In vivo efficacy of the combination of ciprofloxacin and cefotaxime against Vibrio vulnificus sepsis.

Abstract

ObjectivesThe in vivo efficacy of a cefotaxime-ciprofloxacin combination against Vibrio vulnificus and the effects on rtxA1 expression of commonly used antibiotics are unknown.MethodsIn vitro time-kill studies were performed to evaluate synergism. Female BALB/c mice were injected subcutaneously with 1×10(7) or 1×10(8) cfu of V. vulnificus. Antibiotic therapy was initiated at 2 h after inoculation in the following four therapy groups: cefotaxime; ciprofloxacin; cefotaxime-plus-ciprofloxacin; and cefotaxime-plus-minocycline. The cytotoxicity of V. vulnificus for HeLa cells was measured using the lactate dehydrogenase assay; rtxA1 transcription was measured in a transcriptional reporter strain using a β-galactosidase assay.ResultsIn vitro time-kill assays exhibited synergism between cefotaxime and ciprofloxacin. In the animal experiments, the 96-h survival rate for the cefotaxime-plus-ciprofloxacin group (85%; 17/20) was significantly higher than that of the cefotaxime-plus-minocycline (35%; 7/20) and cefotaxime alone (0%; 0/20) groups (PConclusionsCiprofloxacin is more effective at reducing rtxA1 transcription and subsequent cytotoxicity than either minocycline or cefotaxime, and the combination of ciprofloxacin and cefotaxime was more effective in clearing V. vulnificus in vivo than previously used regimens. These data suggest that the combination of ciprofloxacin and cefotaxime is an effective option for the treatment of V. vulnificus sepsis in humans.