HIGH-LEVEL GENTAMICIN-RESISTANT ENTEROCOCCI - IN-VITRO ACTIVITY OF DOUBLE AND TRIPLE COMBINATIONS OF ANTIMICROBIAL DRUGS

The ability of double and triple combinations of antimicrobials with d ifferent mechanisms of action, such as teicoplanin, meropenem, gentami cin and sparfloxacin, to achieve synergisms was investigated in vitro on some moderate-level gentamicin-resistant (MLGR: 8 less than or equa l to MIC less than or equal to 256 mg/l) and high-level gentamicin-res istant (HLGR: MIC > 500 mg/l) enterococci. On MLGR strains, a constant synergistic effect was achieved by a combination of teicoplanin with gentamicin or with meropenem, while generally addition, sometimes clos e to synergism, was exhibited by gentamicin-meropenem, gentamicin-spar floxacin and teicoplanin-sparfloxacin associations. Triple combination s of teicoplanin, meropenem and gentamicin, or teicoplanin, sparfloxac in and gentamicin, always showed a remarkable advantage in terms of sy nergism over double combinations. On HLGR enterococci, the only double association showing an additive effect, sometimes close to synergism, was teicoplanin plus meropenem, while the triple combination of teico planin with gentamicin and meropenem always showed a marked synergisti c effect. An effect very close to synergism was also shown by the comb ination of teicoplanin with sparfloxacin and gentamicin.