Wound Healing Society

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N-acetyl Cysteine Treatment Dismantles Chronic Wound Biofilm
Xin Cathy Li, Jane Kim, Jiabin Wu, Yinsheng Wang, Manuela Martins-Green.
University of California Riverside, Riverside, CA, USA.

BACKGROUND - Chronic wounds affect many people worldwide. In developed countries, 1-2% of the population experience chronic wounds causing a significant financial and psychological burden to individuals and economic burden to the society. Persistent biofilm in chronic wounds leads to microbiome antimicrobial resistance and significantly delays wound healing. Despite the existence of many different treatments, none are effective in dismantling biofilm and simultaneously killing the bacteria.

METHOD - We have previously shown that N-acetyl-cysteine (NAC) can reverse chronic wound biofilm formation in vivo. We hypothesize that NAC creates a microenvironment that affects bacterial survival and interferes with the integrity of the extracellular polymeric substances (EPS) of the biofilm. To test this hypothesis, we developed an in vitro biofilm system using microbiome taken directly from chronic wounds, which primarily contains Pseudomonas aeruginosa, a bacterium that is commonly found in human chronic wounds.

RESULTS - We show that treatment of the biofilm with NAC at concentrations with a pH<pKa, causes death of the bacteria and breakdown of EPS leading to biofilm dismantling. NAC treatment as the culture is initiated leads to bacterial death whereas treatment after the biofilm is established results in biofilm dismantling accompanied by bacterial death. These results suggest that NAC treatment immediately after debridement could prevent return of the biofilm and that if treatment is applied to biofilm without debridement the biofilm will dismantle leading to wound healing. We also show that NAC can penetrate the bacterial membrane, that low pH is important but not sufficient for the actions of NAC and that bacterial death occurs independently of the presence of biofilm. Indeed, we show that both the acetyl and carboxylic groups play a key role in the function of NAC.

CONCLUSIONS - Our results provide insight into the mechanisms by which NAC prevents chronic wound biofilm development and causes disruption of existing biofilm.

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