Antibacterial activity of 0.5% isobaric bupivacaine and 0.5% hyperbaric bupivacaine in vitro

Background and Purpose: The purpose of the study tvas to investigate the antimicrobial effect of 0.5% bupivacaine in isobaric and hyperbaric form on Staphylococcus aureus, Escherichia coli, Enterococcus faecalis, ESBL positive Klebsiella pneumoniae, Pseudomonas aeruginosa and methicillin resistant Staphylococcus aureus (MRSA). Methods: The microorganisms were exposed to 0.5% isobaric and hyperbaric baric bupivacaine for 1-5 hours at 37 degrees C. The overnight culture of the tested microorganisms was inoculated in 5 mL of anesthetics, incubated at 37 degrees C, and samples taken every hour for determination of CFU/mL, diluted serially and seeded on Mueller-Hinton agar (E. faecalis on blood agar). Results: Isobaric solution of 0.5 % bupivacaine reduced the viable cells of E, coli and P. aeruginosa whereas hyperbaric solution of 0.5% bupivacaine reduced the viable cells of E. coli, S. aureus and ESBL positive K. pneumoniae. The hyperbaric solution (P < 0.0001) reduced the E. coli count remarkably more than isobaric (P=0.0053). There tvas no influence of control solutions, neither the sterile 0.9% saline nor the sterile 8% glucose on the growth of any microorganism. Conclusion: With Regard to antibacterial activity on the tested strains, 0.5% hyperbaric bupivacaine has an advantage over isobaric solution.