Antimicrobial activity of lidocaine against bacteria associated with nosocomial wound infection

The authors characterized the in vitro antibacterial properties of clinical doses of lidocaine on isolates of a variety of bacterial pathogens commonly encountered in the setting of nosocomial wound infection (Enterococcus faecalis, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus) as well as a number of resistant strains of methicillin-resistant S. aureus and vancomycin-resistant enterococci. Time- kill studies were carried out on bacteria exposed to various clinical concentrations of lidocaine (0%, 1%, 2%, and 4%) with and without epinephrine (1:100,000). Minimum inhibitory concentrations and minimum bactericidal concentrations were determined for some strains using a broth macrodilution method recommended by the National Committee of Clinical Laboratory Standards. Lidocaine demonstrated a dose-dependent inhibition of growth for all strains of bacteria tested. The greatest sensitivity to lidocaine was shown by gram-negative organisms; the least sensitive was S. aureus. The addition of epinephrine to the focal anesthetic had no effect on the susceptibility of the bacteria to lidocaine. These observations suggest that the surgical benefit of local anesthesia may extend beyond its analgesic properties and may have a role in the prophylaxis and, in the case of methicillin- and vancomycin-resistant bacteria, the treatment of surgical wound infection, mandating a wider application of this modality.