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 commonl y encountered in the setting of nosocomial wound infection (Enterococcus fa ecalis, Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus ) as well as a number of resistant strains of methicillin-resistant S. aure us 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 Nationa l Committee of Clinical Laboratory Standards. Lidocaine demonstrated a dose -dependent inhibition of growth for all strains of bacteria tested. The gre atest sensitivity to lidocaine was shown by gram-negative organisms; the le ast sensitive was S. aureus, The addition of epinephrine to the local anest hetic had no effect on the susceptibility of the bacteria to lidocaine. The se observations suggest that the surgical benefit of local anesthesia may e xtend beyond its analgesic properties and may have a role in the prophylaxi s and, in the case of methicillin- and vancomycin-resistant bacteria, the t reatment of surgical wound infection, mandating a wider application of this modality.