N‐acetylcysteine use as an adjuvant to bone cement to fight periprosthetic joint infections: A preliminary in vitro efficacy and biocompatibility study

When antibiotic laden bone cement is used to manage periprosthetic joint infection (PJI), failure still occurs with its use in up to 30% of cases. Therefore, we designed an in vitro study to assess the bactericidal effect of N‐acetylcysteine (NAC), an antibacterial adjuvant, in cement against planktonic and biofilm forms of common PJI pathogens. NAC (10%, 20%, 30%, 40%, and 50% w/v) added to polymethyl methacrylate (PMMA) and incubated in broth at 36°C. PMMA‐alone and/or culture bacteria alone were used as a negative control. Aliquots of cement elution from each group were taken at 1 day and 1 week and then were investigated for antimicrobial efficacy against the planktonic‐form and the biofilm‐form of Staphylococcus aureus and Escherichia coli. The primary outcome was the residual colony‐forming unit count. The cytotoxicity and mechanical properties of the NAC–PMMA cement‐blocks were also assessed. NAC–PMMA efficacy against the planktonic bacteria was demonstrated at a minimum of 30% at Day 1 and a minimum of 20% at 1 week after (p < .001). NAC–PMMA cement was effective against biofilm at a minimum of 30% of NAC at 1 day and 1 week of cement immersion (p < .001). The PMMA alone group was identified as having the highest cytotoxicity (p < .001). NAC decreased the stiffness (p = .004) and maximum load breaking point of the cement (p = .029). NAC is an effective and biocompatible adjuvant to PMMA in terms of antibacterial activity against Staphylococcus aureus and Escherichia coli. The broad antibacterial spectrum of NAC, its low expense, and minimal cytotoxicity makes it an ideal agent for addition to PMMA cement.