Antimicrobial effects of local anaesthetics

After the introduction of cocaine to the medical practice, local anaesthetics (LA) became essential in pain control. LA infiltration along the incision may be used to provide surgical anaesthesia or postoperative analgesia. This study aimed to compare the antimicrobial effects of the topical antimicrobial agent mupirocine with those of the LA lidocaine and the combination of lidocaine and adrenalin. In our study, the in vitro antimicrobial effects of 1 mL sterile saline, 20 mg/mL mupirocine, 20 mg/mL Lidocaine, and 20 mg/mL Lidocaine and Adrenaline were tested against Staphylococcus aureus American type culture collection (ATCC) 29213, Pseudomonas aeruginosa ATCC 27853, and Escherichia coli ATCC 25922 as Group C (Control), Group M (Mupirocine), Group L (Lidocaine), and Group LA (Lidocaine + adrenaline), respectively. S aureus ATCC 29213, P aeruginosa ATCC 27853, and E coli ATCC 25922 were cultured onto Mueller-Hinton agar (Oxoid, UK) plates for 18 to 24 hours at 37°C. Colonies from these plates were suspended in sterile saline and a 0.5 McFarland turbidity standard suspension (corresponding to 1.5 × 10⁸  CFU/mL) of each isolate was prepared. S Aureus ATCC 29213 inhibition zone diameter values of Group M, Group LA, and Group L were significantly higher compared with the group C (P ˂ 0.05). P aeruginosa ATCC 27853 inhibition zone diameter values of Group M and Group LA were significantly higher compared with the group C (P ˂ 0.05). E coli ATCC 25922 inhibition zone diameter values of Group M, Group LA, and Group L were significantly higher compared to the group C (P ˂ 0.05). LA infiltration along the incision may be used to provide surgical anaesthesia or postoperative analgesia. Considering that LAs show antimicrobial effects besides their analgesic effects, they may contribute to preventing the development and reducing the rate of surgical infections, decreasing the requirement to administer antibiotics. However, caution should be exercised not to antagonise the effective treatment of surgical infections, remembering that controversy on the antimicrobial effects of LAs remains in the literature. Therefore, further comprehensive studies with larger patient populations are warranted to demonstrate the antimicrobial effects of LAs.