Cefotaxime Acts Synergistically with Levofloxacin in Experimental Meningitis Due to Penicillin-Resistant Pneumococci and Prevents Selection of Levofloxacin-Resistant Mutants In Vitro

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American Society for Microbiology

RESUMO

Cefotaxime, given in two doses (each 100 mg/kg of body weight), produced a good bactericidal activity (−0.47 Δlog10 CFU/ml · h) which was comparable to that of levofloxacin (−0.49 Δlog10 CFU/ml · h) against a penicillin-resistant pneumococcal strain WB4 in experimental meningitis. Cefotaxime combined with levofloxacin acted synergistically (−1.04 Δlog10 CFU/ml · h). Synergy between cefotaxime and levofloxacin was also demonstrated in vitro in time killing assays and with the checkerboard method for two penicillin-resistant strains (WB4 and KR4). Using in vitro cycling experiments, the addition of cefotaxime in sub-MIC concentrations (one-eighth of the MIC) drastically reduced levofloxacin-induced resistance in the same two strains (64-fold increase of the MIC of levofloxacin after 12 cycles versus 2-fold increase of the MIC of levofloxacin combined with cefotaxime). Mutations detected in the genes encoding topoisomerase IV (parC and parE) and gyrase (gyrA and gyrB) confirmed the levofloxacin-induced resistance in both strains. Addition of cefotaxime in low doses was able to suppress levofloxacin-induced resistance.

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