In vitro activity of mezlocillin, meropenem, aztreonam, vancomycin, teicoplanin, ribostamycin and fusidic acid against Borrelia burgdorferi

The in vitro susceptibility profile of Borrelia burgdorferi is not yet well defined for several antibiotics. Our study explored the in vitro susceptib ility of B. burgdorferi to mezlocillin, meropenem, aztreonam, vancomycin, t eicoplanin, ribostamycin and fusidic acid. Minimal inhibitory concentration s (MICs) and minimal borreliacidal concentrations (MBCs) were measured usin g a standardised colorimetric microdilution method and conventional subcult ure experiments. MIC values were lowest for mezlocillin (MIC90, less than o r equal to 0.06 mg/l) and meropenem (MIC90, 0.33 mg/l). Vancomycin (MIC90, 0.83 mg/l) was less effective in vitro. Borreliae proved to be resistant to aztreonam(MIC90, > 32 mg/l), teicoplanin (MIC90, 6.6 mg/l), ribostamycin ( MIC90, 32 mg/l), and fusidic acid (MIC90, > 4 mg/l). The mean MBCs resultin g in 100% killing of the final inoculum after 72 h of incubation were lowes t for mezlocillin (MBC, 0.83 mg/l). This study gathered further data on the in vitro susceptibility patterns of the B. burgdorferi complete. The excel lent in vitro effectiveness of acylamino-penicillin derivatives and their s uitability for the therapy of Lyme disease is emphasised. (C) 2001 Elsevier Science B.V. and International Society of Chemotherapy All rights reserved .