BACKGROUND: Synovial fluid culture (SFC) is recommended as one of the major diagnostic criteria by the Musculoskeletal Infection Society (MSIS) for diagnosing periprosthetic joint infection (PJI). Local anesthetic agents are used for anesthesia and analgesia in some clinical settings to relieve pain. As a local anesthetic, lidocaine is safely used in arthrocentesis to obtain synovial fluid. The goal of this study was to determine if infiltration anesthesia with additive-free lidocaine 2% has antibacterial effects that might interfere with subsequent SFC.

MATERIAL AND METHODS: Eight isolates of reference strains of Staphylococcus aureus, Staphylococcus epidermidis, Staphylococcus hominis, Escherichia coli, Klebsiella pneumoniae, Acinetobacter baumannii, Streptococcus pyogenes, and Candida albicans were incubated on the plates. Each bacterial suspension was formed by 50-fold dilution before the test lidocaine 2% was added. For each strain, bacterial suspension was divided into 2 groups (5 samples each) exposed either lidocaine 2% or sterile non-bacteriostatic 0.45% saline. The antimicrobial property of lidocaine 2% was determined by measuring the bacterial density on agar plates incubated for 24 h and comparing it with controls unexposed to lidocaine 2%.

RESULTS: Exposure to lidocaine 2% negatively affected microbial viability in vitro. Of the lidocaine 2% exposure, reference strains but no Streptococcus pyogenes strain resulted in fewer colony-forming units compared with the sterile saline control. The antibacterial property of lidocaine 2% appears to affect the ability to culture the organism in synovial fluid.

CONCLUSIONS: Lidocaine 2% has strong antimicrobial activities against some commonly encountered bacterial strains in PJI. As a result, infiltration anesthesia with additive-free lidocaine 2% before the arthrocentesis procedure may affect the results of SFC. To further evaluate its potential antibacterial usefulness in clinical applications, studies are needed to assess the ability of lidocaine to reduce the risk of iatrogenic infections.

Keywords: Anti-Bacterial Agents, Bacterial Infections, Colony Count, Microbial, Culture, Lidocaine, Synovial Fluid