Antibacterial properties of EMLA® and lidocaine in wound tissue biopsies for culturing

ABSTRACT If a tissue biopsy from a chronic wound is sampled for culture, the antibacterial properties of local anesthetics may pose a problem in producing false‐negative results. The purpose of this study was to investigate the effects of EMLA® (AstraZeneca) and lidocaine on common wound pathogenic bacteria. An in vitro study of a total of 25 clinical isolates and ATCC reference strains of Staphylococcus aureus (including methicillin‐resistant S. aureus), Escherichia coli, Pseudomonas aeruginosa, and Streptococcus pyogenes was conducted. The isolates were exposed to the local anesthetic drugs (and some of their contents separately) at 35°C over a 24‐hour period and time–kill curves were recorded. No culture media were used and saline was used for controls. EMLA® was found to have a rapid acting and powerful antibacterial effect and should not be used before culturing tissue samples. Lidocaine 1% was found not to inhibit the bacterial strains when exposure time was held below 2 hours. We conclude that culturing tissue from a wound biopsy is safe within 2 hours when a pure, preservative‐free lidocaine 1% solution is used.