LETTER
Antimicrobial Activity of Lidocaine, Bupivacaine, Mepivacaine and Ropivacaine on and

Various studies have shown a possible antimicrobial activity of different local anaesthetics, which may affect the results of microbial assessment of biopsies. The purpose of this study was to test the antimicrobial activity of different commonly used anaesthetic agents on Staphylococcus epidermidis, Staphylococcus aureus and Bacillus subtitles to reproduce data and to compare the findings.

Local anaesthetics tested were commercially available solutions of lidocaine (Xyloneural^®, Xylanaest pur.^®), bupivacaine (Bucain^®), mepivacaine (Mecain^®) and ropivacaine (Naropin^®, Ropinaest^®).2%, 1%, 0.5%, 0.25% and 0.1% (20, 10, 5, 2.5, 1 mg/ml) dilutions of these local anaesthetics were prepared with sterile 0.9% saline. Bacteria used in this study were Staphylococcus epidermidis, Staphylococcus aureus and Bacillus subtilis. 10 μl of different local anaesthetic dilution placed on thin wafers were added to Mueller Hinton Agar and cultured. After 24 hours, a zone of inhibition around the wafers was evaluated.

Local anaesthetics in different concentrations did not show any zone of inhibition on Staphylococcus epidermidis, Staphylococcus aureus or Bacillus subtilis.

In summary, neither lidocaine, bupivacaine, mepivacaine nor ropivacaine showed an antibacterial effect on Staphylococcus epidermidis, Staphylococcus aureus and Bacillus subtilis.

Due to these findings this local anaesthetics can be used in daily clinical routine to perform pain free diagnostic procedures in which culture specimens are to be obtained. Due to inconsistent results in prior studies, we recommend to use the lowest concentration possible of the local anaesthetic, also to avoid other possible side effects of local agents.