Sufentanil modifies the antibacterial activity of bupivacaine and ropivacaine

The purpose of our study was to investigate the effect on the growth of Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Enterococcus faecalis (E. faecalis) of bupivacaine at a final concentration of 0.77 mg.mL(-1), ropivacaine at 1.2 mg.mL(-1), and sufentanil at 0.38 and 0.5 microg.mL(-1) (alone or in combination with bupivacaine and ropivacaine).

The strains were diluted to approximately 3 x 10(4) cfu.mL(-1) in Mueller-Hinton broth. The anesthetics (0.5 mL) were incubated with the bacterial suspensions (0.5 mL) for 24 hr at 37 degrees C.

Bupivacaine inhibited the growth of E. coli (59 +/- 0.8%; P < 0.05) and S. aureus (22 +/- 3.6%; P < 0.05). Ropivacaine also inhibited the growth of E. coli (41 +/- 1.2%; P < 0.05) and S. aureus (25.5 +/- 4.1%; P < 0.05). Both anesthetics were ineffective against E. faecalis. Sufentanil only inhibited S. aureus (13.8 +/- 3.1%; P < 0.05) at a concentration of 0.5 microg.mL(-1). Sufentanil modified the antibacterial activity of bupivacaine and ropivacaine. It increased the inhibitory effect of bupivacaine on E. faecalis and S. aureus by 10 +/- 2.1% (P < 0.05) and on E. coli by 7% (P < 0.05). Sufentanil did not increase the inhibitory effect of ropivacaine on the growth of S. aureus. On the other hand, sufentanil reduced the inhibitory effect of ropivacaine on E. coli by 11% (P < 0.05).

Both bupivacaine and ropivacaine alone or combined with sufentanil inhibited the growth of E. coli and S. aureus. E. faecalis was partially sensitive to a bupivacaine + sufentanil mixture. Sufentanil had a partial synergistic effect on bupivacaine and a partial antagonistic effect on ropivacaine's antibacterial activity.