Enterococcus faecalis biofilm rewires neutrophil metabolism to suppress antimicrobial functions

Abstract

Enterococcus faecalis is an opportunistic pathogen that persists in biofilm-associated infections despite robust neutrophil recruitment. How E. faecalis evades neutrophils remains poorly understood. Here, we investigated how E. faecalis biofilms alter effector functions in human neutrophils and a murine wound infection model. We found that E. faecalis biofilm suppresses neutrophil extracellular trap (NET) formation, bacterial engulfment, and neutrophil-mediated control of biofilm growth. This suppression is partly driven by production of lactic acid through the lactate dehydrogenases (LDH) of E. faecalis, which acidifies the extracellular environment, lowers neutrophil intracellular pH, and disrupts glycolysis, the tricarboxylic acid cycle, and the oxidative pentose phosphate pathway. In a murine wound infection model, loss of LDH increased neutrophil recruitment and NETosis. We also found that high bacterial density, a defining feature of biofilms, suppresses NETosis through a lactic acid-independent mechanism. Collectively, these findings identify biofilm immune evasion strategies mediated by bacterial metabolism and the high-density structural organization of biofilm-associated bacteria. TeaserEnterococcus faecalis biofilms suppress neutrophil defenses through lactic acid and high bacterial density.