ronni AG Da Silva 1 2 , Navin S/O Jeyabalan 1 , Siu Ling Wong 1 3 , Kimberly Kline 1 2 4
  1. Singapore Centre for Environmental Life Sciences Engineering, Nanyang Technological University , Singapore
  2. Antimicrobial Drug Resistance Interdisciplinary Research Group, Singapore-MIT Alliance for Research and Technology, Singapore
  3. Lee Kong Chian School of Medicine , Nanyang Technological University , Singapore
  4. Department of Microbiology, Faculty of Medicine, University of Geneva , Geneva, Switzerland

Chronic wound infection is a major global public health issue, with diabetic foot ulcers (DFU) of particular concern. Enterococcus faecalis is one of the most commonly isolated pathogens from infected wounds, including DFU. Neutrophils are highly reactive, inherently short-lived immune cells that play a critical role in bacterial defence. Currently, E. faecalis – neutrophil interactions are very poorly understood. Unexpectedly, extended in vitro infection of neutrophils with E. faecalis did not induce host cell death. Rather, E. faecalis infection significantly prolonged both murine and human neutrophil lifespan even compared to uninfected controls. Quantification of intracellular CFU and assessment of infected cells via confocal microscopy demonstrated that bacteria were phagocytosed by neutrophils regardless of opsonisation and persisted intracellularly out to 24 h p.i. Using RADA, which incorporates into newly synthesised bacterial cell walls to monitor intracellular E. faecalis replication, we observed that E. faecalis actively replicates within murine neutrophils between 6-18 h p.i., followed by a predominately persistent phase between 18-24 h p.i. Examination of murine wound beds and extracted ex vivo cells revealed intracellular E. faecalis within infiltrating neutrophils at 24 h p.i. Investigations are currently underway to host and bacteria cell mechanisms mediating this cell death suppression and intracellular occupation. Such mechanistic insights offer the potential of targeted pharmacological intervention to undermine intra-neutrophil reservoirs of E. faecalis during chronic wound infection.