Antibiotic efficacy against Vibrio vulnificus in the mouse: superiority of tetracycline

Seven antimicrobial agents, all effective against Vibrio vulnificus in vitro, were compared for in vivo efficacy in mice experimentally infected with V. vulnificus strain B3547. Mice were injected s.c. with 1 X 10(8) cells, and i.p. injection of antimicrobials was begun 1.5 hr later when mice were bacteremic and had edematous lesions at the injection site. The study was done in two phases. Phase I was a dose-ranging experiment, using single injections within the range (on a body weight-adjusted basis) clinically useful in humans. Of 12 mice treated with Tetracycline (4 mg/kg), 12 survived at 24 hr, compared to 0 of 21 saline-treated controls, 3 of 10 given ampicillin (32 mg/kg) and 2 of 3 given cefotaxime (20 mg/kg). There were no survivors at 24 hr in groups of 5 to 10 mice treated with cefazolin (32 mg/kg), carbenicillin (80 mg/kg), erythromycin (8 mg/kg) or gentamicin (8 mg/kg). Phase II was designed to simulate clinical conditions using multiple dosing for 30 hr and scoring for survival at 96 hr. Of 12 mice given Tetracycline (3 mg/kg every 12 hr), 12 survived, compared to 1 of 10 given cefotaxime (20 mg/kg every 6 hr), 0 of 12 given carbenicillin (40 mg/kg every 6 hr) and 0 of 12 given saline every 6 hr. Tetracycline thus appears to be the agent of choice among those tested for in vivo efficacy against V. vulnificus in the mouse model.