Killing activities of trovafloxacin alone and in combination with beta-lactam agents, rifampin, or vancomycin against Streptococcus pneumoniae isolates with various susceptibilities to extended-spectrum cephalosporins at concentrations clinically achievable in cerebrospinal fluid

The killing activities of trovafloxacin alone and in combination with beta- lactam agents (extended-spectrum cephalosporins, meropenem), rifampin, or v ancomycin were evaluated against 20 genotypically characterized Streptococc us pneumoniae isolates for which amoxicillin MICs were greater than or equa l to 4 mu g/ml (cefotaxime MICs, greater than or equal to 4 mu g/ml for six strains) at concentrations clinically achievable in cerebrospinal fluid. A t 6 h the mean killing activity of trovaflosacin alone (range, 2.6 to 2.9 l og(10) CFU/ml) did not vary significantly according to the susceptibility o f the strains to beta-lactam agents. The activities of trovafloxacin or van comycin added to the beta-lactam agents and the combination trovafloxacin-v ancomycin were additive or indifferent, Against the ceftriaxone-resistant i solates, the killing activity of the combination of a beta-lactam agent and trovafloxacin did not differ significantly from that of a p-lactam agent a nd vancomycin.